1. Photonics Research Center, Universiti Malaya, Kuala Lumpur, Malaysia
2. Photonics Research Center and Physics Department, Faculty of Science, Universiti Malaya, Kuala Lumpur, Malaysia
3. Department of Electrical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur, Malaysia
4. School of Mathematics, Computer Science and Engineering, City, University of London, London, U.K
5. Optoelectronics Research Centre, University of Southampton, Southampton, U.K