Publisher: C. C. Yang          Editors: Jui-che Tsai, Hsiao-wen Lin          June 20, 2006

News          Special Report          Profiles          Laboratory Descriptions

Latest News

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  Visiting Professor: Dr. Ian T. Ferguson, Georgia Institute of Technology, US.

Since March 1st, Dr. Ian T. Ferguson, an expert in solid-state lighting and wide-band-gap semiconductors, has joined the GIEOE as a Visiting Professor to offer a new course on ¡§solid-state lighting.¡¨  Prof. Ferguson received his Ph.D. degree in Semiconductor Physics from the University of St. Andrews in Scotland and is currently a Professor at Georgia Tech in the U.S.  Professor Ferguson¡¦s expertise include MOCVD growth and fabrication of GaN-Based materials, especially with an emphasis on LEDs for UV and bio applications.  Prof. Ferguson will stay with us till the end of July 2006.

For more information about Professor Ferguson, please visit the website at: http://www.ece.gatech.edu/faculty/fac_profiles/bio.php?id=34

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  Research collaboration with Chi Mei Optoelectronics

Since January of this year, NTU has begun a research collaboration project with Chi Mei Optoelectronics in Tainan, with a total budget of 8 million NTD.  Chairman C. C. Yang serves as the Chief Investigator of this project.  Eight professors are involved in the project, including Hoang-Yan Lin, Chih-I Wu, Jiun-Haw Lee, Jian-Jang Huang from the GIEOE; Yun-Shiuan Liao from the Department of Mechanical Engineering; Wei-Fang Su and Feng-Yu Tsai from the Department of Materials Science and Engineering; and Tzong-Lin Wu from the Department of Electrical Engineering.  This project focuses on the related topics of the display technology.

  Drs. Chen-Shui Tsai and Tingye Li have been appointed to serve as the

      Distinguished Research Chair Professors of the GIEOE

NTU has approved the continuing appointments of Drs. Chen-Shui Tsai (Fellow of IEEE, OSA, SPIE, Academia Sinica) and Tingye Li (Fellow of IEEE, OSA, US National Academy of Engineering, Academia Sinica) as the Distinguished Research Chair Professors of the GIEOE.

  About Dr. Tingye Li

Tingye Li recently retired from AT&T on December 1, 1998.  Until then, he has been a Division Manager in the Communications Infrastructure Research Laboratory of AT&T Laboratories at Red Bank, New Jersey.  He is now an independent consultant in the field of lightwave communications.  Since joining AT&T Bell Laboratories in 1957, he has worked in the areas of antennas, microwave propagation, lasers and optical communications, in which he has contributed more

than 100 journal papers, patents, books and book chapters.  His early work on laser resonator modes established the basis for the understanding of laser operation.  Since the late 1960s, he and his groups have been engaged in pioneering research on lightwave technologies and systems, which are now ubiquitously deployed in all arenas of telecommunications.  His latest work with his colleagues on amplified wavelength-division-multiplexed transmission systems, which they were the first to advocate for upgrading the transmission capacity of long-distance telecommunications networks, has revolutionized lightwave communications.

He holds a Ph.D. from Northwestern University, Evanston, Illinois.  He is a Fellow of the Optical Society of America, the Institute of Electrical and Electronics Engineers, the American Association for the Advancement of Science, and the Photonic Society of Chinese-Americans.  He is also a member of the National Academy of Engineering, the Academia Sinica (Taiwan) and the Chinese Academy of Engineering.  Among the many awards he has received are the IEEE 1975 W. R. G. Baker Prize, the IEEE 1979 David Sarnoff Award, the OSA/IEEE 1995 John Tyndall Award, the OSA 1997 Frederic Ives Medal/Jarus Quinn Endowment, the 1997 AT&T Science and Technology Medal, the 1981 Alumni Merit Award from Northwestern University, and Achievement Awards from the Chinese Institute of Engineers/USA in 1978, the Chinese-American Academic and Professional Society in 1983, and the Photonics Society of Chinese-Americans in 1998.  He was named an honorary professor at many universities in China (including Tsinghua Univ., Shanghai Jiaotong Univ., Beijing Univ. of Posts and Telecommunications, Northern Jiaotong Univ., Fudan Univ., Nankai Univ., Tianjin, Univ., Univ. of Electronic Science and Technology of China, and Qufu Normal Univ.), and was granted an honorary Doctor of Engineering degree by National Chiao Tung University in Taiwan.  He has been active in various professional societies, and was President of the Optical Society of America in 1995.

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  About Dr. Chen-Shui Tsai

Born in 1935, Fellow Tsai graduated from the Department of Electrical Engineering of the National Taiwan University in 1957 and passed the Civil Service Senior Examination for engineers in 1958.  In 1965, he obtained his Ph.D. from the Department of Electrical Engineering of Stanford University.  He worked for three and a half years at Lockheed Palo Alto Research Center and was recruited by

Carnegie Mellon University in 1969 as an Assistant Professor of the Department of Electrical and Computer Engineering and became a Professor in 1974; in 1979, he was recognized as a distinguished professor.  In 1980, Dr. Tsai was employed by the University of California, Irvine, as a Professor of the Department of Electrical Engineering and Computer Science; from 1985 to 1986, for a span of one year and a half, he was the department Chair, and in 1991, recognized once again as a distinguished professor.  Dr. Tsai used to be a Distinguished Research Fellow and Preparatory Director of the Research Center for Applied Sciences of the Academia Sinica.

Fellow Tsai¡¦s research fields include integrated acoustic optics, integrated magnetic optics, magnetic microwave devices, ultrasonic microscopy, and so on.  With many papers and publications, he had won over ten teaching and research awards and recognitions, including International Microoptics Award, Best Paper Award and Distinguished Research Lectureship of IEEE, Distinguished Research Lectureship and Best Teaching Award of the University of California, Irvine.  He is also a Fellow of the Academia Sinica and four international associations: IEEE, OSA, AAAS, and SPIE.

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  Visit of Professor Shun-Lien Chuang, University of Illinois at Urbana-Champaign

Shun-Lien Chuang of University of Illinois at Urbana-Champaign visited the GIEOE on March 22nd, 2006.  He presented a seminar on ¡§Slow Light Using Semiconductor Quantum Devices.¡¨ 

Professor Chuang graduated from the Department of Electrical Engineering of NTU and received his Ph.D. degree in Electrical Engineering and Computer Science from MIT.  From then until now, he has been serving as a faculty member at the University of Illinois, Urbana-Champaign, US.

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  Professor Shou-Chien Shih of Art History made a presentation at ¡§The Photonics

      Forum on the Reflection of the Humanities.¡¨

Professor Shou-Chien Shih was a former Director of the National Palace Museum. He is a Research Fellow in the Institute of History and Philology of the Academia Sinica.  He served as the Director and a Professor in the Graduate Institute of Art History, National Taiwan University. 

On March 24, 2006, Professor Shih was invited to give a talk entitled ¡§Cheng-Kung Cheng Meets Marie-Antoinette?  Humanities Concerns during the Digital Development¡¨ for ¡§The Photonics Forum on the Reflection of the Humanities.¡¨  Faculty and students of the GIEOE participated enthusiastically at the talk.

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Special Report

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  Dr. Tien-Pei Lee visited the GIEOE

          (February 27, 2006)

As a world-renowned expert in photonics, Dr. Tien-Pei Lee is a Fellow of IEEE, OSA, and PSCA (Photonic Society of Chinese Americans).  He is the pioneer in the fields of light-emitting diodes, photodetectors, semiconductor lasars, and theories and applications of optical-fiber communications.  He holds many U.S. and international patents, and published over 200 technical papers and ten specialized books. 

Photo of Dr. Tien-Pei Lee (left) taken with Chairman C. C. Yang

Dr. Lee is not only well accomplished in the field of photonics but also an enthusiast in promoting photonics scholarly researches.  In 1983, he was the Visiting Editor of IEEE Transcations on Electronic Devices; from 1986 to 1988, the Associate Editor-in-chief of IEEE Journal of Lightwave Technology.  He also had served as the committee member or Chairman in many international electro-optics conferences (OSA, IEEE/LEOS, OFC). 

Distinguished internationally in the fields of optical fiber communication and electro-optics, from 1984 to 1997, Dr. Lee was the Chief Researcher and Director of the Electro-Optics Department of Bell Communication Research, Bellcore; in 1997, he was the Program Director of the Electronic and Communications Systems Division of National Science Foundation.  Dr. Lee also consulted for the Department of Electric Engineering of Princeton University and Sarnoff.  He is experienced in integrating and promoting photonics communications, electro-optical technology, and the electro-optics industry.  Currently, he is a consultant of the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. 

During Dr. Lee's visit, he discussed with the faculty members of the GIEOE and provided valuable guidance to the Institute.

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  GIEOE Faculty Visited National Nano Device Laboratories (NDL)

April 24, 2006

National Nano Device Laboratories, Hsinchu Science Park

Professors of the Institute and Director Ni (front row, middle) and Dr. Wu (front row, second from the left) of NDL

On April 24, Chairman Yang led ten professors of the Institute to visit National Nano Device Laboratories (NDL), which is part of the National Applied Research Laboratories.  NDL focuses on the research and development of advanced nano devices technology.  In the past, they emphasized the research on electronic devices.  Recently, NDL expanded the research areas to cover electro-optics, magnetic and biomedical-nano-related research.  Professors joining this visit program include: C. C. Yang, Sheng-Lung Huang, Zhe-Chuan Feng, Chee-Wee Liu, Hoang-Yan Lin, Ding-Wei Huang, Snow H. Tseng, Guo-Dung Su, Jiun-Haw Lee, and Yun-Li Li.  During the visit, the Diretor of the Center, Dr. Wei-Xin Ni, first made a briefing about NDL.  Then he guided the professors a tour for the facilities.  NTU professors and NDL researchers discussed the possibilities of research cooperation.

Pictures from the visit:

Discussion Visiting the laboratories

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  GIEOE Faculty Visited AUO Optronics Corp.

April 27, 2006

Po-Yen Lu, Vice President of AUO (front row, fourth from the left) and professors of the Institute

On April 27, 2006, to promote the research cooperation with AUO, Chairman C. C. Yang led 10 faculty members of the GIEOE to visit AUO, including Professors Sheng-Lung Huang,  Zhe-Chuan Feng, Hoang-Yan Lin, Chih-I Wu, Yih-Peng Chiou, Snow H. Tseng, Guo-Dung Su, Jiun-Haw Lee, Wing-Kit Choi, and Yun-Li Li.  In the past three years, the Institute faculty members have visited AUO once every year for promoting the research cooperation.  After Quanta Display Inc. merges into AUO, AUO will become one of the top three LCD companies in the world.  The other top companies are Korea¡¦s LG and SAMSUNG.  During the visit, AUO¡¦s Executive Vice President, Dr. Po-Yen Lu, and Vice President of AUO Technology Center, Dr. C. T. Liu, joined the presentations of NTU professors and discussed the technical issues for further cooperation.  The Institute has a close cooperation relation with AUO.

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Profiles--Faculty Members

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Sheng-Lung Huang

Professor

Professor Huang received the B.S. degree from the Department of Electrical Engineering, National Taiwan University in 1986, and the M. S. and Ph. D. degrees from the Department of Electrical Engineering, University of Maryland, College Park in 1990 and 1993, respectively.

He joined the Institute of Electro-Optical Engineering, National Sun Yat-Sen University in 1993, and became a Professor in 1999.  He served as Director of the Institute of Electro-Optical Engineering, National Sun Yat-Sen University from April 2003 to Jan. 2006.  Since Feb. 2006, he joined the Graduate Institute of Electro-Optical Engineering and Department of Electrical Engineering, National Taiwan University.

Dr. Huang is a senior member of the IEEE Lasers and Electro-Optics Society (LEOS), and a member of the Optical Society of America and the Photonics Society of Chinese-Americans.  He is presently served as Chairman of IEEE LEOS Taipei Chapter and a Topical Editor of Optics Letters.

Snow H. Tseng

Assistant Professor

Snow Tseng was born in Connecticut, USA.  At the age of five, his family moved back to Taiwan.  As a child, Snow has shown great passion in the mystery of natural science.  As a result, he pursued a major in physics during college and got his bachelor¡¦s degree at National Taiwan University in 1994.  After college, he continued to pursue research in natural science as he worked as a research assistant at the Synchrotron Radiation Research Center (SRRC), Taiwan.  SRRC was one of the most advanced synchrotron research lab in the whole world at that time, where Snow had the opportunity to work with many excellent scientists; he learned knowledge and skills regarding synchrotron radiation, photoemission spectroscopy, and ultra high vacuum techniques.  Later, Snow helped establish a new X-ray photoemission laboratory.  After studying abroad in Taiwan for 18 years, he returned to the United States to further pursue a PhD in soft condensed matter physics at the University of Chicago.

Not sure if it was destiny, Snow was diagnosed of brain tumor (acoustic neuroma) in 1997.  Having gone through 7 brain surgeries, he was on medical leave from graduate school for two years, and walked through the Valley of Death multiple times.  The situation was so nasty that National Taiwan University Hospital was reluctant to accept him as an in-patient.  It is interesting how Snow miraculously survived such catastrophe, and even later became an Assistant Professor at National Taiwan University. 

Due to serious infection of his brain stem, half of Snow¡¦s body was paralyzed¡Xhe eyes couldn¡¦t focus, and had trouble breathing.  During this long tragic period in the hospital, Snow had much time to ponder upon his goal of life.  After he recovered from the illness, Snow decided to switch majors to pursue a PhD in electrical engineering instead at Northwestern University, so that he could do research in the field of biomedical optics.  (Even though Snow was interested in the medical science, he knew he is unlikely to become a medical doctor, since he was never comfortable with bloody scenes.  Therefore, he decided to help improve the medical science instead of being a medical doctor himself.)  More importantly, in addition to exploring the mysteries of Nature, Snow¡¦s goal is to pursue research that is more likely to be realized within his lifespan, so that he will be able to see the outcome of his effort with his own eyes.  Furthermore, he is interested in participating in pushing further the research frontier in biomedical optics.

While pursuing his PhD at Northwestern University, Snow has tried to expand his field of interest and to explore various different fields in order to find where his passion lies.  In the summer of 2000, he worked at Northrop Grumman (a famous defense science company), and learned a lot about systems engineering.  The next summer, Snow worked as a visiting scientist at Sony Computer Laboratory in Tokyo, Japan.  During his visit at the Interaction Laboratory at Sony, Snow had a lot of hands-on experience with the most cutting-edge human-computer interface.  He worked on hardware development in addition to theoretical analysis of tactile feedback mechanisms (this was a new technology, and little theoretical basis has been established at that time.)  As a result, Snow learned to develop new theories and models for a new technology.  In 2002, Snow worked as a visiting scholar at Lawrence-Livermore National Laboratory, California, USA, where he developed a new parallel optical simulation software which later became the foundation of his later research.  These various learning experiences has helped Snow broaden his research viewpoint and built connections with people from various disciplines.  More importantly, through these multi-disciplinary seeking experiences, Snow gradually figured out where his career passion lies and determined his future research direction. 

In February 2006, Snow returned to National Taiwan University for an assistant professor position at the Graduate Institute of Electro-Optical Engineering.  The course he is currently teaching is: ¡§Light Scattering Simulation of Optical Systems.¡¨  Snow¡¦s primary research interest is studying the phenomena of light scattering by macroscopic biological random media by means of rigorous numerical solutions of Maxwell¡¦s equations. 

Due to the extreme complexity of the problem of light scattering by biological tissues, heuristic approximations are commonly employed in the research of tissue optics.   Biomedical optics is one of the foci in modern research.  However, in order to develop effective optical diagnostic techniques, it is necessary to first precisely understand the difference in optical characteristics of normal and abnormal tissues, upon which identification and diagnosis can be made.  By employing the simulation software he has developed, Snow¡¦s research goal is to analyze the optical characteristics of macroscopic biological random media (e.g.: biological tissues), which will help advance the bio-optics technology. 

Snow¡¦s view of the future development of tissue optics is¡Xsome day in the near future, people will be able to have a cheap, real-time cancer screening at any convenience store, such as 7-eleven, Familymart, Walgreens, etc., so that cancers can be early detected and cured at an early stage.

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Yun-Li Charles Li

Assistant Professor

Prof. Yun-Li Charles Li graduated from National Taiwan University (NTU) in 1995 with a bachelor degree in Physics.  After 2-year military service, he pursued his Master and PhD degree with Prof. Schubert in Boston University.  His research work focused on Gallium Nitride (GaN) light-emitting diodes (LEDs) and solid state lighting (SSL) applications.  Prof. Li transferred to Rensselaer Polytechnic Institute with Prof. Schubert in 2002 and received his PhD degree there in 2003.

After his PhD study, Prof. Li joined eLite optoelectronics, Inc. in San Jose, CA, for research on high power LEDs.  He has developed 1 watt and 3 watt LED chip with the patented design of optical vacuum array (OVATM).  The luminous efficiency can achieve as  high as 50 lm/W.  In 2005, he decided to come back to Taiwan and joined Formosa Epitaxy, Inc.  He was in

charge of the Process Integration Department and has developed high power LED chips with double close loop electrode design.

Prof. Li joined Graduate Institute of Electro-Optical Engineering in NTU in 2006.  His research interests focus on GaN material and device applications.  In addition, he is also interested in developing the solid state lighting system with multi-LED chips, so called ¡§Smart Lighting System.¡¨  Smart lighting system takes advantages of the controllability of spectrum from multi-LED illumination sources.  This system is able to be utilized in different illumination systems with very high luminous efficiencies.

For the last few years, the optoelectronics industry has been rising and flourishing.  Taiwan plays a very important role in the world in this field including optical communication, display and light-emitting devices.  However, we don¡¦t have enough key technologies for these industries to prevent from low gross margin or lawsuits of patent infringement.  We do have very well-trained students and engineers with very good knowledge.  What we need to improve is ¡§Innovation¡¨ and ¡§Marketing¡¨ abilities.  Unfortunately, we cannot just study these abilities from books or school education.  We can only learn and cultivate these from our lives with time.  Thus, I would expect students not only study harder but live harder.  Always care about what is happening in the world and the change of it.

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Laboratory Descriptions

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Professor C. C. Yang¡¦s Research Laboratory

1. Metal-organic Chemical Vapor Deposition (MOCVD)

    (1) Growth of InGaN/GaN quantum wells, quantum dots, nano-columns

          and other nitride nanostructures

    (2) Selective growth of InGaN/GaN quantum dots and nano-columns

    (3) Growth of InN and indium-rich InGaN for solar cell application

    (4) Growth of nitride compounds on LiAlO substrate

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The MOCVD system

An atomic force microscopy image of InGaN quantum dots

2. Ultrafast Spectroscopy

    (1) Novel ultrafast spectroscopy techniques

    (2) Ultrafast carrier dynamics in InGaN/GaN nanostructures

    (3) Ultrafast carrier dynamics in ZnO nanostructures

    (4) Ultrafast phenomena of surface plasmon polariton

3. Nano-material Analysis

    (1) High-resolution transmission electron microscopy

    (2) High-resolution X-ray diffraction

    (3) Strain state analysis

4. Photonic Crystals and Surface Plasmonic Crystals

    (1) Modeling of photonic crystals and surface plasmonic crystals

    (2) Fabrication of photonic crystals and surface plasmonic crystals

    (3) Light-emitting devices with photonic crystals and surface plasmonic crystals for light emission

         enhancement

5. Fabrication of White-light Light-emitting Diodes (LEDs)

    (1) Design and fabrication of multi-wavelength LEDs

    (2) Fabrication of red LEDs with InGaN/GaN quantum wells

    (3) Implementation of high-efficiency, phosphor-free, single-chip, all-semiconductor white-light LEDs

    (4) Implementation of white-light LEDs with II-VI nano-crystals

    (5) Fabrication of LEDs with photonic crystals and surface plasmonic crystals

6. Bio-photonics ¡V Optical Coherence Tomography (OCT)

    (1) Spectral-domain optical coherence tomography

    (2) Oral cancer diagnosis with optical coherence tomography

    (3) Simulation of optical coherence tomography

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Professor Sheng-Lung Huang

Solid-State Laser Crystal and Device Laboratory

The major research areas of the Solid-State Laser Crystal and Device Laboratory are on the growth of laser and nonlinear crystal fibers, and laser technologies in order to realize compact and high efficient lasers with excellent mode quality for applications in optical communications, nano-photonics, bio-photonics, and data storages.

The current research directions are listed below:

I.     Cr4+ doped crystal fiber light source and optical amplifiers

Continued growth of broadband high-speed internet has led to an exponential increase of the bandwidth demands on optical fiber transmission line.  The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3 mm to 1.6 mm.  However, the number of channels in wavelength-division-multiplexing (WDM) system depends on the gain bandwidth of optical amplifiers.  There are many types of fiber amplifiers, which can be used to produce optical gains suitable for use at different communication bands.  The standard amplifier is the well-known silica-based erbium-doped fiber amplifier (EDFA), which provides gain in the C-band (1530-1565 nm) and L-band (1570-1605 nm) even in the S-band (1450-1520 nm).  The other types of EDFAs are fluoride- and tellurite-based EDFAs.  Thulium-doped fiber amplifiers can give gain in the S-band. The thulium ions can be doped in fluoride, tellurite or silica glass.  Praseodymium-doped fiber amplifiers can be operated in the O-band.  Fiber Raman amplifier can offer gain at broad spectral region as a suitable fiber and pump are used.

Of all the methods mentioned above, the gain bandwidth cannot fully cover the whole 1.3 to 1.6 mm with a single fiber amplifier as shown in Fig. 1.  It is well known that transition metal doped materials have broadband emission, among them Cr4+ ions and Ni2+ ions have been shown broadband 1.3-1.6 mm emission.  By the addition of a charge-compensating codopant of Ca2+ in Cr:YAG crystal, it has been shown that the percentage of Cr4+ to total Cr doping can go up to 6.5%, which substantially increased the Cr4+ fluorescence intensity.

We have fabricated a double-clad Cr4+:YAG crystal fiber using a codrawing laser-heated pedestal growth (CDLHPG) method, up to 10-dB of gross gain at 1.52 mm has been achieved. System demonstration of the Cr doped fiber amplifier (CDFA) in an optical communication link is our current focus.

II.       Nonlinear frequency conversion using periodically poled crystal fiber

All-optical wavelength converter would provide transparent high-speed signal processing and enable multi-channels to multi-channels simultaneous reconfiguration.  Compared with four-wave mixing in an active Mach-Zehnder interferometer, cascaded second order processes that are quasi phase matched (QPM) is effective for wavelength conversion.  We have fabricated periodically poled LiNbO3 (PPLN) crystal fibers using a novel micro-swing poling mechanism. Quasi phase-matched second-harmonics observed with greater than 15% conversion efficiency was achieved.

To test the tunability of the PPLN crystal fibers, a grazing-incidence optical parametric oscillator (OPO) based on QPM PPLN, provide by Dr. Andy Kung, was used.  When the pump laser was tuned from 1414 nm to 1545 nm, the cascaded second harmonic and sum frequency generates tunable blue-green laser from 471.3 to 515 nm as shown Fig. 2.  Our current research focus is on conversion efficiency enhancement and waveguide formation on the PPLN crystal fibers.

III.    Compact and reentrant ring lasers

Ring laser cavities have been extensively studied and developed for many applications such as single-frequency laser, mode-locked laser, laser gyro, etc.  Compared to standing-wave linear cavities, they have the ability to oscillate in either or both of the two counter-propagating directions.  Uni-directional operation of the ring cavity was obtained by adding intracavity reciprocal and non-reciprocal polarization rotators.  In addition, feedback from the pump beam is eliminated so that the laser amplitude noise is reduced.  However, usually more cavity elements are needed to construct the ring laser and the cavities become bulky.  Astigmatism produced by off-axis reflection from cavity mirrors must also be taken into account in the resonator design.  Our recent invention of the reentrant ring laser makes it possible to have a compact single-frequency laser suitable for intracavity frequency doubling.

Though Nd:YAG has been widely used as the solid-state laser crystals, Yb:YAG laser has received more attention nowadays, it is partly due to the rapid development of InGaAs laser diodes emitting from 900 to 1000 nm, which covers the absorption band of Yb:YAG.  Comparing to Nd:YAG, Yb:YAG has many advantages.  First, the absence of concentration quenching, excited state absorption, up conversion, and cross relaxation allows the doping concentration of Yb:YAG 100% that makes YbAG possible.  The heat dissipation can be improved by a thin gain medium with disk laser configuration.  Secondly, the quantum defect of Yb:YAG (~11%) is much lower than that of Nd:YAG (~24%), less heat is generated in Yb:YAG and is beneficial for high efficiency lasers.  Thirdly, the upper state lifetime ~1 ms of Yb:YAG is around 4 times that of Nd:YAG, which can be used in Q-switched lasers to store more energy.  Fourthly, the broad emission bandwidth ~9 nm of Yb:YAG can be applied in femtosecond mode-locked lasers and tunable lasers.  Another advantage is its wide absorption band ~18 nm near 941 nm, which eases the diode laser pumping.  Quasi-three-level nature is the major disadvantage of Yb:YAG.  Temperature controlling of a quasi-three-level laser crystal is crucial for high optical conversion efficiency.  Recently, we have achieved an efficient and compact Yb:YAG ring laser with a slope efficiency of 39.0%.  Mode locking of the laser is on going to realize a compact femtosecond laser.

References:

1.

J. C. Chen, K. Y. Huang, C. N. Tsai, Y. S. Lin, C. C. Lai, G. Y. Liu, F. J. Kao, and S. L. Huang, C. Y. Lo, Y. S. Lin, and P. Shen, ¡§Composition dependence of the micro-spectroscopy of Cr ions in double-clad Cr:YAG crystal fiber,¡¨ Journal of Applied Physics, 99, 093113, 2006.

2.

Y. S. Lin, C. C. Lai, K. Y. Huang, J. C. Chen, C. Y. Lo, S. L. Huang, T. Y. Chang, J. Y. Ji, and P. Shen, ¡§Nanostructure formation of double-clad Cr4+:YAG crystal fiber grown by co-drawing laser-heated pedestal,¡¨ Journal of Crystal Growth, 289, pp. 515-519, 2006.

3.

C. Y. Lo, K. Y. Huang, J. C. Chen, C. Y. Chuang, C. C. Lai, S. L. Huang, Y. S. Lin, and P. S. Yeh, ¡§Double-clad Cr4+:YAG crystal fiber amplifier,¡¨ Optics Letters, 30, pp. 129-131, 2005.

4.

C. Y. Lo, K. Y. Huang, J. C. Chen, S. Y. Tu, and S. L. Huang, ¡§Glass-clad Cr4+:YAG crystal fiber for the generation of super-wideband amplified spontaneous emission,¡¨ Optics Letters, 29, pp. 439-441, 2004.

5.

L. M. Lee, T. S. Chou, J. C. Chen, S. L. Huang, Y. C. Cho, C. C. Kuo, and H. W. Lee, ¡§In-situ poling of MgO doped lithium niobate crystal fiber by modulation of pyroelectric field,¡¨ Optics Communications, 253, pp. 375-381, 2005.

6.

H. T. Tuan and S. L. Huang, ¡§The analysis of reentrant two-mirror non-planar ring laser cavity,¡¨ Journal of the Optical Society of America A, 22, pp. 2476-2482, 2005.

7.

J. Y. Yi, L. H. Chen, and S. L. Huang, ¡§Efficient and compact Yb:YAG ring laser,¡¨ to appear in IEEE Journal of Quantum Electronics, 2006.

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Please send any comment to eoe5@cc.ee.ntu.edu.tw 

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Graduate Institute of Electro-Optical Engineering, National Taiwan University

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