1. Department of Physics and Astronomy, University of Southern Mississippi, Hattiesburg, Mississippi 39406, USA
2. Department of Physics and Optical Science, University of North Carolina, Charlotte, North Carolina 28223, USA
3. Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, USA and Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27606, USA