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Micro Opto-Electro-Mechanical Systems (MOEMS)

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Outlines

MOEMS overview Applications Packaging

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What is MOEMs? Micro-opto-electromechanical systems

(MOEMS), or optical MEMS, are systems involving micromachining of structures in the micro- to millimeter range whose purposes are to manipulate light.

It is not a special class of Micro-Electro-Mechanical Systems (MEMS) but in fact it is MEMS merged with Micro-optics which involves sensing or manipulating optical signals on a very small size scale using integrated mechanical, optical, and electrical systems .

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Today’s MOEMS devices include Optical Switch , waveguides, moving mirrors and diffractive gratings

______________________ *Micromachining : techniques for fabrication of

3D structures on the micrometer scale Applications include MEMS devices Most methods use silicon as substrate

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MOEMS Fabrication MOEMS devices are typically made

using standard lithography methods giving the advantages of a compact design and fabrication at a low cost.

These devices are usually fabricated using micro-optics and standard micromachining technologies using materials like silicon, silicon dioxide, silicon nitride and gallium arsenide.

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Rockwell Science Center also developed refractive microlens technology, including gray scale photolithography.

 Diffractive microlenses based on binary optic structures are typically fabricated in bulk material by multiple sequential layers of photoresist patterning and reactive ion etching (RIE), to form a multi-step phase profile.

This profile approximates the ideal kinoform lens surface. A special staircase process, called binary optics, is used to fabricate diffractive components.

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With so many successes in Micro-optics and MEMS, Rockwell researchers who were involved in both MEMS and Micro-optics, initiate development of several of innovative photonics ideas combing both technologies.

This was behind the acronym of MOEMS, when both MEMS and Micro-optics were merged in one single IC processing lab.

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MOEMS is a promising multi technology for miniaturization of critical optical systems.

The acronym is defined of three high tech fields of micro-optics, micromechanics, and microelectronics.

MOEMS indirectly could merge in micromachining, microsensors and microactuators if their processes are compatible with integrated circuits.

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Merging all these multi technologies, made MOEMS an ideal knowhow for many industrial demonstrations of commercial devices, such as optical switches, digital micromirror devices (DMD), bistable mirrors, laser scanners, optical shutters, and dynamic micromirror displays.

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Figure 1 : Merging Technology

Hybridization

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MEOMS and commercial applications

Attractive for comercial application because of : batch processing and embossed replication enabling technology for applications that

cannot be addressed, using micro-optics The trend toward miniaturization and

integration of conventional optical systems desirable elements of optical

communication.

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What is the difference between Optical MEMS and

MOEMS ?

Optical MEMS could include bulk optics but MOEMS is truly based on microtechnology

where MOEMS devices are batched processed exactly like integrated circuits, but this is not true in most cases for Optical MEMS.

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Time for Applications !

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Applications

Optical switch Wave guide Moving mirror Diffractive grating   Microlens arrays Microbolometers Bistable Fabry Perot resonator for high

accuracy measurement of gas concentration

Micro-optical microphone to measure air pressure.

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Optical Switch Many optical components are required in the

rapid development of optical networks, including optical switches.

Optical switches in micro-opto-electro-mechanical systems (MOEMS) have many applications because of their excellent features, including low insertion loss and crosstalk.

In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB).

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Optical Switch

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Then , what is Optical switch?

In telecommunication, an optical switch is a switch that enables signals in optical fibers or integrated optical circuits (IOCs) to be selectively switched from one circuit to another.

Away from telecom, an optical switch is the unit that actually switches light between fibers

Fast optical switches, may be used to perform logic operations.

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Example : 3D-MEMS Optical Switch

In a MEMS optical switch, a micro-mirror is used to reflect a light beam. The direction in which the light beam is reflected can be changed by rotating the mirror to different angles, allowing the input light to be connected to any output port.

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3D-MEMS Optical Switch

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3D-MEMS Optical Switch Features

Can switch optical signals without converting them into electrical signals.

Allows compact low-loss switches to be formed on any scale.

Switching can be performed in 10-30 msec.

 

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3D-MEMS Optical Switch usages

Since this device can switch large numbers of optical signals simultaneously, it can be used as a trunk switch for

handling large amounts of traffic, and as a switch in large urban

communication networks.

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Another Application : Waveguide

A waveguide is a structure that guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave.

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Waveguide in MOEMS

Fiber-optic waveguides based (MOEMS) form a significant class of biosensors which have notable advantages like light weight, low cost and more importantly, the ability to

be integrated with bio-systems.

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Example :integrated microfluidic fiber-optic waveguide biosensor .

The fiber-optic waveguide is integrated with bulk micromachined fluidic channel across which different chemical and biological samples are passed through.

The significant refractive index* change due to the presence of biological samples that causes the evanescent field condition in the waveguides leads to optical intensity attenuation of the transmitted light.

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Representative image for waveguide in biosensor

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Refractive index In optics the refractive index or index of

refraction n of a substance (optical medium) is a dimensionless number that describes how light, or any other radiation, propagates through that medium. It is defined as

n= c/v where c is the speed of light in vacuum and v is

the speed of light in the substance. For example, the refractive index of water is

1.33, meaning that light travels 1.33 times as fast in vacuum as it does in water

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The speed of light

The speed of light in vacuum, commonly denoted c, is a universal physical constant.

Its value is 299,792,458 meters per second

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Speed of light

Sunlight takes about 8 minutes 19 seconds to reach Sunlight takes about 8 minutes 19 seconds to reach the Earth (based on the average distance)the Earth (based on the average distance)..

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Micro lenses

Microlens is a small lens, generally with a diameter less than a millimetre (mm) and often as small as 10 micrometres (µm).

The small sizes of the lenses means that a simple design can give good optical quality

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Micro lens and Microlens Array Single microlenses are used to couple

light to optical fibres while microlens arrays are often used to

increase the light collection efficiency of CCD arrays. They collect and focus light that would have otherwise fallen on to the non-sensitive areas of the CCD*.

___________________*A charge-coupled device (CCD) is a device for the

movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value.

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Microlens in Digital Camera

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Applications of Microlenses Microlens arrays are in digital projectors, to

focus light to the active areas of the LCD used to generate the image to be projected.

Current research :microlenses act as concentrators for high efficiency photovoltaics for electricity production.

Form compact imaging devices for applications such as photocopiers and mobile-phone cameras.

3D imaging and displays

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3D imaging Display

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MOEMS packaging

Encapsulation of electronics and sensors has traditionally been used as a protection against the outside environment, but through integration of other functions (e.g. lenses, electric and optic conductors)

Advanced polymer technique has the potential to realize multifunctional encapsulation in combination with 3D-silicon technique and surface technology.

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