[1] PRINCETON UNIV, ADV CTR PHOTON & OPTOELECTR MAT, PRINCETON, NJ 08544 USA
[2] PRINCETON UNIV, PRINCETON MAT INST, PRINCETON, NJ 08544 USA
[3] HUGHES RES LABS, MALIBU, CA 90265 USA
[4] UNIV ARKANSAS, DEPT PHYS, FAYETTEVILLE, AR 72701 USA
[5] UNIV AQUILA, DIPARTIMENTO FIS, LAQUILA, ITALY