Optoelectronics and Semiconductor Group
Professor San-Liang Lee
Ph.D., University of California Santa Barbara, U.S.A.
Field of study: optoelectronic devices, optical communication networks,
optical integrated circuits
Key words: Tunable laser, Optical network, Wavelength conversion
URL: http://homepage.ntust.edu.tw/SLLEE/
Email: sllee@mail.ntust.edu.tw
Phone: 886-2-27376401(voice), 886-2-27376424(Fax)

1. The Subject and Aims of Research
Recent research aims at developing advanced optical switching technologies andkey components for next generation optical networks. The ongoing projects include
multiwavelength laser arrays, tunable lasers, wavelength converters, optical network
switching, optical performance monitoring, and optical signal processing. We are also
developing techniques for photonic integrated circuits, including quantum wellintermixing and hybrid integration. Semiconductor optoelectronic devices forbio-sensing and image display are also under our research interests.
2. Related Recent Research Topics(a) Multiwavelength laser arrays: we have demonstrated 32-wavelength DWDM
laser arrays with accurate wavelength registration and minimal wavelength
fluctuation. The wavelength selectable laser that integrates four novel tunablelasers with a MMI couples was successfully fabricated and can cover forty
50-GHz spaced channels. Currently, we are in collaboration with Prof. Yoshi
Nakano of University of Tokyo to develop multiwavelength laser arrays for
100 gigabit Ethernet applications

Fig.1 Wavelength-selectable lasers integrating 4 lasers and a MMI coupler（device is 3.5mm long）(b) High-speed and high-yield DFB lasers: we have realized coolerless 10Gbps
DFB lasers for metro and access networks. Novel two-section DFB lasers withasymmetric longitudinal structure were demonstrated to have highsingle-mode yield with simple fabrication. For their excellent wavelength andmode stability, the lasers are applied for wavelength conversion and opticalclock recovery.
Laser chip

L1

L2Fig. 2 Schematic of two-section DFB lasers and photo of packaged module(c) Performance Enhancement on WDM-PONs: We have enhanced theperformance by adding a FP etalon before the receiver of each optical network
unit. The etalon performs spectral reshaping and then waveform reshaping tothe downstream signals. This allows the use of low-ER downstream signals

that reduce the intensity fluctuation of RSOA- remodulated upstream signals.
This approach can also extend the transmission distance by reducing thetransient chirp. Colorless operation can still be obtained since the same etalon
can be used to enhance multiple wavelength channels.
(d) Optical performance monitoring for optical networks: we demonstrated
several novel optical performance monitoring techniques for applications inOADM and optical switches to monitor the channel quality, including channel
position, signal level, and OSNR. We are developing the photonic sampling
schemes for monitoring the Q-factor and dispersion.
(e) Optoelectronic devices: we are developing dual-wavelength (1.5/1.57μm)
DFB lasers and resonant-cavity enhanced photodiodes for gas sensing
applications. Novel LED-based linear sources are under development for
display and laser printing applications.
60
I =180mA

I =10mA

B

A

55
50

1.56

45
40

1.54

35
1.52

30

1.50

I = 0mAA

10SMSR (dB)

Wavelength ( μ m)

1.5820304050

252060oTemperature ( C)

Fig. 3 Wavelength switching fordual-wavelength DFB laser

Fig. 4 SEM photo of 2D photonic crystal
made by holographic exposure(f) Quantum well intermixing (QWI): QWI provides selective modification ofheterostructure bandgap profiles on the post-growth materials. We successfully
fabricated high-performance laser diodes using the QWI with low-energy
ion-implantation. Under the process, a blue shift of the wavelength in theintermixed QWs structure can be obtained. Thus, QWI process can be applied
Peak Wavelengthfor the fabrication of monolithic photonic integrated circuits (PICs).
14P+ ions@ bias 60 mA0o

Bias 60 mA @ 20 C

Intensity (dBm)-10Power (mW)

12Point defects
SiO2 implantation mask
InP buffer layer
InGaAsP stop etch layer
InP capping layer
MQW region
InGaAsP SCH
InP substrate

101515.59 nm-20-301520.87 nm-40-50
-60
1490

1500

81510

1520

1530

1524.90 nm

1540

Wavelength (nm)o20 C

1527.90 nm

o630 Co40 C

1531.96 nm

o50 C

4o60 Co70 C

21533.90 nm

00204060

80

100Current (mA)

Fig. 4 Schematic diagrams of the ionimplantation induced QWI process.

Fig. 6 CW L–I characteristics for QWI LD.

3. Selected Publications and Projects
Publications: Chiu-Lin Yao, San-Liang Lee, Ing-Fa Jang, and Wen-Jeng Ho, “Wavelength
Selectable Lasers with Bragg-Wavelength-Detuned Sampled Grating Reflectors,”J.
Lightwave Technology, vol. 24, no. 9, pp. 2480-2489, Sept. 2006.
Patents: San-Liang Lee and Ing-Fa Jang, Adjustable Monolithic Multi-Wavelength Laser
Arrays, U.S. patent 6,432,736. Aug., 2002
Projects: Enabling Technologies for WDM-PONs (NTPO)Awards: Advisor for Best Master Thesis Award of National Science Council, 2003