A Publication of the Photonics Research Centre, Nanyang Technological University
A special inaugural issue
to commemorate the launch of
the Photonics Research Centre
Fibre and Laser
ISSUE 1—SEPTEMBER 2003
About the Photonics Research Centre 4
Some Statistics 4
Biophotonics Research 7
Fibre and Laser Optics Research 8
Femtosecond soliton fibre lasers 10
Electrically tunable dispersion compensator
using fibre Bragg grating 11
MEMS Technology and Devices 12
Thermal characterization of GaAsN epilayer
on GaAs 13
Photonic Materials & Devices Research 14
Photonic Integrated Circuits Research 15
Quantum Well Intermixing 16
Development of High Power Laser Diode
Lasing Characteristics of Nano-Rods 18
Sol-Gel Materials & Applications 18
Organic Light Emitting Diodes (OLED) 20
Liquid Crystal Devices 21
Thermal Imaging 22
Optical Tweezers 25
News Brief 28
National Lecture Competition 2003 29
Photonics Gathering 2003 30
Photonics’La is published by the Photonics Research Centre, School of
Electrical and Electronic Engineering, Nanyang Technological University.
Block S1, Nanyang Avenue, Singapore 639798. Opinions expressed herein
do not necessarily reflect the views of the University.
Copyright c○ 2003 Photonics Research Centre
All rights reserved. Material in this publication may not be reproduced
without written permission. MITA (P) No. 148/09/2003
My congratulations to all the students and
staff of the Photonics Research Centre for
the launch of their newsletters—hotonics'a —in
commemoration of the official inauguration of the
Photonics research in the School of EEE began back
in 1992, when a few academic staff members started
by setting up experiment stations in makeshift space
in the School. In 1994, a designated laboratory was
finally allotted for the first-ever Photonics Research
Laboratory in Singapore, thus laying the groundwork
for the Photonics Research Centre almost 10 years
Today the Centre boasts 23 academic staff, 25research
staff and about 48 research students. Over the
years, 16 Ph.Ds and 48 M.Eng and M.Sc have been
produced in this research area, and well over 200 students
have graduated from NTU with a concentration
in Photonics, and are working in the industry, contributing
to the economy of Singapore.
Photonics is identified by the Singapore Economic
Development Board as a strategic industry and a critical
technology. The School will continue to support
efforts in this area and strive towards making the Centre
a niche of excellence in the Asia-Pacific region.
I encourage readers of this newsletter to browse
carefully the pages of this issue to find avenues for
research collaboration and other meaningful interactions.
School of Electrical and Electronic Engineering
My warmest greetings to all the students and
staff of the Photonics Research Centre for initiating
an innovative Newsletter cum e-magazine —
hotonics'a in conjunction with the establishment
of this new Photonics Research Centre that is
a spin-off from the Photonics Research Group within
the Microelectronics Centre.
The aim of this newsletter to reach out beyond
NTU, especially to the industries and touch base with
the Junior College and Polytechnic students is commendable.
Photonics is still a young and emerging
technology and will continue to appeal to the young
and brightest talents. It is gratifying to note that for
this year, out of the 10 first batch A*STAR Graduate
Scholarships awarded to the NTU graduates, 3 are
joining the Photonics Research Centre.
Today the Centre is poised to grow further, expanding
in cutting-edge areas such as biophotonics,
while strengthening the more traditional areas in optical
communications and photonic materials and devices.
Research in all these areas will bring benefits to
the economy in time to come.
In this inaugural issue of Photonics’La, some of the
current research projects conducted in the Photonics
Research Centre are showcased. I hope you will find
the information useful, and I further encourage you
to follow up with the Centre should you be interested
to find out more.
Assoc. Prof. Tan Ooi Kiang
Head of Division
Division of Microelectronics
This inaugural issue of hotonics'a marks
a major milestone for the Photonics Research
Centre. I take this opportunity to express my sincere
thanks to both staff and students who have put in so
much effort to make this a success.
Photonics, the technology of generating and harnessing
light, is a fast expanding field. While the 20th
Century was known as the Microelectronics Era, the
21st Century is touted to be the Photonics era. The
Microelectronics Era has brought great advances on
all fronts from Science and Engineering to Entertainment
and Communications. A century ago, it took
days or even months for news to propagate from one
end of the world to the other. Today, we can obtain
instant update on all sorts of news at the tap of a button.
It seems true that there is no end to technology
development except for the limitation of our imagination.
Technology that is not available today can be
made available tomorrow if we, in the scientific community,
pull our resources together to make it happen
and this is what Research and Development is all
about. It is with this goal in mind that the Photonics
Research Centre was established.
As a Research Centre, we must aim to harness every
talent within the Centre to make significant contributions
to the scientific community through patents
and the dissemination of our research results through
scientific publications. At the same time, both students
and researchers should work together to maximize
the mileage that can be achieved from the limited
resources that we have. Finally, in this knowledgeintensive
society, we must train our students to think
outside the box and make things that are undoable today,
doable tomorrow even if it means just sowing the
This newsletter reflects the creativity and potential
of the Photonics Research Centre. I hope the readers
will find the information useful.
Assoc. Prof. Tjin Swee Chuan
Photonics Research Centre
FOREWORDS September 2003 3
About the Photonics
The 21st Century is often called the Information
Age. The backbone for a digital information-rich
society is a pervasive fibre-optic network that
carries information in the form of optical pulses transmitted
by semiconductor lasers and received by photodetectors.
Today’s quality of life is directly linked to lasers
and the harnessing of light, which is the basis of Photonics
technology. An enabling technology that underlies
many strategic industries, its importance is universally
recognized, and it is identified by EDB as a critical technology
The Photonics Research Centre (PhRC) in the Nanyang
Technological University (NTU) is dedicated to research
and teaching in the fast-paced field of Photonics science
and technology. The culture of openness, and the broad
range of expertise and equipment in the Centre provide
a stimulating and dynamic environment for researchers
and students from many countries worldwide.
The Centre was founded in 1994 as a photonics research
laboratory, the first of its kind in Singapore. Today
it encompasses 23 academic staff, 26 research staff, and
37 research students, conducting research in three laboratories
in many cutting-edge areas of Photonics. The
research area may be broadly classified in three groups:
• Fluorescent Lifetime studies
• Fluorescent Imaging
• Optical Tweezers
• Bioassay Devices
Fibre and Laser Optics
• Fibre optic and wireless communication
• Fibre Optic Sensors
• Diffractive Optics
• Optical MEMS
• Laser Engineering (Laser Systems)
• Optical Engineering (Discrete Optics Systems)
Photonics Materials and
• Compound semiconductor photonics
• Sol-Gel photonics
• Polymer photonics
• Display devices (OLED, TFEL, LCD)
• Advanced materials and device integration
Our mission is to spearhead research in these strategic
areas, and to facilitate the training of professional manpower
and the transfer of technology to industry.
The PhRC family:
• 23 Academic Staff (including 3 from School of Materials
Engineering and 1 from School of Mechanical
& Production Engineering)
• 26 Research Staff
• 34 full-time Research Students and 3 part-time
• 10 Technicians
• Two research laboratories
• One teaching laboratory
• One joint laboratory with the Network Technology
Total cumulative research funding = S$20,948,154
(63 projects; average funding/project = S$332,510)
Total current research funding S$11,025,006
(18 projects; average funding/project = S$612,500)
2002 43 45
2003 (todate) 56 26
12 patents awarded.
2 (one existing)
The Centre has signed MOUs with international collaborators,
including the TNO Institute of Applied Physics
in Delft, Ècole Nationale Supèrieure, Hong Kong University
of Science and Technology, and Monash University.
Two major MOUs, under final stage of preparation, will
be signed in the near future. The first is to develop a joint
Photonics Laboratory facility with Institut d’Optique,
France and Thales Training Centre, Singapore. The second
is to spearhead joint research activities in Photonics
with Imperial College, U.K.
Education and Training
The Centre has produced 15 PhD’s and 48 MEng and
The undergraduate Photonics Final Year Option was
launched in July 2000 with an initial batch of 23 students.
The cohort increased to 51 students in 2001, and 157 students
in 2002. The core subjects for this option are:
• Semiconductor Optoelectronics
• Optical Engineering
• Laser Engineering
• Fibre Optic Communications
• Optical Design
• Photonic System Design
In the Postgraduate level, with the support of the
Economic Development Board of Singapore, an
MSc(Photonics) program will be launched in July 2003.
16 full-time and 12 part-time students have been offered
admission, out of a total of 195 applicants. The Centre is
also looking for possible collaboration in this MSc Programme
with Imperial College (U.K.) leading to a joint
degree in Photonics.
The curriculum for the MSc program is as follows:
• Modern Optics
• Laser Technology and Applications
• Opto-Electronic Devices
• Optical Fibre
Optional Subjects (Students choose any 4)
• Microoptics and Optical MEMS
• Compound Semiconductor Epitaxial Growth
• Display Technologies
• Optical Data Storage
• Optical Fibre Communications
• Quality and Reliability Engineering
• Advanced Semiconductor Physics
The Centre staff is active in promoting the teaching of
photonics in secondary as well as tertiary institutions.
TheCentrestaff has provided leadership role in organizing
international conferences and local chapters of
professional societies, including SPIE and IEEE LEOS.
Three out of 10 A*STAR postgraduate scholarships
awarded to NTU in 2003 chose Photonics as their research
For enquiries about the Centre please contact
A/P Tjin Swee Chuan at ESCTJIN@ntu.edu.sg. For
enquiries about the MSc Course please contact A/P
Yuan Xiaocong at EXCYUAN@ntu.edu.sg.
ABOUT THE PHOTONICS RESEARCH CENTRE September 2003 5
Fibre and Laser
Dr Tang Dingyuan
A/P Tang Dingyuan
A/P Tjin Swee Chuan
A/P Liu Ai Qun
A/P Yuan Xiaocong
A/P M. K. Rao
Ast/P John Ngo Quoc Nam
Ast/P George Chen Kit Chung
Ast/P Julian Chan Chi Chiu
Ast/P Murukeshan (MPE)
Organization Chart of PhRC
Photonics Research Centre
Centre Director: Dr Tjin Swee Chuan
Dr Tjin Swee Chuan
A/P Tjin Swee Chuan
A/P Yuan Xiaocong
A/P Lim Tuan Kay
Ast/P Ng Beng Koon
Dr Chin Mee Koy
A/P Chin Mee Koy
Prof. Kam Chan Hin
A/P Terence Wong Kin Shun
A/P Au Yeung Tin Cheung
A/P Yuan Shu (SME)
Ast/P Mei Ting
Ast/P Tang Xiaohong
Ast/P Yu Siu Fung
Ast/P Pita Kantisara
Ast/P Sun Xiaowei
Ast/P Ricky Ang Lay Kee
Ast/P Ng Beng Koon
Ast/P Rajesh Menon
Ast/P John Ngo Quoc Nam
External Seminars and Workshops given by Photonics Research Centre Staff
Date Speaker Workshop Topic
14 March A/P Chin Mee Koy 1st Workshop on Microphotonics,
24 July Ast/P Pita Kantisara and A/P Photonics Workshop,
24 July A/P Terence Wong Kin Shun Photonics Workshop,
A Roadmap for III-V Photonics
Phosphorescent and low-k materials
for organic LED
Ast/P Ng Beng Koon and A/P Tjin Swee Chuan
Biophotonics, at the crossroads between biosciences
and photonics, is an emerging field with
great potential and a fertile ground for research.
It is the science of generating and harnessing light to
image, detect and manipulate biological matters. It is
multidisciplinary in nature and incorporates many scientific
disciplines including physics, chemistry, mathematics,
biology, and engineering.
There are currently 4 academic staff in this group
working on optical bioimaging, fibre-optic sensors for
pressure and flow measurements in biological system,
and advanced optical tweezers for the micromanipulation
of biological specimens. The group is engaged in a collaborative
alliance with the University of Washington, Seattle
In the area of optical bioimaging, we are interested in
the application of lasers for the diagnosis of diseased tissues.
In particular, fluorescence spectroscopy has been
used to study diseased tissues, such as plaque in the arteries
of the human body. There is also an ongoing research
programme to develop a handheld optical bioassay
system for monitoring biochemicals in biological fluids.
Such a device will allow healthcare to be decentralised to
the various point-of-care environments, thereby improving
the quality of medical care and resulting in cost savings
through early diagnosis of medical conditions.
Research in fibre-optic biosensors is being pursued to
develop sensors for applications in medical diagnosis and
health monitoring. Some examples are fibre-optic pressure
sensors for orthopaedic applications and total knee
joint replacement surgery, and continuous cardiac output
sensors for the in-vivo monitoring of blood flow.
Advanced optical tweezers that will enable the transfer
of optical gradient force, spin angular momentum,
and orbital angular momentum is currently being investigated
using a double hologram interferometer. This new
optical tool allows dual rotation within the laser beam
and is much more compact than setups employing conventional
techniques. Potential applications include the
simultaneous angular deformation of cell structures and
force measurements [please refer to the feature article on
Figure 1: Fibre Bragg grating embedded into a patella button to
perform pressure mapping during total knee joint replacement
surgery (courtesy of Ms Lipi Mohanty, PhD student)
Figure 2: Manipulating yeast cell with optical tweezer (courtesy
of Mr Lee Woei Ming, PhD student)
BIOPHOTONICS RESEARCH September 2003 7
Fibre and Laser Optics
A/P Tang Dingyuan
The fibre and laser optics (FLO) research
group involves 7 academic staff and 5 research
fellows. Research activity of the group spans a
wider range of topics within the areas of fibre optics and
optic communications, laser physics and engineering, as
well as modern optics such as diffractive optics and nonlinear
Fibre optics and optic communications
During the past decade there has been a tremendous
growth in fibre-optic communication to accommodate
the ever-increasing demand on the capacity
of the global communication systems. Two approaches
are being pursued to increase the capacity of fibre communication
systems: (i) Wavelength division multiplexing
(WDM) technology, where multiple lower bit-rate
communication channels are simultaneously transmitted
in a single optical fibre, and (ii) Soliton communication,
which makes use of the properties of optical solitons to
achieve ultrahigh bit-rate transmissions. Both technologies
require various fibre-based optical devices and components
with special functionality. Our research in this
area has focused on grating-based devices and soliton
In the first area, two fibre Bragg grating fabrication
systems have been built, one based on a pulsed excimer
laser and the other on a CW frequency-doubled argonion
laser. Both systems produce high quality fibre Bragg
gratings (FBG). We are now in the position of design-
ing FBGs of arbitrary transmission. Using these FBGs
we have demonstrated tunable dispersion compensators
with fixed center wavelengths [see article by Prof. John
In the area of soliton fibre laser, our research has attracted
world-wide attention. For the first time we have
experimentally obtained a new type of double-pulse soliton
in passively mode-locked fibre lasers and theoretically
confirmed the existence of this type of optical solitons.
Other related activities in the area include free-space
optic communication and optical MEMS. In the former
area, Prof. George Chen’s group is working on diffuse
holograms for infra-red (IR) wireless communication
and angle diversity photoreceivers. IR has advantage over
Bluetooth for ultra-short reach inter-device communication
because IR radiation offers a virtually unlimited
and unregulated bandwidth. In addition, since IR doesn’t
penetrate through walls, the wavelengths can be reused
and this is particularly suited for office application. In the
MEMS area, the optical MEMS group, under Prof. Liu Ai
Qun, is working on MEMS switches and attenuators, and
discrete-wavelength tunable MEM lasers for optical communications
applications [please see article by Prof. Liu].
Diode-pumped solid-state (DPSS) lasers
Compact, all-solid-state pulsed lasers with large
single pulse energy and variable repetition rate have
wide applications, e.g. in the range finder and laser radar
systems. Such a laser system can be developed based on
the laser active Q-switching technique combined with the
high power diode quasi-cw pumping technology. In a
previous project, in collaboration with Charted Electro-
Optics, Singapore, we have developed a high power 50W
CW diode-pumped solid-state (DPSS) laser. Through
this project we have gained tremendous experience in developing
high power DPSS lasers.
In the development of new types of DPSS lasers, we
have collaborated with scientists in Japan and Russia to
develop the first diode pumped Yb-ions doped ceramic
laser in the world. Pumped with 12.8 W of 940 nm
light we have achieved 0.78 W cw laser emission at the
1.078 µm. By putting a saturable absorber in the laser
cavity, we have also achieved passive Q-switching of the
ceramic laser. The advantages of ceramic lasers are that
large pieces of ceramic are easily available, very high doping
concentrations can be obtained, and the low cost.
Another on-going research project is the investigation
of the diode pumped Nd:GdVO4 lasers. Nd:GdVOV4
is a new laser crystal with high thermal conductivity and
optical efficiency. We have achieved a Q-switched laser
with stable high power, and large single-pulse energy, and
are working toward a high-power mode-locked laser in
collaboration with Shandong University, China.
Apart from the continuous improvement of the conventional
laser Q-switching and mode-locking techniques,
we are also working on other novel techniques to
manipulate the operation of lasers, such as the control of
the emission and the intensity pattern of a laser beam.
It is expected that by using specially designed diffractive
optical element inside the laser cavity, and through manipulating
the laser gain and cavity dispersion laser emission
with novel beam shape and pulse profile could be
Lasers are intrinsically a nonlinear dynamical system.
Our study of the nonlinear dynamics in lasers, which
are well described by the laser equations, have included
the laser chaotic dynamics and its control, laser chaos
synchronization, the temporal and spatial solitons, laser
cavity soliton interactions, etc. For the first time we
have both experimentally and numerically proven that
the Q-switched pulse intensity fluctuation of passively Qswitched
DPSS lasers are in fact a deterministic chaos
phenomenon. This discovery has not only provided a
deep understanding on the phenomenon itself, but also
suggested a completely new technical approach in controlling
or eliminating the fluctuations. Our research on
temporal soliton and its dynamics in a passively modelocked
fibre laser has revealed a new type of twin-pulse
form of solitons. Potentially this new type of solitons
could be used to combat polarization mode dispersion in
high-bit rate optical communication systems.
Our research in the area comprises the diffractive
optics and nonlinear optics research activities.
Nonlinear optics is one of the wonderful areas of modern
optics. It is a direct consequence of the interaction
of high-power, high-brightness coherent laser beams with
materials, resulting in a nonlinear response of the material
property to the light radiance. Using these nonlinear
interactions, one can convert light from one wavelength
to another, and also control light by light to realise lightcontrolled
self-switching photonic devices. Our research
activities in nonlinear optics currently are mainly focused
on optical wavelength conversion, such as laser intracavity
frequency doubling, and parametric optical oscillators.
The past decade has witnessed new developments in
micro-optics based on new materials. In particular,
sol-gel glass, as a low-cost material with good, tunable
optical properties, has been extensively used in the fabrication
of planar waveguides, computer generated holograms,
and micro-optics (especially microlens arrays). In
our research, we have used a hybrid sol-gel technology to
develop the following micro-optical elements:
• A microlens array used as a coupler between a
waveguide array and a fibre array
• A microlens array used as a Shack-Hartmann wavefront
• Micro-optics for extra-cavity and intra-cavity
• Computer generated holograms (CGHs)
• Micro-optics for laser beam addition
Sol-gel Microlens array using an HEBS grey scale mask.
FIBRE AND LASER OPTICS RESEARCH September 2003 9
Femtosecond soliton fibre lasers
A/P Tang Dingyuan
Fiber lasers are a new type of laser system made of
special optical fibre. They have the characteristics of
compact size, ultra stable operation and low cost. Various
modes of operation can be achieved in the lasers: they can
emit either high power continuous light beams, or singlefrequency
ultra-stable optical waves, or ultra stable, ultrashort
optical pulse trains.
A femtosecond soliton fibre laser generates high quality
special optical pulses with pulse duration of merely hundreds
of femtosecond. Unlike conventional optical pulses,
these special pulses, known as solitons, maintain their
pulse shape and width without any distortion in propagating
through long lengths of optical fibre, a property
that is very useful for fibre-optic communication.
If the soliton laser is further operated in combination
with chirp pulse amplification and nonlinear wavelength
conversion techniques, ultra-high peak power, frequencytunable
optical pulses can be generated. This kind of
optical pulses have wide-ranging applications in scientific
research as well as military devices and medical surgery.
Researchers in my group have conducted intensive theoretical
and experimental research on passively modelocked
soliton fibre lasers. They have developed compact,
ultra-stable femtosecond soliton fibre lasers of various
configurations and achieved transform-limited soliton
pulses of duration as short as 250 fs, and high-energy
femtosecond optical pulses of single pulse energy as large
as several tens of nJ. These lasers can be used in a number
of applications, e.g. the injection seeding, two-photon
microscopy and laser radar systems.
Beside the conventional soliton pulse laser our group is
also the first to discover a novel twin-pulse soliton emission
in the lasers. This observation not only confirms
experimentally the existence of the multi-hump temporal
optical solitons, but also makes available for the first
time a unique novel laser system that generates closely
paired optical pulses. A laser beam with such a property
may have a number of special applications, e.g. in
triggered ultrafast photography, laser spectroscopy, and
time-division multiplexing optical communication systems.
In addition, our group has also studied other features
of the soliton fibre lasers, such as the noise-like pulse
emission in which the emitted pulses have very large energy
and ultra-broad optical spectrum. Lasers of such
property are an ideal high power broadband light source,
which may be used for testing fibre optic communication
systems and for optical metrology.
Theoretically, we have developed a model that can accurately
reproduce all features of the lasers observed experimentally.
With this model we can not only understand
the physical mechanism of a specific experimental
effect observed, but also predict and design new features
of the laser and other ultrashort pulse laser systems.
Figure 1: Femtosecond soliton fibre laser developed in NTU.
Figure 2: Optical spectrum of a double-pulse soliton laser
Figure 3: Double-pulse soliton emission of the lasers numerically
Electrically tunable dispersion compensator using fibre
Ast/P John Ngo Quoc Nam, Li Songyang, Zheng Ruitao, A/P Tjin Swee Chuan, A/P Shum Ping
One of the most critical challenges in nextgeneration
high-speed long-haul optical transmission
systems is to overcome the fibre’s chromatic dispersion.
The tunable dispersion compensator (TDC) can
be used to optimise network performance. We have proposed
and developed a novel TDC that can electrically
adjust the chirp of the FBG while maintaining a fixed
centre wavelength. This new method can minimise signal
distortion and crosstalk in a WDM system.
This electrically tunable TDC consists of a uniform
FBG in a fibre that is etched to a prescribed diameter profile,
an on-fibre thin-film heater whose local resistance
varies with position in a prescribed manner along the
grating length, and a negative thermal expansion coefficient
(NTEC) ceramic in which the FBG is mounted [see
Figure 1]. Electrical current flowing through the thin film
will generate a temperature gradient because of the pre-
Fiber with FBG in the center Copper thin-film coating
Conductive paint layer
Negative thermal-expansion coefficient (NTEC) material
Figure 1: Schematic diagram of the proposed tunable dispersion compensating
FBG with fixed central wavelength. When current flows through the thin-film
coating and the conductive paint layer, the bandwidth and chirp of the FBG can
be tuned while the center wavelength is kept fixed.
scribed thickness profile of the metal film. Shrinkage of
the NTEC ceramic imposes a strain gradient on the FBG
because of the prescribed diameter profile of the fibre
with FBG. Both the temperature gradient and the strain
gradient affect the chirp and hence dispersion of the FBG.
At the same time, the center wavelength is kept fixed because
the effects of temperature rise and of compression
of the FBG are such that they offset each other.
To our knowledge, this is the first proposal to combine
the temperature gradient and the strain gradient as a dispersion
tuning technique. As an example to demonstrate
the effectiveness of the proposed method, we have developed
a TDC of 25 mm length, which has a dispersion tuning
range of −178 ps/nm to −302 ps/nm with a central
wavelength shift of as small as 0.17 nm and an applied
electrical power smaller than 0.68 W.
Conductive paint layer
on surface of NTEC
with FBG inside
Figure 2: Photograph of a packaged tunable
FBG dispersion compensator.
Group Delay (ps)
B: Volt=0.4 V; Dispersion= -190 ps/nm
1549.0 1549.2 1549.4 1549.6 1549.8 1550.0 1550.2 1550.4 1550.6
Figure 3: Measured group delay characteristics
of the tunable dispersion compensator.
FIBRE AND LASER OPTICS RESEARCH September 2003 11
MEMS Technology and Devices
A/P Liu Ai Qun
Microelectromechanical systems (MEMS) has
become a key optical technology for making optical
networking components and devices for dense wavelength
division multiplexing (DWDM) systems. Examples
include optical switches, optical crossconnects
(OXCs), reconfigurable optical add/drop multiplexers
(OADMs) and tunable lasers.
A variable optical attenuator (VOA) with a footprint
of 1 × 0.6 mm has been developed using MEMS technology
in the MEMS research group [see Fig. 1]. Exploiting
the surface micromachining technology, the whole device
has achieved a response time of 37 ms, an attenuation dynamic
range of 45 dB, an insertion loss of 1.5 dB, and
a driving voltage of 3.5 − 8 V (better than conventional
VOA systems). The wavelength dependent loss over the
C-band (1528 nm - 1561 nm) is less than 0.9 dB. This
achievement was reported in the magazine Fibre Systems
Europe in 2002.
Figure 1: A scanning electron micrograph of the MEMS VOA
The first achievement of the research team was a
MEMS tunable laser in 2001, which was highlighted in
the U.S. magazine WDM Solutions. In 2003, an “Optical
MEMS Integrated System” was successfully demonstrated
[Fig. 2] and was awarded a Gold Prize at the College of
Engineering (CoE) Technology Exhibition. The contributions
of the MEMS group have generated positive publicity
for NTU as well as the Photonics Research Centre.
 A. Q. Liu, X.M. Zhang, and V.M. Murukeshan, “A novel
device level micromachined tunable laser using polysilicon
3D mirror,” IEEE Photonics Technology Letters, vol.
13, no. 5, pp. 427-429, May 2001.
 “Fully Integrated Micromachine Laser is Tunable”, WDM
Solutions, pp. 10, July 2001.
 A. Q. Liu, X. M. Zhang, V. M. Murukeshan, C. Lu and
T. H. Cheng, “Micromachined wavelength tunable laser
with an extended feedback model”, IEEE Journal of Selected
Topics on Quantum Electronics, vol. 8, no. 1, pp.
73-79, January/February 2002.
 X. M. Zhang, A. Q. Liu, C. Lu and D. Y. Tang, “MEMS
variable optical attenuator using low driving voltage for
DWDM systems”, IEE Electronics Letters, vol. 38, no. 8,
pp. 382-383, April 2002.
 “Low-driving-voltage VOAs Exploit MEMS”, Fibreystems
Europe, pp. 11, June 2002.
 A. Q. Liu, X. M. Zhang, C. Lu, F. Wang, C. Lu and Z. S.
Liu, “Optical and mechanical models for a variable optical
attenuator using a micromirror drawbridge”, Journal
Micromechanics and Microengineering, vol. 13, pp. 400-
Figure 2: A micrograph of a MEMS tunable integrated system
Figure 3: Assoc. Prof. Liu’s team won a gold prize at the CoE
Thermal characterization of GaAsN epilayer on GaAs
Zhao Yimin and Ast/P George Chen Chung Kit
Photothermal technique has gained popularity
because of its non-contact nature. We use pulsed
photothermal reflectance technique to characterise thermal
properties of thin films. As shown in Figure 1, this
technique basically consists of a pump laser and a probe
laser. The pump source is a Nd:YAG laser with a pulse
width of 8 ns. The probe laser is a continuous wave He-
Ne 1-mW laser. To enhance the heat absorption, a metal
layer, preferably gold, is deposited on top of the sample.
The measurement begins with the Nd:YAG laser pulse
incident on the sample surface. The sample surface temperature
rises sharply, and then relaxes with time. This
gives rise to a temperature excursion profile that depends
on the thermal properties of the underlying films and the
thermal resistance between the layers. The heating up of
the sample induces a change in the refractive index on
the surface and hence a change in the reflectance of the
probe beam. Since the temperature and the reflectivity of
gold are inversely related, the temperature profile can be
obtained by capturing the changes in the reflected probe
beam. The thermal properties of the film to be measured
can be obtained by fitting the measured data with
analytical expression for heat conduction.
Figure 1: Experimental geometry of pulsed photothermal
We have applied this method to measure the thermal
properties of Gallium Arsenic Nitride (GaAsN), which is
a relatively novel material for optoelectronic devices. The
advantage of this material is that it can be grown on a
GaAs substrate. The addition of nitrogen (N) into GaAs
decreases the material bandgap, making it suitable for the
fabrication of laser diodes operating at wavelengths of
1.3 µm and 1.55 µm. As high power laser diodes may
be fabricated in GaAsN, characterization of the material
thermal conductivity becomes important, as the material
must be able to dissipate the large amount of heat generated
in the laser diode emitters in order to maintain good
performance and reliability.
To extract the thermal conductivity (KGaAsN) and diffusivity
(αGaAsN = KGaAsN/ρc, whereρ and c are density
and specific heat, respectively) of the GaAsN thin
film from the obtained thermal profiles, we used a threelayer
heat conduction model, which incorporates thermal
resistance (R1, R2) of the two interfaces, based on a
transmission-line theory. Simulated annealing, a global
optimization method, is applied to obtain the optimal fit
to the experimental data. The fitted result is shown in
Table 1. To our knowledge, this is the first time the thermal
conductivity of GaAsN is being reported. No significant
thickness dependence was found within our samples’
thickness range. The average thermal conductivity
is about 27 W/mK and the average thermal diffusivity is
about 0.4 × 10 −6 m 2 s −1 . As expected, the thermal resistance
(R2) of the epitaxial interface between GaAsN and
GaAs is much less than the thermal boundary resistance
between Au and GaAsN (R1).
Figure 2: Surface temperature excursion profile of sample with
thickness of 80 nm
Table 1: Thermal property versus thickness of GaAsN epilayers
on GaAs substrate
Thickness (nm) 20 40 50 80
KAU (W/mK ) 250 235 212 241
KGaAsN (W/mK ) 27 25 28 29
αGaAsN (×10 −6 m 2 s −1 ) 0.9 0.4 0.3 0.4
R1 (×10 −8 m 2 K/W ) 5.8 9.2 6.7 7.1
R2 (×10 −8 m 2 K/W ) 9.4 7.4 5.9 7.4
FIBRE AND LASER OPTICS RESEARCH September 2003 13
Photonic Materials and
A/P Chin Mee Koy
The photonic materials and devices (PM&D)
is a broad and diverse program involving about
12 academic staff and 16 research fellows. The
material-based research can be classified in three broad
categories: (i) compound semiconductors, (ii) glass, solgel
and other oxides, and (iii) Polymers and liquid crystals.
As usual, no single material is perfect. The best scenario
may be to combine the advantages of each material
to form hybrid integrated modules and systems, where
different materials perform useful functions for which
they are eminently suited. The ability to achieve this
hinges on the availability of a wide array of materials with
novel properties. Materials research provides the foundation
for technology development that will lead to important
III-V Semiconductor Photonics
The largest material-based group is in the compound
semiconductors area, especially the III-V
group, which has about 7 academic staff and 8 research
fellows. Besides a slew of equipment for processing, the
group also operates a Metal-Organic Chemical Vapor Deposition
(MOCVD) system for the epitaxy of both GaAs
and InP-based materials.
system (courtesy of
Dr Tang Xiaohong)
The primary advantage of III-V semiconductors is that
they can be used to make active optical devices such as
laser diodes with the right wavelengths for optical communication
applications. Members of the group are pur-
suing high-power lasers, tunable lasers, modulators, and
photodetectors. In fact, so many devices can be made
from the same material that monolithic integration of all
the devices on the same substrate is in principle achievable.
Multi-wavelength laser arrays, for example, has been
achieved by using a technique called quantum-well intermixing
(QWI). Our next goal is to develop photonic integrated
circuits (PIC) that combine a broad range of active
devices with passive devices in the same chip.
Sol-Gel and Silica Photonics
Sol-gel is a colloidal suspension of gelled silica
particles. It can be chemically purified and consolidated
at high temperatures into high purity silica. The
silica can then be modified with a variety of dopants to
produce new glass properties unattainable by conventional
means. One such novel derivative is the photosensitive
hybrid sol-gel glass, which has excellent optical
properties and usually involves a single-step low temperature
fabrication process. This material has provided
a low-cost way to fabricate diffractive optical elements,
such as microlens arrays that may be used to facilitate
coupling between a waveguide array and a fibre array.
We have worked on both passive and active optical
waveguide devices over a number of years. Silica based
materials have been fabricated by the sol-gel technique.
This technique enables various oxide dopants such as
GeO2, TiO2, B2O3, Al2O3, etc. to be easily incorporated
into the SiO2 host to obtain the desired optical properties
of the materials (e.g. refractive index). Recently, the SiO2-
GeO2 system has been developed for various waveguide
based devices. The refractive index can be tailored easily
by varying the GeO2 dopant concentration. Low optical
absorption has been achieved and the technique to obtain
highly photosensitive films has also been developed.
High refractive index change upon UV exposure has been
Polymeric materials are broad and specific properties
can be engineered for specific applications, including
a wide bandwidth of transparency, high electrooptic
(EO) coefficients, or high thermo-optic (TO) coefficients,
making them suitable for very fast (picosecond)
switches as well as low-power, millisecond switches and
variable attenuators. Polymeric passive and active devices
can be easily integrated on any surface of interest, and
passive waveguides can be fabricated easily and at low cost
with excellent control of refractive index and geometry.
This makes polymer-based channel waveguides ideal for
board-level chip-to-chip optical interconnects, and as interlayer
dielectrics and protective overcoats.
Research on polymer and polymer photonics has been
Photonic Integrated Circuits Research
A/P Chin Mee Koy
Integrated optics, or photonic integrated circuits
(PIC), began in Bell Labs over 40 years ago, but has
only entered the industry lexicon in the last 10 years. This
is because of its emerging importance as the surest way to
reduce components cost, which forms a major portion
of systems cost. Integration reduces the number of parts
and hence the level of packaging and assembly required.
It also results in parts with smaller footprints that save
valuable space in central offices. Integrated components
tend to be more reliable and power efficient and hence cut
down operating cost. Because of these advantages, photonic
integration is considered a key to opening the floodgate
of low-cost optical subsystems that will make longterm
sustainable investment in optical networks possible.
Just as microelectronic integration has brought about the
relentless reduction in the price of IC’s, photonic integration,
likewise, can be expected to bring about similar
benefits, and ultimately give the whole industry a path to
The future networks are also migrating toward alloptical
in order to eliminate the optical-electronic-optical
(O-E-O) bottleneck. Based on this evolution, the next
technology requirements are expected to be dominated
by optical switching and routing functionality, with subsystems
such as optical cross-connects (OXCs) and optical
add/drop multiplexers (OADMs) as the lynchpin
products. Many competing switching technologies are
being developed, such as micro-electromechanical systems
(MEMS), arrayed-waveguide gratings (AWG), liq-
carried out jointly in the School of Materials Engineering
and the School of Electrical and Electronic Engineering
for a number of years. A niche area is highlighted below.
Conjugated polymers are organic macromolecules with
alternating single and double bonds along the molecular
chains. The overlap of the pz orbitals gives rise to two
molecular orbitals (HOMO, LUMO) that resemble the
conduction and valence bands in semiconductors. So just
like semiconductor materials, they can conduct electricity
and in some cases, emit or absorb light. This makes
them an interesting (and indeed fascinating) class of electronic
materials to study. Conjugated polymers are strong
candidates for flat panel displays. We have demonstrated
organic LEDs (OLED) using both conjugated polymers
and molecular complexes.
uid crystals, fibre-based Mach-Zehnder, thin-films, and
fibre Bragg gratings. However, all of these switches tend
to be bulky and space-hungry and require complicated
assembly and fibre management. Next-generation product
development will need to drive down both cost and
space. These requirements provide the motif for integration
and favors technologies that are amenable to highdensity
Microphotonic integration is more challenging, and
hence much less mature, than microelectronic integration.
Partly this is due to the large diversity of photonic
devices that need to be integrated. Unlike transistors
which form the bedrock building block for all of electronics,
no photonic equivalent of transistors exists.
Figure 1: A popular commercial laser-modulator product is an
assembly of 10 or more components aligned in free space with
tedious precision. 70% or more of the cost goes into assembly and
packaging. Most of this cost could be eliminated if the laser and
modulator were integrated in a single chip.
Given the strategic significance of photonic integration,
we have formed a PIC research group to spearhead
research in this area. This will be the first such research
PHOTONIC MATERIALS & DEVICES RESEARCH September 2003 15
group in Singapore. Our goal is to develop an integration
platform - a systematic methodology for integrating
as many different devices as possible on the same chip in
a scalable, robust, and low-cost manner. “Scalable” here
means that the complexity of the process does not increase
exponentially with the number of devices; “robust
and low-cost” means that the end products will be much
more manufacturable and low-cost than current technology
can achieve. This technology, therefore, has a good
potential for commercialization.
Figure 2: A prototypical photonic integrated circuit consists of
active and passive device building blocks coupled via some
passive transition block (brown). The PIC is coupled to the
outside world via some coupling modules (green blocks) designed
to improve coupling efficiency with optical fibre (red). Many
PIC’s can be formed this way with a consistent architecture. Such
an integration platform is modular and hierarchical.
Quantum Well Intermixing
Ast/P Mei Ting
By integrating several discrete devices on the same
chip, Photonic Integrated Circuits (PIC) can directly
provide functional modules for optical communication
systems, thus giving more freedom and benefit to the system
Such foreseen evolution has to face many challenges,
foremost among which is the different bandgap energy
requirements for different types of devices. For example,
transparent waveguides need a material with wider
bandgap than that for the laser devices.
Quantum well intermixing (QWI) is an enabling technology
that performs the task of tuning the local bandgap
energy on an epi-wafer after the growth of the epilayers.
Compared to multiple regrowths or selective-area
growths, QWI is a relatively simple technique, involving
only a single-step growth, but capable of generating
multiple devices with different bandgaps in a single postgrowth
The PIC research group is led by Dr Chin Mee Koy,
and consists of Dr Tang Xiaohong, Dr Mei Ting, Dr Yu
Siu Fung, Dr Ng Beng Koon, all of the School of EEE, and
Dr Shu Yuan from the School of Materials Engineering
(SME). The group intends to form collaborations with local
research institutes and industry as well as universities
Figure 3: Examples of compact building blocks: (a) multimode
interferometer and (b) micro-resonator optical filter.
For more information please send inquiries to
email@example.com or Tel: 6790-4011.
Did You Know? The definitions of time and length rely on photonics.
The unit of time (second) is based on atomic clocks, which use lasers
to probe the structure of caesium atoms. Length is determined by the
speed of light (c), and the metre is defined as how far a light beam
travels in 1/c seconds.
Ar plasma exposure
MQW laser structure
Butt joint with perfect allignment
Figure 1: (a) the selective area ICP-QWI process; and (b) SEM
photograph of the extended-cavity laser. 
Prof. Mei Ting’s group in PhRC has pioneered the
research of plasma-based QWI technology and has
obtained several promising preliminary results. Using
Inductively Coupled Plasma (ICP) enhanced QWI,
we have demonstrated large bandgap energy blueshifts
(> 100 nm), selective area bandgap tuning and integration
of laser and low-loss waveguide (with losses less than
12.9 dBcm −1 ). Further study in ICP-QWI will be carried
out as part of the larger program to develop PIC.
 H.S. Djie, et al, “Photonic Integration using Inductively
Coupled Argon Plasma enhanced Quantum Well Intermixing”,
Electron. Lett., vol. 38, no. 25, pp. 1672-1673,
Development of High Power Laser Diode Arrays
Ast/P Tang Xiaohong
High power laser diode arrays are of great interest
because of their compact size and the numerous
applications in diode-pumped solid-state lasers,
Erbium-doped fibre amplifiers, space communication,
smart welding of metals and plastics, thermal printing
and medical treatment, etc.
In PhRC, laser diode bar arrays with optical powers in
excess of 20 watts in continuous-wave (CW) operation,
and a high slope efficiency of 1.1 W/A, have been developed.
The threshold current is about 6 A for a 19-emitter
array, and the threshold current density per device is as
low as Jth = 200 A/cm2 .
Fabrication of high power laser diode arrays involves
device design, material growth, post-growth processing,
device packaging and characterization. The materials
were grown with our own Metal-Organic Chemical
Vapour Deposition (MOCVD) system. The keys to
the success of this project are good material quality and
good packaging for thermal management, and most of all
the dedication of the research team consisting of Dr Bo
Baoxue, Dr Huang Gensheng, Dr Zhang Baolin, and
Dr Zhang Yuanchang.
Did You Know? One of the most powerful ultraviolet laser in the
world, (the 60-terawatt omega, at the Laboratory for Laser Energetics
at the University of Rochester, New York) is used to test fusion experiments.
In less than a billionth of a second, the laser sends the temperature
in a tiny pellet from just a few degrees above absolute zero
to nearly 30 million degrees Celsius—twice as hot as the core of the
sun. For this brief period of time the laser power is about 100 times the
peak power of the entire U.S. power grid.
Figure 1: (a) Laser bars in perspective (b) Laser bar under test on
a copper heatsink.
PHOTONIC MATERIALS & DEVICES RESEARCH September 2003 17
Lasing Characteristics of Nano-Rods
Ast/P Yu Siu Fung
Zinc oxide nano-rods attract special interest
for high efficiency short-wavelength optoelectronic
nanodevices, due to their large excitonic binding energy
of 60 meV and high mechanical and thermal stabilities.
Many zinc oxide nano-rods at a time can be grown vertically
on a sapphire substrate, as seen in Figure 1. The diameters
of the rods range between 60 to 90 nm and their
lengths between 1 to 2 µm. The zinc oxide nano-rods can
be fabricated by MOCVD on sapphire substrates. Our research
interest is on the investigation of the lasing mechanism
inside the nano-rod cavities, and the possibility of
using zinc oxide nano-rods for the future development of
Sol-Gel Materials and Their Applications
Ast/P Pita Kantisara
is a fluid colloidal suspension of solid particles
in a liquid phase where particles are sufficiently
small to remain suspended by Brownian motion, and a
gel is a solid consisting of at least two phases where three
dimensional inter-connected network solid phase entraps
and immobilizes a liquid phase . Sol-gel process is
a process to produce bulk or thin film oxide materials
through the sol-gel chemistry, which involves two reactions
namely: hydrolysis and condensation reactions. The
commonly used precursors are metal alkoxides. Metal salt
solutions and other solutions containing metal complexes
can also be used as precursors. In the hydrolysis reaction,
the alkoxide materials are hydrolyzed by water to form
reactive monomers. The reactive monomers continue to
grow, through series of hydrolysis and condensation reactions,
to form three-dimensional inter-connected network
throughout the sol, which can then subsequently be
made into metal oxides gel. Various solid structures can
be obtained by applying different heat treatment. The
main advantage of the sol-gel process is the ability to
synthesis stoichiometric multi-component oxide materials
with various structures, which are very difficult or almost
impossible to achieve using other techniques. This
enables us to obtain materials with great variety of desired
properties (e.g. photosensitive, luminescent, specific op-
Figure 1: A scanning electron micrograph shows zinc oxide
nanorods grown on a sapphire substrate. Individual nanorods,
when properly detached, can be made to lase when pumped with
355 nm light.
tical constant etc.) for various applications, especially in
photonics. The sol-gel process is also inexpensive compared
to other techniques.
In PhRC, we have used the sol-gel process to synthesize
photonic materials for waveguide based devices, low
k materials, micro-lenses and phosphor thin films.
In our laboratory, we have worked on the sol-gel technique
for both passive and active optical waveguide devices
for a number of years. Recently, we have been developing
the SiO2-GeO2 system for waveguide based devices
such as AWG and other devices based on the materials
photosensitivity. The deposition parameters to obtain
high quality films for photonic devices have been developed
and optimized [2-4]. The refractive index can
be tailored easily by varying the GeO2 dopant concentration.
The technique to obtain photosensitive materials
has also been developed. We have obtained high refractive
index change ∆n, of about 0.01, after UV treatment.
The change in ∆n can be tailored by varying the UV treatment.
Project team: K. Pita, Ngo Quac Nam John, C H Kam,
S C Tjin, Zhang Qinyuan, Charles Ho Kin Fai, Rajni
Low k material
Porous dielectric materials are now finding applications
in high speed IC interconnects and solid state lasers.
Pores are necessary to reduce the material density and
hence the dielectric constant. In addition, pores can act
as nanometer sized receptacles for the embedding of optically
active particles. The technique we have used for
synthesis is a multi-step sol-gel process whereby two precursors
instead of one are used. One of the precursors
crosslink to form a basically linear network while the
other with a different molecular structure forms a highly
branched network. This overcomes the shrinkage problem
that commonly plagues sol-gel films. The reason is
that the precursor forming the highly branched structure
acts as a cushion and provides greater structural integrity
to the film against surface tension forces. By this approach,
a dielectric constant ∼2.5 has been obtained in
silica. This compares well with 3.9 for bulk silica.
Project Team: A/P Terence Wong.
(please refer to Modern Optics under Fibre and Laser Optics
Phosphor thin films
Various phosphor thin films have been developed for
display and lighting applications. Red, green and blue
phosphor thin films have been developed based on the
Zn2SiO4 and Y2SiO5 host materials doped with various
dopants such as Mn, Eu, Ce and Tb [5-9]. The solgel
technique has been employed to obtain stoichiometric
multi-component oxide thin films. Efficient emission
from the phosphor thin films has been obtained. Fig. 1
below shows the green emission of Mn doped Zn2SiO4
thin films for various Mn concentration under UV excitation.
Currently, Y2O3 host materials with various
dopants and co-dopants is being developed to further increase
the emission efficiency.
Project team: K. Pita, CHKam,ChongMunKit.
 C. J. Brinker, G. W. Scherer, “Sol-gel chemistry of sol-gel
processing”, Boston: Academic Press, 1990
 Charles K. F. Ho, Dexter C. L. Gwee, Rajni, K. Pita, Q.
N. Ngo, C. H. Kam, “Planar optical waveguides fabricated
by sol-gel derived inorganic silicate glass”, Proceedings of
11th European Conference on Integrated Optics: Prague-
Czech Republic, 1, 2-5 Apr (2003) 305-308
 Charles K. F. Ho, Dexter C. L. Gwee, Rajni, K. Pita, Q.
N. Ngo, C. H. Kam, “Fabrication and characterization of
optical waveguide material by the inorganic sol-gel process”,
Proceedings of Conference on the Optical Internet
& Australian Conference on Optical Fibre Technology:
Melbourne-Australia, 13–16 July (2003).
 Charles K. F. Ho, K. Pita, Q. N. Ngo, Q. Y. Zhang, C. H.
Kam, “Low optical absorption and high refractive index
GeO2:SiO2 films for waveguide devices by the sol-gel process”,
submitted to Journal of Non-crystalline Solids.
 R. Selomulya, S. Ski, K. Pita, C. H. Kam, Q. Y. Zhang and S.
Buddhudu, “Luminescence Properties of Zn2SiO4:Mn +2
Thin Films by a Sol-Gel Process”, Materials Science and
Engineering B100 (2003), 136–141
 Q. Y. Zhang, K. Pita and C. H. Kam, “Sol-Gel derived zinc
silicate phosphor films for full-color display applications”,
Journal of Physics and Chemistry of Solids 64 (2003), 333–
 Q. Y. Zhang, K. Pita, S. Buddhudu and C. H. Kam, “Luminescent
properties of rare-earth ion doped yttrium silicate
thin film phosphors for a full-colour display”, J. Phys. D:
Appl. Phys. 35 (2002), 3085–3090
 Q. Y. Zhang, K. Pita, W. Ye and W. X. Que, “Influence
of annealing atmosphere and temperature on photoluminescence
of Tb 3+ or Eu 3+ -activated zinc silicate thin film
phosphors via sol-gel method”, Chemical Physics Letters
351 (2002), 163–170
 Q. Y. Zhang, K. Pita, W. Ye, W. X. Que and C. H. Kam,
“Effects of composition and structure on spectral properties
of Eu 3+ -doped yttrium silicate transparent nanocrystalline
films by metallorganic decomposition method”,
Chemical Physics Letters 356 (2002), 161–167
Figure 1: Display of bright green
emission from a Zn2SiO4:Mn2
+ single layer film on SiO2/Si
wafer under a 10 watt UV source
in ambient light
PHOTONIC MATERIALS & DEVICES RESEARCH September 2003 19
Organic Light Emitting Diodes (OLED)
A/P Terence Wong Kin Shun
Organic light emitting devices are like the conventional
inorganic LEDs except that the active
layer are made from molecular thin films composed
mainly of carbon and hydrogen. This emerging optoelectronics
technology began in 1987 with the first small
molecule OLED developed at Eastman Kodak and received
a further boost with the observation of electroluminescence
in thin film conjugated polymers at Cambridge
The most promising area of application for organic
electroluminescent materials is in information displays,
especially large area emissive displays and displays on
curved or flexible surfaces, which have been gaining in
importance in recent years as a result of the growth
of portable wireless devices. OLED provides a viable
medium for a sheet of light on a nonplanar substrate,
something that inorganic LED cannot achieve.
All OLEDs are based on a capacitor type structure
(fig.1). The active organic layers are sandwiched between
two electrodes one of which is transparent. Before a bias
is applied, there are no carriers within the organic layer.
The carriers must be injected from the electrodes. Within
the organic layer, the carriers-electrons and holes - meet
and form entities called excitons. When these excitons
decay, a photon is emitted.
Figure 1: Schematic diagram of an OLED
Research on OLEDs at the PhRC began in 1995. The
initial effort has focused on the synthesis of molecular
complexes and conjugated polymers and the study of
their optical properties. The conjugated polymer studied
was the homopolymer polythiophene and its alkylsubstituted
derivatives. The structural, thermal and thermomechanical
properties of these polymers were studied.
In addition, the direct patterning of the polymer films by
an ultraviolet laser was demonstrated. Discrete OLED devices
were fabricated in-house using these materials (see
Figure 2: Discrete OLED with patterned emission area. Emission
color is yellow
We have worked on improving the efficiency of the devices
by incorporating charge transport layers. We have
studied the use of a mixed organic/inorganic solvent to
electropolymerize polybithiophene at low voltage, and of
an electrochemically deposited polybithiophene layer to
enhance the performance of an OLED. Chemical synthesis
of rare earth metal chelate complexes and oligomers
emitting in the blue and violet part of the spectrum, and
synthesis of conjugated polymer blends and copolymers
are other ongoing works. At present, we are collaborating
with industry to build better devices and the end goal is a
multicolor panel with possibly an active matrix driver.
N N N N
N N N
Figure 3: Examples of conjugated oligomers synthesised
Did You Know? In 1964, William Bennett invented the argon-ion
laser at Yale University. In 2000 his failing eyesight was corrected with
retinal surgery using an argon-ion laser.
Liquid Crystal Devices
Ast/P Sun Xiaowei
With the recent advances in matrix liquid crystal
displays (LCD) in monitor and television (TV)
applications, most of the technical issues including poor
viewing angle and color definition have been addressed to
an acceptable level. However, the response time of LCDs
using nematic liquid crystal (tens of millisecond) is still
not sufficiently fast for video displays. Blurred edge in
moving images impede its acceptance in the television
market. We shall show here a fast response LCD with
three-electrode driving .
Liquid crystal (LC) has the largest birefringence
known. It can be used to fabricate various kinds of optical
devices apart from display devices. For example, it has
been used to fabricate spatial phase modulator (SLM),
optical communication devices, adaptive optical devices
and so on. In the second part, we shall show a LC spiral
phase plate that can be used to generate doughnut beam
of any charge number .
Fast-response hybrid-aligned nematic LC
A new, three-electrode, hybrid-aligned nematic (HAN)
liquid crystal (LC) device for fast response applications
has been developed. The three-electrode configuration
generates electric field horizontally and vertically which
alternately turn the LC cell on and off. The fast response
is realised with both the turn-on and turn-off processes
driven by an electric field. The transmission and response
time of such a LC device as a function of the rubbing angle
were studied. A total response time (rise time plus
fall time) of less than 2 ms (more than ten-time improvement
over traditional twisted nematic LC) was obtained
for a non-optimised HAN LC cell with a cell gap (i.e., separation
between the glass plates sandwiching the LC) of
6 µm. Such a device is promising for video and other applications
where fast response is required.
Figure 1: The alignment of the LC in the x − z plane and y − z
Respons time (ms)
0 10 20 30 40
Rubbing Angle (Degree)
Figure 2: The response time, normalised transmittance as a
function of the rubbing angle
Liquid crystal spiral phase plates
Doughnut beam, a Laguerre-Gaussian (LG) beam, has
been found to contain orbital angular momentum
(OAM), which can be applied in guiding cooled atom,
optical transformation, frequency shifting and study of
optical vortices. To fully explore the potential of LC, LC
spiral phase plates with cell gaps of 7 µm, 20 µm and
30 µm have been fabricated and used to generate doughnut
beams. By stacking these liquid crystal spiral phase
plates, doughnut beams with any charge number (i.e., the
number of 2π phase change across the beam) can be obtained.
High efficiency and flexibility are the advantages
of generating doughnut beams by stacking liquid crystal
spiral phase plates .
For more information please refer to:
 C.Y. Xiang, J.X. Guo, X.W. Sun, X.J. Yin and G.J.
Qi, “A Fast Response, Three-Electrode Liquid Crystal
Device”, Jpn. J. Appl. Phys. 42, L763 -L765 (2003).
 Q. Wang, X.W. Sun and P. Shum, “Generating
doughnut beam with any charge number by liquid
crystal spiral phase plates”, Appl. Opt. (accepted).
article continued on page 27. . .
PHOTONIC MATERIALS & DEVICES RESEARCH September 2003 21
Fu Chit Yaw, Eddie Tan Khay Ming, Yang Kwang Wei
During the SARS epidemic, thermal imaging camera has become almost a household name. Just how does it work and how reliable is
it? The authors explain, and provide some suggestions for improvement.
Thermal infrared (IR) imaging is commonly used for
night vision. During the recent SARS epidemic, thermal
imaging cameras were used for fast and non-contact measurement
of a person’s temperature to determining if the
person has a fever . In many medical cases, temperature
rise or abnormal distribution of temperature may
appear as one of the first symptoms. Therefore, thermal
imaging is also a useful complementary clinical tool to aid
in the diagnosis of other medical condition, most notably
breast cancer (see Ref. 2 for more details).
Let’s first explore how thermal imaging works :
Figure 1: Image courtesy of Infrared, Inc.
1. The focused light is scanned by a phased array of
infrared-detector elements. The detector elements
create a very detailed temperature pattern called a
thermograph. It only takes about one-thirtieth of
a second for the detector array to obtain the temperature
information to make the thermograph.
This information is obtained from several thousand
points in the field of view of the detector array.
2. The thermograph created by the detector elements
is translated into electric impulses.
3. The impulses are sent to a signal-processing unit,
a circuit board with a dedicated chip that translates
the information from the elements into data for the
4. The signal-processing unit sends the information
to the display, where it appears as various colors depending
on the intensity of the infrared emission.
The combination of all the impulses from all of the
elements creates the image.
A thermograph of a human face, taken by one of the authors
(Joel Yang) is shown in Fig. 2 .
Figure 2: A thermograph of a human face take by a commercial
IR camera [courtesy Photonitech Pte Ltd., Singapore]
Now let’s take a look at the physics behind thermal
According to the Planck’s Law (as shown in Fig. 3), the
radiation of an object is determined by the object temperature.
A room-temperature object radiates at the peak
in the wavelength range of 7–14 microns, which is called
long-wave infrared (lwir) waveband. For high temperature
(∼ several hundred ◦ C ) object, the radiation peak
not only rises but also shifts to shorter wavelength, e.g.
the mid-wave infrared (mwir) waveband 3–5 microns).
The Stefan-Boltzmann Law relates the total radiant intensity
I (over the whole frequency range) of a blackbody
with temperature T by I = σT 4 ,whereσ is the Stefan-
Boltzamann constant (5.67 × 10 −8 Wm −2 K −4 ). Therefore,
in principle, the temperature of an object can be determined
from the radiation emitted by the object integrated
over all wavelengths. However, the Planck’s Law
describes the radiation from an ideal object with unity
coefficient of emissivity, the so-called blackbody. Real objects,
however, will emit less radiation as the emissivity
is less than unity. For example, the emissivity of human
body is commonly accepted as 0.95. One can determine
the nominal temperature from the measured radiation by
assuming the real body as a blackbody, but the emissivity
has to be known in order to determine the actual temperature.
Power Exitance [W/(cm 2 ·s·µm)]
0 5 10 15 20
Figure 3: Planck’s blackbody radiation law
Bolometer—the sensor of the thermal
There are two fundamental types of infrared detectors -
thermal detectors and photon detectors. In photon de-
tectors, photo-carriers are generated by absorbing the infrared
photons and the electric signal is proportional to
the number of the received photons. These detectors may
operate in photoconductive, photovoltaic, or photoelectromagnetic
modes. Because the infrared photon energy
(∼ 0.1 eV) is very small, narrow bandgap materials, such
as InSb, PbSnTe and HgCdTe, or multiple quantum wells
have to be used for infrared detection. In order to suppress
the current leakage due to thermionic emission, the
detectors have to work inside a cryogenic cooling system
which is bulky, costly and cumbersome to use.
In thermal detectors, the infrared radiation interacts
with the lattice of material and changes the material
temperature, which is subsequently converted to a measurable
electrical quantity. The electric signal is proportional
to the radiation power. Typical thermal detectors
are thermistors, thermocouples, and pyroelectric/ferroelectric
detectors. The thermal imagers in the
market today use the resistive microbolometer, where a
membrane, thermally isolated from the substrate, is used
to obtain a high temperature rise in response to the incoming
radiation, and an embedded temperature sensitive
resistor subsequently transfer the temperature deviation
into electric signal. A material with large temperature
coefficient of resistivity (tcr) is used to enhance the
sensitivity of the bolometer.
The most promising benefit of thermal detectors is
their ability to operate near room temperature (or an uncooled
environment), where only a temperature stabilizer
(i.e. thermo-electric cooler, tec) is needed rather
than the more complicated cryogenic cooling system,
thus lowering costs and increasing reliability. A commercial
imager uses an array of microbolometers, called Uncooled
Imaging Array, and a Germanium lens to focus the
IR radiation from the target object onto the sensors.
How accurate can an IR detector
measure body temperature?
This question has been raised in response to the rather
controversial claims made by some companies about the
accuracy of the imagers they are marketing. We asked our
expert, Prof Mei Ting, a member of PhRC, who has this
In thermal imaging cameras, the object temperature is
not measured directly, but indirectly through the IR radiation
incident on the detector in the imager. This received
radiation is determined not only by the object temperature,
but also by several other factors.
THERMAL IMAGING September 2003 23
The surface emissivity of the object being imaged is
the biggest unknown affecting infrared thermal measurements.
At present there is no model to describe the precise
relation between the skin temperature and the body
temperature. The practical way of correction is just to
setanoffset, say 0.5 ◦ C. Further work has to be done
to explore this issue for the thermal camera in SARS application.
The emissivity should be determined for each
specific measurement situation.
Other factors that can introduce uncertainties are ambient
temperature, atmospheric transmittances, path radiance,
as well as the intrinsic non-linearities of the
instrument’s electronics. Remote infrared calibration
sources placed in the detection plane can help to suppress
the uncertainty from environment.
Typical radiometric system has a radiometric accuracy
of 2%, which corresponds to a temperature accuracy
±2 ◦ C for a detection range of −20 ∼ 500 ◦ C. Since human
skin temperature varies in a small range, narrowing
down the detection range (i.e. 0 ∼ 40 ◦ C) greatly reduces
the instrument errors. Now, many infrared cameras manufacturers
are able to achieve ±0.2 ◦ Cwithadetection
rangeof0− 40 ◦ C with the above improvements.
 R.James Seffrein, “Thermal Imaging for Detecting
Potential SARS Infection”.
Photonics Research Centre Seminars in 2003
Date Speaker Topic
 Maxtech International Inc., http://www.maxtechintl.com/infrar.htm
 Joel Yang from Network Research Centre (NTRC) is
currently working on a project in collaboration with
Photonitech Pte Ltd., Singapore.
 A. Rogashki, “Infrared Photon Detectors”, Bellingham,
Washington: SPIE Optical Engineering Press,
 P. W. Kruse, “Principles of Uncooled Infrared Focal
Plane Arrays” in Semiconductors and Semimetals, vol.
47: Uncooled Infrared Imaging Arrays and Systems
ed by P.W. Kruse and D.D. Skatrud, pp. 17–42, San
Diego: Academic Press, c1997.
 John Wallace and Kathy Kincade, “Infrared
cameras find hot spots in nuclear
reactor”, Laser Focus World, July 2003.
24 January A/P Chin Mee Koy Photonic Integrated Circuits
7March Ast/P Yu Siu Fung Modeling of Optoelectronics Devices - Past, Present and Future
24 March Prof. Paul French
Imperial College, U.K.
Time-resolved Fluorescence Microscopy
24 March Prof. Kenny Weir
Imperial College, U.K.
Fibre Optic Sensors
4April Ast/P Ricky Ang Lay Kee Intense Beam Interaction with Surrounding Structures
25 April Ast/P John Ngo Quoc Nam Electrically tunable dispersion compensator with fixed center
wavelength using fiber Bragg grating
5 June Ast/P Pita Kantisara Electrochromic Materials and Devices
13 August Dr. Chye Yew Hee
Ferromagnetic/Semiconductor Hybrid Structures for Spin Ma-
18 August Dr. Zhu Furong
Low temperature transparent conducting oxide for flexible or-
ganic light emitting devices
20 August Ast/P Rajesh Menon Zone-Plate-Array Lithography (ZPAL):A novel approach to maskless
8SeptemberDr Han Mingyong
Lee Woei Ming, Zhang Dianwen, Tao Shaohua and Yuan Xiaocong
In nature, light from the Sun provides plants with the
means of making food, and hence energy that sustains
the cycle of life on Earth. In science, light from
laser beams is providing biologists with a new means of
studying the intricate details and functions within single
living cells. It has become a tool to discover life itself.
Laser beams used to trap and manipulate microscopic
particles are called optical tweezers. The first optical
tweezer was demonstrated by Dr Arthur Ashkin  and
co-workers in the 1980s at Bell Labs. They demonstrated
that light can move matter because photons carry linear
momentum (a photon of wavelength λ has a momentum
p = hc/λ, where h is the Planck’s constant, and c
is the speed of light). In their experiment, a highly focused
Gaussian beam was used to create an optical gradient
force on a particle with a higher refractive index
than the surrounding medium. As light refracts when it
passes through the micro-objects, the refraction of light
will cause a change in the photon linear momentum, and
due to the conservation of momentum, a force will result
which acts on the particle in the opposite direction. This
force is directed towards the area of the highest intensity;
hence the particle is trapped in the center of the beam.
Figure 1: 1st type of optical tweezers
Another type of optical tweezer is based on the orbital
angular momentum property of a Laguerre-Gaussian
(LG) beam, TEM∗ 0l , also known as an optical vortex .
In this case, the particles are trapped in the region of zero
intensity at the center of the LG beam [see Fig. 2]. The
optical traps created by the helical LG beams of light (due
to a phase singularity) can also exert optical torques on
the trapped objects. The special intensity profiles of these
beams are created by engineering the phase of the laser
Figure 2: 2nd type of optical tweezers
Figure 3: Irregular shaped optical tweezers
In NTU, we have begun a research project on optical
tweezers only in the past year. Our initial focus is to build
a strong foundation for the fundamental understanding
of optical tweezers. At the moment, we are able to generate
irregular shaped beams to be used as a new form
OPTICAL TWEEZERS September 2003 25
of optical tweezer  [see Fig.3]. These irregular shaped
beams have patterns of dark zones in their cross sections
due to an asymmetric spiral phase. It is possible to generate
tight optical trapping by matching the intensity distribution
with the objects to be trapped.
In addition, we have also created a new version of optical
tweezers with multiple optical forces . The basic
theory behind the multiple-force optical tweezers is
that when two LG beams with opposite and unequal order
of helicity interfere, the resulting beam will appear in
the form of bright invariant spots arranged in a circular
manner. This resulting beam may allow effective stacking
of micro-particles and the creation of 3-dimensional
structures at each of the bright spots (as demonstrated
by Dhlokia ), while still being able to transfer orbital
angular momentum, something which was not possible
The multiple force optical tweezers will be a new optical
tool used for the simultaneous angular deformation
of cell structures. Furthermore, by being able to create
3-dimensional objects, it may be used to create photonic
crystals as well. The novel double hologram set-up
[see Fig. 4] that is used to generate the multiple optical
tweezers can be easily transformed into an attachable
laser module system. This will be much more feasible
than using an expensive SLM or a conventional interferometer.
Such a system is being built in our laboratory [see
Figure 4: The double hologram set-up.
Figure 5: Optical trapping experiment
Potential Applications of Optical
Optical tweezers clearly have many applications in life
and medical sciences. A 1994 study by the U.S. National
Academy of Sciences placed high priority on research into
highly promising new technologies for the control and
manipulation of atoms, molecules, charged particles and
light. The report also predicted that the “optical tweezers
are likely to be invaluable in the Human Genome Project”.
Recently in March’02, Optics Report identified three
additional industries that laser tweezers will have impact
on. These include the $3 billion fertility market, the 100
million electrophoresis (molecular separation) market,
and the micro-machine market expected to reach $100
billion in the next decade.
In in-vitro fertilization, optical tweezers can be used
to assist sperms in swimming towards the eggs, instead
of being surgically inserted which may cause damage to
both sperm and egg. In the study of how viral DNA infects
cells of other organisms, researchers were able to use
optical tweezers to study how the viral DNA infects a living
cell. Better design of drugs to interfere with the viral
DNA packing and new gene therapies may be made possible
by transporting new genetic materials into the cells
using optical tweezers.
 Ashkin, A., Dziedzic, J. M., Bjorkholm, J. E. and Chu,
S.,“Observation of a single-beam gradient force optical
trap for dielectric particles”, Opt. Lett. 11, 288-
 He, H., Friese, M. E. J., Heckenberg, N. R.
and Rubinsztein-Dunlop, H. “Direct observation of
transfer of angular momentum to absorptive particles
from a laser beam with a phase singularity,”, Phys.
Rev. Lett. 75, 826-829 (1995).
 V. Garcés-Chávez, D. McGloin, H. Melville, W. Sibbett
and K. Dholakia, “Simultaneous micromanipu-
continued from page 21. . .
lation in multiple planes using a self-reconstructing
light beam”, Nature 419, 145 (2002).
 D. W. Zhang and X.-C. Yuan, “Novel optical doughnut
for optical tweezers”, Optics Letters (USA), Vol.
28, p. 740-742, (2003).
 W. M. Lee, X.-C. Yuan and D. Y. Tang, “Optical
tweezers with multiple optical forces using double
hologram interference”, Optics Express (USA), Vol.
11, p. 199-207, (2003).
 M.P Macdonald, L Paterson, K Volksepulveda, J.Arlt,
W. Sibbett, K Dohlakia, “Creation and Manipulation
of three dimensional optically trapped structure”,
Science 296, 1101 (2002).
Figure 6: (a) Photograph of the LC spiral phase plate and (b) The doughnut beams with charges 1, 2 and 3 generated
(top) and the corresponding simulated doughnut beams (bottom)
Figure 7: Demonstration of a rotating fan-like interference pattern (vortex) generated by the inference of a doughnut
beam with charge 3 and a Gaussian beam.
OPTICAL TWEEZERS September 2003 27
Physicists Produce Photons Ideal for
Compiled by Zhao JingHua
Advances in Photonics Around the World
Physicists at the Max Planck
Institute for Quantum Optics
in Garching, Germany,
have used a rubidium atom
that was strongly coupled
to a high-finesse optical
cavity (above) to produce,
on demand, a sequence of
single photons with welldefined
and identical properties.
The photons are created
by an adiabatically driven stimulated Raman transition
between two atomic ground states. This process is performed
in a unitary way and is therefore reversible, which
the researchers say makes it ideal for sending and receiving
single photon states within a quantum-computing network.
The group described the process in the Aug. 5 issue
of Physical Review Letters.
Electrical pulses break light speed
Pulses that travel faster than light have been sent over a significant
distance for the first time. Alain Hache and Louis
Poirier of the University of Moncton in Canada transmitted
the pulses through a 120-metre cable made from a coaxial
“photonic crystal”. To create their cable, the Canadian
researchers joined together five-metre sections of coaxial
cable with alternating electrical impedance. They sent
electromagnetic pulses with frequencies between 5 and
15 MHz through the cable, and found that the group velocity
reached 3 times the speed of light for frequencies
in the absorption band. This was remarkable in comparison
with many existing information systems that are based
on coaxial cables with data speed of just two-thirds the
speed of light. The achievement that utilized the backreflection
caused by impedance mismatch raise hopes that
data could travel through electronic communications systems
at almost the speed of light.
A Hache and L Poirier 2002 Appl. Phys. Lett. 80 518
A breakthrough in teleportation
When physicists teleported photons for the first time in
1997, they had to destroy the photons to be sure that the
teleportation had been successful. Now a team at the University
of Vienna has managed to teleport photons without
destroying them. Jian-Wei Pan and colleagues believe
that their method could be the next step towards longdistance
quantum communication. In a standard telepor-
tation experiment, a laser is directed at a crystal with nonlinear
optical properties. Occasionally the photon will
be “down-converted” into two lower energy photons, and
sometimes these photons will have their polarizations entangled
wherein one of them is vertically and the other
horizontally polarised. By using a filter to reduce the intensity
of the photons that are going to be teleported, the
researchers were able to significantly reduce the number
of spurious detection events. The Vienna team could be
97% certain that the state had been teleported to a photon
without actually having to detect it. Such a high accuracy
means that the teleported photons could be used
in “quantum repeaters” for long distance communication.
The team now hopes to combine these results with a technique
known as entanglement purification to further develop
quantum communication over long distances. (J -.W
Pan et. al. ,Nature, 421 721, 2003).
Laser takes up gene therapy
Scientists in Germany have used a Ti:sapphire laser to
transfer DNA into a cell. Femtosecond lasers improve the
transfer of DNA into cells and could advance the fields
of gene therapy and DNA vaccination, according to Uday
Tirlapur and Karsten König of Friedrich Schiller University
U. Tirlapur and K. König, Nature, 418 290
See-Through Thin-Film Transistor
Transparent electronics may
seem the stuff of science
fiction, but engineers from
Oregon State University and
Hewlett-Packard Co. in
Corvallis, Ore., have developed
transistors that they hope
will find applications in liquid
crystal displays and elsewhere.
They reported the devices,
which display optical
transmission in the visible portion of the electromagnetic
spectrum of approximately 75 percent, in the Feb. 3 issue
of Applied Physics Letters.
The team fabricates the N-type semiconductor devices
by depositing a layer of indium tin oxide and aluminium
titanium oxide on a glass substrate. The zinc-oxide channel
and indium-tin-oxide source and drain electrodes are
subsequently added to the stack by ion-beam sputtering.
Making presentations work:
National Lecture Competition
Charles K. F. Ho
3rd price overall: Development of optical materials
by the sol-gel process
Competition Organizers: Institute of Minerals, Metals
and Materials, UK and Institute of Materials, East
Flashback: March 2003 – South-east Asia Regional
Competition in NTU, Singapore.
Now the Finals, London, UK
Taking the london tube to the venue on the East
End, I really felt that I could not have been more
prepared (with all the first year presentation trials,
onfig progress report and the regional qualifier presentation).
Upon arrival, I found myself submerged in a
crowd of academic and industry representatives from the
world of material science. Like everyone else, I was overwhelmed
by the unique ambience and the interior decoration
of the building (see photos). It was full of medieval
armour suits, which gave me shivers down my spine. Just
can’t help the thought that these suits might be haunted
by their owners. Furthermore, the Master of the Worshipful
Company of Armourers and Brasiers (the main corporate
sponsor and they make armours!), indicated that this
very same building dates back all the way to the 1600s. It
survived the ‘Great London Fire’ in 1666 and ‘The Blitz’
during wwii. This just helped to feed my imagination
about these armours jumping down from the wall!
With all the opening addresses, the finals officially
kicked off with the first contestant taking the stage.
Scrolling down the program, I found that I was the only
oversea representative. So it was me versus the entire
United Kingdom! WOW, it could be rough. Then I
thought to myself with some pride...it did somewhat
made sense for me to represent the overseas region as I
was born in Hong Kong, studied in UK, moved to Canada
and now studying in a Singapore University. These countries
represent a good portion of the commonwealth!
The presentations of the other finalists from different
regions of the UK covered a broad spectrum of applications:
biomaterials, instrumentation, composite materials,
materials simulation, making of bells, etc. They were
all entertaining and informative in their own way. Soon,
it was my turn to educate the audience about materials in
photonics. Taking a deep breath, I cracked a joke with the
crowd, and I was 15 mins away from the hope that all my
extravagant expenditure in London could be covered by
the prize money. I started my timer...The presentation
was so well rehearsed that I was actually finished with one
minute to go! It took me about 10 seconds to bring myself
to believe my stopwatch and another 10 to figure out
what to say to make the most out of the remaining 40 s.
And then I said my grace and took my next breath!
After a delicious buffet dinner, the long awaited moment
arrived. VIPs assembled on the stage. The announcement
came with me taking the third place overall.
Well, I really didn’t mind to hear my name a few
more minutes later (when they announced the 2nd and
NATIONAL LECTURE COMPETITION 2003 September 2003 29
1st place). Anyway, I realized soon after that the most precious
gift from the competition was not the prize money,
but the recognition. VIPs and other attendees then came
to extend their congratulations. For those who could appreciate
my work, they even offered me employment and
collaboration in the future. This, I think, is pretty priceless.
On the whole, I feel that I had put on an impressive
performance and established a respectable image for ntu
and Singapore. Mission Accomplished!
Publishing our work in renowned journals or magazines
is of course the big thing in research. However, I
would like to encourage my colleagues to be aware of all
the opportunities around you. You maybe able to submit
Benjamin Tay Chia Meng
The very first social gathering under the aegis of Photonics
Research Center (PhRC) was held earlier this year at
Yunnan Corner, NTU. 80% of the lecturers, staff, technicians
and postgraduate students attended this momentous
event which was packed with games, prizes, food
and loads of fun. Everyone got to mix over drinks
and games, a pleasant respite from laboratories and lecture
classes...The Guest of Honour was our Head of the
Microelectronics Division, A/Prof Tan Ooi Kiang, and
your work to competitions, awards and scholarships held
by institutes and professional societies. With a little luck,
At last, I would like to give credits to my two supervisors
(Asst. Prof. Ngo Quoc Nam and Asst. Prof. Kantisara
Pita) for their generous and effective guidance. And I
must complement the Admin team in the School of eee,
on the First Year Evaluation process for research students.
It has ultimately contributed to the success of my showing
at this competition.
For details on this competition, please see the following
the Chairman of the event was the Director of PhRC,
A/Prof Tjin Swee Chuan. They kicked off the event by
revealing some of the hard work behind the scene that
paved the road to the establishment of the PhRC. Dr Tjin
reported the future plans for the Centre, including research
collaborations with Imperial College (U.K.) and
Thales Training Centre (Singapore). The logo for the
Centre, selected from a pool of entries, was then unveiled
for the first time.
Congratulations to Hery Djie who designed the winning
After a refreshing international lunch buffet, the guests
were treated to an audio-visual delight presented by the
Photonics Production team. The video drama covered
the different facets and faces of our Labs with a bit of sitcom
to spice things up. The film is a tribute to all the
members of the Centre and a reminder that as a team,
nothing is impossible. Then we ‘excited’ our guests into
motion through a series of games like “Lossy Waveguides”
in which contestants had to finish a drink using
straws with holes in them. A difficult task, indeed, be-
sides the mess. Other games include “Who wants to be
a MUUUMMMMIE” in which the contestants raced to
wrap a MUMMY in toilet paper, and also “Optical Message
Transmission”, where members of a group try their
hands at charades.
The climax of the event was marked by the exotic Indian
dance performed by members of the Centre drawn
from various nationalities, who gave their best to show
the audience the nifty footwork and choreography that
made up traditional Indian dances. The event closed with
prize presentation to the winners of the games and lucky
draws. A fruit cake topped with Snow White and the
Seven Dwarfs figurines and a single candle was cut to celebrate
of the fresh start of Photonics Research Group as
a research Centre. At the end of the day, everyone took
something home, some good laughs, a full stomach, some
prizes and best of all good times with friends, colleagues
Thanks to all the volunteers who had contributed their
time and effort in planning the event and making it come
true. It would not be as successful were it not for the enthusiasm
and creativity of the organizers. You know who
PHOTONICS GATHERING 2003 September 2003 31
Some pictures from the gathering
The Event Organizing Team.
In case you haven’t notice,
we are getting bigger!
Enjoying the buffet lunch.
The game is about to begin!
Everybody is having a good time.
Prof. Tjin and his rendition
of the Hare & Turtle race.
Indian food, anyone?
“Dandiya”, or dance with sticks,
performed by a group of PhD students.
The Centre welcomes the following staff and students
– Asst/P Julian Chan Chi Chiu
– Asst/P Rajesh Menon
– Dr Tamil Selvan, January 2003
– Dr Wu Jiu Hui, February 2003
– Dr Rudi Irawan, March 2003
– Muhammad Fueyz Karim, March 2003
– Dr Li He Ping, April 2003
– Chen Qing, June 2003
– Moh Ken-Jin, June 2003
• PhD students
– Zhao JingHua, January 2003
– Fu Chit Yaw, February 2003
– Balpreet Singh Ahluwalia, March 2003
• MEng students
– Yu Jia, January 2003
A Memorandum of Understanding (MOU) has been
signed between NTU (School of EEE), Institut d’Optique
(France) and Thales Research and Technology (France).
The purpose of the MOU is to promote closer relations
and exchanges in the fields of signal and image processing,
optics, telecommunications, microelectronics and
Professor André Ducasse, Director Général from Institut
d’Optique, Mr Dominique Vernay, Thales Technical
Director, Mr Patrick Plante, Director of Thales Singapore
and Professor Er Meng Hwa, Dean of School of EEE,
NTU, signed the MOU on July 2003, bringing into existence
a collaboration between the institutions which will
bring research to new heights.
Events which are covered in the MOU includes:
• The exchange of teaching and research staff between
• The exchange of information on academic and research
programmes available in each institution
• The formation research teams on subjects of common
• To welcome undergraduates, Posgraduate students
and Post doctoral fellows in appropriate programs,
both current and future
• To encourage mutual participation in conferences,
seminars and courses organized by each institution
Lipi Mohanty has given birth to a baby girl on 17th July.
She is healthy and weight in at 3.7kg! Best wishes from all
Upcoming Photonic Conferences
IOOC 2003 14th International Conference on Integrated
Optics and Optical Fibre Communication.
September 21–25, 2003. Rimini, Italy
LEOS 2003 16th Annual Meeting of the IEEE
Lasers & Electro-Optics Society. October
26–30, 2003. Tucson, Arizona
ICMAT 2003 International Conference on Materials
for Advanced Technologies. December 7–12, 2003.
CLEO/Pacific Rim 2003 The 5th Pacific Rim
Conference on Lasers and Electro-Optics.
December 15-19, 2003. Taipei, Taiwan
Did You Know? The vibrant colours on many butterflies are not due to
pigments (i.e. biochemistry) but optical diffraction (photonics) caused
by the physical structure of the wing surface. An aquatic creature
called a sea mouse produces iridescent colours using hairs with arrays
of microscopic holes, creating what is known as a photonic band gap.
Natural structures such as these are being studied for their application
to photonic devices.
PHOTONICS GATHERING 2003 September 2003 33
A message from the Editor
It is definitely an exciting time for us at the PhRC in Singapore.
As a PhD student myself, it is most certainly a
benefit for us to have the Centre gaining more exposure.
And this was the vision that Lee Woei Ming saw early on
this year: an e-magazine to promote our work in photonics
both at home in Singapore and abroad. True to
our passion, we swiftly put together an editorial team and
made this publication a reality in a short time span of a
few months. As much as this issue of Photonics ’La marks
the first year of the PhRC, it is the first time for many of
the student editors participating in an editorial team of a
scientific literature. I would like to take this opportunity
to acknowledge all my colleagues who shared the same
vision as Steve and sacrificed their own time to help kick
start this inaugural issue. In particular, our layout/design
guru, Chrisada, has become the backbone of our production
team in this special issue. He had contributed im-
hotonics'a —what a feisty name! It is a name that
conjures up many images—for me, the vigour of Latin
dances and romance on a Caribbean beach. . .
What is Photonics? Simply put, it is the knowledge that
revolves around the Photon, the particle of Light, just as
Electronics is the knowledge around the Electron, the unit
of electric charge.
If this seems abstract, think of the first moment in your
life, when you opened your eyes for the first time, and
were greeted with dazzling brightness and images...Such
were the first gifts of Light! Without light from the sun,
Life as we know it would be impossible.
The study of light and its interaction with matter led
to a special form of light not found in nature, the Laser,
which in turn led to a myriad form of applications. Advances
in the technology for harnessing the power of
light continue unabated. Discoveries are constantly being
made in the laboratories worldwide.
Some of these discoveries are being made here in
NTU’s Photonics Research Centre, as you will find out
in these pages.
In Biophotonics, optical tweezers for manipulating
DNA, and femtosecond optical pulses for taking snapshots
of the molecules, are exciting examples of how light
may be used to understand life itself.
In this information age, light is the superhighway in
which information flows without friction. New fibre-
mensely to the uniqueness of our publication with his
personal touches from the front to the back cover. And
most of all, we salute our faculty advisors Assoc. Profs.
Chin Mee Koy and Tjin Swee Chuan for their tremendous
effort in enlightening us with their invaluable suggestions
and editorial assistance.
In the future, we hope to involve a bigger team of students
and staff alike to put together an even bigger feast of
good articles, both technically and visually. If you would
like to experience the thrill of editing future issues of
hotonics'a , or to contribute in any other way, please
feel free to email us at firstname.lastname@example.org.
Let’s enjoy Photonics’La!
Charles K.F. Ho
optic components and high-speed optical devices are
constantly being invented to push the limits of optical
Started 10 years ago, the Photonics Laboratory has matured
into a research center with some renown and a
wide range of activities, attracting some of the best students
from the region and producing graduates who have
helped to build a nascent photonics industry in Singapore.
This inaugural issue of Photonics’La is an appropriate
and timely vehicle to mark the 10th year milestone, and
to commemorate the inauguration of the research group
In addition, the special collectible edition provides useful
information on the research and teaching activities
within the Centre for our sponsors, collaborators, supporters,
and the public at large.
The idea for the newsletter and its name was conceived
by a group of enthusiastic students. As their faculty advisor,
I applaud the zest and creativity with which they have
brought to the editorial process. I also wish to acknowledge
my colleagues for contributing the many research articles
for this special issue. Thanks!
Vive Le Photonics!
A/P Chin Mee Koy
ZUGO PHOTONICS PTE LTD
Established in 1994, we are the premier Regional
Distributor in South East Asia, specializing in photonics,
industrial and scientific laser systems, fiber optics
components for telecommunications, optical networking
solutions, infrared camera systems, and devices for
semiconductor manufacturers. We distribute major
brands that are reputable global market leaders in their
respective fields. These names include:
• JDS Uniphase
• Lambda Physik
• FLIR Systems
• Quantel Lasers
• Ophir Optronics
• Prior Scientific
• Rsoft Design
• Spectron Lasers
Zugo Photonics Pte Ltd
55 Kaki Bukit View,
Kaki Bukit Techpark II,
Tel: (65) 6844 0055
Fax: (65) 6844 0655
Your partner in advanced technology.
249 Jalan Boon Lay, Singapore (619523), Tel : 65-66607060
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From ideas deas to experimental setup,
prototype, prototype, and and beyond… beyond…
EINST Technology provides
you with solutions for your
research needs. We specialize
in Imaging, Microscopy, Optics
We work with researchers across
various disciplines to crystallize
ideas into experimental setup,
providing components, modules,
instruments and turnkey solutions.
EINST provides the level of support
you require so that you can focus
on your research, not your setup.
EINST Technology Pte Ltd
627A Aljunied Road, #09-07, BizTech Centre, Singapore 389842 Tel: (65) 67485828;
Fax: (65) 67489113; Email: email@example.com
Contact us now to discuss your needs with our
Contact us at firstname.lastname@example.org
Editor-in-chief Charles K. F. Ho
Assoc. Prof. Chin Mee Koy
Assoc. Prof. Tjin Swee Chuan
Editor Benjamin Tay
Writers/Reporters Fu Chit Yaw,
Zhao Jing Hua, Chong Mun Kit
Eddie Tan Khay Ming
Layout/Design Chrisada Sookdhis
Graphics Designer Steve Lee Woei Ming
Photographer Eddie Tan Khay Ming
Public Relations Joanne Huang
Supporting staff Hery Djie,
Jesudoss Arokiaraj, Zhang Xu Ming
Treasurer Yong Kim Lam