1. Geballe
Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
2. Department
of Electrical Engineering, Stanford University, Stanford, California 94305, United States
3. Micro
and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell
Berrie Nanotechnology Institute, Technion−Israel Institute of Technology, Haifa 32000, Israel
4. CREOL,
The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, United States