1. Department of Electrical and Computer Engineering, George Washington University, 800 22nd St., Washington, District of Columbia 20052, USA
2. Nanofabrication and Imaging Center, George Washington University, 800 22nd St., Washington, District of Columbia 20052, USA
3. Omega Optics, Inc., 8500 Shoal Creek Blvd., Bldg. 4, Suite 200, Austin, Texas 78757, USA