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The European magazine for photonics professionals optics.org
HIGH - POWER DIODE L ASERS
ROADMAP PREDICTS INDUSTRIAL ROUTE FOR DIODE SOURCES
October 2007 Issue 154
E DUCATION
Developing nations benefi t from active learning initiative
LIQUID LE N SE S
Liquid lens modules move into auto-focus applications
ACQUI SITION
Consolidation in infrared imaging as FLIR buys Cedip
EDITORIALEditor Jacqueline HewettTel +44 (0)117 930 [email protected]
Reporter Marie FreebodyTel +44 (0)117 930 [email protected]
Reporter Tim HayesTel +44 (0)117 930 [email protected]
Senior production editor Alison GardinerTechnical illustrator Alison Tovey
EUROPE/ROW SALESBusiness development manager Adrian ChanceTel +44 (0)117 930 1193 [email protected]
Group advertisement manager Rob FisherTel +44 (0)117 930 1260robert.fi [email protected]
Advertisement manager Cadi JonesTel +44 (0) 117 930 1090 [email protected]
Senior sales executive Katrina DavisTel +44 (0) 117 930 1284 [email protected]
Sales executive Matthew GreenTel +44 (0) 117 930 1028 [email protected]
US SALESSales executive Tim MarshallIOP Publishing Inc, Suite 929, 150 South Independence Mall West, Philadelphia PA 19106, USATel +1 215 627 0880. Fax +1 215 627 [email protected]
CHINA SALESChina sales executive Ann HouShenzhen Yongge Advertising Co Ltd, Rm 1106Xinwen Building, No. 2 Shennan Zhong RoadShenzhen, Guangdong, PRCTel +86 755 82091822. Fax +86 755 [email protected]
ADVERTISING PRODUCTIONAdvertising production coordinator Ruth Stuart-TorrieTel +44 (0)117 930 [email protected]
Advertising production editor Mark Trimnell
CIRCULATION AND MARKETINGSubscription and circulation manager Mikael WigartTel +44 (0)117 930 [email protected]
ART DIRECTORAndrew Giaquinto
PUBLISHERClaire Bedrock Tel +44 (0)117 930 [email protected]
OPTICS & LASER EUROPEDirac House, Temple Back, Bristol BS1 6BE, UK Tel +44 (0)117 929 7481 Editorial fax +44 (0)117 925 1942 Advertising fax +44 (0)117 930 1178 optics.org/oleISSN 0966-9809 CODEN OL EEEV
SUBSCRIPTIONSComplimentary copies are sent to qualifying individuals. For readers outside registration requirements: £116/7168 ($208 US and Canada) per year. Single issue £11/715 ($19 US, Canada and Mexico). Contact IOPP Magazines, WDIS Ltd, Units 12 & 13, Cranleigh Gardens Industrial Estate, Southall, Middlesex UB1 2DB, UK.Tel +44 (0)20 8606 7518. Fax +44 (0)20 8606 7303
© 2007 IOP Publishing Ltd. The contents of OLE do not represent the views or policies of the Institute of Physics, its council or its offi cers unless so identifi ed. Printed by Warners (Midlands) plc, The Maltings, West Street, Bourne, Lincolnshire PE10 9PH, UK.
For the latest news about optics and photonics, don’t forget to visit optics.org.
Cover Constant innovation is driving diodes towards industrial markets p26
NEWS5 Business FLIR snaps up Cedip in 762 m deal• CMOS sensors see NIR• People
9 Editorial Overcoming shortages
TECHNOLOGY11 Applications Pulsed fi bre lasers reach new levels• Polymer opals inspire new markets
14 R&D Laser pulses turn water into ice• Interferometry images live cells in 3D• Opaque materials let light through
16 Patents Nexxus Lighting receives patents for its LED lighting
• Osram grants Citizen Electronics licensing deal
FEATURE S17 Autofocus liquid lenses target new applications Liquid-lens technologies designed to meet the insatiable demands of the mobile-phone industry are now being deployed in other imaging systems. Philippe Ruffi n explains to OLE how Varioptic is adapting its products for an increasing number of uses.
21 Organic polymers aid quest for silicon laser Overcoming silicon’s intrinsically poor light emission is a problem that many research groups are tackling. Graham Turnbull and Ifor Samuel describe how their hybrid silicon-polymer laser could pave the way towards optical chip-to-chip interconnects.
26 Industrial markets beckon for HPDLs Changes in the design and manufacture of laser diodes are seeding fundamental shifts in the way that we think about the cost and reliability of high brightness laser systems. Robert Martinsen of nLight Corporation tells OLE more.
29 Active learning inspires new interest in optics UNESCO’s Active Learning in Optics and Photonics project is making the fi nal preparations for its latest workshop to stimulate interest in optics in developing countries. Marie Freebody speaks to Minella Alarcon of UNESCO to fi nd out more.
33 Emission tailors SLEDs to many markets Superluminescent diodes combine the advantages of LEDs and laser diodes in a single compact package. Christian Vélez and Chris Armistead detail the factors to consider when purchasing SLEDs and the applications that are already using the source.
PRODUCTS37 Spectroradiometer• Diode laser stack arrays• Thermal camera
REGUL ARS50 Back chat
I s sue 154 October 2007 Content s
OVT’s new CMOS sensor features NIR capability p6
Striking colours from fl exible polymer opals p12
Finnish team takes a new look at pine needles p14
Thinking of buying an SLED? Read our guide p33
D PHYSICS TODAY 8 x 101/2 ,
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5OLE • O c tober 20 07 • o p t i c s .o r g /o l e
NEWSBUSINE S S 5 E DITORIAL 9
ACQU I SIT ION
FLIR Systems of the US has announced plans to acquire a controlling interest in Cedip Infrared Systems, the French developer of infrared (IR) cam-eras and stabilized gimbaled sys-tems. The acquisition improves FLIR’s international distribution network, adds new products and technology to its portfolio (such as cooled mid-wave IR cameras) and gives the company an import-ant manufacturing and technol-ogy base in Europe.
“The time was right for both companies to enter this agree-ment,” Craig Stoehr, FLIR’s director of investor relations, told OLE. “No particular mile-stone has been reached. We plan to leave the manufacturing in France and do not anticipate any job losses at this time.”
Under the terms of the agree-ment, the controlling sharehol-ders at Cedip have agreed to sell 67.8% of the share capital for 741.4 m. FLIR will then look to purchase all of the remaining shares in Cedip in line with French practice, bringing the total value
for the acquisition to 762.7 m.The transaction is subject
to various closing conditions, including the authorization of the French Minister of Finance and Economy. “We are planning to purchase all of the remaining shares to the extent possible,” commented Stoehr. “Our plan is to close prior to year end.”
When the transaction has closed, Cedip’s IR camera opera-
tions will be integrated into FLIR’s thermography division. Cedip’s Polytech subsidiary, which is located in Eskilstuna, Sweden, will be integrated into FLIR’s government systems divi-sion. Polytech specializes in mid-size, low-cost, highly stabilized gimbal systems, and its products will expand FLIR’s portfolio of stabilized multisensor systems.
FLIR anticipates cost savings
through integrated distribution and lower manufacturing costs from utilizing FLIR IR sensors in certain Cedip products. “Our plans for any overlapping prod-ucts have still to be decided at this point, as have our plans for the Cedip brand name,” said Stoehr.
For the f iscal year ended December 2006, Cedip reported a revenue of 718.2 m and an operating income of 73.1 m. As of 31 December 2006, the com-pany had net cash-on-hand of 715 m. FLIR anticipates that this transaction will be neutral to its 2008 earnings and accretive in subsequent years.
“We are pleased to announce this transaction,” commented Earl Lewis, CEO of FLIR. “The Cedip team has an outstanding reputation for designing and man-ufacturing high- performance cameras and will provide FLIR with complementary products and capabilities to help drive growth in key market segments worldwide. I welcome Cedip’s dedicated and hard-working employees to FLIR.”
FLIR snaps up Cedip in €62 m deal
A UK-led team of scientists has won EU approval to prepare the ground for a laser-based nuclear fusion facility. The high power laser energy research (HiPER) team will now start a three-year project to defi ne the technol ogies that will be used to build an experimental prototype.
“Getting the laser technology right will be critical,” Anne-Marie Clarke, HiPER’s project manager, told OLE. “We need to decide whether to use existing laser-based fusion techniques, such as those used in the Laser Mégajoule in France, or whether to develop new diode-pumped solid-state laser technology.”
Other large-scale laser facil-
ities, such as Mégajoule and the National Ignition Facility in the US, have been designed for mili-tary applications, but the primary purpose of HiPER will be to gen-erate energy from nuclear fusion. The team is therefore focusing on an all-optical “fast ignition” fusion process that it believes will be more suitable for commercial power-generation plants.
This fast ignition is a two-step process. First, a laser that can deliver 0.2–0.3 MJ in a few nano-seconds is directed at a fuel pellet 2 mm across. This creates enough pressure to compress the pellet to a diameter of a few microns and to generate temperatures of tens of millions of degrees.
Second, a short-pulse high-power laser (70–100 kJ in 10 ps) is used to ignite the gas. The fast-ignition technique is expected to require a smaller laser than convent iona l la s er- f u s ion approaches – which typically demand several megajoules of laser energy to create the con-ditions needed for fusion – and should also ease the tolerances on the laser profi le.
According to HiPER project coordinator Mike Dunne, the laser physics behind fast igni-tion is now being investigated by researchers around the world. The ultimate aim for the HiPER project is to develop the technol-ogy needed for a commercial
power-generation plant.One of the goals of this three-
year preparatory project will be to decide where to site the facility. The UK is currently the front run-ner, but Clarke says that HiPER would welcome bids from other member nations.
Another key objective will be to pull together a consortium of nations and funding agen-cies that will contribute to the facil ity’s construction costs, currently estimated at $1 bn (70.7 bn). The HiPER project is already formally supported by seven European nations, inclu-ding the UK, the Czech Republic, France, Greece, Italy, Portugal and Spain.
FUNDING
Laser fusion project wins approval from the EU
Cedip Infrared Systems makes products for a number of markets including airborne analysis (bottom left) and mechanical testing in the automotive industry (top right).
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6 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
NEWS
BUSINESS
NIGHT VI SION
CMOS sensors see NIR
The latest CMOS CameraChip image sensors from OmniVi-sion Technologies (OVT), US, are sensitive to near-infrared (NIR) light up to 1050 nm. The company is targeting its OV7710 and OV7950 products at auto-motive and security applications where it says that a single dual-mode sensor will simplify system designs and reduce costs.
“The sensor records the interior of a car for security applications,” Inayat Khjasha, product director at OVT, told OLE. “For pedestrian detection and other ‘forward-looking’ applications, the sensor is placed behind the rear-view mirror. This technology is being evaluated by a signifi cant number of top-tier suppliers (that provide sensor modules to OEMs) in the US, Europe and Japan.”
OVT says that a number of undisclosed “process-level” enhancements have expanded the sensor’s spectral sensitivity. “There is a level of NIR detection
inherent in CMOS to start with, which we have further enhanced so that low-power LEDs may be used and the resulting image quality is much improved,” com-mented Khjasha.
The dual-mode nature of the sensor means that a standard col-our image is produced in daylight conditions and then, as ambi-ent light levels fall, the sensor switches automatically to a black-and-white night-vision mode.
“NIR is used when the visible light goes below 1 lux,” said Khja-sha. “When the target cannot be seen in visible light, the switch to
the NIR mode is executed.” Both the OV7710 and OV7950
sensors are commercially avail-able and all new releases for the automotive and security markets will feature NIR capability. The visible and NIR images are the same size in terms of the number of pixels and are acquired at the same frame rate for both sensors.
“Our process level enhance-ments are significantly better than those offered by anyone else and we cannot divulge more information at this stage for com-mercial reasons,” he concluded.
IN BRIEF
FU N D I N G
Syntune of Sweden, a developer
of single-chip tunable lasers, has
closed a second round of venture
capital fi nancing worth SEK 47.8 m
(75.1 m).
FI N A N C I N G
The m.u.t group has announced
its transition from a GmbH into a
joint stock company under German
law to expand production and
development capacity. The former
partners of the GmbH hold the
majority of the shares, while 30%
are available for open trading.
CO N T R AC T
BAE Systems will design and
develop a digitally enhanced
night-vision goggle as part of the
US Army’s Enhanced Night-Vision
Goggle programme. The helmet-
mounted goggle will digitally
combine video imagery from a low-
light-level visible sensor and an
uncooled longwave infrared sensor
on a single colour display located
in front of the soldier’s eye.
EX PA N S I O N
SensL of Ireland, a developer of
low-light detectors and modules,
has opened a US offi ce in
Mountain View, California. The
SensL US offi ce will be headed up
by the company’s chief commercial
offi cer Joseph O’Keeffe.
DI S T R I B U T I O N
Photon, a US manufacturer of
beam-profi ling instrumentation,
has signed a distribution
agreement with Bfi Optilas for
Switzerland and Italy.
GAS SE N SING
Hamamatsu Photonics of Japan is sampling its fi rst single-wave-length quantum cascade laser (QCL) operating continuous wave (CW) at room temperature. Mass production is scheduled to begin in January 2008 and the company is targeting its device at trace gas measurement systems.
“The QCL is a mid-infrared source operating in the 5–8 μm
region,” Craig Palmer, assistant sales manager at Hamamatsu Photonics, told OLE. “Output power depends on the operating conditions and is typically a few milliwatts CW or a few hundred milliwatts pulsed.”
“Room temperature operation was a request from our custom-ers,” added Palmer. “For an instru-ment that is required to operate remotely, liquid nitrogen is not a convenient means of cooling.”
The fi rm is now providing sam-
ples of the QCL to Japan-based, as well as international, manufac-turers of analytical instruments. Hamamatsu expects there to be no issues with the production release. Palmer commented that “production capacity should not be a problem”.
Although Palmer could not comment on the lifetime of the device, he did add that mean-time-to-failure data is currently being accumulated. The material sys-tem of the QCL was not disclosed.
Hamamatsu’s QCL senses trace gases
Images taken using the night mode (left) and day mode (right) at low light levels.
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8 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
BUSINESS
NEWS
PEOPLE
IMAGE SE N SORSDirk Rüttgerodt has been
appointed managing director
for commercial management at
Baumer Optronic. The German
company is a manufacturer
of digital image acquisition
components and smart vision
sensors. The previous commercial
manager, Oliver Vietze, has now
been appointed to the management
board of the Baumer Group.
MICRO - OP TIC SJan Lobbezoo has been named
chairman of the board of directors
at Heptagon, a Swiss developer of
wafer-scale micro-optics. He has
more than 30 years’ experience
of working in senior management,
which includes previous positions
at Philips Semiconductors
and Taiwan Semiconductor
Manufacturing Company.
TE LECOM SNeoPhotonics, a developer of
optical components for the
telecommunications industry, has
appointed Benjamin Sitler as vice-
president of worldwide sales to
oversee the company’s sales force
and distribution partnerships. He
was previously vice-president for
tunable products, a product line
that came to NeoPhotonics via
its November 2006 acquisition of
Paxera, which Sitler co-founded.
OP TOE LEC TRONIC SRobert Friel has been appointed
president and chief operating offi cer
of PerkinElmer and is due to be
elected chief executive offi cer in
February 2008. At that time Greg Summe will become executive
chairman of the board and will
remain as such through the annual
shareholders meeting in April 2009.
L ASE R DIODE SPhotonic Products, the UK laser
diode and optoelectronics supplier,
has appointed two new sales
managers in the US and a new sales
assistant in the UK. Paul Bonsi is
sales manager for north-western
US and western Canada, while Gary Polio is sales manager for eastern
US and eastern Canada. Tracy Duckworth has joined as sales
assistant at the UK headquarters.
ME TROLOGYRoger Xiao has been appointed
Asia Pacifi c sales director for
Labsphere’s light metrology,
spectroscopy and refl ective
materials products. He will be
based in Shanghai, China.
COATING SMichael Kennedy has joined
Laseroptik where he will be
responsible for the production
of high-power coatings and will
assist the company in supporting
customers with complex coating
requirements. He previously
directed thin-fi lm production at
Linos Photonics.
DI SPL AYSPhilippe Lambinet has joined
STMicroelectronics as corporate
vice-president and general manager
of the home entertainment and
displays group. He will report
directly to president and CEO
Carlo Bozotti and will be responsible
for ST’s Grenoble site in France.
E XCIME R SOURCE SMotohiko Tahara has been
appointed president of Cymer Asia
Pacifi c. He will be responsible for
expanding Cymer’s markets for
excimer laser sources across Asia.
NEWS
EDITORIAL
OLE • O c tober 20 07 • o p t i c s .o r g /o l e 9
Overcoming shortagesWhen the editorial team got together to discuss the content for this issue, there were two topics that we wanted to cover: the skills shortage in the photonics industry and the roadmap that will take diode lasers into industrial applications. Both of these subject areas are in response to your feedback and I hope that you enjoy our coverage.
On the skills shortage, turn to our regular back chat feature that is on p50. OLE spoke to Per Stenius, the CEO of Finnish fi rm Liekki Corporation, to fi nd out how a small high-tech company copes with the challenge of fi nding the right people. Stenius told us that this is a massive issue for his fi rm and that recruiting internationally is the only option.
To put the extent of the problem into perspective, here’s just one comment that Stenius made: “It seems that more and more companies recognize that the war for talent is on-going on a global scale. We have to embrace a multicultural approach if we want the best teams.”
The back chat feature has been a regular addition to OLE this year and we have dealt with a number of issues: transferring technology from the lab into industry; making acquisitions; and copy-cat syndrome to name just a few. Are there any other issues or problems that your company is facing or that you feel we should be covering? If so, please get in touch. We want to try and pass on advice and experience from people who have “been there and done that”.
With that thought in mind, we have put together an article on UNESCO’s Active Learning in Optics and Photonics (ALOP) programme. ALOP introduces teachers in developing countries to active learning with the hope that it will enable them to teach optics more effectively. In the light of the skills shortage that we are facing in this industry, it is programmes like ALOP that could generate a new stream of future employees. Please turn to p29 to fi nd out more.
Can I also point you in the direction of pp26–27 where you can read Rob Martinsen’s article on the improvements in diode lasers that will push the devices into industrial applications. Although diode lasers have struggled to gain a share of the materials processing market, Martinsen believes that this is all about to change in the next couple of years.
Jacqueline HewettE-mail [email protected]
“Strategies to combat the global skills shortage are a priority for many fi rms.”
Jacqueline Hewett
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11OLE • O c tober 20 07 • o p t i c s .o r g /o l e
TECHNOLOGY
Pulsed fi bre lasers reach new levels ULTR AFAS T TEC HNOLOGY
Researchers in Germany have unveiled a mode-locked high-energy fibre laser with a per-formance that they say rivals state-of-the-art bulk femto-second oscillators for the first time. The laser produces 265 nJ ultrashort pulses and the team believes that power scaling beyond the 1 μJ-level is possible with the current design (Optics Express 15 10725).
“Bulk femtosecond oscillators are expected to offer a few 100 nJ of energy, a few watts of average power and a pulse duration of a few 100 fs, and that is exactly the range we have with our fi bre laser,” Bulend Ortac from the Frie-drich-Schiller University in Jena told OLE. “Our pulse energy is one order of magnitude higher than so far reported for fi bre oscillators in the 1 μm wavelength region.”
The peak power and pulse energy scaling of mode-locked fi bre lasers has, to date, been lim-
ited by nonlinear effects (such as Kerr-nonlinearity) that occur as light propagates along the fi bre. To overcome this, Ortac and col-leagues have enlarged the fi bre’s mode area that in turns reduces the nonlinearity.
“Low-nonlinearity large-mode-area fi bres open up the possibil-ity of energy scaling,” explained Ortac. “A newly designed low-nonlinearity single-transverse mode ytterbium-doped photonic crystal fibre and a laser design that controls the nonlinear effects has allowed our laser system to reach this performance level.”
The team’s passively mode-locked large-mode-area fi bre laser uses a sigma cavity confi guration and a 976 nm pump diode laser. At this wavelength, the fi bre has an absorption of 30 dB/m, which reduces the required length of fi bre to just 51 cm.
“Passive mode-locking is achieved using a real saturable
absorber based on a multilayer GaAs/AlAs Bragg mirror and a low-temperature MBE-grown InGaAs quantum-well structure in front of the mirror,” said Ortac. “The saturable absorber mirror (SAM) has high nonlinear modu-lation depth with fast relaxation
time. Self-consistent intra-cavity pulse evolution is obtained by the combined action of the SAM and the active fi bre so dispersion com-pensation is not needed.”
Above the mode-locking threshold of around 2 W average output power, the laser delivered a single-pulse train with a repeti-tion rate of 10.18 MHz. The group recorded a maximum average output power of 2.7 W, corre-sponding to a pulse energy of 265 nJ. The laser’s central wave-length was 1031.7 nm and pulses were compressed by an external transmission-grating pair down to a duration of 400 fs.
“We are developing even higher pulse energy with better control of nonlinear effects and designing a new real saturable absorber with a high optical damage threshold,” commented Ortac. “We have had contact with industrial partners but there are no fi xed plans as yet to commercialize this laser.”
SPAC E
A research and development con-tract between Intense, UK, and the European Space Agency will lead to the development of high-power, high-efficiency laser-diode arrays for solid-state laser pumping applications in space.
The PULSAR (PUmp Laser Stacks with Aerospace Reliability) programme is focused on improv-ing the reliability and effi ciency of laser diode stacks at 808 nm. The
aim is to achieve 1.2 kW of power under pulsed operation with an electro-optical effi ciency of 65%. The diodes will also be required to meet the demanding lifetime specifi cation of 12 billion shots in space. The PULSAR pro-gramme will run for 2.5 years, with research results to be pub-lished in journals and at techni-cal conferences.
Arrays with these character-istics will save a considerable amount of power once deployed on space vehicles and will reduce
heat-removal requirements.Key to the project’s success will
be Intense’s quantum-well inter-mixing (QWI) process, an inte-gration technology that allows the properties of a quantum-well structure to be modified after growth to include passive and active sections in the same laser cavity. The QWI technol-ogy involves passive waveguides located at the laser facets to form non-absorbing mirrors (NAMs), passivating the facet regions of the laser.
Further improvements in pumping effi ciency will be inves-tigated, including the use of vol-ume Bragg gratings to narrow and stabilize the array’s emis-sion spectrum. Their integra-tion with the diode arrays will be assessed in co-operation with a US manufacturer.
“We are optimistic we can reach these ambitious goals based on the success of the DARPA SHEDS initiative where laser efficiency was improved by over 20%,” said John Marsh of Intense.
High-power diodes head for space
This image shows the cross section of the 70 μm core diameter rod-type photonic crystal fi bre used in this experiment. It includes a hexagonal lattice of air holes with a diameter of 0.9 μm and a hole-to-hole spacing of approximately 12.7 μm.
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APPLICATIONS 11 R&D 14 PATE NTS 16
12 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
TECHNOLOGY
APPLICATIONS
SECURIT Y
Polymer opals inspire new marketsA method for mass-producing polymer opals with colour-tun-ing characteristics has been unveiled by researchers in the UK and Germany. The method pro-duces strongly coloured mater-ials, which could open up a range of decorative, sensing, security and photonic applications (Optics Express 15 9553).
“We have discovered a way to make these structures cheaply in large volume, but also a new way to make strongly coloured materials,” Jeremy Baumberg of the University of Southampton, told OLE. “We have produced polymer opal sheets 100 m long and 1 m wide, and see no problem in scaling this up.”
Baumberg’s polymer opals are a type of photonic crystal consisting of a 3D lattice of plastic spheres, each a few hundred nanometres across that are “glued” together with a more f lexible polymer
material. The lattice structure refl ects light in such a way as to produce a colour that depends upon the angle of refl ection.
“Normally, synthetic opals are produced by sedimentation where glass spheres are allowed to settle in a vial that can take months to make a well ordered structure,” commented Baumberg. “Other methods such as spinning pre-cursor solutions in a solvent have proved hard to control.”
Baumberg’s Southampton team worked with colleagues at the Deutsches Kunststoff-Institut in Germany to demonstrate an industrial method of producing 3D ordered structures using con-ventional plastics. The team also found that adding nanoparticle dopants into the lattice enhanced the scattering.
“Although the dif ference in refractive index between the spheres and surrounding
medium is small, adding tiny nanoparticles in between the spheres leads to an enhancement of colour,” explained Baumberg. “We use transparent polymers and add a small amount of car-bon nanoparticles in order to get intense metallic greens, oranges, reds and blues.”
One of the more interesting applications exploits the fl exible
nature of the fi lms. “The fi lms can stretch across edges and around corners,” commented Baumberg. “Leading airplane manufact-urers have expressed interest in coating tailplanes with these striking colour solutions.”
Security-sensitive applica-tions, such as banknotes or credit cards, could also benefi t from the hard to replicate appearance of these materials.
“There are applications such as smart packaging or sensing in which the fi lms can be chem-ically programmed to respond visually to low levels of environ-mental targets,” added Baum-berg. “Food packaging could change colour to indicate if the food inside it is spoiling.”
The team has received a $2 m (71.44 m) grant from the UK EPSRC to look at the physics, applications and production of the polymer opals.
IMAGING
Applications such as analytical and environmental science, med-ical and biotechnology, and genet-ics and fl uorescence measurement could all benefit from Schott’s latest interference fi lters. Called Veril fi lters, the product uses thin layers to transmit or refl ect vari-ous colours of the spectrum.
“Our Veril fi lters are all-pur-pose interference bandpass fi lters with a central wavelength that
varies linearly over the length of the glass substrate,” Ulf Brau-neck, head of coating filters at Schott, told OLE. “Depending on the position of a 1 mm slit along the fi lter’s base length, the char-
acteristics will differ.”Whereas standard interference
fi lters only transmit and block one particular waveband, Brauneck explains that a Veril fi lter follows a pre-defi ned progression through-out its entire surface.
“The fi lter’s central wavelength varies remarkably linearly over the length of the fi lter, whereas the maximum transmission and half width vary only slightly over the spectral range,” said Brau-neck. “The typical long wave blocking range is twice the value
of the centre wavelength with an average transmittance of <=10–4
within the blocking range.”Although Veril filters were
first developed in the 1980s, Schott says that it has made significant progress in refin-ing the wavelengths, improv-ing processes and developing customer-specific dimensions, spectral requirements and dif-ferent linear dispersions. Veril filters are standardized for the 400–700 nm and 400–1000 nm wavelength ranges.
Filters feature variable bandpass
The fl exible nature of the opals could be exploited by a number of applications.
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um
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Veril fi lters have a variable bandpass.
SC
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Advanced Photonix, Inc.
The API AdvantageULTRAFAST LEADING EDGE HIGH RELIABILITYVERTICALLY INTEGRATED
CUSTOMOPTOELECTRONIC
SOLUTIONS
14 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
TECHNOLOGY
R&D
MATE RIAL S
Laser pulses turn water into ice Using laser pulses to crystal-lize supercooled water into ice may seem counter-intuitive, but that’s exactly what researchers in Germany and the UK have achieved. Because the pulses can be focused to a specifi c point in the liquid, the researchers believe that their technique will be valu-able for future material and crystal growth studies (Physical Review Letters 99 045701).
“We wanted to highlight the mechanisms behind sonocrys-tallization, where ultrasound triggers the nucleation of a supercooled liquid,” researcher Robert Mettin of the Univer-sity of Göttingen told OLE. “We replaced the sound wave with a focused laser pulse to generate a single, well controlled and local-ized bubble in the liquid.”
A supercooled liquid is one that has been chilled to below its normal freezing point without crystallization occurring. Rely-ing on a process called acoustic cavitation, sonocrystallization uses ultrasound to trigger nucle-ation (crystal formation). The sound waves generate bubbles in the supercooled liquid and the
collapse of these bubbles leads to crystallization.
Mettin and colleagues, inclu-ding one from Unilever Corpor-ate Research in the UK, focused single 8 ns pulses from an Nd:YAG laser emitting at 1064 nm into a cuvette containing the supercooled water. Each pulse, which had an energy between 1 and 2 mJ, was focused to a 50 μm diameter spot. The team used a high-speed CCD camera to capture the response in the liquid after each pulse had been fi red.
“The focused laser pulse locally evaporates the water causing a strong pressure wave and a bubble of water vapour and other gases to grow,” explained Mettin. “The bubble subsequently collapses, which causes a second strong pressure
wave. We believe that the strong transient increase of pressure in the supercooled liquid close to the bubble causes nucleation.”
Mettin adds that the water shifts into a “pressurized regime” for a short time, which leads to a much larger supercooling effect and increases the likelihood that an ice crystal will form.
“We could achieve supercool-ing down to –8 °C otherwise the liquid freezes spontaneously,” said Mettin. “Once a crystal was initi-ated, the whole volume froze.”
The team is now devising a set of experiments to fi nd out more about the nucleation trigger. “We are interested, for example, in direct measurement of the high pressure waves and other bub-ble conditions with (or without) nucleation,” concluded Mettin.
ECOLOGY
Measurements of monochro-matic backscattering from individual Scots pine needles, approximately 0.5 mm wide, have been made by a Finnish team (Applied Optics 46 4916).
“Information on backscat-ter from coniferous forests is needed to develop models of forest ref lectance and canopy radiative transfer that can then be used in forest monitoring,” Sanna Kaasalainen of the Finn-
ish Geodetic Institute told OLE.The team believes that this is
the fi rst time that individual nee-dles have been examined in this way. Broad leaves have been stud-ied in some detail as part of vari-ous climate studies, but data on conifer needles has been scarcer simply because of the diffi culty in studying such small objects.
The solution involved a spe-cially constructed instrument, based on standard techniques
used for backscattering measure-ments and CCD photometry, but modifi ed to suit a small target. A diffuser smoothed out the laser beam and a 2 mm iris in front of the diffuser enhanced the angu-lar resolution suffi ciently to allow
accurate measurements.Kaasalainen and colleagues
identifi ed strong backscattering peaks (the coincidence of the inci-dence and scattered light paths) from both sides of a needle when illuminated by a 1064 nm 10 mW laser. Such backscatter enhance-ment is called a “hot spot” and the team measured an increase in brightness of up to 40%.
“Our purpose was not to present a data bank on hot-spot signatures of a range of pine needles, but to test a measurement technique and obtain preliminary results,” said Kaasalainen. “We feel that these results are unique.”
Finnish team has fresh look at pine needles
Optical studies of pine needles will improve our understanding of forests.
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Frames of ice crystal growth from the high-speed observations show the bubble and ice-crystal growth following a laser shot. The laser-induced plasma is visible in the fi rst frame (top left, 0).
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15OLE • O c tober 20 07 • o p t i c s .o r g /o l e
R&D
TECHNOLOGY
MICROSCOPY
Interferometry images live cells in 3DResearchers in the US have unveiled an interferometry tech-nique that they say has produced the fi rst 3D images of a living cell without having to alter the cell beforehand. Created by physi-cist Michael Feld and colleagues at the Massachusetts Institute of Technology, the technique involves shining a laser beam through a biological sample at different angles to record a 3D image with sub-micrometre reso-lution (Nature Methods 4 717).
Tiny biological samples must normally be prepared before they can be viewed in 3D. Cells, for example, often have their inner components highlighted with fl uorescent dyes. However, such modifi cations can disrupt a cell’s normal functions, limiting the possibilities for analysis.
Feld and colleagues have done away with such preparations and instead use the optical properties of the cell in its natural state to generate a 3D image. First, a laser
beam is split into two – one beam goes through the sample while the other bypasses it. The beams are then recombined and shone onto a digital camera where they produce an interference pattern.
From this, the US team deduces the phase difference between the two beams, which changes according to the refract ive index of the material that the beam passes through. By mapping this refractive index, a 2D image of the cell’s interior is generated.
To get a 3D image the resear-chers placed a mirror in front of the sample and rotated it incre-mentally with a galvanometer. For each rotation, which alters the angle of the laser beam through the sample, they record an interference pattern.
Feld and colleagues demon-
strated their technique – called tomographic phase microscopy – by imaging a cervical-cancer cell. For the fi rst time, an unal-tered cell’s detailed 3D struc-ture with elements, such as the nucleus, can be seen.
“Accomplishing this has been my dream, and a goal of our labor-atory, for several years,” said Feld. “For the fi rst time the functional activities of living cells can be studied in their native state.”
The resolution currently stands at about 0.5 μm, but the group says that it should be able to improve it to 0.15 μm or less. The hope is that tomographic phase microscopy will complement electron micro-scopy, which can probe as small as 10 nm but requires samples to be frozen or coated in a layer of conductive material.
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Feld and colleagues produced a 3D image of a HeLa cell with a transverse resolution of 0.5 μm and a longitudinal resolution of 0.75 μm. The nucleus (shown in green) is surrounded by cytoplasm (shown in red).
Mic
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Embedding a microfibre coil res onator (MCR) in Tefl on over-comes the problems of stability and reliability seen when such structures operate in air, say researchers at the UK’s Opto-electronics Research Centre in Southampton. Thanks to the unique optical and mechanical properties of the Teflon-coated devices, they have the potential
to be crucial elements in future micro- and nano-photonic devices (Optics Letters 32 2164).
“A considerable fraction of the transmitted power can propagate in the evanescent field outside of a nanowire,” researcher Fei Xu told OLE. “Light can be con-fi ned to a very small area over a long length to observe nonlinear interactions. Nanowires can also be bent while remaining rela-tively strong mechanically.”
An MCR is a coiled single mode optical microfi bre where the diam-eter and the distance between the
adjacent turns are comparable with the wavelength of the trans-mitted radiation. It also benefi ts from low bend loss and low losses at the fi bre’s input and output.
Previous MCRs, such as a knot or self-coupling design where the coils of the resonator are in contact, have not been stable in air. “The loss of these microfi bres would increase with time,” said Xu. “This problem can be solved by coating the MCR in a low-loss, low-index material like Tefl on.”
SE N SORS
Microfi bres benefi t from Tefl on coating
The resonator was manufactured by wrapping the microfi bre around a low refractive index rod. If the microfi bre was not wrapped around the rod tightly, the resonating conditions were lost.
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16 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
TECHNOLOGY
R&D
Opaque materials let light through SCAT TE RING
PATENTS
To search for recently published applications, visit http://www.wipo.int/pct/en/ and http://ep.espacenet.com.
AWARDNexxus Lighting receives patents for its LED lighting technologyUS fi rm Nexxus Lighting has received two patents
relating to its LED lighting technology. The fi rst US
patent (number 7,229,027) describes a device
that incorporates a light chamber to house LED
lights for illuminating streams from a waterfall. The
second, (number 7,244,037), is for a detachable
LED pool light. “Illuminated waterfalls are used in
swimming pools, portable spas and fountains,”
said Steve Faber, Nexxus’s director of engineering.
“The pool light patent provides an added
disconnection feature that no one else can offer.”
LICENSINGOsram and Seoul Semiconductor agree to share their LED patentsA cross-licence agreement has been signed
between Korean company Seoul Semiconductor
and Osram. Under the agreement, both parties
will refrain from raising objections against
patent rights relating to white and visible LED
technologies, and will co-operate in defending
these rights. “This mutually benefi cial agreement
will further pave the way for closer co-operation
between our companies,” said Chung Hoon Lee,
president of Seoul Semiconductor.
Osram grants Citizen Electronics licensing agreement for white LEDsOsram of Germany has signed a licensing
agreement with Japanese fi rm Citizen
Electronics. The agreement gives Citizen the
ability to use Osram’s intellectual property
developments in its white LED products.
“We are pleased that this agreement signals the
end of our dispute and that Citizen Electronics
has recognized the importance of our intellectual
property,” said Rüdiger Müller, CEO of Osram.
INFRINGEMENTSharp files patent infringement against Samsung ElectronicsSharp has fi led a lawsuit against Samsung
Electronics in the US District Court for the
Eastern District of Texas. It claims that Samsung
has infringed fi ve of its US patents (4649383,
5760855, 6052162, 7027024 and 7057689)
relating to LCD technology.
In the complaint, Sharp requests that the
district court award compensatory damages
to Sharp and prohibit the sale of the infringing
products. Sharp also requests a trial by jury.
APPLICATIONLG Philips files application for flexible display technologyLG Philips has applied for a patent to cover
its fl exible electrophoretic display technology
that uses oil and water to produce images. The
motivation is to produce a fl exible display that
is cheaper than fl exible OLEDs. The idea is that
such displays are based on tiny plastic cells
containing oil and water and are connected
to plastic electrodes. The patent states that
the image is displayed as a result of applying
an electric fi eld, causing movement of the
electrolytic and non-electrolytic layers.
By constructing wavefronts that invert the diffusion of light, researchers in the Netherlands say that they can focus coherent light through opaque scatter-ing materials. The result could aid a number of lines of research including spectroscopy in scat-tering media and metamaterials (Optics Letters 32 2309).
“Light propagation in opaque materials such as biological tis-sue is dominated by diffusion,” Ivo Vellekoop of the MESA+ Research Institute at the University of Twente told OLE. “Since diffuse light has no preferential direc-tion, it seems impossible to direc-tionally transmit light through a multiple scattering material.”
As Vellekoop and his colleague Allard Mosk discovered, the answer was to modify the incident wavefront of the laser beam. The method relies on interference: the incident light is manipulated in such a way that the scattered light
interferes constructively to form a sharp focus after it has passed through the opaque material.
Vellekoop and Mosk start by illuminating the sample with a focused plane wave. Behind the sample there is a random mixture of constructive and destructive interference leading to a small signal in the form of a speckle pattern.
“We divide the incident wave-front into segments and cycle
the phase of each segment,” explained Vellekoop. “This allows us to fi nd the phase at which the light from each segment inter-feres constructively with the small initial background signal. Once we know the optimal phase for each segment, we program a phase modulator with the opti-mal incident wavefront, and a single bright focus appears behind the sample.”
The researchers have success-
fully tested their phase-altering algorithm on titanium dioxide pigment, daisy petals, eggshell and a human baby tooth – thicknesses varied from 10 μm to 1.5 mm. The algorithm creates a spot that is up to 1000 times brighter than a nor-mal diffuse transmission spot.
“The algorithm is fully auto-matic and performs a meas-urement for each segment and constructs the optimal wave-front,” explained Vellekoop. “The time required to construct the wavefront depends on the number of segments. A contrast of 10 can be achieved in a mat-ter of seconds, while a contrast of 1000 takes over 15 minutes.”
The team is now working with materials such as porous gallium phoshide. “We are also working on wavefront optimization using local nanoscale probes that can be put inside tissue and investi-gating real-time wavefront con-struction,” concluded Vellekoop.
randomspeckleplane
wave
stronglyscatteringsample
shapedwave
focusedlight
stronglyscatteringsample
a) b)
Fig. 1(a): shows how opaque white objects scatter incident light. When laser light is used, a completely unpredictable interference pattern, known as speckle, is formed. (b): by exactly matching the wavefront of the incident light to the scattering in the opaque object, the object acts as a lens that focuses light sharply.
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17OLE • O c tober 20 07 • o p t i c s .o r g /o l e
LIQUID LENSES
Autofocus liquid lensestarget new applications
The mobile-phone market has driven many of the changes that imaging systems have undergone in recent years. The industry continues to require cameras not only with enhanced performance but also modules that are cheaper and smaller than their predecessors. These constant demands have inspired new technologies, many of which can be deployed in other imaging applications. Miniature variable focus optics is just one of these technologies.
At Varioptic, we are pioneering liquid-lens solutions and have seen that markets such as webcams, barcode readers, secur-ity and medical are launching or develop-ing products that include variable focus. Here, we outline why we believe that mov-ing to an autofocus set-up based on liquid lenses would benefi t these key sectors.
Autofocus with liquid lensesAutofocus is a standard feature in all of today’s digital cameras. These systems use electromechanical technologies such as stepper or piezo motors to precisely translate the lenses with respect to each other. Although these systems work well, they are expensive, diffi cult to miniatur-ize, have a limited number of cycles, and can fail to meet the tight optical tolerances required because of friction between the mechanical components.
Our liquid-lens solution uses electrowet-ting technology to produce variable focal length lenses with no moving parts. These lenses have been commercially available for over a year for a variety of applications including mobile phones. Liquid-lens tech-nology is characterized by a wide range of focal lengths that enable very close focus; high optical quality; fast and consistent response; and fi nally by its robust nature with no moving parts to wear or break.
Varioptic’s lenses use a watertight cell that contains two nonmiscible liquids. The shape of the liquid interface is controlled by a voltage, which when applied, changes the power of the lens. The interface is in
contact with a conical metallic part that is coated with an insulating fi lm several microns thick (see fi gure 1).
When an electrical voltage is applied, charges accumulate on both sides of the insulating fi lm. This applies a force to the interface, which deforms and assumes a convex shape. This effect is both reversible (because the system presents a very weak hysteresis) and rapid.
In this configuration, manufacturers benefi t from an extremely robust module that enables a rapid autofocus of <500 ms; uses very little energy (around <15 mW); and can be manufactured at low cost in very large numbers (>1 million per month).
Since the launch of our fi rst liquid lens in January 2006 (the ARCTIC 320), we have continually added to our portfolio.
All liquid-lens products share very high
Liquid-lens technologies designed to meet the insatiable demands of the mobile-phone industry are now being deployed in other imaging systems. Philippe Ruffi n explains to OLE how Varioptic is adapting its products for an increasing number of uses.
ON
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Description Unit ARCTIC 414 ARCTIC 416 ARCTIC 314 ARCTIC 320Mechanical Pupil diameter mm 2.3 2.3 3 3 Dimensions mm 7.75 × 1.4 7.75 × 1.6 7.75 × 1.4 10.5 × 2.5Optical Focal range cm 8.5 to ∞ 6 to ∞ 10 to ∞ 5 to ∞ (12 diopters) (18 diopters) (10 diopters) (20 diopters) Resolution up to 3 Mp up to 3 Mp up to 5 Mp up to 2 Mp Wave front μm <0.250 <0.250 <0.1 <0.5 error (RMS) Transmittance % 97 97 97 95 @ 587 nmElectrical Driving voltage Vrms 0–60 (1 kHz) Dissipated power μA 200Environ- Operating T° °C –20 to 60mental Storage T° °C –40 to 85 Operating cycles >1 000 000
Table 1: Varioptic’s product portfolio
Fig 1: Applying a voltage changes the power of the lens. These changes are both reversible and rapid.
18 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
LIQUID LENSES
performance and quality levels on critical parameters, either optical (such as trans-mission and wavefront error) or electrical (such as low dissipated power). Typical specifi cations are given in Table 1, p17.
Advantages of liquid lensesLiquid lenses provide advantages over tra-ditional mechanical actuators in the three critical areas outlined below.
Reliability and robustnessWhereas mechanical systems are rated to a
few hundred thousand cycles, liquid lenses with no moving parts have been tested to more than 30 million cycles. This is partic-ularly useful for very high cycle-rate appli-cations, such as barcode reading systems.
Mechanical robustness is also a seri-ous concern for consumer and industrial applications. Liquid lenses are not affected by vibrations or drop tests and can operate from –20 to 60 °C and can be stored in con-ditions from –40 to 85 °C.
Response timeFast response time is a key requirement in many applications, including biometrics, barcode readers and webcams. The two critical issues that usually plague tradi-tional solutions are hysteresis and long settling times.
A high hysteresis requires system designers to use tricks to avoid missing the best focus position. A liquid lens does not suffer from hysteresis so the design is much simpler and more reliable.
Mechanical actuators move the lens up and down the optical axis to vary focus. However, before the system can capture the images necessary to perform the auto-focus calculations, the lens must reach a stable, settled state that takes around 50 ms for each step (and there are typically up to 20 steps). This limits the time-to-focus (TTF) for still images and the frame rate of the system if it is in video mode.
For example, a rate of 25 frames per sec-ond (fps) requires frame capture within 40 ms, so a 50 ms settling time would mean that the autofocus algorithm can only run every other frame. One option is to reduce the frame rate to 20 or 15 fps and to run the autofocus with every frame. In compar-ison, the liquid lens can run comfortably at 40 ms giving 500 ms TTF and good video-mode performance.
RepeatabilityRepeatability is the ability of an actuator to constantly and accurately return to the same position for the same input command and is critical in open-loop applications. To be classifi ed as repeatable, an actuator should not suffer from hysteresis or from drifts in time. It should also be possible to model the response curve in tempera-ture. The response of a liquid lens is highly repeatable and linear in the main oper-ating range of –5d to 13 d optical power with a slope equal to 1 per 1 Vrms.
Autofocus applicationsWebcams
Webcams were designed originally for low pixel counts mainly associated with the video transmission requirements of the CIF format. Poor quality images at very
Varioptic produces a range of liquid-lens modules for both consumer and industrial markets.
Va
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Mobile phone
FPD
LCD
Notebook
The Industry standard for Display adjustment in the production line
Unmatched ease of operation for fast luminance and chromacity measurement
High accuracy even at low luminance levels
Multiple probe expansion for large and small display sizes
For quality inspection of Luminance, chromacity, White Balancing, Gamma and Contrast on any LCD, PDP, OLED or FED display
The essentials of imaging
The new world of DisplaysRequires accurate control devices
CA-210COLOR ANALYZER
Highest accuracy levels for optical devices such as LCD’s, PDP’s, Organic El’s, FED’s and LED’s
Spectro-rad iometer CS-1000A
Best price performance ratio for optical devices such as LCD’s, PDP’s, Organic El’s, FED’s and LED’s
ChromaMeter CS-200
Konica Minolta Sensing Europe B.V.
U.K. Branch, MK92BE Central Milton Keynes, England, [email protected], www.konicaminolta.eu
20 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
LIQUID LENSES
low frame rates were acceptable due to transmission speed constraints. With the increased availability of broadband access (meaning larger image fi les can be trans-mitted faster), high-definition products and megapixel screens, users now expect better image quality, and this is driving the move to higher-pixel webcams.
A typical webcam is placed in front of a laptop and must show everything from a close-up view of an object to overviews of a scene. With these factors and an increase in pixel count, an autofocus soon becomes mandatory. Other important considera-tions for webcam imaging systems are a fast response time to maintain good focus when the webcam is in use, and silent operation to avoid an irritating background noise every time the focusing system moves.
Barcode readersBarcodes readers are increasingly required to scan 2D barcodes. Using standard fi xed-focus lenses, manufacturers usually develop several designs to cater for both long- and short-range requirements. With autofocus, it is possible to have a single product that covers both needs, enabling users to scan items from as close as 5 cm to infi nity. Criti-cal factors for this application are response time, repeatability (as barcode readers work
in an open-loop architecture) and reliability (with in excess of 10 million cycles).
Biometrics readersFace-, iris- and fi ngerprint-recognition sys-tems are being marketed for applications such as law enforcement, immigration con-trol and military, as well as increasingly for consumer applications such as access con-trol in hotels or private homes and device security in place of PIN codes. Current fi xed-focus imaging systems can be cumbersome with the holder having to follow a series of instructions to move closer or further away to “manually” adjust the focus. Using auto-focus gives a much better user experience, provided that the variable focus system has: a fast response time (in a closed-loop system); good repeatability; is easy to inte-grate into the existing system; and is both reliable and robust (as it may be unattended and exposed to harsh conditions).
Medical applicationsEndoscopes, fi brescopes and dental cameras all rely on the user to adjust the focus manu-ally and a reliable autofocus makes these tools less tedious to handle. The require-ments on the autofocus system are a very close distance to focus (often below 1 cm), reliability (to comply with medical environ-mental targets) and silent operation.
Low-vision systems are designed to help people with reduced vision from glaucoma or cataracts. These can be hand-held or fi xed for manual or computer-assisted use. Such instruments require an autofocus to cap-ture the target scene or image prior to dis-playing it with the required improvements. Given this usage scenario, a very high level of repeatability and reliability is expected from the autofocus actuator as well as the ability to focus at distances below 10 cm.
Future developmentVarioptic is continuing to broaden its range of liquid-lens products and to monitor the new opportunities that are emerging with the development in CMOS sensor technol-ogy. Here, pixel sizes are moving to 1.75 μm for a 0.25 inch 3 Mpixel sensor, and the next milestone is a 1.4 μm pixel size. We are also developing larger optical systems for imagery and ophthalmology applications. Today, Varioptic has a range of available products to meet current market demands and has also developed a clear roadmap to meet future market requirements.
Philippe Ruffi n is marketing product manager at Varioptic. For more information, e-mail philippe.ruffi [email protected].
21OLE • O c tober 20 07 • o p t i c s .o r g /o l e
SILICON PHOTONICS
Organic semiconductors aid quest for silicon laser
Organic semiconductors are attractive materials for wavelength-tunable visible solid-state lasers. The simple processing and excellent optical properties of these light-emitting plastics makes them suit-able for integration with other optoelec-tronic technologies.
In the Organic Semiconductor Centre at the University of St Andrews, UK, we have been developing compact polymer lasers and optical amplifi ers. We are also explor-ing hybrid organic–inorganic lasers that could provide a new route to chip-to-chip optical interconnects. This work aims to address silicon’s long-standing limitation for optoelectronic applications, that it is a very ineffi cient light emitter. Such novel sources, which can be fabricated simply using standard CMOS processing, offer a cost-effective new way of implementing optical chip-to-chip interconnects and addressing a current bottleneck in high-speed computing.
Organic semiconductor lasersOrganic semiconductors are effi cient, vis-ible light emitters that can be processed simply from solution or by thermal evapor-ation. Since the discovery of electrolumi-nescence in organic semiconductors, there has been considerable progress in devel-oping organic light-emitting diodes for displays and applications including tran-sistors, solar cells and lasers.
These remarkable materials come in three sub-groups: small molecules, long-chain conjugated polymers and highly branched dendrimers. Small molecules are usually thermally evaporated to form amorphous fi lms or grown as molecular crystals. The polymers and dendrimers may be deposited from solution; essentially they are semiconductors that can be printed to assemble optoelectronic devices.
As laser gain media, conjugated polymers have many distinctive features. Firstly, they exhibit very strong absorption bands, with peak extinction coeffi cients of approximately
105 cm–1. Large optical gain cross-sections (10–15 cm2) also give rise to substantial gain in very compact devices. They typically have emission bandwidths of >100 nm and changes in chemical structure can tune the emission from 400 to 700 nm (fi gure 1). Optical gain is possible throughout the vis-ible spectrum making conjugated polymers well suited to applications such as tunable lasers or broadband amplifi ers.
Unlike conventional laser dyes, poly-mers show little emission quenching with increased concentration. Indeed, they can exhibit fl uorescence quantum effi ciencies of 50% and higher in the undiluted solid state. Polymers naturally form four-level energy
systems in which exciton migration along disordered polymer chains, plus vibrational and structural relaxations, substantially separate the absorption and emission bands. This allows simple optically side-pumped geometries to be used for lasers where the peak absorption can be 105 cm–1, and the residual absorption at the laser’s emission wavelength is typically <30 cm–1.
The polymer’s capacity for simple processing from solution is also relevant and many different microresonator con-fi gurations have been demonstrated, inclu-ding microcavities, microrings, distributed feedback and photonic crystal lasers. To illustrate this processing simplicity, micro-ring whispering-gallery-mode lasers can be made by dip coating an optical fi bre in a polymer solution. Wavelength-scale struc-tures for active photonic crystals can read-ily be moulded into polymer fi lms using soft lithographic techniques.
Recent advances in materials and reso-nators have led to very low threshold pulsed operation enabling us, and also groups from Braunschweig and Karlsruhe, to report organic semiconductor lasers pumped by an InGaN diode laser. In terms of applications, there has been an exciting recent demonstration by the MIT group of polymer lasers intrinsically working as sensors for ultralow vapour concentra-tions of explosives.
Together with partners at Imperial College within the UK Ultrafast Photon-ics Collaboration, we have demonstrated high-gain polymer optical amplifi ers and ultrafast sources and modulators for data-comms applications. Our review of organic semiconductor lasers gives a detailed over-view of these and other recent advances (Chemical Reviews 107 1272).
Adding light emission to siliconSilicon is the dominant material in mod-ern electronics and the mass fabrication of wavelength-scale structures is extremely well developed. However, there is a growing
Overcoming silicon’s intrinsically poor light emission is a crucial problem that many research groups are tackling. Graham Turnbull and Ifor Samuel describe how their simple hybrid
silicon-polymer laser could pave the way towards optical chip-to-chip interconnects.
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Fig. 1 (top): Fluorescence spectra of three semiconducting conjugated polymers, with their chemical structures shown as insets. Fig. 2 (bottom): (a) schematic of the polymer-silicon hybrid laser; (b) SEM image of a side view of the silicon-on-insulator resonator; (c) SEM image of a top view of the silicon mirror grating.
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22 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
SILICON PHOTONICS
need for high-bandwidth interconnects on silicon chips, which may be addressed in the future by integrating optoelectronic compo-nents directly onto the silicon processors.
For optoelectronics, silicon has a sig-nifi cant limitation: it is an indirect band-gap semiconductor and an intrinsically poor light emitter. To overcome this poor optical emission efficiency, researchers have pursued approaches including opti-cally excited Raman and nanopatterned silicon lasers; quantum confinement in silicon nanocrystals; the use of rare-earth dopants and bonding of III-V semiconduc-tor lasers to silicon chips.
Our alternative approach combines microstructured silicon resonators with light-emitting organic semiconductors. Despite the strong absorption of silicon at visible wavelengths, under optical pump-ing, our hybrid silicon-polymer structure works as a red surface-emitting laser (Applied Physics Letters 91 051124).
Integrating a solution-processed poly-mer adds only a simple supplementary fabrication step, compatible with standard CMOS processing, and does not require careful electrical or optical coupling to the silicon wafer. Crucially, our approach also adds visible light emission to the silicon at
wavelengths easily detected by conven-tional silicon photodetectors.
There are two significant challenges to overcome when integrating organic semiconductors with silicon. The fi rst is the substantial absorption of silicon at the visible wavelengths of the polymer photo-luminescence, and the second is silicon’s high refractive index, which complicates the way that the laser emission is confi ned within a polymer waveguide.
Our hybrid device uses a distributed Bragg reflector resonator design and is
based on a silicon-on-insulator (SOI) sub-strate (figure 2, p21). Two periodically microstructured silicon segments act as mirrors, while the silicon epilayer between these is removed, exposing the buried SiO2
layer. A thin fi lm of the organic amplifying medium covers the whole structure.
Due to the higher refractive index of the polymer compared with SiO2, a polymer waveguide is formed between the two silicon mirrors with a confi nement factor limited only by the thickness of the poly-mer layer. The area between the two peri-odically microstructured silicon refl ectors also reduces the absorption of laser light by the silicon.
To fabricate our devices, we used react-ive ion etching to reduce the 220 nm-thick silicon epilayer of the SOI substrate to 30 nm. We then defined the Bragg mir-rors using electron-beam lithography and reactive ion etching, which in turn exposes the underlying oxide layer.
The silicon microstructured mirrors comprise linear gratings with a period of 360 nm. For an operating wavelength of around 630 nm, the stop-band of the Bragg mirrors is due to second-order diffraction and provides both in-plane feedback and a surface-emitted output coupling of the laser light. The mirror spacing is 50 μm and the entire structure is coated with a thin fi lm of the proto-typical conjugated polymer MEH-PPV, to form a polymer waveguide that supports a single transverse mode.
To characterize the laser, we used 1.2 ns pulses at 5 kHz from a frequency-doubled microchip laser to optically excite the hybrid structure at room temperature. The spectral characteristics of the polymer laser were then measured using a fi bre-coupled CCD spectrometer.
Surface-emission spectra from our hybrid lasers, below and above lasing threshold, are shown in fi gure 3. Below threshold, spontaneous emission from the red-light-emitting polymer couples to several optical modes with wavelengths within the stop-band of the Bragg mirrors. These modes can be seen as a series of nar-row peaks.
For excitation energies above 45 nJ, the intensity of the lowest wavelength modes increases at a faster rate, corresponding to the onset of lasing. At higher pumping lev-els (not shown) these dominate the emis-sion spectrum. Not all of the longitudinal modes reach threshold, which we attribute to a variation in surface-emission losses across the in-plane stop-band of the mir-rors. Our lasers are tunable over 20 nm, with typical pulse energies in the picojoule
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OLE • O c tober 20 07 • o p t i c s .o r g /o l e
SILICON PHOTONICS
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24
range (Applied Physics Letters 91 051124). The threshold gain for lasing was calcu-
lated to be 370 cm–1, indicating that the in-plane mirror refl ectivities are <20%. The refl ectivity is quite low due to the surface-emission and silicon absorption from the Bragg mirrors, and can be increased with optimized grating design. The optical gain in the silicon-polymer laser is comparable with values achieved with silicon nano-crystals and nanopatterned crystalline silicon (the latter at cryogenic tempera-tures) and very large compared with silicon-Raman lasers. The high gain sur-mounts the absorption loss and allows very compact lasers to be fabricated – an import-ant factor for high-density integration.
Future developmentsOur present lasers are optically pumped but we envisage using the underlying silicon chip to modulate the emission either via charge injection or an applied electric fi eld to encode information. For interconnects, a move to higher repeti-tion rates is necessary. Semiconducting polymer lasers operating at MHz frequen-cies have recently been reported by the Braunschweig group, suggesting that triplet accumulation is less significant than in conventional dye lasers.
One key problem to be solved in the longer term is achieving electrically pumped lasing. Polymer LEDs have been demonstrated with p-doped silicon as a hole injection layer. However, charge-induced absorption and fi eld quenching are currently recognized as substantial obstacles to injection lasing in organic semiconductors. Electrical excitation is also a problem for lasers based on silicon nanocrystals and rare-earth dopants. While electroluminescence is possible, an electrically pumped silicon-based laser remains a major outstanding goal.
Graham Turnbull (e-mail [email protected]) and Ifor Samuel are from the Organic Semiconductor Centre at the University of St Andrews. For more information see www.st-andrews.ac.uk/~osc.
“Our hybrid silicon-polymer structure works as a red surface-emitting laser.”
26 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
HIGH-POWER DIODE LASERS
Industrial markets beckon f
Industrial markets for material processing set some of the most stringent benchmarks for cost, performance and reliability and to date, diode lasers have seen only mod-est penetration into this space. At nLight, we believe that this will all change over the next couple of years.
Today, the fundamental difference is the collective progress that is being made in metrics that we usually consider to be opposing or competing. For example, new products are being introduced that scale power and brightness signifi cantly in con-fi gurations with unprecedented durability, longer lifetimes and lower costs.
The collective impact of these improve-ments will not only strengthen the value of direct-diode solutions over legacy technol-ogies, but should also accelerate the adop-tion of solid-state and fi bre laser systems as the cost, performance and reliability of the diodes improve.
Equally important are the changes about to happen within the manufacturing infra-structure for high-power diodes. New oppor-tunities will require an order of magnitude expansion of today’s production capacities to supply millions of units per year, forcing increased automation and process control reminiscent of the silicon industry.
Industrial markets will benefi t greatly from such an increase in volume of diodes as costs fall to potentially disruptive levels and quality standards are made stricter. Laser-based material processing will then become faster, better and cheaper than conventional technologies.
Cost-performance trendsThe “Moore’s Law” of the high-power semiconductor laser industry follows the dollar per watt trend for a centimetre-bar. Figure 2 shows the exponential decline in average selling price (ASP) over the past 20 years and its correlation with increases in rated power over the same period (a commercially available product with a minimum expected lifetime of 10 000 h is implied). If the past trend continues, an 808 nm bar will reduce to half of the cur-rent ASP within 4–5 years.
Perhaps more relevant to high-growth markets is the power scaling that we expect to see from the single emitters that are used to pump high-beam-quality fi bre lasers, end-pumped solid-state and compact disk lasers. The thirst for greater power in a fundamental mode beam will continue and broad-area single emitters with stripe widths from 50 to 500 μm will fuel much of the growth.
High-brightness, single-emitter pack-ages that can effi ciently aggregate power to kilowatt levels are beginning to roll out with free space and fi bre-coupled options. This approach to scaling power, brightness and reliability in a small, low-cost, conduc-tion-cooled format will likely refocus our Moore’s Law to the true demands of the marketplace, such as dollar per effi cient, bright watt per hour of expected lifetime.
Performance and reliabilityWhat is making this power scaling pos-sible? Higher device eff iciencies and packaging with improved heat transfer characteristics are critical, but certainly not the only factor.
The challenge of realizing a 200 W, 808 nm bar product rests primarily with the required reliability advancements. Elec-trically isolated coolers that do not require de-ionized water; strain-balanced material systems that allow for bar-bonding with hard solders; and fl uids that can leverage the latent heat exchange associated with mixed phase fl ows are among the key ini-tiatives in roadmaps for higher power bars.
To ensure lifetimes of several tens of thousands of hours, facet protection to guard against catastrophic optical mir-ror damage (COMD) became mandatory when facet intensities exceeded 30 mW/μm of emitting aperture at 808 nm. Im-purity-induced disordering and epitaxial passivation have proven effective by creat-ing high-bandgap, non-absorbing regions (windows) at the facets. Large waveguides and long cavity lengths offer additional means to combat COMD by reducing opti-cal fi eld intensities, current densities and junction temperatures.
Pulsed operationLasers for material processing are typically modulated rather than operated continu-ous wave (CW). Pulse formats are tailored to a specifi c application and can have vir-tually any combination of short or long pulses (microseconds to seconds) with low to high duty factors (1–50%).
Pulsed operation has been a major hur-dle blocking the diode laser’s entry into industrial markets because of fundamental material compatibility issues, namely, the strain mismatch between GaAs and cop-per. High-power diode-laser packaging has historically relied on indium solder to accommodate the high thermal perform-ance of copper heat sinks and, under CW and limited pulsed operation, bar prod-ucts have demonstrated over 30 000 h of expected lifetime with such packaging.
Changes in the design and manufacture of laser diodes are seeding fundamental shifts in the way that we think about the cost and reliability of high brightness laser systems. Robert Martinsen of nLight Corporation tells OLE more.
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27OLE • O c tober 20 07 • o p t i c s .o r g /o l e
for high-power diode lasers
Hard solder packagingIt is not surprising to fi nd that indium is being phased out as a solder for laser-die attach. The high fatigue strength and low creep characteristics of eutectic gold-tin (AuSn 80/20) solder, for example, offers a superior lifetime under pulsed conditions, long-term stability of wavelength and polarization, as well as high temperature operation.
The conundrum is that GaAs lasers can-not tolerate being AuSn-soldered to copper heat sinks as the strain mismatch would far exceed the stress fracture limit of the laser. The high modulus, shear strength and solidifi cation temperature of eutectic AuSn requires a GaAs die to be mated with an expansion-matched heat-sink material.
Given today’s material choices, this means losing approximately half of the ther-mal conductivity you once had with copper in the critical zone immediately under the chip (where most of the thermal resistance is accounted for). Therefore, devices tend to be “hard soldered” to relatively thin, lower conductivity, expansion-matched sub-mounts such as CuW, AlN, CuMo or BeO, which in turn are bonded to a copper heat sink. While this approach reduces the ther-mal resistance penalty for pulsed reliability, today’s sub-mount materials can result in around a 50% higher junction temperature compared with traditional indium-on-cop-per packaging for the same device.
Solutions to this dilemma include dia-mond-metal matrix and nanoparticle composites that are well matched to the expansion coefficient of GaAs, and have
equivalent, or better, thermal conductiv-ity compared with copper. A great deal of material science research has still to be done. While the prospects are compelling, a number of practical considerations still need to be resolved.
Success depends on how well the compos-ite material suppliers address the demanding and peculiar requirements for p-side-down laser die bonding. This interface is critical to maintaining junction temperatures consist-ent with several tens of thousands of hours of lifetime in the presence of extraordinary heat fl ux (>2 kW/cm2) and high-tempera-ture environments.
Since the thermal and mechanical requirements of high-power diode lasers far exceed those for microelectronics, the semiconductor laser industry will have to drive this innovation and develop the supply chain rather than be a follower of advanced thermal management technologies.
The importance of high effi ciencyIn order to improve the overall system reliability at higher power and with lower cost, effi ciency improvements become key. It is worth noting that a strategy of sim-ply using larger chip sizes can also lower junction temperatures by increasing the thermal footprint with the heat sink, but inevitably leads to higher costs (dollar per watt) given fewer available chips per wafer and reduced packaging yields.
Reducing the waste heat load has enor-mous implications. Less internal heat generation leads to lower junction tem-
peratures and longer lifetimes, but also the cost and complexity of thermal man-agement becomes more consistent with large markets.
When high-effi ciency diode lasers are then used to pump low quantum defect brightness converters such as Yb-doped fibre lasers, disk lasers and upper laser level excited solid-state Nd lasers, a new generation of high-brightness technology unfolds. Compact, air-cooled, near-diffrac-tion-limited industrial lasers in the 100Wto kilowatt-class not only become a distinct possibility, they are already being offered as fi bre laser heads for less than $40/W.
What’s nextNothing creates momentum in innovation like high-volume opportunities. Entirely new markets for high-power diode lasers are emerging because critical thresholds for performance, reliability and cost are being reached. These ramps in production are driving the initiatives that are vitally important to industrial lasers.
By examining the timing of these mul-tiple volume markets and tracking the progress in semiconductor laser bright-ness, effi ciency and cost over the past 10 years, the following fi ve projections seem reasonable for the next four years: AuSn-bonded centimetre-bars will con-
tinue to serve high-power, low-bright-ness applications in direct-diode material processing and side-pumping;
Fibre-coupled lasers at the important wavelengths for pumping and direct material processing will have wall-plug efficiencies exceeding 65%, simplifying thermal management dramatically; Single-emitter-based packages will drive
the lowest available cost per bright, reliable watt – a more meaningful fi gure of merit for industrial applications; Facet passivation and disordering technol-
ogies will continue to promote the scaling of single-emitter brightness to >60 mW/μm at 808 nm and >80 mW/μm at 9xx nm;
Reliability and cost considerations for industrial applications will favour distri-buted, fault-tolerant, single-emitter-based packages, shedding their reliance on high-current drivers and sophisticated cooling.
Robert Martinsen is vice-president of product engineering at nLight Corporation, US. For more information see, www.nlight.net or e-mail [email protected].
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Fig. 1 (top middle): Initiatives driving semiconductor laser roadmaps are in strong alignment with the industrial market needs for material processing. Fig. 2 (top left): Price-performance trend for high-power centimetre-bars at 808 nm and 9xx nm wavelengths. Fig. 3 (middle left): Brightness of high-power laser diodes for direct material processing and pumping wavelengths between 800 and 980 nm. Fig. 4 (bottom left): Effi ciency outlook for high-power laser diodes with wavelengths between 800 and 980 nm. Fig. 5 (top right): Waste heat reduction with effi ciency advancements and improved thermal management.
29OLE • O c tober 20 07 • o p t i c s .o r g /o l e
EDUCATION
Active learning inspires new interest in optics
Does thinking back to your school days evoke memories of enthusiastic teachers who inspired you to take your studies fur-ther? This desire to motivate young stu-dents in developing countries is at the heart of UNESCO’s Active Learning in Optics and Photonics (ALOP) project.
Now in its fourth year, ALOP aims to introduce teachers in developing coun-tries to “active learning” and enable them to teach optics more effectively. ALOP’s last workshop was held in Brazil in July and preparations are now in full swing for the December event in Mexico.
Why was the ALOP project set up?The United Nations Educational and Cul-tural Organization (UNESCO) initiated the project in November 2003 to generate interest in optics and photonics among stu-dents, especially in developing countries.
We think that too few students are interested in physics because of the way it has been taught traditionally. We need to change the way that we teach, not just optics and photonics, but physics in gen-eral. This is particularly important for young people in their fi rst or second year at university, or those in their fi nal years of high school.
Under the ALOP project, UNESCO organ-izes workshops in various developing coun-tries to promote creativity and innovation in the way that introductory physics is taught. What we really offer is a training of trainers. The workshops are designed to encourage teachers in developing countries to adopt a more interactive teaching approach, known as active learning, to generate interest in physics among their students.
What is active learning?Active learning uses hands-on exercises and experiments in class. Students are encouraged to work in groups where there is a lot of discussion and exchange of ideas. The students really gain knowledge of phys-ics through these activities. With guidance
from the teacher acting as a facilitator, they fi nd out the correct answers from the results of the activities and then reach con-clusions amongst themselves.
We have designed experiments that use simple equipment and can be easily reproduced. No lectures are involved. The
facilitator stands up for a few minutes to give a short explanation, but long and bor-ing lectures are absolutely forbidden. This is an activity-based, discovery approach where the students have the opportunity to learn through exercises and from the results of the experiments.
UNESCO’s Active Learning in Optics and Photonics project is making the fi nal preparations for its latest workshop to stimulate interest in optics in developing countries. Marie Freebody speaks to Minella Alarcon, programme specialist at UNESCO, to fi nd out more.
The active learning approach uses an activity-based, discovery approach. Students have the opportunity to learn through hands-on exercises and simple experiments that can be easily reproduced.
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30 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
EDUCATION
What are the goals of the project?We encourage the teachers to carry on practising the hands-on activities by themselves, using our training manual as a guide. We want them to use the method and activities in their own classes and to design their own experiments. This is why we try to use simple materials, so that the teachers can get ideas and possibly make their own materials. We want to ensure that they don’t have to spend too much money on equipment.
Our ultimate hope is that the people we’ve trained will be inspired to organize their own local workshops and to pass on the active learning method.
What do typical workshops involve?The workshops are usually held in the phys-ics department of a university and cover eight topics. These are an introduction to active learning; geometrical optics; lenses and optics of the eye; interference and dif-fraction; atmospheric optics; and optics in communication, which is made up of two modules. The fi nal module is called action research with the light and optics concep-tual evaluation (LOCE). This LOCE mod-ule was developed to measure how much the students have learned. It is important
for the workshop participants to take this test so that they know how to use it to do action research and become familiar with the type of questions.
A typical workshop lasts for fi ve days. ALOP organizes around two workshops each year, taught by six facilitators from various countries. Between 30 and 40 teachers are invited to attend from various universities or high schools in the region. We usually divide the participants into 10 activity groups of 3–4 people per group. They are then introduced to active learn-ing and perform the hands-on experiments themselves. The workshop uses a teaching manual as well as simple teaching aids, which are all distributed free of charge at the end of the workshop.
Can you describe a typical experiment used in a workshop?One of our most popular experiments is using lenses to form images. The lens that we use in this demonstration is a large, round, transparent covered plastic con-tainer with water added to it.
We use two small bulbs to show how the lens forms the image. The students don’t just draw the rays, they see the rays coming from the bulbs passing through the “lens”
in this demonstration. This experiment allows the students to actually see the real image formed, instead of it just being drawn on the board.
Who teaches the workshops?We prefer to call the teacher a facilita-tor – they are a facilitator rather than an authority in the classroom. The idea is that they facilitate the activities and direct the discussions. They frame questions so that the students are guided to the correct answer. We currently have six facilita-tors from universities around the world. They are all volunteers who have gener-ously lent their expertise, time and effort to develop the modules and the materials used in this project.
The facilitators are experts in physics edu-cation. They are either involved in optics and photonics research or teaching and they are experienced in the active learning method. They have been chosen because they have a good knowledge of both.
Who attends the workshops?Most of the participants are university teachers. However, the background of the participants is not always the same and differs from country to country. For exam-ple, a recent workshop held in Africa was attended mainly by high-school teachers.
This means that the preparation is not the same for each workshop, but we try to be aware of this situation. On the fi rst day of the workshop we have a “getting to know each other” session to fi nd out the background of the participants and adapt the workshop accordingly.
How do you decide what country to hold a workshop in?Selecting the country is a diffi cult decis-ion. ALOP asks the local organizers within the potential host country to meet basic requirements.
The project’s fi rst workshop was held in Ghana at the University of Cape Coast in 2004. Since then, workshops have taken place in Tunisia, Morocco, India, Tanzania and Brazil, with one scheduled to take place in Mexico this December. A lot of countries have expressed their interest in hosting a workshop, however, due to the time it takes
“Long and boring lectures are absolutely forbidden.”
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32 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
EDUCATION
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to prepare for an event, we can only man-age about two per year.
Currently, we have fi ve countries asking for workshops in 2008 including Zambia, Nepal, Romania, Cameroon and Colom-bia. To qualify, they must prepare a venue with access to electricity, tables, chairs and basic laboratory facilities. For example, we require 10 optical benches with lens holders for each of the 10 activity groups.
How is ALOP funded?The ALOP project is funded by UNESCO that contributes $10 000 per workshop. It also receives contributions from the Inter-national Society of Optical Engineering (SPIE), the US National Academy of Science (NAS), the International Centre for Theor-etical Physics, Essilor and the American Association of Physics Teachers.
Each workshop costs between $30 000 and $35 000, which includes air fares, accommodation, materials and the train-ing manual. Some sponsorship is fi xed, for example ALOP receives $20 000 per year from SPIE. Some are not fi xed, such as contributions from the US NAS that funds the American facilitators’ travel to a workshop.
We ask the local organizers within the host country to assist in raising funds for regional travel and local expenses, such as accommodation and meals for all par-ticipants and the facilitators. Usually we have participants attending from nearby countries. For example, at the Brazil work-shop we had some participants attend from Argentina, Uruguay and Mexico.
What does the future hold for ALOP?We are increasingly faced with the chal-lenge of needing to train more regional facilitators. We’ve already had some fol-low-up activities – trainees in Morocco and Tunisia have started to organize and lead their own workshops and were so inter-ested that they have initiated translations of the modules into French. This is a good example for other groups to follow.
Following the workshop in Brazil, the par-ticipants wanted translations into Spanish and Portuguese so that they could adapt the manual and materials to train their high-school teachers. We are now in the process of translating the training manual into French and, in fact, next year we might deliver one of the workshops in French.
Minella Alarcon works in the natural sciences sector in UNESCO. ALOP is implemented under the Physics Programme led by Minella Alarcon. For further details on the ALOP project e-mail [email protected].
33OLE • O c tober 20 07 • o p t i c s .o r g /o l e
PRODUCT GUIDE
Emission properties tailor SLEDs to many markets
Superluminescent light-emitting diodes (SLEDs) are semiconductor-based light sources that combine the broadband optical spectra characteristics of LEDs with the diffraction-limited and spatially coherent emission of an edge-emitting laser diode. This combination is extremely useful for applications that require a good beam quality without unwanted interfer-ence effects such as speckle, which are related to the high temporal coherence of narrowband sources.
SLED basicsAn SLED is based on a p-n junction that is embedded into an optical waveguide. When electrically forward-biased, the device shows optical gain and generates amplifi ed spontaneous emission (ASE). This ASE or superluminescence is light that has been optically amplifi ed by the process of stimu-lated emission in a gain medium.
SLEDs are designed with high single-pass amplifi cation for the spontaneous emis-sion generated along the waveguide but, unlike laser diodes, insuffi cient feedback to achieve lasing action. The cavity modes are suppressed by tilting the waveguide with respect to the end facets and also by applying an antirefl ection coating to each facet (see fi gure 1). Suppressing the cavity modes results in a smooth emission spec-trum with low ripple. For SLED manufac-turers, the main technological challenge is to achieve high optical output powers combined with a smooth spectrum.
Because an SLED emits light from a waveguide, the spatial coherence of the light is similar to that seen from an edge-emitting laser. This spatial coherence means that typically more than 50% of the chip facet power can be coupled into a singlemode fi bre – a similar effi ciency to an edge-emitting laser diode.
SLEDs are particularly advantageous for applications requiring high spectral power density with very good beam quality. The large optical bandwidth (equivalent to low temporal coherence) also benefi ts applica-
tions where interference causes problems such as speckle or ghost signals.
Today’s state-of-the-art SLEDs have singlemode output powers of several tens of milliwatts and 3 dB optical bandwidths of typically 60 nm. The material composition of the light-generating active region deter-mines the SLED’s emission wavelength. Devices emitting in the range of 650–1000 nm are based on gallium arsenide, while devices emitting between 1000 and 1700 nm are based on indium phosphide.
Choosing an SLEDMost of the applications that rely on SLEDs typically use devices emitting around the centre wavelengths of 800, 1300 and 1550 nm. It is important to note that many other wavelengths are available that give users substantial fl exibility (see fi gure 3, p34). SLEDs operating in the 800 nm range are used in fi bre-optic gyroscopes and medical applications, while at 1300 and 1550 nm the main markets are data-coms, telecoms and sensors.
As well as the centre wavelength, the other important parameters to keep in mind when specifying an SLED are its power, 3 dB bandwidth, the ripple and package type. In terms of output power, it is important to clarify if it is ex-facet or from a singlemode or multimode fi bre.
It is also worth remembering that there is a significant trade-off between high output power and large bandwidth. This can be overcome by producing an SLED with a fl at-top-shaped spectrum instead of a Gaussian. However, this can be det-rimental for applications requiring very short coherence lengths.
When specifying ripple (the suppression of the cavity modes) you should defi ne not only the maximum acceptable value but also the spectral resolution that is used for the measurement.
It should be noted that SLEDs are very temperature sensitive and this is crucial when choosing the package type. Because an SLED essentially behaves like a laser diode below threshold, it must be actively
Superluminescent diodes combine the advantages of LEDs and laser diodes in a single compact package. Christian Vélez and Chris Armistead detail the factors to consider when purchasing SLEDs and the applications that are already putting the source to good use.
a)
b)
ARCARC
λ
λ
P
P
fibre-coupled
output
Fig. 1 (left): (a) shows a schematic view of a multimode Fabry–Perot laser and its emission spectrum. (b) shows a schematic view of an SLED. Cavity resonances are suppressed by tilting the active waveguide and applying antirefl ection coatings (ARCs) to the facets. This results in a smooth output spectrum. Fig. 2 (right): SLEDs can be supplied in a variety of packages including butterfl y (top) and DIL (bottom).
EX
ALO
S
EX
ALO
S
34 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
EXALOS provides Superluminescent Light Emitting Diodes
(SLEDs) that offer the largest bandwidths and highest powers
available in the marketplace. Our SLEDs cover wavelengths from
650 to 1700 nm at different power levels.
Our NEW EXS8410 SLED series offers devices at ~840 nm with
50 nm Bandwidth (FWHM) and 7 mW of Output Power from
Single Mode fiber.
EXALOS’ SLEDs are the ideal light source for spectral OCT and
multichannel fiber Bragg gratting interrogation.
Please contact us at [email protected] or
call at +41 43 444 60 90 (Europe) or +1 215 752 2115 (USA)
www.exalos.com
PRODUCT GUIDE
All your laser safetyequipment and complianceservices from one source.Design, supply and install.
Tel +44 (0)1202 770740www.lasermet.com See us at Photonex Stand B21
Onestopshop.
temperature controlled. Pigtailed devices are normally delivered with a built-in tem-perature sensor and thermoelectric cooler. If not cooled properly, the SLED’s output power will drop and its wavelength will increase with temperature. If your design includes uncooled SLED modules, such as TO-CAN, then this must be accounted for in the optical system design. Some typical packaged devices are shown in fi gure 2.
SLED applicationsOptical coherence tomography (OCT) is an emerging technology for producing high-resolution cross-sectional medical images of tissue on the micron scale in real time. OCT is the direct optical ana-logue of ultrasound but as light is unable to penetrate beyond 2 mm in most non-transparent tissues, OCT is limited to opti-cally transparent tissues and ophthalmic or endoscopic examinations.
An SLED’s large optical bandwidth together with its good suppression of the cavity modes allows short coherence lengths from some tens of micrometres down to just a few micrometres. Its high output powers also permit the fast scan times required in ophthalmologic, cardiovascular and gas-trointestinal imaging applications.
EXALOS is leading the development of new SLEDs with increased spectral band-width, Gaussian shape and high optical output power. Such characteristics will lead to higher image resolutions and allow tissue characterization on a scale never before pos-sible within the human body. This technol-ogy has the potential to dramatically change the way that scientists see and understand the human body in order to diagnose and treat diseases more effectively.
Another key SLED application is in navi-gation systems, primarily those in avionics and aerospace that use fi bre-optic gyro-scopes (FOGs) to make precise rotation
measurements. FOGs measure the Sagnac phase shift of optical radiation propaga-ting along a fi bre-optic coil when it rotates around the winding axis. When a FOG is mounted within a navigation system, it tracks changes in orientation.
The basic components of a FOG (shown in fi gure 4) are a light source, a singlemode polarization-maintaining fi bre coil, a cou-pler and a detector. Light from the source is injected into the fi bre in counter-propa-gating directions using the optical coupler. When the fi bre coil is at rest, the two light waves interfere constructively at the detec-tor and a maximum signal is produced.
–10
pow
er d
ensi
ty (
dB
m/0
.1 n
m)
700
wavelength (nm)
–20
–30
–40
–50
–60
–10
pow
er d
ensi
ty (
dB
m/0
.1 n
m)
1100
wavelength (nm)
–20
–30
–40
–50
–60
750 800 850 900 950 1200 1300 1400 1500 1600 1700
Fig. 3: EXALOS supplies a variety of short (left) and long (right) wavelength products.E
XA
LOS
TM
ELECTRO-OPTICAL PRODUCTS CORP.P.O. BOX 650441 • FRESH MEADOWS, NY 11365 • TEL: (718) 997-8100 • FAX: (718) 997-8102www.EOPC.com [email protected]
Choppers & ModulatorsTUNING FORK CHOPPERS
ROTATING CHOPPERSPOCKELS CELLS, Q-SWITCHES
MODULATING SYSTEMSPOLYCHROMATIC MODULATION SYSTEMS
TUNABLE FILTERS, AOTF, FREQUENCY SHIFTERSELECTRO-OPTICAL & ACOUSTO-OPTICAL MODULATORS
Scanners & DeflectorsRESONANT SCANNERSELECTRO-OPTICAL SCANNERSBEAM DEFLECTORSACOUSTO-OPTICAL DEFLECTORSX,Y SCANNERSSCANNING SYSTEMSPOLYGONS
MOTORIZED FILTER SELECTORSPHOTODIODE AMPLIFIERS
ELECTRICAL TO OPTICAL & OPTICAL TO ELECTRICAL CONVERTERS
FIBER OPTIC VIDEO LINKSFIBER OPTIC POWER METERS
FIBER OPTIC LASER TACHOMETERSSINGLE & DUAL LASER LIGHT SOURCES
ShuttersSHUTTER / CHOPPERSLASER SAFETY (INTERLOCK) SHUTTERS
Electro-optical Products Corp. is a manufacturer and supplier of stock, custom and OEM components and sub-systems with drive electronics for light, plasma and laser light for industrial, scientific, medical, aerospace and military applications worldwide.
Our result driven team will help you select the best suited cost-effective components and sub-systems to integrate into your one-of-a-kind project or your OEM production and turn your creative ideas into successful products.
OLEOctPage35 24/9/07 11:07 Page 1
36 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
PRODUCT GUIDE
When the coil rotates, the two light wavestake different optical paths that depend on the rotation rate. The phase difference between the two waves varies the intensity at the detector and provides information on the rotation rate.
SLED-based gyroscopes rely on the large bandwidth of the source to reduce both the scattering along the fi bre and refl ections at the facets of the internal optical compo-nents, which could decrease the sensitivity at very low rotation rates.
A FOG and its associated embedded opti-cal source must be low cost, stable, reliable, compact and have low power consumption. In the past, wavelength stability over time was a major drawback of semiconductor-based broadband light sources like SLEDs compared with fi bre-based light sources such as erbium-doped fi bre-amplifi ers.
At EXALOS, we have successfully over-come this drawback by developing SLEDs that are less sensitive to wavelength shifts induced by temperature or aging. Novel materials and material structures have made it possible to improve the wave-length stability of our devices by a factor of four compared with conventional devices. Further work is in progress with the target of achieving wavelength stabilities down
to the 10 parts per million range. SLEDs with this performance will help to reduce the size and cost of FOGs substantially.
Broadband optical sources are also used to test fi bre-optic components. One exam-ple is characterizing optical components used in coarse wavelength division multi-plexing (CWDM), which requires multiple wavelength sources. Our broad range of SLEDs means that several sources with wavelengths spanning the whole CWDM band can be integrated in a single piece of test equipment. In optical networks, SLEDs are used to measure the polarization mode dispersion of optical fi bres.
Many features inherent to SLEDs make them the preferred sources for these appli-cations. First, SLEDs are fully compatible with the wavelengths used in optical com-munication systems. Second, the SLED’s optical waveguide allows light to be coupled
efficiently into singlemode optical fibres. Finally, we believe that our SLEDs are effect-ive solutions to the pressures of today’s tele-communications carrier market, which requires products that are cost effective, reli-able, enable better productivity and reduce the number of testers in the fi eld.
The fi nal main SLED application is fi bre-optic sensors for strain and temperature measurements in civil engineering, struc-tural analysis and composite material manufacturing. Fibre-optic sensors have a number of advantages over conventional sensors. For example, they are immune to electromagnetic fi elds, they have the ability to measure at many points along a single fi bre and they can be embedded within, or bonded to, structures making them a highly flexible solution. Over the past 25 years there has been continual improvement in the quality and performance of fi bre-optic sensors. EXALOS SLEDs are used for these applications because of their large optical bandwidth and robustness.
Christian Vélez is CEO and Chris Armistead is engineering manager at EXALOS AG of Schlieren, Switzerland. For more information, please see www.exalos.com or e-mail [email protected].
50% 2 × 2coupler
SM PM fibre coil
SLED
detector
Fig. 4: Basic diagram of a fi bre-optic gyroscope.
EX
ALO
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37OLE • O c tober 20 07 • o p t i c s .o r g /o l e
PRODUCTSIf you would like your company’s products to be featured in this section,
send your press releases and images to Marie Freebody (e-mail [email protected]).
IR and THz bandpass fi ltersLake Shore Cryotronics
Lake Shore Cryotronics
has introduced a line of
band-pass and narrow
band-pass fi lters with
central wavelengths
(CWLs) from 15 to
200 μm. The fi lters are patterned with cross-
shaped holes. CWL transmissions of up to 80%
have been achieved with a CWL tolerance of
±0.1 μm and out-of-band transmission down
to 0.5%. The fi rm says that the fi lters have
excellent thermal properties and offer stable
and repeatable performance down to 4K. Each
fi lter is 1 mm in depth and can be used with
standard fi lter wheels, cryostats and compact
optical instruments.
www.lakeshore.com
High-power diode lasersIntense
The HPD6020 line of
830 nm high-power
single-emitter laser
diodes is now available
from Intense. Emitting
up to 200 mW in a single
mode with high beam
quality, the devices are based on the company’s
quantum-well intermixing technology that is
said to increase a laser diode’s brightness and
reliability while avoiding catastrophic optical
mirror damage.
The fi rm quotes a reliability in excess of
11 million operating hours. The lasers are
available in a selection of standard packages
including 5.6 and 9 mm, and C-mount. Monitor
photo diodes are optionally available on the 5.6
and 9 mm packages. Other wavelengths in the
HPD Series 6000 family are available on request.
www.intenseco.com
Line-scan cameraSUI
Spectroscopy and
machine vision are the
ideal applications for
the new SU-LDH digital
line scan NIR/SWIR
camera from SUI. The
camera is available in a
variety of confi gurations based on the company’s
LC series of linear arrays. Standard or extended
InGaAs wavelength ranges are available from 0.8
to 1.7 μm and 1.0 to 2.2 μm.
SUI adds that this latest camera increases
line rates for 1024 pixels to over 40 000 lines/s.
Square pixels for machine vision or rectangular
pixels for spectroscopy can be selected and
confi gured with optional 256, 512, or 1024 pixel
arrays on a 25 μm pixel pitch, or alternatively a
50 μm pixel pitch for 256 and 512 arrays.
www.isr.goodrich.com/sui
SpectroradiometerGlen Spectra
Glen Spectra has
replaced its PR-650
SpectraScan with the
new PR-655 model. The
PR-655 comes with an
array of enhancements
that are said to make spectrally based photometric
and colorimetric measurements even easier.
Equipped with a rechargeable Lithium-ion
battery, the PR-655 uses a fast-scanning multi-
element detector spectrometer with a spectral
resolution of 3.12 nm per pixel. The system is
controlled by a 56 ×75 mm colour touch screen
and, following a measurement, it displays data,
colour spectral and CIE graphs. Stand-alone
operation means that no PC is required – not even
to see the spectrum. The PR-655 can be controlled
via SpectraWin software over a USB or Bluetooth
interface, or using text-based commands.
www.glenspectra.co.uk
DFB lasersLaser Components
The SPECDILAS-D
DFB lasers from Laser
Components, which
are traditionally used
in spectroscopic
applications, are now
available fi bre coupled. The SPECDILAS-D-BTF
devices are available at selected wavelengths
from 1270 to 1854 nm and conform to both the
Telecordia Standard and RoHS regulations.
www.laser-components.com
Ultrafast sourcesFemtoLasersThe Fusion range of compact Ti:sapphire oscillators
from FemtoLasers uses dispersive mirror
technology to provide broadband intracavity group
delay dispersion compensation. This results in
high-quality near-bandwidth-limited sub-10 fs
pulses from a low threshold oscillator (sub-20 fs for
the Fusion 20 model). Output powers range from
100 to 800 mW, it has a beam divergence of less
than 2 mrad, a TEM00 spatial mode, M2 less than
1.3 and a noise of less than 0.05% rms.
www.femtolasers.com
PRODUCTS
OLE • O c tober 20 07 • o p t i c s .o r g /o l e38
Diode laser stack arraysDILAS
DILAS has released
its highest-power
conduction-cooled,
quasi-continuous wave
(QCW) stack array
to date. Available in
confi gurations of 100 or 150 W per bar, specifi c
combinations of wavelength and power can be
customized upon request. The stack arrays are
said to suit commercial solid-state laser pumping,
defence and OEM applications.
Standard emission wavelengths are 808, 940
and 980 nm. The fi rm adds that its high fi ll-factor
bars, which can be stacked vertically, measure
1 cm long and feature a vertical pitch in the stack
as small as 0.4 mm. A typical operating current
and voltage for the diode laser stack arrays is
listed as 100 A at less than 2 V, while beam
divergence is specifi ed as less than 40° by 10°
FWHM, with a duty cycle maximum of 2%.
www.dilas.com
Gigabit-Ethernet cameraSvs-Vistek
Svs-Vistek’s monochrome
5 Mpixel svs625 camera
is now available with
a Gigabit-Ethernet
interface. This eliminates
the need for a frame
grabber and allows image data to be transmitted
easily over distances in excess of 100 m.
The svs625 is a progressive-scan camera
based on a 2/3 inch sensor with a resolution of
2448 ×2048 pixels. It has a frame rate of 15 full
images per second, although in “partial scan
mode”, where the images are smaller, the read-
out rate is faster. Binning with 1 ×2, 2 ×1 and
2 ×2 pixels is also implemented. The camera
comes with the company’s confi guration software
that allows parameters such as gain, offset or
exposure time to be adjusted.
www.svs-vistek.com
Single-emitter diode lasersPacer International
Pacer International is
now supplying Alfalight’s
high-effi ciency 808 nm
single-emitter diode
lasers. The AMx-808BW
devices are available
from Pacer in a 2 W
fi bre-coupled 6-pin package and 2.5 W chip-
on-carrier C-mount and Q-mount options. The
diode lasers feature wavelength stabilization
technology and do not require any cooling or
external components to maintain wavelength,
which is said to reduce their energy consumption
by up to three times compared with thermally
controlled pump lasers. Each device has a
LASER BEAM DELIVERY SYSTEMThe kineFLEXTM is an efficient and robust laser beam delivery system for use in biomedical instruments and semiconductor metrology applications.
Single wavelength and multi-wavelength versions are available from 405 to 830nm.
www.point-source.com/ole
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Wavefront Analysis> Shack-Hartmann Analyzer> Deformable Mirror
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OLE • O c tober 20 07 • o p t i c s .o r g /o l e
PRODUCTS
39
monolithic grating integrated directly onto the
semiconductor chip and is quoted as having
a peak power conversion effi ciency of 52%, a
30 °C wavelength locking range over the entire
0.2–2.5 W output power and a ±1.5 nm centre
wavelength tolerance.
www.pacer.co.uk
Diode laser stackJenoptik Laserdiode
The JOLD-x-Q-8A is the
fi rst passively cooled
quasi-continuous wave
(QCW) diode laser stack
from Jenoptik Lasediode. The QCW stack can
be air cooled and comprises eight bars with an
optical output power of up to 200 W QCW per
bar. The fi rm specifi es an optical output power
of up to 1600 W for a typical operating current of
195 A and duty cycles up to 2%, or up to 1200 W
at 150 A for duty cycles up to 4%. The typical
operating voltage is less than 17 V in both cases.
The centre wavelength at 25 °C is 808 nm
and the expected lifetime is listed as more than
1 GShot. Pumping solid-state and fi bre lasers,
illumination and medical applications are all
potential markets.
www.jold.com
Wafer-scribing systemsNew Wave ResearchThe AccuScribe 2112 and AccuScribe 2150
high-speed wafer-scribing systems from New
Wave Research are said to deliver a throughput
of 12–14 wafers/h, a 20% or greater speed
increase over their predecessor, the AccuScribe
AS2000FX. Both products reach this level of
performance thanks to a high effi ciency and
stable UV DPSS laser.
Capable of supporting 4-inch wafers, both
platforms feature a high level of automation and
can be customized easily. The 2112 features
automated alignment, positioning, focus and
partial wafer scribing. The operator only needs
to load the wafers in and out of the scriber.
The 2150 is nearly identical to the 2112, but
eliminates the need for an operator.
www.new-wave.com
Diode laser protectionAMS Technologies
The DiodeGuard from
VueMetrix is now
available through
AMS Technologies.
Incorporating a new
circuitry design, the
DiodeGuard is said
to protect against cascade failure of diodes
operating in series. Available with the Vue-MV-21
laser diode controller, the combination is said to
improve the reliability of fi bre lasers and direct
diode material processing systems.
Cascade failure occurs when a diode in a
series shorts, causing an instantaneous drop
in the forward bias voltage. With a switched-
mode power supply, this voltage drop results
in a current surge that can cause catastrophic
destruction of the remaining diodes. DiodeGuard
is designed to prevent these incidents from
affecting the entire diode string.
www.ams.de
Thermal cameraCedip Infrared Systems
The Jade LR is a third-
generation thermal
camera from Cedip
Infrared Systems
optimized to provide
high-quality long-range images. Based around
a trifocal design, it uses three motorized lenses
(25, 80 and 320 mm focal length) that can be
switched by a single command to provide optimal
detection at distances ranging from 5 to 25 km.
The camera uses an InSb focal plane
array sensor sensitive between 3 and 5 μm,
and features 14-bit digital electronics and a
compact weatherproof housing. The fi rm adds
that the camera is fully compliant to military
specifi cations and is ideal for IR measurement in
airborne, naval or ground operations.
www.cedip-infrared.com
Laser diodesPhotonic Solutions
Distributed by Photonic
Solutions in the UK, the
2495-L3 series of fi bre-
coupled single-emitter
laser diodes offers
4 W of optical output
power at 808 nm. This source is said to be ideal
for pumping solid-state materials such as Nd:YAG
and Nd:Vanadate to generate 1064 nm. A 4.5 W
version is available at 812 nm for applications with
broader wavelength tolerances, such as medical
and dental. JDSU says that the 2495-L3 laser
diodes are a reliable optical pumping alternative to
conventional multi-emitter (bar) diode lasers.
www.psplc.com
Resonant cavity LEDHamamatsu
The fi rst product in a
new range of resonant
cavity LEDs has been
released by Hamamatsu
and is said to generate high output power and
allow fast modulation. The L9907 generates in
excess of 1 mW of output power from a 100 μm
emission area and allows transmission of data at
bandwidths of over 100 Mbit/s. The product was
developed in response to the need to send higher
bandwidths down polymer optical fi bre.
www.sales.hamamatsu.com
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PRODUCTS
OLE • O c tober 20 07 • o p t i c s .o r g /o l e
Telecentric lensesSill Optics
Sill Optics has added fi ve
microscopic video lenses
to its range of telecentric
lenses. The lenses are
designed with a large
numerical aperture (up
to 0.25 in object space)
to increase the resolution of small structures.
Available magnifi cations are 3× (S5LPJ2533), 5×
(S5LPJ2555), 6× (S5LPJ2566), 7× (S5LPJ2577)
and 8× (S5LPJ2588) and can cover camera sizes
of up to a maximum of 12 ×12 mm.
The company says that the 8× lens has a
maximum resolution of nearly 400 lp/mm in object
space and can image structures just 3 μm in size.
Distortion is in the range of 0.05% and the working
distance for all models is between 90 and 100 mm.
The lenses are available with a C-mount and
variable iris. Best results are said to be achieved
with small band LED illumination from green to red.
www.silloptics.de
Data-acquisition softwareVertilonVersion 2.1 of Vertilon’s PhotoniQ software
is targeted at high-speed scanned imaging
applications such as fl uorescence confocal
microscopy. The most signifi cant new feature is a
data-acquisition mode designed specifi cally for
rapid, continuous data collection. When operated
in this mode, the fi rm says that a PhotoniQ system
can acquire and store very large multichannel
images in its image buffer in a few seconds. A
typical high-end PhotoniQ system takes only 2.5 s
to acquire a complete image of one million pixels
at 32 channels per pixel. Other features in the
upgrade include trigger counting and automatic
pixel indexing that simplify the interface between
the PhotoniQ and the user’s application software
and image-scanning hardware.
www.vertilon.com
Line-scan cameraFirstsight Vision
A CameraLink version
of DALSA’s Spyder3
line-scan camera is
now available through
Firstsight Vision. Based
on dual line-scan technology, the Spyder3 is said
to offer three times more responsivity and twice
the line rates of previous models with throughput
rates of 80 MHz. Typical applications include
glass-edge inspection, industrial metrology and
medical and scientifi c imaging.
The Spyder3 CL is available with 1 k and 2 k
resolutions and is fully back-compatible with the
Spyder or Spyder2 because the pixel size and
fi ll factor remain unchanged. The camera is also
available with a Gigabit Ethernet interface.
www.fi rstsightvision.co.uk
High Power Fiber Lasers > CW up to 200Watts> Pulsed up to 20Watts> 1550nm up to 10 Watts
CO2 Lasers> Air & Water cooled CO2 Lasers> Power from 10W up to 200Watts> ROHS Compliant
Laser Diode Modules> UV, Visible, IR> CW, Pulsed or Modulated> Circular & Elliptical Beam
DPSS & YAG Lasers> Compact Module UV to IR> High Power YAG up to
1600Watts
www.bfiopt
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Photonics for Europe
+32(0)14 570 670
+45 46 55 99 99
+33(0)1 60 79 59 00
+49(0) 89 89 01 35-0
+ 39 02 535 831
+34 91 453 11 60
+31(0)172 44 60 60
+44(0)1908 326 326
+49 18 56 58 30
BFi OPTiLAS European Offices :
Laser Sources
Flexible OptomechanicalBuilding Blocks
• Cage Assembly Rods
• Alignment and Cage Plates
• Slip Plate Positioner
• Cage, Rotation, and Prism Mounts
• XY Translator
• Cage Cube
• Post, Mounting, and Cage Adapter
• New 16mm Series
CageSystems
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Request Your NEW Version 19 “Tools of the Trade“Catalog with Over11,000 Products.
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OLE • O c tober 20 07 • o p t i c s .o r g /o l e42
LEDsAvago Technologies
Avago Technologies has
unveiled a new series of
Extra Bright II oval red,
green and blue LEDs
for the electronic signs
and signals market. The
fi rm’s series of 4 and
5 mm oval through-hole LED lamps have been
designed for use in full-colour applications such
as passenger signs, variable message signs,
scoreboards and channel lighting.
The HLMP-Lx63 (4 mm) and HLMP-Hx63
(5 mm) series of LEDs provide an oval-shaped
radiation pattern, a wide viewing angle and high
illumination intensity. The company adds that
electronic signs can now be designed using fewer
individual LEDs to provide equivalent brightness.
www.avagotechlighting.com
Aspherical cylinder opticsasphericonasphericon can now produce customized
aspherical cylinder optics in plano-convex,
plano-concave, bi-convex or bi-aspherical
forms. Specifi c lenses with a cylinder surface
and spherical and aspherical rear surfaces are
available. The outer shapes can be circular,
rectangular or square formed. The company adds
that it can manufacture components in almost
every variety of glass, fused silica as well as
glass ceramics. All cylinders can be supplied with
refl ective or antirefl ective coatings available from
the ultraviolet to the infrared.
The production method uses advanced
CNC-grinding and polishing machines. A
proprietary 4-axis zonal polishing process
leads to a surface form error of up to 1.0 μm. In
addition, a correction-polishing technique can
reduce lokal form errors and give form accuracies
of up to 0.3 μm. Depending on material used, the
fi rm says that surface qualities better than
5/ 1 ×0.063 and roughnesses Rq<0.002 μm
(RMS) can be achieved.
www.asphericon.com
Camera and development packageMatrox Imaging
The Matrox Iris E-Series
smart camera from
Matrox Imaging is now
available with a Design
Assistant development
environment. The Design
Assistant allows users to instruct the camera to
capture, process and remotely display images and
communicate with external devices. An integrated
html editor and layout tool allows users to create
a custom web-based operator view to monitor the
application. The camera is available as a single
body or remote head with processor design.
www.matrox.com
market-driven understanding of technology
Features:
• 3648 pixels
• 16 bit controller
• Pre-configured optical engine
• All inclusive: Slit, grating, software
• Made in Germany
www.mut-group.com
Incl. software TRIWin 3.0
• Data acquisition
• Data processing
• Data presentation
• Data analysis
• Data export
m·u·t AG, Am Marienhof 2, 22880 Wedel, GermanyTel.: +49 (0)4103 9308-0 Fax.: +49 (0)4103 9308-99
TRISTAN® USB
Accessories available:
• Light sources, fiber optics
• Optical integrators
• Cuvette holders
• Software
€1,499.-+ VAT, freight, UV versions: €1,699.-
PRODUCTS
OLE • O c tober 20 07 • o p t i c s .o r g /o l e 43
Thermoelectric coolersMicropelt
The MPC-D303
series of microchip
thermoelectric coolers
from Micropelt is one of
the company’s smallest
devices with a cold-side
area of only 0.98 mm2. Supporting a maximum
temperature difference of over 60 K, the
device is suitable for laser and photonic sensor
manufacturers whose applications require a large
bandwidth of thermal control.
Based on the fi rm’s thin-fi lm thermoelectric
technology, the MPC-Dx series has a cooling
power of up to 100 W/cm2 and can achieve
temperature changes faster than 180 K/s. The
MPC-D303 is fabricated on silicon wafer using
standard semiconductor processes and has a
maximum operating temperature of 200 °C.
www.micropelt.com
High-power diode laserLumicsThe fi bre-coupled LU09xxC300 high-power diode
laser system from Lumics offers 300 W of optical
output power at either 915, 940 or 975 nm. The
optical power is delivered via a fi bre bundle of
45 single-emitter laser diode modules, which are
terminated into a SMA connector.
The operating temperature range is quoted as
5–35 °C and the diode lifetime at up to 100 000 h
mean time to failure. The source comes in a
19-inch, 2U rack mount with a depth of 316 mm
and the electrical supply input is 110 /220 V AC.
The rack mount unit is equipped with a forced
air-cooling system and RS232 interface. The fi rm
also offers an OEM version, which can be used in
existing or new production equipment.
www.lumics.com
Ultrafast amplifi erCoherent
The new Legend Elite
Duo from Coherent is
an integrated ultrafast
amplifi er that delivers
pulse energies over
6 mJ at a repetition rate of 1 kHz and a pulse
width of less than 40 fs with an M2<1.5. The
laser is based on a two-stage amplifi er design.
The fi rst stage features the same high-power
regenerative amplifi er as the Legend Elite, while
the second stage is a linear amplifi er that uses a
thermoelectrically cooled Ti:sapphire crystal.
The amplifi er uses a high-power Evolution-HE
laser to pump both stages at over 45 mJ/pulse.
According to the fi rm, the high-power amplifi er
provides faster and more precise results and is
suitable for applications such as pumping multiple
tunable OPAs for pump-probe photochemistry and
ultrafast spectroscopy techniques.
www.coherent.com
80% of All Orders From EuropeReach Your Lab the Next Day
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Luminit off ers Light Shaping Diff usersto fi t laser applications in a variety of shapesand angles.Glass-on-Glass diff users can withstand up to 500°C and very high damage thresholds.
Light Shaping Diff user
www.luminitco.com
• Homogenize source
• Eliminate hot spots
• Control divergence angle
• Reduce speckles
Circular
Elliptical
ExtremeElliptical
SIOS Meßtechnik GmbHAm Vogelherd 46
D-98693 Ilmenau / GERMANYTel.: +49-(0)3677/6447-0 E
Internet: http://www.sios.demail: [email protected]
Fax: +49-(0)3677/6447-8
SIOSMeßtechnik GmbH
Triple-Beam Plane-MirrorInterferometer
SP-TR Series
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Length measurement ranges, each axis: 2 m
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Resolutions: 1 nm / 0.02 arcsec
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OLEOctPage44 25/9/07 08:49 Page 1
PRODUCTS
45OLE • O c tober 20 07 • o p t i c s .o r g /o l e
Multichannel detectorsHORIBA Jobin Yvon
HORIBA Jobin Yvon’s
range of multichannel
detectors now includes
the Symphony CCD and
InGaAs arrays with LN2
cooling; the Synapse
CCD arrays with
thermoelectrical cooling and the Sygnature CCD
and PDA ambient temperature linear detectors.
All detectors are compatible with the company’s
range of spectrometers, with focal lengths from
140 mm to 1.25 m.
The Symphony and Synapse CCDs are available
in 14 different chip formats including open
electrode, back illuminated and back illuminated
with deep depletion. The low cost “plug and play”
Sygnature detector is available as a 3648 pixel
CCD for high sensitivity, or a 1024 pixel
photodiode array for wide dynamic range.
www.jobinyvon.co.uk
Programmable radiometerLabsphere
Labsphere has
launched the SC6000
programmable
radiometer and
photometer with a
system controller that allows for up to 100
programmed calibrations. The company
explains that users can create, upgrade or
expand a calibration easily using a variety of
interchangeable detector assemblies, integrating
spheres, light sources and power supplies.
The SC 6000 can monitor luminous and radiant
fl ux, luminance, radiance, intensity, illuminance
and irradiance. The fi rm says that the product
is ideal for controlling calibration systems,
photometric and radiometric monitoring of
camera calibration systems, lamp measurement,
photometry and laser power measurement. The
system controller is compatible with Si, Ge,
InGaAs and other photovoltaic detectors.
www.labsphere.com
Coating clusterSUSS MicroTec
SUSS MicroTec believes
that its coating cluster
combines an effi cient
and fl exible production
setup with short lead
times. The Gamma
XPress has been developed for wafer bumping
and LED manufacturing applications.
The coating cluster is available in a variety
of confi gurations including gold bump coating;
under bump metal or redistribution coating; high-
volume LED coating as well as standard and dry
fi lm developing.
www.suss.com
Sweden: [email protected] • Tel +46 86382800USA: [email protected] • Tel +1 9733311191UK: [email protected] • Tel +44 1592770000
www.spectrogon.com
SPECTROGONOptical filters • Coatings • Gratings
• Pulse stretching/compression
• Telecom• Laser tuning• Monochromators• Spectroscopy
• Stock available
UV, VIS, NIR, IR
• Bandpass• Longwave-pass• Shortwave-pass• Broad-bandpass• Neutral Density
• Service stock
Optical Interference Filters
Holographic Gratings
17-18 October Coventry, UK
Stand: C24
• Scintillation crystals • Linear & two dimensional arrays
• Detector assemblies • Infra-red optics • Custom products
CrystalMaterials
Westwood, Margate, Kent CT9 4JL, UK
Tel: +44(0)1843 231166Fax: +44(0)1843 290310email: [email protected]
www.hilger-crystals.co.ukwww.newport.com
Copyright ©2007 StockerYale Inc. All rights reserved.www.s tocke rya le . com
StockerYale Inc.Tel.: (514) 685-1005 Fax: (514) [email protected]: STKR
For a list of our distributors, please visit our website
GAUSSIAN TOFLAT-TOP
Gaussian (Input)
Flat-Top (Output)
• Patent pending technology• Square or rectangular patterns• Dimension of beam from
150 x 150 μm up to several cm• Compatible with UV, visible, and
near-IR laser sources
Applications include:• Bio-detection• Flow cytometry• Optical character recognition• Microprocessing
Gaussian to Flat-Top using refractive beam shaping optics.
Flat-Top2 Generator
OLEOctPage46 24/9/07 10:24 Page 1
PRODUCTS
OLE • O c tober 20 07 • o p t i c s .o r g /o l e 47
Translation stagePhysik Instrumente
Physik Instrumente has
introduced the M-122
palm-top-sized precision
translation stage. The
device has a travel range
of 25 mm, a drive speed
of up to 20 mm/s and a
linear optical resolution
of 0.1 μm. The ballscrew stage with linear encoder
has a footprint of just 60 ×86 ×20 mm and also
boasts a long lifetime and low maintenance.
M-122 stages can be combined to form
very compact XY and XYZ systems. Typical
applications include metrology, quality-
assurance testing, micromaching, photonics
packaging and fi bre positioning.
www.pi.ws
Light sourcesMoritex
Moritex has announced
an expanded family of
four battery handle light
sources for industrial
endoscopes to suit
different applications
and budgets. The family now includes a
simple, low-cost Maglite-style handle, halogen
and xenon lamp handles as well as a high-
performance LED handle. An adapter can turn
the LED handle into a torch.
The LightScope industrial endoscopes are
designed for visual inspection of tight and
inaccessible locations. Available with rigid or
fl exible probes, each product is equipped with
high-quality optics to ensure distortion-free viewing
with true colour reproduction. Focus is adjustable
from 10 mm to infi nity and C-mount compatibility
means that all LightScopes can be interfaced to
mobile video or digital recording systems.
www.moritex.com
Vacuum instrumentsPfeiffer Vacuum
The MPT 100 transmitter
expands Pfeiffer
Vacuum’s DigiLine of
vacuum instruments.
Combining a Pirani and a
cold cathode sensor, the
unit is compatible with
existing controllers and accessories, offers a broad
measurement range from 5 ×10-9 to 1000 mbar
and is insensitive to gas inrush. The two sensors
are carefully matched to eliminate the possibility
of contamination. According to the fi rm, this makes
the MPT 100 suitable for coating systems. The cold
cathode sensor can be switched on and off using
an external software command to avoid interfering
with the vacuum process.
www.pfeiffer-vacuum.net
Optical Components section> Standard Laser Optics> Interference Filters> Laser Crystals & Rods> Opto-Mechanical Mounts
Scanners & Modulation> Scanner & Galvanometer> Acousto & Electro Optics> Mechanical & Safety Shutters
Photodiodes & Detectors> UV, Visible, and IR Photodiodes> Avalanche - APD Diodes> Position Sensing Detectors> Power & Energy Detectors
Optical Components & Accessories
www.bfiopt
ilas.c
om
Photonics for Europe
+32(0)14 570 670
+45 46 55 99 99
+33(0)1 60 79 59 00
+49(0) 89 89 01 35-0
+ 39 02 535 831
+34 91 453 11 60
+31(0)172 44 60 60
+44(0)1908 326 326
+49 18 56 58 30
BFi OPTiLAS European Offices :
PRODUCTS
OLE • O c tober 20 07 • o p t i c s .o r g /o l e48
Power-over-CameraLinkLeutron Vision
Leutron Vision is
launching what it says
will be the fi rst PicSight
cameras and Picport-
PCI frame grabbers
with Power-over-CameraLink (PoCL) onto the
market. In this confi guration, the camera’s power
supply is provided directly via PoCL through the
CameraLink cable and no separate devices or
cables are required. Leutron says that not only will
this help to cut costs but, with only one cable and
a Mini-CL socket, the installation of CameraLink
solutions will be a lot easier and camera housings
can be much more compact.
“Our range of PoCL-enabled PicSight cameras
and PicPort frame grabbers, all compatible
with the GenIcam Standard (Generic Interface
for Cameras), represents a major step towards
‘plug and play’ for CameraLink applications,”
commented Mathias Leumann, chief executive
offi cer of Leutron Vision.
www.leutron-vision.de
LED driverIntegrated System Technologies
Integrated System
Technologies has added
a 210 W, three-channel
LED driver to its iDrive
range. The iDrive 1000
is said to deliver twice
the power density of the iDrive Lite and combines
high-power density with leading PSU effi ciency.
The device allows users to select the forward
current digitally and independently on all three
channels between 500 and 1000 mA in 50 mA
increments. The iDrive provides a forward voltage
range of up to 55 V per channel. Additional
features include a master/slave option; increased
internal preset programmes and user-selectable
thermister settings.
www.istl.com
NIR CMOS cameraIntevac
Intevac claims that its
MicroVista-NIR camera
represents a major
technological advance
for CMOS imaging. The
company says that the
camera is the world’s
fi rst back-thinned
CMOS to be optimized for NIR imaging. It adds
that the camera has NIR imaging performance
matching or exceeding more expensive CCD-
based cameras.
The focal place array has a resolution of
1280 ×1024, 10.8 μm square pixels and high
quantum effi ciency between 700 and 1000 nm.
The fi rm says that the array has a 100% fi ll factor,
1 Bay StreetStirling, NJ 07980Telephone: 908-647-6601Fax: [email protected]
THE FIBER OPTIC SOLUTIONS COMPANY
fiberguideindustries
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A powerful laser delivery system in a sur-geon’s skilled hand helps cure people. Thesemedical laser systems are made possible byutilizing Fiberguide Industries new SuperguideSPCH and Anhydroguide APCH fibers.Superguide SPCH and Anhydroguide APCHare large core multi-mode fibers. They havea numerical aperture of 0.39 and employ ahard clad silica coating. With increased beamintensity, this exceptional coating offerssuperior fiber strength and reduces staticfatigue in humid environments.Superguide SPCH and Anhydroguide APCHfibers offer excellent connection alignmentand they have a high core to clad ratio. Thesefibers are also made available in silica/silicahard clad fiber that have a N.A. of 0.22 andan attenuation of <10dB/km@850nm. The0.22 versions are named Superguide SFHSand Anhydroguide AFHS.The finest medical laser delivery system startswith Superguide SPCH and AnhydroguideAPCH fibers. Call Fiberguide Industries todiscuss your specific requirements.
OLE • O c tober 20 07 • o p t i c s .o r g /o l e
PRODUCTS
49
supports 30 frames/s full frame and comes with
a CameraLink data port. Applications include
biometrics, NIR microscopy, low-light NIR
imaging, medical imaging, hyperspectral imaging
and surveillance.
www.intevac.com
Point-diffraction interferometerESDI
A vibration-insensitive
point-diffraction
interferometer (PDI)
has been developed
by ESDI. The company
says that the Intellium PDI with HyperPhase is
the fi rst simultaneously phase-shifting vibration
insensitive PDI to be commercially available.
The HyperPhase module is supported by ESDI’s
IntelliWave Interferometric Acquisition and
Analysis software.
The PDI is compatible with input beams from
3 to 25 mm in diameter and laser sources from
480 to 1800 nm. Applications include laser beam
diagnostics, collimation and alignment testing of
transmissive optical systems.
www.engsynthesis.com
Vibration surveysKinetic Systems
Kinetic Systems is now
offering on-site vibration
surveys for sensitive
equipment. Engineers
from the company
measure the potentially
damaging vibration
amplitudes and frequencies in customer facilities.
All information is plotted on graphs (log-
scale, narrow-bandwidth spectrums, modifi ed
to octave or third-octave bands) and supplied to
the customer in a complete report.
www.kineticsystems.com
ADVERTISERS’ INDE X
The index is provided as a service and, while every effort is made to ensure its accuracy, Optics &
Laser Europe accepts no liability for error.
Advanced Photonix Inc www.advancedphotonix.com 12Avantes BV www.avantes.com 42B&W Tek Inc www.bwtek.com 46CVI Technical Optics Ltd www.cvi-tol.co.uk OBCDiffraction International Ltd www.diffraction.com 22Docter Optics www.docteroptics.com 23ELCAN Optical Technologies www.elcan.com 25Electro-Optical Products Corp www.eopc.com 35ESCO Products www.escoproducts.com 23EXALOS www.exalos.com 34Fiberguide Industries Inc www.fi berguide.com 48Financiere BFi Optilas S.A.S www.bfi optilas.avnet.com 38, 41, 47Fischer Connectors Holding SA www.fi scherconnectors.com 9Gentec Electro-Optics Inc www.gentec-eo.com 11GWU Lasertechnik Vertriebs GmbH www.gwu-group.de 20Hamamatsu Photonics UK Ltd www.hamamatsu.com 8HGH Systems Infrarouges www.hgh.fr 24Hilger Crystals www.hilger-crystals.co.uk 46IMT Masken und Teilungen AG www.imtag.ch 18IPG Photonics Corp www.ipgphotonics.com 35Jenoptik Polymer Systems GmbH www.wahl-optoparts.com 45Konica Minolta Sensing Europe B.V www.konicaminolta-3d.com 19Laser Components (UK) Ltd www.lasercomponents.co.uk 14
Laser Quantum Ltd www.laserquantum.com 37Lasermet Ltd www.lasermet.com 34Lasertel Inc www.lasertel.com 48Leister Process Technologies www.leister.com 30Liekki Oy www.liekki.com 36Luminit www.luminitco.com 44m.u.t. GmbH www.mut-gmbh.de 42Melles Griot USA www.mellesgriot.com 4Newport Spectra-Physics www.newport.com 23Mikropack GmbH www.mikropack.de 45Multiwave Photonics www.multiwavephotonics.com 44New Focus Inc www.newfocus.com 10Oerlikon Optics www.optics.unaxis.com 31Ophir Optronics Ltd www.ophiropt.com 6, IFC, IBCPCO AG www.pco.de 47Photon Energy AWL GmbH www.photon-energy.de 44Photon Inc www.photon-inc.com 49Physik Instrumente (PI) GmbH & Co KG www.physikinstrumente.com 15Point Source Ltd www.point-source.com 38Quantel www.quantel.fr 32Quintessence Photonics www.qpc.cc 13Reed Exhibitions Japan Ltd www.reedexpo.co.jp 31Sill Optics GmbH & Co KG www.silloptics.de 32SIOS Mebtechnik GmbH www.sios.de 44Spectrogon AB www.spectrogon.com 46SPIE USA www.spie.org 28Stocker Yale Canada Inc www.stockeryale.com 46Texas Instruments www.dlp.com 7Thorlabs GmbH www.thorlabs.com 39, 41, 43 Xmark Media Ltd www.photonex.org 43 visitvisit
wwwwww.photon-inc.com .photon-inc.com to find your Photon dealerto find your Photon dealer
NanoScanPrecision Beam
Profiler
NIST Traceable
♦♦ Beam size measurement precision >±0.5%
♦♦ 12-bit signal digitization♦♦ High dynamic range♦♦ Silicon, germanium, and
pyroelectric detectors♦♦ Wavelength range from
190nm – >100μm♦♦ Power range from
~100nW – 5kW♦♦ Pulsed beams >2kHz“I am very impressed at theperformance and speed thatthese heads have. Integrationwith the NanoScan Software via ActiveX was also a pleasure.”
-Bryan Joles Symbol Technologies
50 OLE • O c tober 20 07 • o p t i c s .o r g /o l e
BACK CHAT
With a PhD in quantum optics and a mas-ters in economics, Per Stenius has both the technical and business knowledge that seems to be in short supply in the photon-ics industry today. Stenius is a partner in Stratos Ventures, a venture capitalist fi rm that invested in Liekki when it was founded in 1999. He was appointed chief executive offi cer of Liekki in 2003, with the objective of turning the company around after the telecoms bubble burst.
Why is there a lack of skilled workers in the photonics industry?Making a laser is becoming increasingly challenging, as more sophisticated inte-grated technologies, such as disk and fi bre lasers using very advanced components, are brought to the markets.
We are seeing the same kind of develop-ment in the photonics industry that we saw in the electronics industry. Today, semicon-ductor circuits are very complicated; few people truly understand all of the details, and only a handful of large companies can produce the most advanced chips. I think that the depth of knowledge and breadth of skill required is increasing in photonics, and more experts are needed. Many com-panies are fi nding it challenging to build suffi cient depth and breadth across technol-ogies required for their advanced products.
What is the solution to this shortage?For us, the only solution is to recruit internationally – you have to look at your available skill pool on a global basis and adapt to that situation. It seems that more and more companies recognize that the war for talent is on-going on a global scale. We have to embrace a multicultural approach if we want the best teams. From an EU perspective, collaboration between European countries is absolutely cru-cial to stay competitive. But I would say that we need to go even further than that – European collaboration is only the fi rst, albeit crucial, step.
Fortunately we are seeing a migrating expert population especially in smaller high-tech companies, such as Liekki. They take on the world when they hire, not just a specifi c country.
How does the shortage affect Liekki?Recruiting is no longer as simple as posting an advert in the local newspaper. We now require a much broader approach and use a multitude of channels.
It is diffi cult for a smaller start-up com-pany to have a dedicated human resources (HR) team, but a good HR process is cru-cial for international recruiting. Despite being a fairly small company with about 40 employees, we have ended up employ-ing people from China, Romania, Russia, the US, Germany, France, the UK and even India. HR has had to handle the recruiting process including immigration laws and the various regulations that apply.
Given that we need to compete on a glo-bal basis and build a globally leading team, we need to invest in the right resources. We learnt this the hard way, by experiencing the telecom bubble burst and emerging on the other side. We became aware of where to look for the talent that we needed to transform the company.
Early on we found that some of our domestic employees felt annoyed that we were recruiting externally and abroad for certain specialist positions. They couldn’t understand why Finnish people were not fi lling these positions. Nowadays, they’ve learned that these recruits bring a lot of expert talent to the table, are dedicated to their job and also add a taste of their cul-ture to the company.
At Liekki, we like people with business savvy who also have a strong technologi-cal spike, however this is hard to fi nd. Since fi bre-optic technology is still developing
rapidly, we have more need for in-depth technical knowledge in the sales process than many other businesses.
Is there a country or region that produces more skilled workers?No, I think that every region contributes something. Finland, for example, produces a lot of good fi bre manufacturing process and equipment people, and quality assur-ance people, but we are still fairly weak on the photonics applications side.
There are massive centres such as Jena, Germany and Southampton, UK, where there is a really broad spectrum of phot-onics and optics knowledge. In France, we fi nd a lot of good laser application knowl-edge, and in India we fi nd interesting fi bre manufacturing knowledge.
How does Liekki ensure that it hires the right people?We have built a network of recruiting chan-nels both locally and abroad. We are very active at conferences, we advertise in spe-ciality magazines in all regions and use the web to reach a global audience. A key part of this is our close ties with select univer-sities and key professors around the world. To ensure that we have a supply of junior resources we have professors in Germany for example, who send interns for project work at Liekki. We also hope to hire some of these when they graduate.
To achieve a rigorous process for hiring, our staff must put in a fair amount of their time assessing new candidates. We also follow a structured approach in reviewing background material and references. Doing this on a global basis has its own challenges, but we feel that the process is working well.
We encourage a company culture that embraces all nationalities, so that people have an easier time adapting to their new environment. We assist with both paper-work and practical aspects, such as fi nding a place to live. All of this leads to greater productivity and job satisfaction. Having brought many different nationalities to this community has helped the company develop, and I think that our staff today appreciate the global environment that our company offers.
Overcoming the skills shortage in the photonics industry pushes companies to recruit internationally.Per Stenius, CEO of Liekki Corporation, describes how a smaller high-tech fi rm approaches this challenge.
Global thinking tackles the skills shortage in the photonics industry
Per Stenius, CEO of Liekki Corporation (middle row, centre), with his international workforce.
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