About the authors PARAS N. PRASAD is Professor of Chemistry and Director of Photonics Research Laboratory at the State University of New York at Buffalo, where he has been since 1974. He is the coeditor of the books Nonlinear Optical and Electroactive Polymers and Nonlinear Optical Effects in Organic Polymers. Dr. Prasad was an Alfred P. Sloan Fellow and received two gold medals from Bihar University for standing first in his MSc and BSc exams. He received a PhD in chemistry from the University of Pennsylvania in 1971. DAVID J. WILLIAMS has been Head of Molecular and Optical Electronics Laboratory at Eastman Kodak Company since 1985. Previously, he was manager of the Chemical Research Area at Xerox Corporation. He is the editor of the book Nonlinear Optical Properties of Organic and Polymeric Materials and a member of the American Chemical Society and Optical Society of America. Dr. Williams received his PhD in chemical physics from the University of Rochester in 1968.