1. Department of Electrical Engineering and Computer Science, University of California, Irvine, California 92697, USA
2. Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California 90089, USA
3. Photonics Initiative, Advanced Science Research Center, New York, New York 10031, USA
4. Department of Electrical Engineering, City College, City University of New York, New York, New York 10031, USA