1. School of Electronic Engineering, Heilongjiang University, No. 74 Xuefu Road, Harbin 150080, China
2. Heilongjiang Provincial Key Laboratory of Micro-nano Sensitive Devices and Systems, Heilongjiang University, Harbin 150080, China
3. Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ, UK