1. Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
2. Department of Physics, Queens College of the City University of New York, Queens, NY 11367, USA.
3. Physics Program, Graduate Center of the City University of New York, New York, NY 10016, USA.
4. Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY 10031, USA.
5. Department of Electrical Engineering, City College of The City University of New York, New York, NY 10031, USA.