Luo, Yi
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Dr, Professor of Electronic Engineering, Tsinghua University, Beijing

Vice Director of Tsinghua National Lab of Information Science and Technology

Education Background

Mar. 1990 -- Ph.D. degree, Dept. of Electronic Engineering, The University of Tokyo, Tokyo, Japan, Dissertation: "Studies on Gain-Coupled DFB Semiconductor Lasers." Advisor: Prof. Kunio Tada. During his doctoral course, systematic studies on gain-coupled distributed feedback semiconductor lasers were carried out for the first time by Dr. Luo. He proposed and fabricated two kinds of gain-coupled distributed feedback semiconductor lasers with loss grating and gain grating using LPE and MOVPE, respectively.


Mar. 1987 -- M.S. degree, Dept. of Electronic Engineering, The University of Tokyo, Japan. Thesis: "Studies on the Gratings Used in DFB Semiconductor Lasers."  Advisor: Prof. Kunio Tada. During that time, Prof Luo made many experiences in the field of grating fabrication, dry etching and LPE epitaxy.


July 1983 -- B.S. degree, Div. of Physical Electronics, Dept. of Electronic Engineering, Tsinghua University. Major: Microwave Devices.


Working Experience

Dec. 1992- Full Professor, Dept. of Electronic Engineering, Tsinghua University, Beijing, P. R. China. 

Main research activities: Studies of gain-coupled distributed feedback lasers and monolithic integration of such lasers with electro-absorption modulator, and other kind of semiconductor optical devices.

During the recent 10 years, he has put many efforts into the studies on high quality group III-N materials’ epitaxy by MOCVD and MBE, blue and green LEDs and their applications for solid state lighting.

 

April 1992-Dec. 1992: Lecturer, Dept. of Electronic Engineering, Tsinghua University, Beijing, P. R. China.

Main research activities: Fabrication of GaAlAs/GaAs gain-coupled distributed feedback lasers with a loss grating using MBE.

 

April 1990-Mar. 1992: Member of Research staff, Optical Measurement Technology Development Co., Ltd., Musashino-shi, Tokyo 180, Japan. 

Main research activities: Studies on high performance gain-coupled distributed feedback semiconductor lasers using MOVPE. In this period, many leading work such as gain-coupled DFB laser with a conduction-type-inverted loss grating, ultralow chirp short optical pulse generation using gain-coupled DFB lasers were carried out by him.

 

Principle Professional Society Activities:

Convener of the Electronic Science and Technology Discipline, Discipline Review Group of the sixth Academic Degrees Committee of the State Council (China) (2009-present)

Expert of the Group of 863-8 area (2011-present)

Overseas Editor of Japanese Journal of Applied Physics (2004-present)

Overseas Editor of Applied Physics Express (2004-present)

Associate Editor of Journal of Lightwave Technology (2007-2012)

Associate Editor of IEEE Journal of Quantum Electronics (1996-1998)

Program committee member of ECOC (European Conference on Optical Communication) (2007-present)

Session Chair of 2013 International Nano-Optoelectronics Workshop (iNOW), Corsica, France (2013)

Organizing Committee Member of the Asia-Pacific Workshop on Widegap Semiconductors (APWS), Tamsui, Taiwan (2013)

Steering Committee Member of the 2012 International Nano-Optoelectronics Workshop, Berkeley and Stanford, USA (2012)

Program committee member of International Semiconductor Lasers Conference (2012, 2010, 2008)

Steering Committee Member of the 2011 International Nano-Optoelectronics Workshop, St. Petersburg, Russia and Würzburg, Germany (2011)

Co-chair of 2010 International Nano-Optoelectronics Workshop (iNOW), Beijing and Changchun, China (2010)

Scientific program committee Member of the 18th International Vacuum Congress (IVC-18), Beijing, China (2010)

Program committee member of Indium Phosphide and Related Materials conference (2010, 2008, 2007)

Advisory Committee member of the 2009 SODC (5th Joint Symposium on Opto- & Micro-elctronic Device and Circuits) (2009)

Steering Committee Member of the 2009 International Nano-Optoelectronics Workshop, Stockholm and Berlin, Germany (2009)

Program Committee and Session Chair of APOC (2001—2009)

International Advisory Committee member of the 2nd International Conference on Display and Solid State Lighting (2008)

Steering Committee Member of the 2008 International Nano-Optoelectronics Workshop, Lake Saiko and Shonan Village, Japan (2008)

Co-chair of 2007 International Nano-Optoelectronics Workshop (iNOW), Beijing and Lanzhou, China (2007)

Chair of Organizing Committee, The Eighth Chinese Optoelectronics Symposium, Taiyuan, China (2006)

Steering Committee Chairman of Sixth China Hi-Tech Fair International Forum on Semiconductor Lighting (2004)

Co-chair of Semiconductor and Organic Optoelectronic Materials and Devices, SPIE, Beijing (2004)

Conference Chair of Photonics Asia (2002)

Executive and Steering Committee Co-Chairmen of International Topic Meeting on Photoectronics,ITMPE’97(1997)

Steering and Program Committee Co-chair of International Symposium on Information Science and Technology, ISIST’96 (1996)

 

 

Scientific Accomplishments:

(1) High performance nano-optoelectronic devices and high-power electronic devices:

Quantum devices based on nano-structures are key components for quantum information technologies. His group is among the first to propose the single photon emitter based on quantum dot (QD) coupled with photonic crystal (PhC) cavity. Comprehensive investigation of the fundamentals of single photon sources has been carried out, including the PhC cavity mode properties, the cavity quantum electromagnetic dynamics, and the fabrication processes of PhC structures. He also proposed applicable models for the generation of entangled photon pairs on demand. Moreover, he did much fundamentals work on AlGaN/GaN based high-power electronic devices such as high electron mobility transistors (HEMTs) and Schottky barrier diodes (SBDs), including optimizing the 2-dimensional electron gas structures, Ohmic and Schottky contact, current collapse mechanism and passivation techniques.

 

(2) Three dimensional freeform optical system design method and optical system innovation in LED illumination. 

Usually, the design of optical system with prescribed luminance distribution pattern is essentially equivalent to solving a second order nonlinear Monge-Ampere partial differential equation, to which an analytic solution is normally difficult to find. For the first time, he proposed a simple and utility optical energy mapping model based on variable-separation and conservation of energy, then invented numerical simulation methods with nimble feedback correction function to resolve the problems faced in the construction of free-form optical surfaces, including strong normal vector errors, slow convergence and so on. This method has a serious advantages, e. g. physical model is very simple; almost arbitrary illumination distribution pattern can be realized by single freeform optical surface; compact freeform optical surfaces can be easily obtained, and so on. On the other hand, he brought forth many ideas concerning light distribution for LED lamps to eliminate optical contamination and waste. He invented several optical systems, including peanuts-type lenses for LED illumination. Up to now, over 280 thousand sets of LED lamps with the peanuts-type optical system have been installed. On the source system level, he invented the basic luminaire structure, which meets the requirements of total flux and thermal dissipation by alternating the number of LEDs with plane topology.

His work on optical system design of LED illumination shows for the first time the excellent energy-saving capabilities of LED lamps compared with traditional ones. Moreover, his work has significantly promoted the solid state lighting lamp industry of mainland China, which now has become the largest all over the world.

 

(3) 100 lm/W high power white light emitting diode (LED) material epitaxy and device fabrication technology:

He is also a pioneer to promote the solid state lighting based on III-nitride light emitting diodes (LEDs) in mainland China. Even today, he is one of the most important persons to plan and develop China’s LED industry. In 2001, he took the lead in industrialization of GaN-based LEDs in mainland China, and established the first whole LED product line from epitaxy to package at the time. He brought forward the two-dimension patterned substrate, designed and realized novel InGaN/GaN multiple quantum well (MQW) structure to decrease the dislocation density from 109 cm-2 to 107 cm-2, enhancing the radiation recombination efficiency of blue LEDs about 25% while maintaining stable peak wavelength over a wide injection range. This work is helpful to minimize the influence of polarization field in InGaN/GaN MQWs and improve the quality of LEDs. For the problem of the efficiency droop at high injection current, he clarified the reasons as the carrier delocalization and carrier leakage.

Due to the strong chemical bond of the III-nitrides, it is difficult to obtain high etch rate and low surface damage simultaneously. Based on the comprehensive investigation of the balance between chemical and physical etching mechanism, he developed inductively coupled plasma dry-etching technique with controllable selective etching ratio, low damage, and smooth etched surface. This work enriches the processing approaches of nitride micro/nano-structures, and makes it possible to fabricate some novel devices. Based on the above technological breakthroughs and other related technologies, he studied and developed high power white LEDs with luminous efficiency over 100 lm/W.

 

(4) Achievements on molecular beam epitaxy (MBE) technology:

He reported the all MBE grown AlGaAs/GaAs gain-coupled DFB lasers for the first time. He was the first in the mainland of China to investigate the solid phosphorus source MBE technology. By using valved-cracker cells, the fundaments of MBE growth of III-V compound semiconductors with two group V elements are investigated, and a novel thermodynamic model has been developed to simulate the growth process. His group has achieved the first lasing of 1.55μm wavelength range strained InAsP/InGaAsP MQW laser grown by SSMBE. Furthermore, his group has made comprehensive research on the growth of III-nitrides by plasma-assisted MBE. Especially, they have obtained high-quality AlN epi-layers which are among the best reports by MBE.

 

(5) Monolithically integrated light sources with DFB lasers and electro-absorption (EA) modulators:

Since early 1990s, he started the research on monolithic integrated light sources in China and incorporated gain-coupling mechanism in the integrated devices. In 1995, monolithic integration of 850 nm gain-coupled DFB laser and EA modulator was realized based on an independently proposed identical epitaxial layer (IEL) structure for the first time. In an IEL structure, the same active layer is shared by both the laser and the modulator, thus the device fabrication process is greatly simplified. Based on the optimization of the novel InP-based quantum well structure for laser diodes and modulators, invention of the fabrication technology resulting in very small device capacitance and wideband microwave packaging technology, he has successfully developed high-speed integrated light source transmitter modules for 2.5 Gb/s, 10 Gb/s, and 40 Gb/s optical fiber communications in China.

 

(6) Gain-coupled distributed feedback (DFB) lasers:

In 1988, Yi Luo proposed a novel absorption grating structure to provide periodical gain fluctuation, and for the first time realized a gain-coupled DFB laser. Purely gain-coupled DFB laser was then invented in 1990 by forming a novel gain grating structure based on MOCVD growth. Shortly after his return to China, an all-MBE-grown gain-coupled DFB laser was invented with novel GaAlAs/GaAs material growth technology in 1994. Compared with traditional index-coupled DFB lasers, gain-coupled DFB lasers exhibit a series unique properties, including high dynamic single-mode yield, low frequency chirp under modulation, high resistance to external optical feedback, and the possibility of ultrashort single-mode pulse generation. His original work has started the research of gain-coupled DFB lasers as a new kind of excellent light source for high-speed optical communications.

The control of the grating coupling strength is the bottleneck for the practical application. He brought forward a novel gain-coupled DFB LD structure in which grating coupling coefficienct can be easily controlled. Meanwhile, he developed the numerical design method for DFB LDs which can accurately simulate arbitrary grating structure.

 

Publications:

Published more than 240 journal papers. 100 papers in English are listed below.

 

1. L. WANG, D. YANG, Z. B. HAO and Y. LUO, Metal-organic-vapor phase epitaxy of InGaN quantum dots and their applications in light-emitting diodes, Chinese Physics, 24(6) (2015), 067303.

2. L. WANG, Y. C. XING, Z. B. HAO, Y. LUO, C. Z. SUN, Y. J. HAN, B. XIONG, J. WANG, and H. T. LI, Evaluation of internal quantum efficiency of blue light emitting-diodes, Scientia Sinica Physica, Mechanica & Astronomica, 45(6) (2015), 067304.

3. B. WANG, L. WANG, Z. B. HAO, and Y. LUO, Study on improving visible light photocatalytic activity of Ag3PO4 through morphology control, Catalysis Communications, 58(2015), 117-121.

4. Y. L. HU, Z. B. HAO, L. WANG, C. GENG, Y. LUO, and Q. F. YAN, Nano-fabrication and related optical properties of InGaN/GaN nanopillars, Nanotechnology, 26(7) (2015), 075302.

5. X. L. MAO, H. T. LI, Y. J. HAN and Y. LUO, Polar-grids based source-target mapping construction method for designing freeform illumination system for a lighting target with arbitrary shape, Optics Express, 23(4) (2015), 4313-4328.

6. C. WU, J. WANG, W. W. ZHANG, and Y. LUO, Modeling and simulation of ion-filtered inductively coupled plasma using argon plasma, Japanese Journal of Applied Physics, 54(3) (2015), 036101.

7. L. WANG, Y. C. XING, Z. B. HAO, and Y. LUO, Study on carrier lifetimes in InGaN multi-quantum well with different barriers by time-resolved photoluminescence, Physica Status Solidi B-Basic Solid State Physics, 252(5) (2015), 956-960.

8. X. W. LIU, C. Z. SUN, B. XIONG, L. NIU, Z. B. HAO, Y. J. HAN, and Y. LUO, Smooth etching of epitaxially grown AlN film by Cl2/BCl3/Ar-based inductively coupled plasma, Vacuum, 116(2015), 158-162.

9. D. YANG, L. WANG, W. B. LV, Z. B. HAO, and Y. LUO, Growth and characterization of phosphor-free white light-emitting diodes based on InGaN blue quantum wells and green-yellow quantum dots, Superlattices and Microstructures, 82(2015), 26-32.

10. J. LIN, B. XIONG, C. Z. SUN, D. MIAO, and Y. LUO, Analysis of frequency response of high power MUTC photodiodes based on photocurrent-dependent equivalent circuit model, Optics Express, 23(17) (2015), 21615-21623.

11. J. D. YU, L. WANG, D. YANG, Z. B. HAO, Y. LUO, C. Z. SUN, Y. J. HAN, B. XIONG, J. WANG, and H. T. LI, Improving the internal quantum efficiency of green InGaN quantum dots through coupled InGaN/GaN quantum well and quantum dot structure, Applied Physics Express, 8(9)(2015), 094001.

12. J. B. KANG, Z. B. HAO, L. WANG, Z. L. LIU, Y. LUO, L. WANG, B. XIONG, C. Z. SUN, Y. J. HAN, J. WANG and H. T. LI, Studies on carrier-blocking structures for up-conversion infrared photodetectors, Acta Physica Sinica, 64(17) (2015), 178502.

13. L. WANG, Z. B. HAO, Y. LUO, J. B. KANG, L. WANG, B. XIONG, C. Z. SUN, J. WANG, Y. J. HAN, H. T. LI, L. WANG, W. X. WANG, and H. CHEN, Semiconductor up-converter based on cascade carrier transport for infrared detection/imaging, Applied Physics Letters, 107(13) (2015), 131107.

14. W. Y. LI, Y. LUO, B. XIONG, C. Z. SUN, L. WANG, J. WANG, Y.J. HAN, J. C. YAN, T. B. WEI, and H. X. LU, Fabrication of GaN-based ridge waveguides with very smooth and vertical sidewalls by combined plasma dry etching and wet chemical etching, Physica Status Solidi A-Applications and Materials Science, 212(10) (2015), 2341-2344.

15. Y. X. E, Z. B. HAO, J. D. YU, C. WU, R. Z. LIU, L. WANG, B. XIONG, J. WANG, Y. J. HAN, C. Z. SUN, and Y. LUO, MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation, Nanoscale research letters, 10(1) (2015), 383.

16. C. Z. SUN, D. LIU, B. XIONG, Y. LUO, J. WANG, Z. B. HAO, Y. J. HAN, L. WANG, H. T. LI, Modulation Characteristics Enhancement of Monolithically Integrated Laser Diodes Under Mutual Injection Locking, IEEE Journal of Selected Topics in Quantum Electronics, 21(6) (2015), 1802008.

17. X. L. MAO, H. T. LI, Y. J. HAN and Y. LUO, A two-step design method for high compact rotationally symmetric optical system for LED surface light source, Optics Express, 22(S2) (2014), A233-A247.

18. X. N. ZHAO, B. XIONG, C. Z. SUN and Y. LUO, Low drive voltage optical phase modulator with novel InGaAlAs/InAlAs multiple-quantum-barrier based n-i-n heterostructure, Optics Express, 21(21) (2013), 24894-24903.