1. Department of Electro-Optics and Photonics, University of Dayton, Dayton, Ohio 45469, USA
2. Department of Materials Science and Engineering, University of Central Florida, Orlando, Florida 32816, USA
3. Department of Information Engineering, University of Padova, Padova 35131, Italy
4. Department of Information Engineering, University of Brescia, Brescia 25121, Italy
5. US Army AMRDEC, Charles M. Bowden Research Laboratory, Redstone Arsenal, Alabama 35898, USA