1. Heriot-Watt University Malaysia, Putrajaya, Malaysia
2. Photonics Research Centre, Universiti Malaya, Kuala Lumpur, Malaysia
3. North Carolina Agricultural and Technical State University, Greensboro, North Carolina, USA
4. School of Energy and Chemical Engineering, Xiamen University Malaysia, Sepang, Malaysia
5. Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia