University of Texas at Austin, ECE Department, February 23, 2015
D. Wasserman
Dept. of Electrical and Computer EngineeringMicro and Nanotechnology Lab
University of Illinois Urbana Champaign
Making the Mid-Infrared Nano with Designer Plasmonic Materials
University of Texas at Austin, ECE Department, February 23, 2015
Sponsors
AFOSR/AFRL
NSF
DOE
Sandia National Labs
Army Research Office
Graduate Students
Lan Yu
Will Streyer
Runyu Liu
Daniel Zuo
Sergio Hidalgo
Narae Yoon
Collaborators• UMass Lowell
• Prof. Viktor Podolskiy
• UIUC
• Prof. Bill King
• Prof. X. Li
• Prof. Songbin Gong
• Prof. LynfordGoddard
Post-Doc: Yujun Zhong
Stephanie Law (now UDel)
Students, Collaborators, Sponsors
Undergrads
Travis Hamilton
Joshua Surya
Zipporah Goldenfeld
Sukrith Dev
Daniel Schwartz
• Sandia National Labs
• Eric Shaner
• Jin Kim
• U. Delaware
• Prof. J. Zide
• Yale University
• Prof. M.L. Lee
University of Texas at Austin, ECE Department, February 23, 2015
Outline
• Introduction
– Why the mid-infrared?
– Building a mid-IR tool-kit
– Why nano mid-IR?
– Overview of plasmonics/metal optics
• Mid-IR metal optics with noble metals
– Beam steering and shaping, sensing, active devices, selective thermal emission
– Challenges of noble metals in the Mid-IR
• Development of engineered mid-IR metals
– Growth and Characterization
– Integration into meta-surface, metamaterial structures
• Future Work– Integration of optoelectronic, plasmonic materials
– Moving to Far-IR?
• Conclusions
University of Texas at Austin, ECE Department, February 23, 2015
www.daylightsolutions.com
Why the Mid-Infrared?
• Everything absorbs in the mid-IR
• The mid-IR is home to fundamental vibrational resonances of a wide range of molecules
• Sensing
– Breath Analysis
– Industrial Process Monitoring
– Environmental monitoring…
University of Texas at Austin, ECE Department, February 23, 2015
Why the Mid-IR?
• Everything emits in the mid-IR…..
• Important frequency range for defense applications– Thermal imaging
– Countermeasures
•www.imaging1.com
(Sierra Pacific
Innovations)
•www.el-op.com
(Elbit Systems
Electro-optics)
www.army.mil
University of Texas at Austin, ECE Department, February 23, 2015
Why the Mid-IR?
• BAE’s ADAPTIV technology
• Uses ‘pixels’ temperature controlled with ‘semi-conducting’ cooling technology…
– 70K temperature shift for a 1cm x 1cm area requires ~10W.
– To cover a tank in this, not including dissipating heat produced by coolers….
http://www.baesystems.com/Businesses/LandArmaments/Divisions/GlobalCombatSystems/Vehicles/ProductsPlatforms/Adaptiv/Adaptiv_video/index.htm
University of Texas at Austin, ECE Department, February 23, 2015
Why the Mid-IR?
The Mid-IRas an optics/photonics
test-bed
Energy Harvesting
Far-IR (Reststrahlen Band)
OpticsNear-IR/VisibleOptoelectronics
Mid-IR Applications
Sensing(Bio, Health, Industrial,
Environmental…)
ImagingThermal, Night Vision
Cameras
Optoelectronics:Detectors, Sources,
modulators…
Fundamental Science:Light-matter
interaction, epsilon near zero materials,
subwavelength optics, plasmonics,
metamaterials, metasurfaces…
University of Texas at Austin, ECE Department, February 23, 2015
Building a Mid-IR Tool-Kit
• Want a flexible “optical infrastructure” for development of
– New sources (LEDs, surface emitting lasers, low-cost emitters)
– New Detectors (high-speed and sensitivity, low-cost)
– New sensor platforms, nano-scale devices and materials.
• Plasmonics and Metamaterials?
𝜆 = 10𝜇𝑚
University of Texas at Austin, ECE Department, February 23, 2015
Metals• How do we describe interaction of metals with AC fields?
-+ + + +
+ + + +
+ + + +
- - -
- - - -- - - -
𝐸
𝑚𝑑2 𝑥
𝑑𝑡2= 𝑞𝐸 − 𝑚𝛾
𝑑 𝑥
𝑑𝑡
𝐸 = 𝐸𝑜𝑒−𝑖𝜔𝑡 𝑥
𝑥 = 𝑥𝑜𝑒−𝑖𝜔𝑡 𝑥
𝑥𝑜 = −𝑞
𝑚
1
𝜔2 + 𝑖𝛾𝜔𝐸𝑜
• Treat metal as a dielectric material with both bound electrons and n free electrons.
• For free electrons
𝑃𝑓𝑟𝑒𝑒 = 𝑞𝑛 𝑥 = −𝑞2𝑛
𝑚
1
𝜔2 + 𝑖𝛾𝜔𝐸 = 𝜀𝑜𝜒𝑒𝑓𝐸
𝜀𝑚𝜀𝑜 = 1 + 𝜒𝑒𝑏 + 𝜒𝑒𝑓 𝜀𝑜 = 𝜀𝑠 + 𝜒𝑒𝑓 𝜀𝑜“background” relative permittivity
from bound electrons
𝜒𝑒𝑓 = −𝑞2𝑛
𝑚𝜀𝑜
1
𝜔2 + 𝑖𝛾𝜔= −
𝜔𝑝2
𝜔2 + 𝑖𝛾𝜔
𝛾 =1
𝜏
𝜀𝑚 = 𝜀𝑠𝜀𝑜 1 −𝜔𝑝
2
𝜔2 + 𝑖𝛾𝜔
𝜔𝑝2 =
𝑞2𝑛
𝑚𝜀𝑠𝜀𝑜
Plasma
frequency
Metal
permittivity
• m results from response of free, bound carriers to E field.
-
-
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic Building Blocks
𝑘𝑠𝑝𝑝 =𝜔
𝑐
𝜖𝑑𝜖𝑚𝜖𝑑 + 𝜖𝑚
SPP: Guided mode propagating at interface between metal (z<0) and dielectric (z>0).
z
x
• SPP is bound mode, propagates on metal surface
LSP: Localized mode oscillating on a subwavelength (3D) particle (𝜀𝑚 < 0) surrounded by dielectric (𝜀𝑑 < 0)
z
x
𝐸𝑜𝑢𝑡 ∝𝜀𝑚 − 𝜀𝑑
(𝜀𝑚 + 𝑋𝜀𝑑)
𝑎3
𝑟3𝐸𝑜
• LSP mode is localized to subwavelength particles
University of Texas at Austin, ECE Department, February 23, 2015
Applications for Plasmonics
• Spectral Filtering (displays?)
• Waveguiding (optical interconnects?)
• Sensing (SERS)
• Nanophotonics
• Localized Heating
C. Genet and T.W. Ebbesen, “Light in Tiny Holes”, Nature, 445, 4 (2007).
R. Zia et al, “Plasmonics: the next chip-scale technology”, Mat. Today, 9, 20 (2006).
Nie, S.; Emory, S. R., Science (1997)
CZ Ning, ASU
L. R. Hirsch, …, N. J. Halas and J.L. West, Nanoshell-mediated near-infrared thermal therapy of tumors under magnetic resonance guidance, Proc. Nat. Acad. Sci., 100, 13549 (2003).
Oara Neumann, Alex Urban, Jared Day, SurbhiLal, Peter Nordlander, and Naomi J. Halas. Solar Vapor Generation Enabled by Nanoparticles. ACS Nano 2013, 7, 42-49
University of Texas at Austin, ECE Department, February 23, 2015
So Why Plasmonics?
• Offers strong mode confinement in– 1DSPP
• Optical interconnects
• Enhanced sensing for thin films
• Strong interaction with 2D geometries
– 3DLSP
• Enhanced interaction with ultra-subwavelength molecules, detectors, or light emitters
• Enhancing non-linear effects
• Localized absorption/heating for photothermal applications
• Dual use for metal: electrical contact/optical material
• Plasmonics/Metamaterials/Metasurfaces has promised so many exciting advances in optics and optoelectronics!
University of Texas at Austin, ECE Department, February 23, 2015
Metamaterials/Plasmonics (circa 2000)
University of Texas at Austin, ECE Department, February 23, 2015
Metamaterials/Plasmonics (circa 2015)
University of Texas at Austin, ECE Department, February 23, 2015
Outline
• Introduction
– Why the mid-infrared?
– Building a mid-IR tool-kit
– Why nano mid-IR?
– Overview of plasmonics/metal optics
• Mid-IR metal optics with noble metals
– Beam steering and shaping, sensing, selective thermal emission
– Hybrid metal/dielectric structures
– Challenges of noble metals in the Mid-IR
• Development of engineered mid-IR metals
– Growth and Characterization
– Integration into meta-surface, metamaterial structures
• Future Work– Integration of optoelectronic, plasmonic materials
– Moving to Far-IR?
• Conclusions
University of Texas at Austin, ECE Department, February 23, 2015
Example: Beam Steering
• From Visible/Near-IR
Theory of Highly Directional
Emission from a Single
Subwavelength Aperture
Surrounded by Surface
Corrugations, L. Martin-
Moreno, et al, Phys. Rev.
Lett., 90, 167401 (2003)
8.8 9.0 9.2 9.4
-20
-10
0
10
20
An
gle
(o)
10.0 10.2 10.4
Wavelength (m)
Plasmonic mid-infrared beam
steering, D.C. Adams, S.
Thongrattanasiri, T. Ribaudo,
V. Podolskiy, and D.
Wasserman, Appl. Phys. Lett.,
96, 201112 (2010).
Beam engineering of quantum cascade lasers, N. Yu, Q.
Wang, F. Capasso, Laser Photonics Rev. 6, 24-46 (2012).
• To Mid-IR
University of Texas at Austin, ECE Department, February 23, 2015
Example: Sensing with LSPR
K.A. Willets, R.P. Van Duyne, “Localized
Surface Plasmon Resonance Spectroscopy
and Sensing” Annu. Rev. Phys. Chem., 58,
267-297, 2007.
• From Visible/Near-IR
• To Mid-IR
Adato R, et al. Ultra-sensitive vibrational spectroscopy of protein
monolayers with plasmonic nanoantenna arrays. Proc. Nat.
Acad. Sci. 2009, 106, 19227-19232.
“Strong coupling of molecular and mid-infrared perfect
absorber resonances”, J.A. Mason, G. Allen, V.
Podolskiy, and D. Wasserman, IEEE Photonics
Technology Letters, 24, 31 (2012)
University of Texas at Austin, ECE Department, February 23, 2015
Scaling to Mid-IR Metal Permittivity
*From JC:
PB Johnson and
RW Christy,
Optical Constants
of Noble Metals,
Phys. Rev. B, 6,
4370 (1972)
Solid lines: Drude
fit to JC
University of Texas at Austin, ECE Department, February 23, 2015
SPPs
0.0
0.5
1.0
1.5
2.0
2.5
0 1 2 3 4 5 6
k (m-1)
En
erg
y (
eV
)
Au/Air SPP
Light
VISIBLE
Near-IR
Mid-IR
University of Texas at Austin, ECE Department, February 23, 2015
Scaling to Mid-IR
SPP
Propagation
Length
SPP
Dielectric
Penetration
Depth
NIR/MIRVis/NIR
University of Texas at Austin, ECE Department, February 23, 2015
𝛼 = 4𝜋𝑎3𝜖𝑑 − 𝜖𝑚𝜖𝑚 + 2𝜖𝑑
Stiles, et al, “Surface-Enhanced
Raman Spectroscopy”
Annu. Rev. Anal. Chem., 1, 601
(2008) 𝛼 = 4𝜋𝑎3𝜖𝑑 − 𝜖𝑚𝜖𝑚 + 2𝜖𝑑
Scaling to Mid-IR
- Adjusting geometry (X) and d can redshift…but not to 5-10µm range….
University of Texas at Austin, ECE Department, February 23, 2015
Challenges in Plasmonics
• General Challenges– Losses
– Limited Choice of Materials
– Wavelength flexibility
• For mid-infrared– With traditional metals
• SPPs are loosely bound: no subwavelength confinement.
• LSPs closer to antenna resonances than ‘plasmonic’
• What can we do?– Nothing. Simply work within limitation provided.
– Avoid specific challenges with new types of architectures?
– New materials.
University of Texas at Austin, ECE Department, February 23, 2015
Beam shaping from plasmonic surfaces (doing nothing)
“Multiscale beam evolution and shaping in
corrugated plasmonic structures”, S.
Thongrattanasiri, D.C. Adams, D. Wasserman and
V. Podolskiy,Optics Express, 19, 9269 (2011).
University of Texas at Austin, ECE Department, February 23, 2015
Leveraging Loss (doing nothing)
• In Near-IR
• In Mid-IR
“Strong absorption and selective thermal emission from mid-infrared metamaterials”, J. Mason, S. Smith, and D. Wasserman, Appl. Phys. Lett., 98, 241105 (2011).
N. Liu, M. Mesch, T. Weiss, M. Hentschel, H.
Geissen, “Infrared Perfect Absorber and Its
Application As Plasmonic Sensor” Nano-Lett.
10 (2010) 2342-2348
C. Wu, B. Neuner III, and
G. Shvets, “Large-area
wide-angle spectrally
selective plasmonic
absorber” Phys. Rev. B
84 (2011) 075102
University of Texas at Austin, ECE Department, February 23, 2015
5 10 15 20
0.0
0.5
1.0
Wavelength (m)
Emmissivity
Reflectivity
Leveraging Loss
0 5 10 15 20Em
itte
d P
ow
er/
d(a
rb.
un
its)
Wavelength (m)
Perfect Blackbody
Greybody (=0.5)
Metamaterial (on)
Metamaterial (off)
If the emission resonance can be
“turned off”, corresponds to ~100K
change in recorded temperature on
IR imager!!
Proof of Principle
4 5 6 70.0
0.2
0.4
0.6
0.8
1.0
1.2
Reflectivity
Wavelength (m)
160nm SOG
294nm SOG
426nm SOG
615nm SOG
University of Texas at Austin, ECE Department, February 23, 2015
Avoiding Loss
• Collaboration with X. Li at UIUC, V. Podolskiy at UML.
• Integrating plasmonic materials with dielectric structures can give us the best of both worlds.– Uniform electrical contact
– Lower losses
University of Texas at Austin, ECE Department, February 23, 2015
Avoiding Losses
2.8 µm
University of Texas at Austin, ECE Department, February 23, 2015
Micrometer light waves at the nano-scale
• Traditional Metals allow for subwavelength confinement at short wavelengths– enhanced sensing
– nano- optoelectronics
– nanophotonic waveguiding
– but lots of losses
• At long wavelengths– We can leverage losses with wavelength
scale structures, use for selective thermal emission
– We can use ‘antenna-like’ structures for sensing
– But we can’t go subwavelength, much less nano…
5 10 15 20
0.0
0.5
1.0
Wavelength (m)
Emmissivity
Reflectivity
University of Texas at Austin, ECE Department, February 23, 2015
Outline
• Introduction
– Why the mid-infrared?
– Building a mid-IR tool-kit
– Why nano mid-IR?
– Overview of plasmonics/metal optics
• Mid-IR metal optics with noble metals
– Beam steering and shaping, sensing, active devices, selective thermal emission
– Challenges of noble metals in the Mid-IR
• Development of engineered mid-IR metals
– Growth and Characterization
– Integration into meta-surface, metamaterial structures
• Future Work– Integration of optoelectronic, plasmonic materials
– Moving to Far-IR?
• Conclusions
University of Texas at Austin, ECE Department, February 23, 2015
Drude model
Optical response of semiconductor modeled with Drude formalism
Tune plasma frequency by changing doping
Combination of doping and small effective mass lead to plasma frequencies in NIR/MIR
Leads us to MBE-grown III-V’s (InAs, InSb…)
𝜖 𝜔 = 𝜖𝑠 1 −𝜔𝑝
2
𝜔2 + 𝑖𝜔Γ2= 𝜖𝑠 1 −
𝜔𝑝2
𝜔2 + Γ2+ 𝑖𝜖𝑠
Γ𝜔𝑝2/𝜔
𝜔2 + Γ2
𝜔𝑝2 =
𝑛𝑒2
𝜖𝑠𝜖0𝑚∗
University of Texas at Austin, ECE Department, February 23, 2015
Doped InAs films
5 10 150.0
0.2
0.4
0.6
0.8
1.0009 Si:InAs n=3.25x10
19 cm
-3 t=1.6m
Re
fle
ctio
n,
Tra
nsm
issio
n
Wavelength (m)
Experimental R
Experimental T
Experimental transmission scaled up by 20
ovens
SiAlGaInAs
Substrate
Undoped
Buffer
Doped InAs
University of Texas at Austin, ECE Department, February 23, 2015
Doped InAs films
5 10 150.0
0.2
0.4
0.6
0.8
1.0009 Si:InAs n=3.25x10
19 cm
-3 t=1.6m
Re
fle
ctio
n,
Tra
nsm
issio
n
Wavelength (m)
Experimental R
Experimental T
Fitting R
Fitting T
Experimental transmission scaled up by 20
p=8.4m
=4.4x10-13
s
ovens
SiAlGaInAs
Substrate
Undoped
Buffer
Doped InAs
University of Texas at Austin, ECE Department, February 23, 2015
Doped InAs films
• Tune plasma wavelength from 5.5m to 17m—across much of MIR
• Extremely low losses at plasma frequency
University of Texas at Austin, ECE Department, February 23, 2015
Epsilon Near Zero Materials
• Can transmit more light through a subwavelengthslit on ENZ than with a low-loss, high- dielectric
Adams D C, Inampudi S, Ribaudo T, Slocum D, Vangala S, Kuhta N A, Goodhue W
D, Podolskiy V A, Wasserman D. Funneling light through a subwavelength aperture
with epsilon-near-zero materials. Phys. Rev. Lett. 2011, 107, 133901.
University of Texas at Austin, ECE Department, February 23, 2015
Thin Film Interference
~𝜆/4
University of Texas at Austin, ECE Department, February 23, 2015
Phase, Scaling vs. Thickness
University of Texas at Austin, ECE Department, February 23, 2015
Doped Si
• Can we do this in the mid-IR with doped semiconductors?
• Yes, with greater control and efficiency, because we can control BOTH the dielectric AND the metal!
University of Texas at Austin, ECE Department, February 23, 2015
Tunable Perfect Absorption
Experiment Model
University of Texas at Austin, ECE Department, February 23, 2015
Selective Thermal Emission
• Can control emission by control of Ge thickness!
“Strong absoprtion and selective emission from engineered metals with dielectric coatings”, W. Streyer, S. Law, G. Rooney, T. Jacobs, and D. Wasserman, Optics Express (2013)
University of Texas at Austin, ECE Department, February 23, 2015
Localized surface plasmons
6 7 8 9 10 11 120.020
0.025
0.030
0.035
0.040
0.045
0.050 1.2m dot transmission
1.7m dot transmission
1.2m dot reflection
1.7m dot reflection
Wavelength (m)
Tra
nsm
issio
n
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Reflection
GaAs
𝐸𝑥𝑡~𝜖𝑑 − 𝜖𝑚𝜖𝑚 + 2𝜖𝑑
“Mid-infrared designer metals”, S. Law, D.C. Adams, A.M.
Taylor, D. Wasserman, Opt Exp 2012 20 12155-65.
University of Texas at Austin, ECE Department, February 23, 2015
Near field AFM (w/ King group)
1750cm-1 on resonance
1 um
Scan Direction
Scan Direction
Light
Propagation
E-field
direction
University of Texas at Austin, ECE Department, February 23, 2015
Designer Plasmonics Perfect Absorbers
“All-Semiconductor Negative-Index Plasmonic Absorbers”
S. Law, C. Roberts, T. Kilpatrick, L. Yu, T. Ribaudo, E.A.
Shaner, V. Podolskiy, and D. Wasserman, Physical Review
Letters 112, 017401 (2014).
University of Texas at Austin, ECE Department, February 23, 2015
All-Semiconductor Nano-Antennas For Infrared Sensing
“All-Semiconductor Plasmonic Nanoantennas for
Infrared Sensing”, S. Law, L. Yu, A. Rosenberg,
and D. Wasserman, Nano-Letters, 2013.
University of Texas at Austin, ECE Department, February 23, 2015
All-Semiconductor Nano-Antennas For Infrared Sensing
University of Texas at Austin, ECE Department, February 23, 2015
Outline
• Introduction
– Why the mid-infrared?
– Building a mid-IR tool-kit
– Why nano mid-IR?
– Overview of plasmonics/metal optics
• Mid-IR metal optics with noble metals
– Beam steering and shaping, sensing, active devices, selective thermal emission
– Challenges of noble metals in the Mid-IR
• Development of engineered mid-IR metals
– Growth and Characterization
– Integration into meta-surface, metamaterial structures
• Future Work– Integration of optoelectronic, plasmonic materials
– Moving to Far-IR?
• Conclusions
University of Texas at Austin, ECE Department, February 23, 2015
In(Ga)Sb Insertion Layers in InAs(Sb)
• However, we may have found a potential way around all of the above problems…
• In(Ga)Sb QDs in InAs(Sb) matrix– Lattice mismatch very similar to InAs/GaAs
– Band alignment very different
University of Texas at Austin, ECE Department, February 23, 2015
In(Ga)Sb Insertion Layers in InAs(Sb)
• Strong luminescence – Compatible with our highly doped material
– Strong surface emission (LEDs?)
University of Texas at Austin, ECE Department, February 23, 2015
Preliminary Results
• These emitter structures can be integrated with our designer ‘plasmonic’ material
n+ InAs
undoped InAs
InSb QWs
3 4 5 6 7 8 9 100.0
0.1
0.2
0.3
0.4
0.5
PL
In
ten
sity (
a.u
.)
Wavelength (m)
University of Texas at Austin, ECE Department, February 23, 2015
Detector Development
• Type-II Superlattice Detectors– Thus far we have focused on detector characterization
– Moving towards growth and detector fabrication
University of Texas at Austin, ECE Department, February 23, 2015
25 30 35 400.0
0.2
0.4
0.6
0.8
1.0
Re
fle
ctio
n
Wavelength (m)
11 18
12 18
13 18
14 18
15 18
Moving to the Far-IR
5.5
mW
7.1 mW
Area: 1 cm x 1 cm
Temp: 600 K
University of Texas at Austin, ECE Department, February 23, 2015
Conclusions
The mid-infrared is a dynamic wavelength range for both a range of real world applications, and as a test bed for understanding light-matter interaction.
Mid-IR Plasmonics with Traditional Metals
1) Fundamentally different than near-IR/Vis
2) Plasmonics, without subwavelength confinement, and/or
3) Can leverage, avoid losses for new architectures, applications…
Mid-IR Plasmonics with Engineered Metals
1) Crystalline, low-loss, high quality and wavelength-flexible materials
2) Can support mid-IR LSP, used for IR sensing applications
3) Integration with semiconductor active media
Future Work:
Leverage what we have learned to develop new structures, devices, and wavelength ranges!
University of Texas at Austin, ECE Department, February 23, 2015
Tunable Perfect Absorption
Experiment Model𝐻
𝐸
𝜃
𝜃
University of Texas at Austin, ECE Department, February 23, 2015
Designer Plasmonic PAs
4 6 8 10 12 14 160.0
0.2
0.4
0.6
0.8
1.0
Re
fle
ction
Wavelength (m)
w=2.4, =4
w=1, =2
n+ InAs
SI GaAs
TM
TE
w
• Absorption resonance is largely independent of lateral geometry!
University of Texas at Austin, ECE Department, February 23, 2015
Designer Plasmon PAs
• Incident light couples into negative index modes
• Propagates in “plasmonic crystal”
University of Texas at Austin, ECE Department, February 23, 2015
5 6 7 8 9 10 11 120.0
0.2
0.4
0.6
0.8
1.0
Reflection
Wavelength (mm)
2.4 4.0 215nm
3.0 5.0 320nm
1.8 3.0 370nm
200 400 600 800 1000 12000
20
40
60
80
100
Exp.
FDTD
Absorp
tion (
%)
Etch Depth (nm)
0.3 0.4 0.5 0.6 0.7 0.80
20
40
60
80
100
Absorp
tion (
%)
Fill Factor (w/L)
170.0
180.0
190.0
200.0
210.0
220.0
275.0
375.0
475.0
575.0
675.0
775.0
875.0
975.0
1075
1140
5 6 7 8 9 10 11 120.0
0.2
0.4
0.6
0.8
1.0
Reflection
Wavelength (m)
1.0 2.0 180nm
1.4 3.0 175nm
1.6 3.0 220nm
1.8 4.0 204nm
2.4 4.0 215nm
a b
c d
w(µm), L(µm), d(nm)
w(µm), L(µm), d(nm)
TM
TE
TE
TM
University of Texas at Austin, ECE Department, February 23, 2015
LSPR simulations Modeled absorption using quasistaticapproximation
Simulated pucks with COMSOL
Law S, Adams D C, Taylor A M, Wasserman D. Mid-
infrared designer metals. Opt Exp 2012 20 12155-65.
University of Texas at Austin, ECE Department, February 23, 2015
Near field IR-AFM
University of Texas at Austin, ECE Department, February 23, 2015
Near field AFM1750cm-1 on resonance 1600cm-1 off resonance 1300cm-1 off resonance
Signal on resonance 3x larger than signal off resonance Able to observe localized heating in pucks in the near field!
Topography Experiment Model
1750 cm-11750 cm-1
Modeling agrees experiment ..Able to image localized mode?
University of Texas at Austin, ECE Department, February 23, 2015
Burstein-Moss effect
Δ𝐸 =ℎ
2𝑚∗(𝑛)
3𝑛
8𝜋
23
Films are transparent out to telecom
frequencies
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic Optoelectronics• Interband transitions?
• Need narrow (direct) bandgap, low effective mass, high doping
• What about InSb?
0.5
1.0
5 10 150.0
0.2
Refle
ctio
n
5E18
1.3E19
1.9E19
3.2E19
8.6E19
>1E20
Tra
nsm
issi
on
Wavelength (m)
5 10 150.0
0.2
0.4
0.6
0.8
1.0
In
SbL
InS
b
Wavelength (m)
77K
150K
185K
218K
250K
300K
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic Optoelectronics
• Intersubband transitions in QDs– Weak emission, incompatible with narrow band-gap material
• InSb– Can dope such that plasma frequency > band-gap, but
optoelectronic properties are poor, at limit of doping
1 2 3 4 5
0.01
0.1
1
Tra
nsm
issio
n
Wavelength (m)
5E18
1.3E19
1.9E19
3.2E19
8.6E19
>1E20
>>1E20
Ioffe.ru
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic/Optoelectronics
– So-Called Sub-Monolayer Quantum Dots?
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic/Optoelectronics
• We have ‘metals’ which we can grow epitaxially, but how do we integrate these with optoelectronic devices?– Looking for novel sources of mid-IR light…
– Self Assembled Quantum Dots?
University of Texas at Austin, ECE Department, February 23, 2015
Plasmonic/Optoelectronics
– Lithographically Defined Quantum Dots?
“Electroluminescence from Quantum Dots Fabricated with Nanosphere Lithography”, L. Yu, S. Law, and D. Wasserman, Appl. Phys. Lett. 101, 103105 (2012).
University of Texas at Austin, ECE Department, February 23, 2015
Coupling to Molecular Absorption Resonances
University of Texas at Austin, ECE Department, February 23, 2015
Flat Plasmonic Gratings