the science and technology of photonic crystalshomepages.rpi.edu/~wangg/passion for physics 2006...

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The Science and Technology of Photonic Crystals

Shawn-Yu LinConstellation Professor of Physics

(Harnessing Light at Nano-Scales)

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Shawn Lin• Born in Taiwan

• B.S @ National Taiwan University

• Ph.D. @ Princeton University

• Post-doctor fellow @IBM T J Watson

• Distinguished MTS @ Sandia Nat. Labs

• Constellation Professor @ RPI

Integrated photonicsMicro-photonicsSi-photonicsEnergy-saving devices

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CONTENT

(I) Motivation (4)

(II) Definition and Introduction (12)

(III) Two Applications

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(I) 20th Century: Modern Electronic Revolution

SSemiconductor Si

STransistor Science & Technology

• Bell Lab• IBM

Integrated Circuit (IC)• Integrated Micro-System

Nano-System

Applications• Computer• Satellite• Missile

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(II) 21 Century: Information Age• Optical signal processing.(broadband, routing, switching, delivering)

Fiber & Optics

Photonic Chip

• Photonic Chip • Optical Semiconductor (photonic crystal)

(III) 21 Century: Energy Conservation and Conservation

6How can we use less? Energy-saving devices.

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“energy conversion devices”--- the key scientific challenge

Energy crisis?But the world is full of energy!

Sun

India: solar electric water pump

Biomass power plant

Solarpanel

Anderson, Cal (50MW) (fm TM Lu)

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CONTENT

(I) Motivation

(II) Definition and Introduction

(III) Two Applications

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“If only it were possible to make dielectric materials in whichelectromagnetic waves cannot propagate at certain frequencies,all kinds of almost-magical things would be possible.”

---John MaddoxNature 348, 481 (1990)

Photonic Crystal:- New structural material- Light

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Photonic Crystal is an Optical Semiconductor.(It has the power to control light on-chip)

Photonic Crystal

Silicon Ge Semiconductor

The first silicon photonic crystal made in 1998. (on-chip control of light)

The first transistor made in 1948.(on-chip control of electrons)

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(II) Definition of Photonic CrystalSi

SiO2

(from JDJ)

Silicon Crystal Structure Photonic Crystal StructureIssues:Fabrication

3D topologySymmetryµm and nm scale

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3D Silicon Photonic Crystals(a diamond lattice symmetry)

Silicon Substrate (Nature Sep. 1998)

1.5µm

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(1) Photonic Crystal and Crystal Symmetry

1

2

4

3

1234

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(1) For the Past Five Years, There Has Been Rapid Advances in The Realization of 3D Lattices.

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42

1

23

4

DiamondLatticeStructure

AB

C

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Three Classes of Photonic Crystals

3D1D 2D

200nm(MIT) (Sandia) (Sandia)

3D diamond lattice builton a Si substrate.

1D hole-array built on A SOI substrate.

2D hole array builtfrom GaAs on Al-oxide.

Formation of Bands and Gaps in a Photonic Crystal

k

fBand Gap

Wavevector, k

co, speed of light

co/ n 3D mirrorEM vacuum

- in a photonic crystal;- Photonic DOS discontinuous;- clean gap of insulating photonic

states.

- in free space;- Photonic DOS continuous;- linear (speed of light).

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.

(2) We Have Also Come to Realized The Full Potentialof The Unique Photonic-Crystal Dispersion.

- mold the flow of light on-chip -

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Brillouin Zone

Γ ΓX' K L K

Complete photonic band-gap

(c/a

)Fr

eque

ncy,

ω,

Wavevector, k

(guide, bend; op. interconnect)

(prism, polarizer, rotator)

Dispersive dispersionBirefringent dispersionAn-isotropic dispersion

Band-edge

( )kxtie −ω

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(3) Micro-Photonics and Nano-Photonics(characteristic feature size)

aw

1998

Gap wavelength: λ ~ 10 µmRod-to-Rod spacing: a = 4.3 µmWidth of Rod: w =1.2 µm

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Nano-Structutral Photonics

Near Infrared (1.55 m)

Blue

Ultra-violet

µ

EUV

op communication

blue/green LED

UV and EUVoptics

Ope

ratin

g W

avel

engt

h (n

m)

Minimum Feature Size (nm)

10 100110

100

1000

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Photonic Crystal(New material for controlling light)

• 3D mirror• On-chip integration

• Micro-photonics• Nano-photonics

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Applications

1. “Dielectric” photonic-crystal Information Technology (5)

2. “Metallic” photonic-crystal Energy

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*Efficient Light Source*

*Efficient Electricity Generation*

E&M Responsepassiveactive

Photonic Lattice is a New Material That Could Lead to a Wide Range of Technological Breakthroughs.

*Communication Chip*

New Material Revolutionvia Nano-Structuring!

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(1) Integrated Optics Application: (Control the Flow of Light; Cavity Lasers)

Op Interconnect• guide• bend• cross• splitter• etc

Nature March ‘97(MIT JDJ, Nature)

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12

3 45 67

4

2 2

6 6

WG InputLight-out

Light-in

Micro-Cavity (Q~300-1000) 90-degree Bend

~λ

Linear Guide (no data yet)

Ch1

Ch2

LightInput

120-degree Splitter

(A. Scherer, Caltech)

Experimental Realization of Guide, Bend, Splitter and Cavity Laser

Nano Lasers Bragg Fiber

Si

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The First Realization of 3D Silicon Photonic Crystal Operating at Communication Wavelengths, λ~1.55µm

180nm

(Wired magazine)

180nm6-inch waferuniform

Optics Letters 24, 49 (1999).

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What’s Next:

At optical wavelengths:GuidesBendsSplittersFiltersSwitchesLossesIn-coupling (fiber)Out-coupling (fiber)Optical network

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Full 6-Inch Wafer

3D “Metallic” Photonic-Crystal (the third kind)

10mm

(2, 0.5, 0.35, 0.18, 0.10 µm)

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Light Emission

Light Emission

The Operating Principle of These Light Emitters Are Different.

(1)LightEmittingDiode

(2)IncandescentLamp

VB

CB e-1e-1 e-1 e-1

+ + + ++

Semiconductor

Band gap

0

0.2

0.4

0.6

0.8

1

1.2

1.42ω∝

0

0.2

0.4

0.6

0.8

1

1.2

1.4Metal

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The Photonic-Crystal Emitter Is Perhaps The Third One.

Spon. Thermal Emission

0

0.2

0.4

0.6

0.8

1.0

PhotonicBand Gap

Freq

uenc

y

Light EmissionPhotonic DOS

PhotonicBand Gap

(3) Photonic-Crystal Emitter

Engineered DOS

(EM Vacuum)

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(2) Photonic-Crystal As an Efficient Light Emitter:

a0=1.5µm

a0=2.8µm

a0=5µm

0

2

4

6

8

10

0 1 2 3 4 5 6 Lattice Constant a

o (µm)

filling fraction ~30%

0

2

4

6

8

0 5 10 15 20 25Wavelength (µm)

Em

issi

on In

tens

ityao

40% Electric-to-optical efficiency Variable Emission-λCompact (~Watts/cm2)

λ=1.5, 4, 6, 7.5 µm

“ Device’s micro/nano−structure does matter! ”

(3) Lighting Application: An Incandescent Lamp Is Fundamentally Inefficient, Due To Its Broad Emission.

0

50

100

150

200

250

300

350

0 1 2 3 4 5Wavelength ( µm )

T=3000K

T=2500K

T=2000K

BB Radiation: Broad band

Eye-response: Narrow band

Wien Law:

Pow

er D

ensi

ty (W

/cm

2 )

[ ]kmT opeak −≅× µλ 2898

visible

(invented 1889by T. Edison)

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By A Proper Length Scaling, The Band-Edge PositionCould Be Shifted From 4, 2µm To Visible Wavelengths

0

0.2

0.4

0.6

0.8

1

-3 0 3 6 9 12 15 18Wavelength (µm)

"400nm"

band gap

1.8µm λ=4µm

emission

−λ= 4 and 1.8 µm (experimental result)− λ~400nm (simulation result with Au)

- Fabrication: feature size ~ 100-150nm. (Multi-layer e-beam/ nano-imprint) - Material: dielectric constant/ melting point. (material limit)

New materialSmall dimension

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33

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(4) Portable Electricity:The Successful Realization of a λ~2µm Emitter Is Important

for Thermal Photo-Voltaic (TPV) Power Generation

“A TPV generator converts radiation energy ( Qr ) into

electrical energy ( P ).”

* Compact! Quiet! Efficient! High power!

Basic Principle of a TPV system:Schematic of TPV Generator

Thermal emitter

PV Cell

Filter

burner

(Scientific American, p. 90-95, September 1998; Physics World, Aug. 9.49, 1998)

For A Conventional TPV System, Its Efficiency and Power Are Limited

By The “Broad” Thermal Radiation Spectrum

Modify thermal emission,Prevent light leakage at long-λ~70% of wasted radiation energy !!

1 2 3 4 5 6 7 8Wavelength (µm)

Ideal radiation pattern: Step function

suppressedemission

Eg(GaSb)

0

5

10

15

20

1 2 3 4 5 6 7 8Wavelength (µm)

BB Cavity Radiator (T=1500K)

η~11%,

P~3W/cm2

GaSb Response

Pow

er D

ensi

ty (W

/cm

2 )

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A PBG Narrow-Band Emitter Is Promising For Enhancing TPV Conversion Efficiency and Power

0

5

10

15

20

1 2 3 4 5 6 7 8Wavelength (µm)Q

r, P

ower

Den

sity

(W/c

m2 )

suppressedemission

Eg,GaSb PV Cell

(λ scaled by 30%)

3D “Tungsten” photonic lattice1.1µm

2

468

10

30

50

900 1100 1300 1500 1700 1900T (K)

Photonic Crystal

Emitter Window GaSb Cell

Reflector

BB

Stru.- WEr-Oxide

Conversion E

fficiency

(* upper limit case, Zenker et al IEEE Tran. Elec. Dev. Vol. 48, 367, 2001)

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a0=1.5µm

a0=2.8µm

a0=5µm

0

2

4

6

8

10

0 1 2 3 4 5 6 Lattice Constant a

o (µm)

filling fraction ~30%

0

2

4

6

8

0 5 10 15 20 25Wavelength (µm)

Compact and efficient Infrared light source(λ=1-10µm; P=100mW-10W)

Em

issi

on In

tens

ity

0

10

20

30

40

0 2 4 6 8 10 12 14Wavelength (µm)

λ=1.5 µm

Compact and efficient λ=1.5µm Pump Source( P=1W-10W; Area< 0.5 cm2)

Em

issi

on In

tens

ity

Electricity generation using thermal photo-voltaic technology Near-Visible Light Emission

ThermalRadiator

GaSbCell

0.5-1.5 µm 0.5µm

0.35 µm 0.18µmBurner