1. Optical Physics Division, Corning Research and Development, Sullivan Park, Corning, New York 14831, United States
2. Department of Electrical and Computer Engineering, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
3. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
4. Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
5. School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, United States