This work is partially supported by National Natural Science Foundation of China (11774102), the Scientific Research Funds and Promotion Program for Young and Middle-aged Teacher in Science & Technology Research of Huaqiao University (ZQN-YXS04, 17BS412), Open Fund of IPOC (BUPT), National Research Foundation Singapore (NRF) (NRF-CRP13-2014-05), European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement (No. 798916) and Singapore Ministry of Education Academic Research Fund Tier 1 (RG89/16).
Optical whispering gallery mode (WGM) microresonators have attracted great attention due to their remarkable proper- ties such as extremely high quality factor, small mode volume, tight confinement of modes, and str...