Our research theme exists at the interface
between optical physics and material science, i.e. light-matter
interaction. Besides the physical interest, potential application is
always our strong driving force for the research. Current research
activities will focus on but not limited to the following topics.
Optical spectroscopic
characterization
Optical spectroscopy provides a powerful tool for
understanding the physical properties of a wide range of condensed
matters. The investigated materials cover from the traditional inorganic
semiconductors (bulk, quantum dots, wires and wells), organic semiconductors
to artificial materials (organic/inorganic hybrid structures and
composites). We are interested in the investigation of electronic
structures, various elemental excitations and their dynamic process in
semiconductor structures; energy transfer; charge separation and
transport in various organic blends and organic/inorganic composites. The
clarification of the underlying physics is very important for both
fundamental physics interest and development of optoelectronic devices.
Optoelectronic Devices
On the basis of understanding the optical properties of a
wide range of materials, we will dedicate to develop useful
optoelectronic devices. For example, we will seek to utilize wide bandgap material systems to develop surface emitting
lasers for the important blue-green to ultraviolet wavelength range.
Taking advantage of the unique material properties inherent to wide bandgap materials, especially high excitonic oscillator strength and high exciton binding energy, it is expected to directly generate
solid state lasers in blue-green to UV wavelength range with high power
and high beam quality for a wide range of applications. The relevant
material processing techniques will be further developed to form high
quality microcavity in the strong coupling
regime, which will makes it possible to experimentally explore the
exciting physics of Cavity Quantum Electrodynamics and new concept
devices-room temperature polariton lasers.
Plasmonics Optics
In practical light emitting devices, the overall efficiency
depends on not only the internal quantum efficiency of the active
materials but also on the external conditions. Photonic crystals and
surface plasmon coupling are two effective
approaches to improving the light extraction rate from the active materials.
Surface plasmon polaritons
are created via the coupling of light to the motion of the conduction
electrons at a metallic interface. Enhanced emission from the surface plasmons is possible due to the large density of
states in their dispersion diagram. Excitation of surface plasmon polaritons within
the metal at nano-scale can create strong local
optical fields, which can be exploited for numerous applications, such as
single-molecule fluorescence, surface-enhanced second harmonic generation
and surface-enhanced Raman scattering etc. Photonic devices at nano-scale are possible because light can be confined
this way to dimensions below the diffraction limit of light. More over,
it has been shown that the hybrid metal/dielectric layers with particular
geometry display interesting transmission properties for electromagnetic
waves including wavelength selectivity, particular emission angle
distribution and even negative refractive index. Therefore the related
research is expected to have great impact on photonics and biomedical
detection.
Applications of Photonics
The combination of photonics and biotechnology may provide
some of the most exciting scientific and commercial prospects. Successful
commercial examples include corrective eye surgery and dentistry by
lasers etc.. New applications have also been
found for lasers in biomedical imaging, optical tomography and optical
biochips which use light to excite specially designed fluorescent
chemicals that can reveal important features about each cell such as how
it responds to a drug or whether or not it is diseased. However, there
are still a lot remained unknown in the interaction between photons and
bio-molecules, and big space exist in the use of light for both
diagnostic purposes and as a powerful tool for manipulating material on
cellular and sub-cellular length scales. We are interested in intra- and
inter biomolecules-photo-driven biological
processes with the aim of understanding how nature efficiently converts
solar energy to perform critical biological functions. The tools related
to the research include FRET based probes, anisotropic spectroscopy,
surface-enhanced Raman scattering, time-resolved fluorescence and
absorption, selectively excited fluorescence etc. The combination of
these techniques and nano materials (e.g.
carbon nanotubes and plasmon
resonant nano-metals etc.) can be used to
generate nanoscale biosensors. Such research
will be undertaken by synergic cooperating with chemists and biologists.
Post-doctoral
researcher positions available
There are three
Postdoctoral Research Fellow positions immediately available in my group
in the research fields of Optoelectronic Materials and Devices. Exciting
research projects have been deployed for five years. Interested
candidates with strong research background in optics, semiconductor
physics and/or material science should send an updated CV, a cover letter
describing their past research experience to Dr. Handong Sun at hdsun@ntu.edu.sg.