Research Topics

Prof CHEAH, Kok Wai

Supervisor: Prof. CHEAH, Kok Wai  (Tel: (852) 3411-7033; email:

1.          Optical Properties of Organic Complexes

2 photon up conversion luminescence    Organic luminescence materials are new materials that have been recently being actively investigated by many research groups. It has new physics, since organic materials have different electronic structure and therefore require a different interpretation in their luminescence mechanism. Working with chemists from our own Faculty of Science and other university, we are investigating the energy transfer process that leads to linear and non-linear emission in these new materials. These include the temperature dependent photoluminescence characteristics, quantum efficiency, and response time. These materials are very new and considerable amount of physics is waiting to be discovered.

2-photon up-conversion luminescence

2.          Solid State Light Phosphor

White light phosphor for solid state lighting  With the emergence of new display and lighting systems such as PDP and solid state lighting, we have began to investigate the luminescence mechanism of novel phosphors that can be applied in these areas. Most of these are rare earth based and particular crucial is the interaction between rare earth elements and their host materials. Significant amount of work is done through industrial support. Our main task is to investigate their optical properties including photo- and electroluminescence characteristics, response time, and absorption characteristics.

3.          Anisotropic Metamaterial

Superlens and optical bistability properties of multi-layer anisotropic metamaterials are being studied. In superlens, we studied a system consisting of two complementary anisotropic metamaterials that can support the ordinary evanescent modes and focus these modes through negative refraction to form a sub-wavelength image. Theoretical result shows that this is feasible and we are working on the experimental verification. Fig. 3 shows Magnetic flux density distribution in C-slab superlens at , a pair of slits with width of 30nm and center to center separation 60nm is illuminated by a normally incident TM wave along the positive direction of x axis, resolvable super-resolution images of the slits are obtained at the image plane of the C-slab.