a
State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou, China
E-mail: jinchjun@mail.sysu.edu.cn
;
Fax: +86 2084112282
;
Tel: +86 2084112282
b
Optoelectronics Research Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, Scotland