[1] Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou, Zhejiang, Peoples R China
[2] Royal Inst Technol, Joint Res Ctr Photon, Stockholm, Sweden
[3] Zhejiang Univ, Hangzhou, Zhejiang, Peoples R China
[4] Royal Inst Technol, Dept Microelect & Appl Phys, S-16440 Kista, Sweden