Center for Advanced Research in Photonics Department of Electronic Engineering, The Chinese University of Hong Kong Focus Areas Photonic Signal Processing.

Center for Advanced Research in PhotonicsDepartment of Electronic Engineering, The Chinese University of Hong Kong

Focus Areas• Photonic Signal Processing• Planar waveguide devices

Research Team:Professors K. T. Chan, Chester Shu, Hon Tsang, Chinlon Lin+ 4 research staff + 15 graduate students

Optoelectronic Laboratory


Examples of Research Output

• All-optical signal processing– Photonic ADC– Polarization diversity loop for polarization insensitive operation– Wavelength conversion using

• FWM in SOA• Birefringence Switching• Dual wavelength injection locking

– Data Modulation Format Conversion (RZ to NRZ and NRZ to RZ)– OTDM demultiplexing

• Waveguides– Polarization dependent frequency and polarization dependent loss compensation via

• FIB trimming• Magnetostrictive layer deposited on waveguide

– InGaAsP Waveguide Fabry-Perot filter (high speed tuneable via current injection)– Nonlinear Applications of SOI waveguides : Raman Amplification– Material properties (measure dispersion, Kerr effect & TPA in SOI waveguides)

• Ultrafast optics and nonlinear optics– Spectral measurement in time domain using dispersion – Two photon autocorrelation using InGaAsP and Si waveguides– Terahertz pulse generation and detection using ion implanted GaAs

200

240

280

320

360

400

-8 -6 -4 -2 0 2 4 6 8

Delay time (ps)

TP

A s

ign

al (

a.u

.)

T.K.Liang and H.K.Tsang, APPL PHYS

LETT 81 (7): 1323 AUG 2002


• Sampling in optical domain and quantization in electronic domain

Optical SourceSampling

Transducer

quantization

Optical Demux

Digital signal

processor

quantization: electrical signal

: optical signal

Microwave signal

Optical Source : Time and wavelength-interleaved pulses

Photonic ADCLee KL, Shu C: “Switching-wavelength pulse source constructed from a dispersion-managed SOA fiber ring laser” IEEE PHOTONICS TECHNOLOGY LETTERS 15 (4): 513-515 APR 2003

/ Fiber laser


•10 channel output from1 = 1560.14 to10 = 1569.47 nm

•Channel spacing: 1.03 nm

•Suppression of non-lasing mode > 20 dB

10 Gigasample/s Photonic ADC using 10-wavelength sampling pulses

•Overall repetition rate: 10 GHzIndividual operated at 1 GHz

•Pulse width: 21-26 ps

•Timing jitter < 0.2 ps


All-optical wavelength conversion

M.W.K. Mak, H.K. Tsang and K.Chan: “Widely tunable polarization-independent all-optical wavelength converter using a semiconductor optical amplifier,” IEEE Phot. Tech. Lett., vol.12, 525-527 (2000)

Input signal Converted signal

10 ps / div 10 ps / div

40 Gb/s wavelength conversion-12.0

-11.0

-10.0

-9.0

-8.0

-7.0

-6.0

-5.0

-36 -34 -32 -30 -28 -26

Received optical power (dBm)

log(

BE

R)

0.9 dB

Back-to-back

Converted

SOA

Pump 2 (P2)Pump 1 (P1)Signal (S)

C1

ConvertedSignal

PC1

PC2 PC3

PC4

PC5PBS

1 2

3

A

B

C

D

sP1

P2

CIsolator

WDM Demultiplexer

OC


Wavelength conversion: BOP FWM without external optical pump

Pump 1

OutputSOA

Signal

Pump 2

K. K. Chow, C. Shu, M. W. K. Mak and H. K. Tsang, “Widely tunable wavelength converter using a double-ring fiber laser with a semiconductor optical amplifier,” IEEE Photonics Technology Letters, vol. 14, pp. 1445-1447, October 2002.


Tunable 40Gbit/s optical source

HDF

SOA

PC2 Isolator

FFP

OpticalCouplerOC

C1

2

3

PC1

FPLD

RF Synthesizer

Output

Dispersive frequency multiplication

Mode-locked SOA fiber-ring laser

Mark W.K.Mak and H.K.Tsang: “Dispersive Frequency Multiplication for Wavelength-Tunable High Repetition Rate Pulse-Train Generation,”Optical Fiber Communications 2001

(Anaheim), 2001.

02468

101214161820

1540 1545 1550 1555 1560 1565 1570

Wavelength (nm)

Pul

sew

idth

(ps

)


Optical CDMA

Wang X, Lee KL, Shu C, Chan KT: “Multiwavelength self-seeded Fabry-Perot laser with subharmonic pulse-gating for two-dimensional fiber optic-CDMA,” IEEE PHOTONICS TECHNOLOGY LETTERS 13 (12): 1361-1363 DEC 2001


High speed tunable filter

• Tunable waveguide filter

Substrate

Guiding region

Cladding layer

High reflectivity coatingAnti-reflection coating

FP cavity made by anisotropic etching

(CAIBE)Input waveguide Output waveguide

E

E'

MM

H.K. Tsang et al. “ Etched Cavity InGaAsP/InP Waveguide Fabry-Perot Filter Tunable by Current

Injection,” IEEE J. Lightwave Tech, vol.17, p.1890-1895 (1999)

0

1

2

3

4

5

0 10 20 30 40 50 60

Current Injection (mA)

Pe

ak

Tra

ns

mis

sio

n S

hif

t (n

m)


Polarization compensation by magnetostriction

Magnetostriction: anisotropic strain induced by magnetic field

Saturation Magnetostriction constant ()=fractional change in length

External Magnetic field direction

y

x

SiliconThermal oxide

Buried OxideSilicon

SiliconThermal oxide

Ferromagnetic film

Buried OxideSilicon

0.0

0.5

1.0

1.5

No B-f ield B-f ield applied

DGD (ps)

Rib oxide w ith annealing

Whole w aveguide covered by TiO2

Whole w aveguide covered by CoFe

0

2

4

6


PDL (dB)

0.0

0.5

1.0

1.5


DGD (ps)

Rib oxide w ith annealing

Whole w aveguide covered by TiO2

Whole w aveguide covered by CoFe

0

2

4

6


PDL (dB)

P.S. Chan, H.K. Tsang, “Magnetostrictive Polarization Compensation on SOI Rib Waveguide”, 8th OptoElectronics and Communications Conference, Shanghai, China, Oct 2003.


Focused Ion Beam Etching for mode conversion and PDF adjustment

P.S. Chan, H.K. Tsang, C. Shu, “Mode Conversion and Birefringence Adjustment via Focused Ion Beam Etching for Slanted rib Waveguide walls”, to appear in Optics Lett. Nov. 2003.

Gallium Ion

Side view of trimmed portion of rib.

0%

20%

40%

60%

80%

100%

0 50 100 150

TE TMPercentage of Mode Conversion

Trim Length (m)

Top view of trimmed rib SOI waveguide by 45 degrees, 10m

-16

-14

-12

-10

-8

-6

1550.02 1550.06 1550.10 1550.14 1550.18

Wavelength (nm)

Output

power (dBm)TE

TM

Compensated

by 10um FIB

trimming

WITHOUT

compensation


Silicon oxynitride switch

A Zhang and KT Chan “Characterization of the optical loss of an integrated silicon oxynitrideoptical switch structure,” Appl. Phys. Lett., Vol. 83, No. 13, 29 September 2003

trench for liquid crystal material for switching


New topics of current interest

• Raman gain in silicon waveguides (HK Tsang)

• Quantum encryption using multiphoton entanglement generated from spontaneous parametric down conversion (KT Chan)

• Photonic Crystal Fibers for signal processing and sensors (CT Shu)

Si

SiO2

Si (substrate)

n+p+

DFB Laser

MonochrometerPower Meter

Couplerwaveguide

1683 1684 1685 1686Stokes (nm)


Future Directions in planar waveguides & nanophotonics

• Possible future directions:– Miniaturization of planar waveguide components using silicon wires

• Requires considerable investment to improve dry etching capability (HKUST equipment is inadequate for etching submicron waveguides)

• Work needed on improving coupling loss and polarization dependence

– Periodic structures (thin film photonic crystal)?

From Richard M. De La Rue “Photonic Crystal and Photonic Wire Devices and Technology” ECOC 2003

“The technological problems involved in fabrication with sufficient precision and acceptable propagation losses continue to present a major challenge for device engineers and physicists.”

“… the likely impact of photonic crystal and photonic wire…is considerable. Within a small number of years, we are likely to witness moderately high volume production of devices which will incorporate the thinking that has been developed over a period of sixteen or more years”


• A 3-year project with $12.334 million total funding from ITF and sponsors

Project period: June 2001- May 2004

Funded by:

W.T. and H. S. ChanW.T. and H. S. ChanChristian ServiceChristian Service

Foundation LimitedFoundation Limited

Major Equipment:• Optical Thin Film Coating System• Laser Welder• Automated Alignment System• Polishing System• Auto-Stepback Wedge Bonder• Precision Die Bonder• Wafer scriber

Photonic Packaging Laboratory


Mission:To help build a photonic packaging infrastructure in Hong Kong by:1. support R&D in industry and academia;2. technical training;3. facilitate technology transfer to industry.

Technical Team:13 engineering faculty staff from IE, EE, and ACAE departments, plus 3 full-time technical staff(Dr. Ming Li, April PS Chung, MT Yeung)

PI : Hon Tsang, Chester ShuCoordinator: Frank Tong

Photonic Packaging Laboratory


Ferrule & single mode fiber

Protector (rubber)

Ferrule housing

TO-housing

TO-PD

Ferrule & single mode fiber

Protector (rubber)

Ferrule housing

TO-housing

TO-PD

DFB Laser P-I Curve

0

0.5

1

1.5

2

0 5 10 15 20Current (mA)

Ou

tpu

t p

ow

er (

mW

)

Bare chipUn-cool BTF

DFB laser diodes packaged in-house using the laser welder reach up to 70% coupling efficiency.

Butterfly Type Edge Emitting Laser (BTF-FP/DFB)

Ferrule holder

Thermistor

Laser Diode (LD)

Monitoring Photodiode (PD)

-TEC+TEC

-PD+PD

Thermistor

+LD

-LD

Submount

Protector ring

Thermal Electric Cooler (TEC)

Lens

DFB Laser P-I Curve

0

0.5

1

1.5

2

0 5 10 15 20Current (mA)

Ou

tpu

t p

ow

er (

mW

)

Bare chipUn-cool BTF

DFB laser diodes packaged in-house using the laser welder reach up to 70% coupling efficiency.


Ferrule holder

Thermistor

Laser Diode (LD)


-TEC+TEC

-PD+PD

Thermistor

+LD

-LD

Submount

Protector ring


Lens


Ferrule holder

Thermistor

Laser Diode (LD)


-TEC+TEC

-PD+PD

Thermistor

+LD

-LD

Submount

Protector ring


Ferrule holder

Thermistor

Laser Diode (LD)


-TEC+TEC

-PD+PD

Thermistor

+LD

-LD

Submount

Protector ring


Lens

Packaged Components:

Lasers, Photodetectors

Pigtailed TO-Can photodetector

Butterfly FP/DFB laser module

• AR and HR coated FP Laser

Milestone 1 – Fiber attach and basic optical coatings

1 Gb/s

Completed 31/7/2002


• AR coatings (<0.05% reflectivity) on Si and III-V semiconductors

HR overlay coatings to enhance reflection and reduce PDL from gold mirrors

Milestone 2: High Specification CoatingsCompleted 28/2/2003

material t (nm)

8. Ta2O5 192

7. SiO2 310

6. Ta2O5 192.89

5. SiO2 308.7

4. Ta2O5 193.19

3. SiO2 308.04

2. Ta2O5 193.32

1. SiO2 278.61

0. Au 50

Si sub.


Milestone 4: Fiber array attachment and MEMS packagingdue 30/11/2003

Si optical bench

Glass

Collimating fiber

Si U-grove / V-grove

Bonding padsSupporting Si

MEMS

Output 1 Output 2

Input 2Input 1


Milestone 5: Multi-component packaging

• Development of novel self-aligned flip-chip technology for hybrid integration of laser arrays to planar waveguides

• Collaboration with Institute of Semiconductors, Chinese Academy of Sciences in Beijing on fabrication of compatible FP laser array

• Collaboration with Shipley on photoresist suitable for 3D topography (needed for patterning metal at bottom of trench

due 31/5/2004

waveguide Laser chip

Side alignment pedestals

Ti/Au/Ti/SiO2 Plated Ni/Ausolder

Side alignment

pedestal

Laser die

Substrate

Center for Advanced Research in Photonics Department of Electronic Engineering, The Chinese University of Hong Kong Focus Areas Photonic Signal Processing.

Documents

advanced research

optical domain

research staff

wavelength pulse source

gbs wavelength conversion

external optical pump

electrical signal

output soa signal pump