1. Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, Agere Systems, 600 Mountain Avenue, Murray Hill, New Jersey 07974, Agere Systems, 9333 S. John Young Parkway, Orlando, Florida 32819, National Institute of Standards and Technology, Polymers Division, 100 Bureau Drive, Gaithersburg, Maryland 20899-8541, and Departments of Materials Science and Engineering and Physics, University of Michigan, Ann Arbor, Michigan 48109