Reconfiguring Photonic Metamaterials

Eric Plum, Jun-Yu Ou, João Valente, Jianfa Zhang, Nikolay I. Zheludev

Optoelectronics Research Centre & Centre for Photonic Metamaterials

University of Southampton, UK

UK-China Physics Workshop, Beijing, China, 7 - 8 Dec 2012

www.nanophotonics.org.uk

Metamaterials at the University of Southampton

Southampton, UK

Optoelectronics Research Centre

Fractal chiral metamaterial decoration

Mountbatten Cleanrooms (£120M cleanroom complex)

Centre for Photonic Metamaterials www.metamaterials.org.uk

The Mountbatten Cleanrooms a world-class flexible facility for materials, processes and devices

• Silica fibre fabrication

• Compound glass fibre fabrication

• Microstructured fibres

• Planar waveguide fabrication

• 10 nm e-beam lithography

• Photolithography

• Robotic mask aligner

• 2 x DualBeam FIB/SEM

• Helium ion microscope

• Dry and reactive ion etching

• Field-emission SEM

• SiGeC epitaxy & deposition

• Ge quantum dot growth

• Atomic layer deposition

• 2300C diffusion & annealing

• High-purity inert atmos. furnaces

• Glass extrusion

• Deep Si etching

• Ion/e-beam-induced deposition

• Sputtering/e-beam/thermal evap.

• Nanoimprint

• CVD carbon nanotube growth

• PECVD Si and Ge nanowire growth

• Oxide and nitride deposition

• Rapid thermal annealing

• Wet chemistry

• Scanning (multi)probe microscopy

• DC/RF device characterisation

• Chalcogenide glassmaking

• Dip-pen nanolithography

• Nanoscribe 2-photon polymerization

• Thermogravimetric/mechanical analysis

• 3D optical surface profilometry

Southampton Centre for Photonic Metamaterials

www.metamaterials.org.uk

Tunable/Switchable Metamaterials in Southampton

Si3N4

membrane

Metamateria

l (Gold)

Chalcogenide

glass layer

360 nm

Switchable metamaterial (ChG), [Appl. Phys. Lett. 96, 143105 (2010)]

Quantum Flux Exclusion, [Scientific Reports 2, 450 (2012)]

Superconducting EO modulator, Southampton

Ultrafast nonlinear metals, [Adv. Mater. 23, 5540 (2011)]

Graphene, [Opt. Express 18, 8353 (2010)]

Reconfigurable Metamaterials

H. Tao, Padilla, Averitt et al (2009)

RTA@350˚C

RTA@450˚C RTA@400˚C

50µm

Rapid thermal annealing

Stretchable substrate

I. Pryce, H. Atwatter et al. (2010) F. Huang, J. Baumberg (2010)

Stretchable substrate

Nanoscale features & movements are required for photonic metamaterials

Structural tunability

Aydin et al. (2004)

M.Lapine, Y. Kivshar et al (2009)

W.M. Zhu, A.Q. Liu et al. (2011)

Y.H.Fu, A.Q. Liu and N.I. Zheludev et al (2011)

MEMS reconfigurable meta-molecules

10µm

From controlling meta-molecules to controlling arrays

Meta-molecular spacing controls optical properties

Tuning

Tunable split-ring

Tunable nanoantenna

Tunable chirality

Challenge: Nanometre scale synchronized control of >103 metamolecules

Temperature Currents

Voltages

+ -

- +

+ -

-

Reconfigurable Metamaterials controlled by…

Towards Nano Reconfigurable Metamaterials

Bimorph: A bilayer of two materials with different thermal expansion coefficients will bend upon

temperature change.

1μm

500nm 3μm

Heating

Cooling Bending proportional to

• Temperature change

• Thermal expansion difference

• Length/thickness

Large tuning requires long, thin

structures L/t ~ 100

Towards Nano Reconfigurable Metamaterials

1μm

500nm 3μm Solution:

Meta-molecules on longer cantilever

Temperature-Controlled RPMs: Concept

Moving bridge

Meta- molecule

Heating

Cooling

Fixed Bridge

Heating

Cooling

Anchor point

Temperature-Controlled RPM: Fabrication

Au on both sides of Si3N4 membrane

Meta-molecules patterning by FIB Bridges cut through

Alternating Gold slits removed by FIB

Flip Sample

Silicon nitride Au

Au

Temperature-Controlled RPM: Optical Characterization

LN2 Cryostat

UV-visible-NIR Micro-spectrometer

Sample

Au - Si3N4 - Au

Au - Si3N4

500nm

140nm

125nm

225nm

350nm

50nm

J. Y. Ou, E. Plum, L. Jiang, and N. I. Zheludev, Nano Letters 11(5), 2142 (2011)

Temperature-Controlled RPM: Performance

Reversible continuous tuning by cooling/heating Relative changes in transmission up to 50%

1000 1100 1200 1300 1400 1500 1600 1700

6

8

10

12

14

Tra

nsm

issi

on

, T

(%

)

Wavelength (nm)

270K

202K

176K

151K

100K

76K

1000 1100 1200 1300 1400 1500 1600 1700-10

0

10

20

30

40

50

60

Rel

ati

ve

Tra

nsm

issi

on

Ch

an

ge

(%)

Wavelength (nm)

270K

202K

176K

151K

100K

76K

Cooling

Heating

Cooling

Heating

J. Y. Ou, E. Plum, L. Jiang, and N. I. Zheludev, Nano Letters 11(5), 2142 (2011)

Current-controlled RPMs

U

Resistive heating using currents can replace ambient temperature changes

Temperature Currents

Voltages

+ -

- +

+ -

-

Reconfigurable Metamaterials controlled by…

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

Applied Voltage V/Vth

Sp

acin

g d

/d0

Stable solution

Instable solution

Electrostatically Controlled RPM: Concept

+ - + + + +

+ + + +

- - - -

- - - -

- - - -

Electrostatic Control of Spacing

• Equilibrium

– Restoring force ~ k (d0-d)

– Electrostatic force ~ Q2/d=C2V2/d

– Capacitance ~ 1/acosh(1+ d/2r) [parallel wires]

• Electrostatic

– Tuning

– Switching (on/off)

– Memory (low holding voltage)

off

on

tuning

Switch on

restoring force wins

Electrostatic force wins

Switch off

stable

instable

d

2r

• V ~ 1V

• d ~ 100nm

• E ~ 10 MV/m

Electrostatically controlled RPM

+ - + + + +

+ + + +

- - - -

- - - -

- - - -

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev, Nat. Nanotechnol. (2013), DOI:10.1038/nnano.2013.25

35 µm

Electrostatically Controlled RPM: Concept

Optical field

Static field

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev, Nat. Nanotechnol. (2013), DOI:10.1038/nnano.2013.25

Electrostatically Controlled RPM: Tuning

-2

0

2

4

6

8

1000 1200 1400 1600 1800 2000

Wavelength (nm)

ΔR/R

off (

%)

Tunable Reflectivity

2.4V

0V

-6

-4

-2

0

2

4

6

1000 1200 1400 1600 1800 2000

Wavelength (nm)

ΔT/T

off (

%)

2.4V

0V

Tunable Transmission

-5

-4

-3

-2

-1

0

0 0.5 1 1.5 2 2.5

Voltage (V)

ΔT/T

off (

%)

1330 nm

Continuous & Reversible Tuning

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1

Applied Voltage V/Vth

Sp

acin

g d

/d0

Stable

Instable

Theory

Switch on

Switch off

on

tuning

tuning

Below switching voltage…

• Tunable transmission

• Tunable reflectivity

• Continuous and reversible

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev, Nat. Nanotechnol. (2013), DOI:10.1038/nnano.2013.25

off on

+ +

- -

- - +

+

- - +

+

- - +

700 nm

High-Contrast Electrooptical Switch

20 pg (pico-gram)

0

10

20

30

40

50

1000 1200 1400 1600 1800 2000

T,

%

Wavelength, nm

20

30

40

50

60

70

1000 1200 1400 1600 1800 2000

R,

%

Wavelength, nm

-100

0

100

200

0

10

20

30

40

50

1000 1200 1400 1600 1800 2000

ΔT/T

off, %

T,

%

Wavelength, nm

-40

0

40

80

120

20

30

40

50

60

70

1000 1200 1400 1600 1800 2000

ΔR/R

off,

%

R,

%

Wavelength, nm

250%

110%

• Switching voltage ~3V

• Switching time ~500 ns

• Switching energy ~ 100 fJ

• 20% red-shift upon switching

• High contrast switching

on off

No

rmalized

Op

tic

al e

lectr

ic f

ield

0

1

Optical ele

ctr

ic fie

ld

off on

off on

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev,

Nat. Nanotechnol. (2013), DOI:10.1038/nnano.2013.25

Fast Electrooptical Modulator

• Sub-wavelength thickness

• No need for polarizers

• MHz bandwidth

• 10 µW power consumption

• Effective electro-optic coefficient ~ 10-5 m/V 5 orders of magnitude higher than in LiNbO3

~

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev,

Nat. Nanotechnol. (2013), DOI:10.1038/nnano.2013.25

Various Designs

Summary: Reconfigurable Photonic Metamaterials

• A flexible plaform for controlling metamaterial optical properties

• High contrast tuning & switching

• MHz modulation bandwidth

• 100 fJ switching energy

• Electro-optic effect exceeding natural materials by ~5 orders of magnitude

Temperature-controlled metamaterials

Voltage-controlled metamaterials

+ -

- +

+ -

-

J. Y. Ou, E. Plum, L. Jiang, and N. I. Zheludev, Nano Letters 11(5), 2142 (2011)

Thank you for your attention!

J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev, Nat. Nanotechnol. (2013),

DOI:10.1038/nnano.2013.25