1. Division of Physics and Applied Physics; School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore 637371 Singapore
2. Centre for Disruptive Photonic Technologies; School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore 637371 Singapore
3. School of Electrical and Computer Engineering; Oklahoma State University; Stillwater OK 74078 USA
4. Biomedical Engineering Department; College of Engineering; University of Dammam; Dammam 31441 Saudi Arabia