1. Morgan State University; Department of Physic and Engineering Physics; 1700 East Cold Spring Lane Baltimore MD 21251 USA
2. University of Toledo; Department of Physics and Astronomy; 2801 West Bancroft Toledo OH 43606 USA
3. Huazhong University of Science and Technology; School of Optical and Electronic Information; No. 1037, LuoYu Road Wuhan 430074 China
4. Virginia University; Department of Materials Science and Engineering, School of Engineering; 395 McCormick Road Charlottesville VA 22904 USA