1. Photonics Devices and Systems Group; Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Rd; Singapore 487372 Singapore
2. Data Storage Institute; Agency for Science, Technology and Research (A*STAR), DSI Building, 5 Engineering Drive 1; Singapore 117608 Singapore
3. Massachusetts Institute of Technology; 77 Massachusetts Ave. Cambridge; MA 02139 USA