1. Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, USA.
2. Photonics Initiative, Advanced Science Research Center, City University of New York, NY, USA.
3. Physics Program, Graduate Center, City University of New York, New York, NY, USA.
4. Department of Applied Physics, California Institute of Technology, Pasadena, CA, USA.
5. Jet Propulsion Laboratory, Pasadena, CA, USA.