1. Polymer Research Institute, Polytechnic University, 6 Metrotech Center, Brooklyn, New York 11201, and Faculty of Science and Technology, Keio University, Yokohama 223-8522, and ERATO, Koike Photonics Polymer Project, K2 Town Campus 144-8 Ogura, Saiwai-ku Kawasaki 212-0054, Japan