Affiliation: | 1. Institute of Optics and Photonics, Shanghai Jiaotong University, Shanghai 200030, P. R. China;Department of Physics, Nantong Teachers College, Nantong 226007, P. R. China; 2. Department of Physics, East China Normal University, Shanghai 200062, P. R. China; 3. Department of Chemistry, Shanghai Teachers University, Shanghai 200234, P. R. China; 4. Institute of Optics and Photonics, Shanghai Jiaotong University, Shanghai 200030, P. R. China |