微腔光子学微腔光子学MicrocavityMicrocavity photonicsphotonics----Organic/Inorganic hybrid materials Organic/Inorganic hybrid materials based optical based optical microcavitiesmicrocavities and and applicationsapplications

Lei Xu

Department of Optical Science and EngineeringFudan University, Shanghai 200433, China

OutlinesOutlines

•• BackgroundBackground•• Important works in the fieldImportant works in the field•• Our worksOur works•• ConclusionConclusion

Researches on：

Microcavity optics

Materials and devices for integrated optics

Novel optical properties driven by ultrafast laser pulses irradiation

Photonics development =

New materials +

New device structures

Electronics

Micro-electronics

Integrated Circuit

VLSI circuit

Nano-electronics

Photonics

Micro-photonics

Integrated optics

Large scale integration

Nano-photonics

Vertical integration

光子芯片光子芯片 Photonic chipPhotonic chip

Optoelectronic system on chip

Optical interconnects

Optical Optical microcavitymicrocavity are important are important element in photonic integrated circuitelement in photonic integrated circuit

www.research.ibm.com/photonics/

A Fabry-Perot cavity

ν

FSR

Δν

Q = ν/ΔνFSR = c/2nLLight intensity in a cavity:Cavity enhancementPurcell effect )1/(

)2/(sin)/2(1)1/(

0220

RRF

IF

RII

−=

>>+

−=

π

ϕπ

transmission

transmission

I0

λmnd =2Mode formation requirement

• Light generation– Laser & cavity-enhanced LED

• Light routing and manipulation– Optical filters for WDM– Modulators and switches– Slow light: CROW

• Light interaction with matter– Cavity-enhanced photodetector– Spectroscopy and sensing– Non-linear optics– Optical tweezers & MOEMS– Cavity QED

Applications of optical cavities

Conventional cavity

Micro-cavity

VCSELs - vertical cavity surface emitting lasers

material difficulties: optical and electrical confinement

electrodes must be transparent

distributed Bragg reflector (DBR) mirrors (requires R > 99.9%)

active region

electrode

substrate

n-type DBR

p-type DBR

electrode

Edge emitters

Conventional lasers

requires cleaved surfaces and coat with thin film to control reflectivity

substraten-type

p-typeelectrode

Whispering gallery modes: Total internal reflection (TIR)

top-face

θinc

n(ω)

substraten-type

p-typeelectrode

electrodeactive region

electrodes must be transparent

mirrors

100% reflectivity from sidewalls

Vahala, Nature, 2003

High Q cavities: very low threshold laserUniversal cavity structure: UV laser 圣保罗教堂回音壁 瑞利

Optical microcavities

History of micro-cavity1939 Dielectric Resonators

(Propose WGM to create high-Q optical resonators)R. D. Richtmyer

1961 Stimulated emission into optical whispering modes of spheres(First experimental observation of WGM millimeter-sized

dielectric spheres of CaF2:Sm++ )C. G. B. Garret, W. Kaiser and W. L. Bond

1980 Observation of resonances in the radiation pressure on dielectric spheres

(Liquid droplets of micrometer-sized cavities)A. Ashkin and J. M. Dziedzic

1986 Lasing dropletsS. X. Qian, RK Chang

1992 Whispering-gallery mode micro-disk lasers (Two-dimensional semiconductor circular micro-disks)

S. L. McCall, A. F.J.Levi, R. E. Slusher

Topics (2010 ICTON)•Microcavity lasers and LEDs•Microresonator-based bio(chemical) sensors•Single-molecule sensors•Coupling and transport phenomena•Slow-light structures•Cavity opto-mechanics•Tunable cavities•Tuning optical properties of single emitters with microcavities•Optical bistability in microcavity structures•Quantum information processing with microresonators•Localized and quasi-localized photonic states in aperiodicstructures•Cavity polaritons and plasmons

Materials for optical microcavities

Semiconductors (Si, III-V, nano-materials)

RE-doped glasses

SiO2

Crystals (LiNbO3)

Polymers

Important Works

Science 280,1557 (1998)

标志性工作标志性工作11

标志性工作标志性工作IIII

Er doped silica sphere

Nature 421,925 (2003)

标志性工作标志性工作IIIIII

Cavity mode photon lifetimeτ=43ns, Q = 3 × 108

Ultralow level optical nonlinearity generation

Label-free optical bio-sensor detects environmental RI change

ANALYTICA CHIMICA ACTA 620, 8, 2008

Bio-sensing using optical microcavities

Tran

smis

sion

Wavelength

RI change

Using two microcavities with different chemical surface modification to detect DNA

Sensitivity: 6 pg/mm2

Biophysical Journal 85, 1974 (2003)

Optics Letters 31, 1319 (2006)Optics Express 15, 15523 (2007)

Opto-fluidic sensor

Single molecule detection with ultra-high Q cavity

Science 317, 783 (2007)

2πRn=mλ

whispering gallery modes (WGM)

Directional emissionDirectional emission

Stable WGM:Tunneling leakageWeak outputpoor directionality

588 590 592 5944000

5000

6000

7000

8000

Inte

nsity

(a.u

.)

Wavelength (nm)

in water P

Chaotic WGM:Refractive leakageIntense output possible

PHYSICAL REVIEW A 67, 023807 (2003)

Spiral-shaped cavity

Appl.Phys.Lett. 84(14) 2004

Physical Review Letters 100, 033901 (2008)Applied Physics Letters 94, 251101 (2009)

))cos(1()( 0 ϕεϕ += RR

Combining high Q and directional emission

Limacon type cavity

Wavelength conversion by changing the optical length of a cavity

Requirement for microcavity:High Q to allow long photon lifetime in the cavity

Nature Photonics 1, 293 (2007)

Optical frequency comb generation

Nature Photonics 450, 1214 (2007)

Frequency comb: 频率梳 Nobel prize 2007bring together ultrafast and ultra-precision

f = mf0 + foffset

Optical buffer with coupled microcavities

Nature Photonics 1, 65 (2007)

High Q surface plasmon polariton whispering gallery modes

Nature 457, 455 (2009)

ω = ck/n

ω << ck/nn >>1

Surface plasmon polariton表面等离子极化子

Opto-mechanics

Photo-energy/

Mechanical energy

conversion

Cool the microcavity to μK

(ground state of mechanical vibration)

Our worksOur works

C C O

O

Si

OC3H

OC3H

OC3H

(CH2)3H2C

H3C

SiO2PMMA

Zr OC3H8

ZrO2

Photo-induced polymerization

MAPTMS ZPO

Easy to prepare thin films of excellent optical quality

Easy control of refractive index

Versatile doping to obtain photonic materials (active, nonlinearoptical, …

Our approach: Organic-inorganic Materials

3英寸硅片上的集成光子器件

Integrated optical devices based on pattern-able organic/inorganic hybrid materials

Optics Express 14, 6029 (2006)Optics Express 16, 3172, (2008) Optics Express 16, 9844, (2008) J. Appl. Phys. 94, 4228 (2003) Invited talk: OECC, APOC

0 2 4 6 8 10 12 14 16

-25

-20

-15

-10

-5

0

cross-portbar-port

Inte

nsity

(dB

)

Applied Power (mW)

Switching power 5mW

20 30 40 50 60 70 80 90 100-40

-30

-20

-10

0

Temperature [oC]

Max

imum

Atte

nuat

ion

[dB

]

Thermal stability > 100 oC

采用可光学加工的复合材料，获得光学功能突出,兼备有机和无机材料优异性能的集成光子器件

Si

950 1000 1050 1100 1150 1200

-50

-40

-30

-20

-10

0

10

20

90 100 110 120 130 140 150

0

5

10

15

20

25

30

35

1051 1052 1053 1054 1055

-40

-30

-20

-10

0

10

Out

put P

ower

(dB

m)

Wavelength (nm)

η = 88.4%

Out

put P

ower

(mW

)

Pump Power (mW)

Outp

ut P

ower

(dBm

)

Wavelength (nm)

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.80.0

0.5

1.0

1.5

2.0

2.5

Yb

conc

entra

tion

(a.u

.)

Radius (mm)

均匀掺杂 分布掺杂

974 nm diode laser

OSA

980/1053 nm WDM

1053 nm fiber grating

Yb doped fiber

R=99% R=3.5%

Heavy Yb doping optical fiber and fiber laser

分布掺杂的溶胶-凝胶法制备重掺杂Yb光纤预制棒, Yb浓度均匀分布, 保证拉制的光纤高质量。

IEEE J.Lightwave Technology 26 3256 (2008) Slope efficiency 88%

Materials modification by laser light irradiation-To generate novel or enhanced optical functions

Optics Letters 2009Chemical Physics 2009J.Chem.Phys. 2008Appl.Phys.Lett., 2007

-150 -100 -50 0 50 100 150 2000.0

0.5

1.0

OK

E si

gnal

(a.u

.)

Delay Time (ps)

fs laser irradiated (6.5GW/cm2,50μm/s)

as prepared

非线性增强

飞秒激光辐照使硫系玻璃的三阶光学非线性系数增强50％, 可用与波导光开关，

缩短器件尺寸

1555 1556 1557 1558 1559-63

-62

-61

-60

-59

-58

Opt

ical

Pow

er (d

Bm

)

Bragg Wavelength (nm)

双折射产生两个谐振峰，可用一根光纤同时传感温度和应力， 可用于高灵敏度传感

飞秒激光直写的波导光放大器

Directional Lasing From Extremely Deformed Directional Lasing From Extremely Deformed MicroMicro--cavitycavity

a)

b)

c)

d)

buffer layerSi

active layermask

PMMA layer

microcavity

Fabrication Process

RhB doped photo-patternable organic/inorganic material

RhB doped organic/inorganic hybrid coatings

fiber

Direct UV patterning using organic/inorganic hybrid materials

Circular Disks and Square Disks

Improvement of Boundary Roughness after PMMA Coating

Bare disk Cladded disk

collecting lens

focusing lens

mirrorNd:YAG laser

532 nm

microcavity

optical multi-channelfiber bundle

monochromator

CCD

Computer

polarizer

Experimental Setup

耦合微腔 coupled microcavities

耦合微腔可以产生新颖的光学现象photonic molecule (PM)asymmetric-photonic molecule (AM)

IEEE JSTQE 12, 71 (2006)

θ=27.8º

Near field detection direction

fiberθ=27.8º

cavity shape

586 588 590

5000

10000

15000

Inte

nsity

(a.u

.)

wavelength(nm)

Directional laser emissionDirectional laser emission

Δθ=1.2 o

584 586 588 590 592

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

em

issi

on In

tens

ity

Wavelength (nm)0 60 120 180 240 300 360

0

5000

10000

15000

20000

25000

30000

35000

Emis

sion

Inte

nsity

(arb

.uni

t)

Emission angle θ (degree)

P

R

S 110o

30o

θ

L.Shang, et al., Appl.Phys.Lett., 92,071111 (2008)

extremely deformed microcavity

Single frequency whispering gallery mode laser

580 590 600 610 620 630 6400

50

100

150

200

250

Inte

nsity

(ar

b. u

nit)

Wavelength (nm)

R

eff

2

eff

Rn2

mRn2

πλλ

λπ

=Δ

=

Whispering gallery mode micro-ring laser

nm600nm40m50R

==Δ=

λλμ

@.

Much smaller than gain spectra

Smaller cavity Lower Q fabrication difficulties, electric & optical coupling

602 603 604 605 606 607 6080

50

100

150

200

250

Δλ

580 590 600 610 6200

6000

12000

Inte

nist

y (a

.u.)

Wavelength (nm)

Planar random cavity laserQ. Song & L Xu, Phys.Rev.Lett., 96, 033902 (2006), Opt.Lett. 32, 373 (2007)

VCSEL

DFB

effB n2Λ=λDye doped organic/inorganic hybrid DFB laser

Conventional single frequency (mode) selection techniques

600 605 610 615 620 625 630 635

0.0

0.4

0.8

1.2

1.6

2.0

25oC-o

34oC-o

25oC-e

34oC-e

34.5oC

Nor

mal

ized

Em

issi

on In

tens

ity

Wavelength(nm)

λmnd =2

Composite cavity laser

游标效应 Vernier effect:

1/L1

1/L2

1/(L2-L1)

L2

L1

L1=L2+δ

Mode selection in asymmetric coupled microcavity laser

D2D1

620 621 622-300

0

300

600

900

1200

1500

Inte

nsity

(ar

b. u

nit)

Wavelength (nm)

small ring resonancelarge ring resonance

RhB doped organic/inorganic hybrid coatings

fiber fiber

fiber fiber

dye/hybridcoating

Hybrid coating

Monochromator

CCD

580 590 600 610 620 630 6400

50

100

150

200

250

Inte

nsity

(ar

b. u

nit)

Wavelength (nm)

a

580 590 600 610 6200

200

400

600

800

1000

1200

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

c

590 600 610 620 6300

100

200

300

400

500

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

b

)( 21eff

2

DDn −≈Δ

πλλ

Modulation width

Neff=1.5, D=125μm, ΔD=6μmΔλ=10 nm

Modulated emission spectrum from coupled cavities

D2D1

105 110 115 120 125

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

I STH /

I TH

D1 (μm)

Multi-mode suppression

590 600 610 620 630 640 650

0

20

40

60

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

590 600 610 620 630 640 650

0

40

80

120

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

590 600 610 620 630 640 6500

500

1000

1500

2000

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

2ed peak

Incrasing pump power

596 598 600 602 604

0

10

20

30

40

50

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

b

Angular emission

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

400

Inte

nsity

(arb

.uni

t)

Emission Angle (degree)

J.Ryu, PRA 74, 013804 (2006)

Near field pattern Far-field pattern

θ

Tapered fiber coupled single frequency coupled microcavity laser

620 622 624 626 628 630

0

100

200

300

400

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

620 622 624 626 628 630

0

40

80

120

In

tens

ity (a

rb.u

nit)

Wavelength (nm)

Tapered fiber 1.5 μm

APM

600 610 620 630 640 650 66010

100

1000

10000

100000

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

aOutput

Waveguide edges

600 610 620 630 640 650 660100

1000

10000

100000

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

b

Single frequency oscillator + pre-amplifier

Integrated single mode micro-laser on chip L.Shang & L.Xu, Optics Letters, 33,1150 (2008)

Toward a unidirectional single frequency laser on chip

Spiral cavity

G.D.Chern et al,, APL 83,1710 (2003)

G.D.Chern, et al., Opt. Lett. 32, 1093 (2007)

A coupled spiral cavity

)/()( πεφφ 21RR 0 +=

0

30

6090

120

150

180

210

240270

300

330

580 590 600 610 6200

20

40

60

80

100

120

140

160

180

0 40 80 120 160 200 240 2800

500

1000

1500

2000

Inte

nsity

(a.u

.)

Pumped Power Density (μJ/cm2)

Inye

nsity

(a.u

.)

Wavelength (nm)

TE TM

a

Unidirectioanl emission from Spiral microcavities

590 600 610 620 6300

50

100

150

200

250

300

350

400

450

500

0 10 20 30 40 50 60 70 80 90 1000

50

100

150

200

250

300

350

Inte

nsity

(a.u

.)

Pumped power density (μJ/cm2)

Wavelength (nm)

a

Pump threshold=45 μJ/cm2

SpiralPump threshold=130 μJ/cm2

Ring: resonatorSpiral: resonance filter

Ring-spiral coupled microcavity resonance

600 605 610 615 620 625

0

10

20

30

40

50

60

Inte

nsity

(a.u

.)

Wavelength (nm)

forward backward

600 605 610 615 620 6250

50

100

150

200

Inte

nsity

(a.u

.)

Wavelength (nm)

forward backward

0

30

6090

120

150

180

210

240270

300

330

Uni-directional single mode lasing

Incrasing pump power

X.Wu & L.Xu, Appl.Phys.Lett. 93, 081105 (2008)

Single mode microcavity laser: possible applications

UV single mode laser: difficulty in conventioanl cavity fabrication (DBR)

Optical sensing

Passive sensing vs Active sensing

light propagation light emission

High Q, high sensitivity

Precisely controlled experiment, (critical coupling)

Single channel detection

Single frequency tunable input laser (<< 0.1 pm)

Parallel (2D) fast detection

Simple experimental setup

need high resolution spectrometer (> 10 pm)

Special mechanism to reduce spectral resolution requirement

Coupling variation induced ultrahigh sensitive label free bio-sensor by using single mode coupled microcavity laser

H Li & L. Xu, JACS 131,16612 (2009)

Setup

PumpSpectro--meter

Coupled Asymmetric Active MicrocavityCollection Lens

• Resonance shift vs hopping

1.345 1.350 1.355 1.360

623.75

623.80

623.85

623.90

623.95

624.00

Wav

elen

gth

(nm

)

Refrective Index1.3380 1.3383 1.3386 1.3389

-0.8

-0.4

0.0

0.4

0.8

ln(I

hopp

ed/I or

igin

al)

Refractive Index

Bio-sensing result

480pg/mL

80pg/mL

No BSA

Hopped mode

Wavelength

600 601 602 60

5648

4032

2416

BSA Con.(ng/mL) Wavelength(nm)8

0 10 20 30 40 50 60 70 80 90-3.6-3.0-2.4-1.8-1.2-0.60.00.61.21.82.43.0

BSA Lysozyme Goat IgG FITC-BSAln

(Iho

pped

/I orig

inal)

Concentration of BSA Solution (ng/mL)

Minimum observable BSA concentration80 pg/ml

Conventional sensing Coupling sensing

High RI agent

RI change sensing vs coupling variation sensing

Sticking of bio sample in the coupling region changes coupling coefficient

Reason of mode hopping

Imaging of fluorescent protein (cypet, FIRC-BSA)

613.5 614.0 614.5 615.0 615.5

Wavelength(nm)

No BSA

Second mode

First mode300ng/mL

622.0 622.5 623.0 623.5 624.0

Wavelength(nm)

No BSA

300ng/mLsingle mode

Thick polymer coating blocks coupling region

Thin polymer coating leaves coupling region partly open

1.330 1.332 1.334 1.336 1.338 1.340

0.00

0.04

0.08

0.12

0.16

Wav

elen

gth

shift

Δλ(

nm)

Refractive index

Sample A Sample B

Conventional RI sensing

Further proof of coupling variation induced ultrahigh sensitivity