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Dielectric Resonator Nano-Antennas:Dielectric Resonator Nano Antennas:A Pathway to Efficient Optical Antennas
C. Fumeaux, W. Withayachumnankul L. Zou, M. Klemm
Functional Materials and
C. M. Shah, A. Mitchell, M. Bhaskaran, S. Sriram
Microsystems Research Group
1iWAT 2014 - Sydney
A li d El t ti G i Ad l idApplied Electromagnetics Group in Adelaide:Antennas and FSS across the spectrum
RF-inspired
2500 µm(a)
pnano-structures
Outline
Introduction1
2 Scaling of Dielectric Resonators Antennas
3 Reflectarray of Optical DRAs: Design and experiment
4
e ecta ay o Opt ca s es g a d e pe e t
C4 Conclusion
3Introduction Scaling DRAs Optical DRAs Conclusion
Manipulating light at sub-wavelength scale:Optical antennasp
sensingspectroscopylight emissionEnhancing the efficiency light emissionphotodetectionon-chip communicationoptical components
And/or resolution for
p p
“Anomalous” ReflectorsFlat LensesNiu et al., Opt. Express
21(3), 2875 (2013)
α β
500 µm(a)Yu et al., Science
4Introduction Scaling DRAs Optical DRAs Conclusion
334, 333 (2011) Withayachumnankul et al., Adv. Opt. Mat 1, 443 (2013)
Optical antennas: 1970’s to today 1970‘s 1977‘s 1991
10 μme.g. A. Javan’sgroup,
W tipMetallic base
by E. Wiesendanger, F. Kneubühl, Appl. Phys. 13(4) (1977)
Grossman et al. (NIST)Appl. Phys. Lett. 59 (25) (1991)
g p,MIT
1990‘s2000‘s
Wilke et al. (ETHZ)Appl. Phys. B 58, 87-
95 (1994) “Antennas for light”, Novotny & van Hulst, Nature Photonics 5,
1990 s
Fumeaux et al. (ETHZ, CREOL)Appl Phys B 63
, ,83–90 (2011)
Sun et al., Nano Lett. 12,
5
CREOL)Appl. Phys. B 63 (1996)
Introduction Scaling DRAs Optical DRAs Conclusion
6223 (2012)
Current research on optical antennasConventional optical antenna structure:
“Antennas for light”, Novotny & van Hulst, Nature Photonics 5, 83–90 (2011)
Resonant metallic antenna on top of dielectric
1. Fabrication accuracies down to a few nanometres
Current fabrication methodsFocused ion beam millingElectron beam lithography
Sun et a
Nano Lett6223 (20
2. High Ohmic loss of metal at optical frequencies
Th ti l t h tl f t lli t t ( l i )
al., . 12, 12)
The optical antenna research mostly focuses on metallic nanostructures (plamonics)
One possible solutions for higher efficiency:Optical dielectric resonator antennaOptical dielectric resonator antenna
Scale down 200 000 ti !
Filonov et al., Appl. Phys. Lett. 100, 201113 (2012)
6
200,000 times!
Introduction Scaling DRAs Optical DRAs Conclusion
( )
εDielectric Resonator AntennasDielectric resonator antennas
εr
e ect c eso ato a te as• Dielectric resonator in open
environment• Low-order resonant modes
have low radiation Q factor→ good radiators!
• Introduced by Long et al. (1983) Characteristics of DRA• Small size (εr ≈ 10 typically)• Larger bandwidth than patch• High efficiency• Versatility
Si li it f it ti
7Introduction Scaling DRAs Optical DRAs Conclusion
• Simplicity of excitation
Fundamental cylindrical DR modesModes index m n l+δTE: transverse electric
TM t tiΦ ρ z
TM: transverse magnetic
HE, EH: hybridETE H TM
HTE δ01 E
TM δ01 JM
E
H E
H HEM δ11M
8
From: Kajfez, Glisson & James, MTT-32(12), 1609ff (1984)
Introduction Scaling DRAs Optical DRAs Conclusion
High efficiency DRA at MMWhigh efficiency
Ø = 2.6 mmh = 1.1 mm
Ø = 3.18 mm
DRA Microstripantenna
36 GHz
antenna
80%>90%
Lai et al T-AP 56(11)
9
Lai et al., T AP 56(11), 3589 (2008)
Introduction Scaling DRAs Optical DRAs Conclusion
Towards experimental demonstration of optical DRAhigh efficiency
Optical dielectric resonator antenna concept
Optical antenna structure:
Optical dielectric resonator antenna concept
Aim: R d lli l i
Resonant dielectric on top of metal
Reduce metallic losses in RF-inspired nano-antennas
Dielectric resonator optical antenna
10Introduction Scaling DRAs Optical DRAs Conclusion
Outline
Introduction1
2 Scaling of Dielectric Resonators Antennas
3 Reflectarray of Optical DRAs: Design and experiment
4
e ecta ay o Opt ca s es g a d e pe e t
C4 Conclusion
11Introduction Scaling DRAs Optical DRAs Conclusion
Frequency & Material selection
T t fTarget frequency:HeNe red laser (λ = 633 nm)
Materials:Close collaboration
z y
xClose collaboration with nano-fabrication team
x
Chosen dielectric resonator material:
Relative permittivity of8.29 in X and Y direction
TiO2 with thickness 50 nm
Silver permittivity 16 05+j0 57 at 474 THz (calculated from the Drude model)
6.71 in Z direction
12
Silver permittivity −16.05+j0.57 at 474 THz (calculated from the Drude model)
Introduction Scaling DRAs Optical DRAs Conclusion
Scaled model of DRA
Plane wave excitationPlane wave excitationFundamental HEM 11δ mode
Find resonance by varying radiusFind resonance by varying radius
E-field TiO2
Silverxz
90
H-field TiO2
0
45 Phase (
Magnitude and phase of H field
Silveryz
HEM11δ mode field distributions -90
-45
(degree)
13
HEM11δ mode field distributions
Introduction Scaling DRAs Optical DRAs Conclusion
Scaling from Microwave to Optical frequencies
D/λ
SignificantPlasmonic
effects!
X10-5
14
5 GHz500 THzeffects!
Introduction Scaling DRAs Optical DRAs Conclusion
Efficiency: from microwaves to visible frequencies
DR: Properties of TiO2Metal: Silver
X10-5
15
5 GHz500 THzIntroduction Scaling DRAs Optical DRAs Conclusion
Outline
Introduction1
2 Scaling of Dielectric Resonators Antennas
3 Reflectarray of Optical DRAs: Design and experiment
4
e ecta ay o Opt ca s es g a d e pe e t
C4 Conclusion
16Introduction Scaling DRAs Optical DRAs Conclusion
Optical reflectarrays…Reflectarrays
( i l i i l )Meta-surfaces
( G li d S ll’ l )( equivalence principle) ( Generalized Snell’s law)• Dates back from the 1960’s• Relatively mature techniquesy q• Sophisticated realizations • Scalable to optical frequencies
www ecs umass edu
Different approaches and languages
17
www.ecs.umass.edu
Introduction Scaling DRAs Optical DRAs Conclusion
Optical reflectarray of dielectric resonator antennas
E i t l d t tid
Experimental demonstrationusing simple reflectarray
Gradient meta-surface“„Gradient meta-surface
I t d i h φ6-element reflectarray
Introduce progressive phase φthrough variation DR radius
α β α β θDeflection
angle θg
18
Mirror Reflectarray
Introduction Scaling DRAs Optical DRAs Conclusion
6-element sub-arrayNormal incidence
6-element reflectarray
Resonance20 o
Simulated scattered E field
19
from a 6-element sub-array
Introduction Scaling DRAs Optical DRAs Conclusion
FabricationFunctional Materials and Microsystems Research GroupSchool of Electrical and Computer Engineering
20Introduction Scaling DRAs Optical DRAs Conclusion
Fabricated samples
4-element reflectarrayDeflected beam angle: 27°
6-element reflectarrayDeflected beam angle: 20°
9-element reflectarrayDeflected beam angle: 12°
Area: 40 μm x 40 μmA 130 130 l t
21
Array: 130 x 130 elements
Introduction Scaling DRAs Optical DRAs Conclusion
MeasurementMeasurement setup (Top view) Reflection Deflection
Best sample: 6-element array
22Introduction Scaling DRAs Optical DRAs Conclusion
6-element reflectarray 2D Beam pattern
Reflection Deflection
Radiation patternRadiation pattern
Ratio of specular reflectionRatio of specular reflectionto deflected power: 1: 4.42
Overall efficiency: 40%
23
3D beam pattern recorded by linear CCD detectorOverall efficiency: 40%
Introduction Scaling DRAs Optical DRAs Conclusion
Conclusions• Scaling of dielectric resonator antennasg
shows their high efficiency up to the infrared & visible light regimes
• Nano-photonic devices can take inspiration from antennas and benefit from techniques developedantennas and benefit from techniques developed in the antenna community
• Improved Efficiency of optical DRAWork in Progress
p y p• All dielectric antennas• DRA lens-array
Cl ki
24
• CloakingIntroduction Scaling DRAs Optical DRAs Conclusion
AcknowledgementsThe authors acknowledge the ARC through the following fellowships and projectsDP1095151, DP1092717, DP110100262,DP1095151, DP1092717, DP110100262, LE100100215, FT100100585
Thank you forL. Zou et al., “Dielectric resonator
nanoantennas at visible Thank you for your attention!
frequencies”, Opt. Express 21(1), 1344-1352 (January 2013)
25Introduction Scaling DRAs Optical DRAs Conclusion
