1. Centre for Optical and Electromagnetic Research National Engineering Research Center for Optical Instruments College of Optical Science and Engineering Zhejiang University Hangzhou 310058 China
2. Ningbo Research Institute Zhejiang University Ningbo 315100 China
3. Ningbo Solartron Technology Co., Ltd Ningbo 315034 China
4. Shanghai Institute for Advanced Study Zhejiang University Shanghai 200135 China
5. E. L. Ginzton Laboratory and Department of Electrical Engineering Stanford University Stanford CA 94305 USA
6. JORCEP School of Electrical Engineering Royal Institute of Technology (KTH) Stockholm S‐100 44 Sweden