1. Microelectronics Research Center, Electrical and Computer Engineering Department , University of Texas at Austin , Austin , Texas 78758, USA
2. Omega Optics, Inc. , 8500 Shoal Creek Blvd., Bldg. 4, Suite 200 , Austin , Texas 78757, USA
3. Department of Physics, Faculty of Science , King Abdul-Aziz University , 80203 Jeddah 21589, Saudi Arabia
4. Department of Electrical and Computer Engineering , George Washington University , Washington , DC 20052, USA