1. University of Arkansas, Department of Physics, Fayetteville, Arkansas 72701, United States
2. University of Arkansas, Microelectronics-Photonics Program, Fayetteville, Arkansas 72701, United StatescShippensburg University of Pennsylvania, Department of Physics, Shippensburg, Pennsylvania 17257, United States
3. University of Arkansas, Department of Physics, Fayetteville, Arkansas 72701, United StatesbUniversity of Arkansas, Microelectronics-Photonics Program, Fayetteville, Arkansas 72701, United States