[1] Harbin Inst Technol, Natl Key Lab Tunable Laser Technol, Harbin 150080, Peoples R China
[2] San Francisco State Univ, Dept Phys & Astron, San Francisco, CA 94132 USA
[3] Univ Calif Berkeley, NSF Nanoscale Sci & Engn Ctr, Berkeley, CA 94720 USA
[4] Nankai Univ, TEDA Appl Phys Sch, Tianjin 300457, Peoples R China
[5] Univ Cent Florida, Coll Opt, CREOL, Orlando, FL 32816 USA