1. Institute of Photoelectronic Thin Film Devices and Technology Tianjin Key Laboratory of Thin Film Devices and Technology Engineering Research Center of Thin Film Photoelectronic Technology Nankai University Tianjin 300350 China
2. College of Physics Science and Technology Hebei University Baoding 071002 China
3. Key Laboratory of Weak-Light Nonlinear Photonics Ministry of Education School of Physics Nankai University Tianjin 300071 China