1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore 637371 Singapore
2. School of Electrical and Electronic Engineering, Luminous! Center of Excellence for Semiconductor Lighting and Displays; Nanyang Technological University; Nanyang Avenue Singapore 639798 Singapore
3. Centre for Disruptive Photonic Technologies (CDPT); Nanyang Technological University; Singapore Singapore 637371 Singapore
4. Department of Electrical and Electronics Engineering, Department of Physics, and UNAM-National Nanotechnology; Research Center Bilkent University; Bilkent Ankara