1. Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260-1500, USA
2. Department of Physics and Astronomy, Theodore Jorgensen Hall, 855 North 16th St., University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
3. Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1900, USA