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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