[1] Univ Hong Kong, Dept Phys, Hong Kong, Hong Kong, Peoples R China
[2] Univ Hong Kong, Dept Elect & Elect Engn, Hong Kong, Hong Kong, Peoples R China
[3] Hong Kong Baptist Univ, Dept Phys, Kowloon, Hong Kong, Peoples R China
[4] Univ Hong Kong, Dept Chem, Hong Kong, Hong Kong, Peoples R China
[5] Univ Queensland, Sch Informat Technol & Elect Engn, Brisbane, Qld 4072, Australia