1

The Science and Technology of Photonic Crystals

Shawn-Yu LinConstellation Professor of Physics

(Harnessing Light at Nano-Scales)

2

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

3

CONTENT

(I) Motivation (4)

(II) Definition and Introduction (12)

(III) Two Applications

4

(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

5

(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.

7

“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)

8

CONTENT

(I) Motivation

(II) Definition and Introduction

(III) Two Applications

9

“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

10

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)

11

(II) Definition of Photonic CrystalSi

SiO2

(from JDJ)

Silicon Crystal Structure Photonic Crystal StructureIssues:Fabrication

3D topologySymmetryµm and nm scale

12

3D Silicon Photonic Crystals(a diamond lattice symmetry)

Silicon Substrate (Nature Sep. 1998)

1.5µm

13

(1) Photonic Crystal and Crystal Symmetry

1

2

4

3

1234

14

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

13

42

1

23

4

DiamondLatticeStructure

AB

C

15

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).

16

.

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

- mold the flow of light on-chip -

17

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

18

(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

19

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

20

Photonic Crystal(New material for controlling light)

• 3D mirror• On-chip integration

• Micro-photonics• Nano-photonics

21

Applications

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

2. “Metallic” photonic-crystal Energy

22

*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!

23

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

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

Nature March ‘97(MIT JDJ, Nature)

24

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

25

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).

26

What’s Next:

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

27

Full 6-Inch Wafer

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

10mm

(2, 0.5, 0.35, 0.18, 0.10 µm)

28

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

29

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)

30

(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)

31

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

32

33

34

(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 )

35

36

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)

37

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