After spending one year as a Postdoctoral Research Fellow at Caltech and four years as a Senior Research Scientist at Kaman Sciences Corporation’s Dikewood Division in Santa Monica, California, he joined the faculty of the University of Pennsylvania, where he rose through the ranks and is currently H. Nedwill Ramsey Professor. He was the graduate group chair of electrical engineering from July 1993 to June 1997. He is a member of the Board of Reviewing Editors of the Science magazine, and is on the editorial boards of the journals American Chemical Society (ACS) Photonics, Applied Physics Letters (APL) Photonics, Nanophotonics, IEEE Open Journal of Antennas and Propagation, and eLight. He was on the editorial boards of many journals in the past.