1. Key Laboratory of Polar Materials and Devices (MOE) and Department of OptoelectronicsEast China Normal University Shanghai 200241 P. R. China
2. National Lab for Infrared PhysicsShanghai Institute of Technical PhysicsChinese Academy of Sciences Shanghai 200083 P. R. China
3. Collaborative Innovation Center of Extreme OpticsShanxi University Taiyuan Shanxi 030006 P. R. China