1. Institute of Materials Research and Engineering; Agency for Science; Technology and Research (A*STAR); 2 Fusionopolis Way, Innovis #08-03 Singapore 138634 Singapore
2. Department of Optics and Optical Engineering; University of Science and Technology of China; Hefei Anhui 230026 China
3. Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications; Institute of Photonics Technology; Jinan University; 601 Huangpu Avenue West Guangzhou 510632 China
4. Department of Electrical and Computer Engineering; National University of Singapore; 4 Engineering Drive 3 Singapore 117576 Singapore
5. Data Storage Institute; Agency for Science; Technology and Research (A*STAR); 2 Fusionopolis Way, Innovis #08-01 Singapore 138634 Singapore
6. Division of Physics and Applied Physics; School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore 637371 Singapore
7. Faculty of Physics; Lomonosov Moscow State University; Moscow 119991 Russia