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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.
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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
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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
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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:
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Discussion |
Visiting the laboratories |
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GIEOE Faculty
Visited
AUO Optronics Corp.
April 27, 2006
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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. |
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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
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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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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
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3. Nano-material
Analysis
(1) High-resolution
transmission electron microscopy
(2)
High-resolution X-ray diffraction
(3)
Strain state analysis
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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
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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
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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. |
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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.
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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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National Taiwan University
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