1. Photonics Initiative Advanced Science Research Center City University of New York New York NY 10031 USA
2. Department of Electrical Engineering City College of The City University of New York New York NY 10031 USA
3. Walter Schottky Institute Technical University of Munich 85748 Garching Germany
4. Department of Physics and Astronomy Texas A&M University College Station TX 77843 USA
5. Physics Program Graduate Center City University of New York New York NY 10016 USA