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.