Ye Zhou1, Su-Ting Han2. 1. Institute of Microscale Optoelectronics and Institute for Advanced Study, Shenzhen University, Shenzhen 518060, P. R. China. 2. Institute of Microscale Optoelectronics and Institute for Advanced Study, Shenzhen University, Shenzhen 518060, P. R. China. sutinghan@szu.edu.cn.