1. General Dynamics Information Technology, San Antonio, Texas 78234, United States
2. Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, Texas 78249, United States
3. Optical Radiation Bioeffects Branch, Bioeffects Division, Air Force Research Laboratory, Fort Sam Houston, Texas 78234, United States
4. Department of Physics, The University of Texas at Arlington, Arlington, Texas 76019, United States