Making the Mid-Infrared Nano with Designer Plasmonic …•SPP is bound mode, propagates on metal...

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


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


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


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…


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

http://www.imaging1.com/

http://www.el-op.com/

http://www.army.mil/


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

http://www.baesystems.com/Businesses/LandArmaments/Divisions/GlobalCombatSystems/Vehicles/ProductsPlatforms/Adaptiv/Adaptiv_video/index.htm


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…


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


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.

-

-


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


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

http://pubs.acs.org/doi/abs/10.1021/nn304948h


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!


Metamaterials/Plasmonics (circa 2000)


Metamaterials/Plasmonics (circa 2015)


Outline

• Introduction






– Beam steering and shaping, sensing, selective thermal emission

– Hybrid metal/dielectric structures







• Conclusions


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


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)


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


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


Scaling to Mid-IR

SPP

Propagation

Length

SPP

Dielectric

Penetration

Depth

NIR/MIRVis/NIR


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….


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.


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).


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


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


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


Avoiding Losses

2.8 µm


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


Outline

• Introduction













• Conclusions


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∗


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


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


Doped InAs films

• Tune plasma wavelength from 5.5m to 17m—across much of MIR

• Extremely low losses at plasma frequency


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.


Thin Film Interference

~𝜆/4


Phase, Scaling vs. Thickness


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!


Tunable Perfect Absorption

Experiment Model


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)


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.


Near field AFM (w/ King group)

1750cm-1 on resonance

1 um

Scan Direction

Scan Direction

Light

Propagation

E-field

direction


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).


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.


All-Semiconductor Nano-Antennas For Infrared Sensing


Outline

• Introduction













• Conclusions


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


In(Ga)Sb Insertion Layers in InAs(Sb)

• Strong luminescence – Compatible with our highly doped material

– Strong surface emission (LEDs?)


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)


Detector Development

• Type-II Superlattice Detectors– Thus far we have focused on detector characterization

– Moving towards growth and detector fabrication


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


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!


Tunable Perfect Absorption

Experiment Model𝐻

𝐸

𝜃

𝜃


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!


Designer Plasmon PAs

• Incident light couples into negative index modes

• Propagates in “plasmonic crystal”


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


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.


Near field IR-AFM


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?


Burstein-Moss effect

Δ𝐸 =ℎ

2𝑚∗(𝑛)

3𝑛

8𝜋

23

Films are transparent out to telecom

frequencies


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


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


Plasmonic/Optoelectronics

– So-Called Sub-Monolayer Quantum Dots?



• 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?



– 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).


Coupling to Molecular Absorption Resonances


Flat Plasmonic Gratings

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Making the Mid-Infrared Nano with Designer Plasmonic …•SPP is bound mode, propagates on metal...

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