1. School of Optics and CREOL, University of Central Florida, Orlando, FL 32816-2700, USA
2. ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Dept. of Signal Theory and Communications, 08034 Barcelona, Spain
3. ETH Honggerberg, Swiss Fed. Inst. of Tech., Zurich CH-8093, Switzerland
4. Electro-Optic Div., Soreq NRC, Yavene, 81800, Israel