1. Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, United States
2. Department of Physics and Astronomy, University of California, Irvine, California 92697, United States
3. Theiss Research, Inc., La Jolla, California 92037, United States
4. Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
5. Fibertek, Inc., Herndon, Virginia 20171, United States
6. US Army Research Laboratory, Adelphi, Maryland 20783, United States
7. US Army Research Laboratory, Playa Vista, California 90094, United States
8. Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China