1. Department of Applied Physics and State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Donghua University, Shanghai 201620, China
2. National Laboratory for Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai 200083, China
3. Faculty of Physics and Electronic Technology Hubei University, Wuhan 430062, China; Department of Applied Physics Xi’an Jiaotong University, Xi’an 710049, China