1. Bio-Inspired Sensors and Optoelectronics Laboratory, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, USA
2. Nano Convergence Research Center, Korea Electronics Technology Institute (KETI), 111, Ballyong-ro, Deokjin-gu, Jeonju-si, Jeollabuk-do 54853, South Korea
3. Department of Physics and Astronomy and CIERA, Northwestern University, 2131 Tech Drive, Evanston, Illinois 60208-2900, USA
4. Photonics Research Center, University of Malaya, 50603 Kuala Lumpur, Malaysia