Polarization-dependent optical gain in crystal and glass composed of excited-state intramolecular proton transfer organic molecules

Amplified spontaneous emission (ASE) associated with excited-state intramolecular proton transfer (ESIPT) was investigated in a single crystal and a glass of acetic acid 2-{4-[2-(2-hydroxy-phenyl)-4,5-diphenyl-imidazole-1-yl]-phenyl}-ethyl ester molecules. The polarization-dependent ASE was analyzed in an effort to understand the structural evolution involved in the ESIPT photo-cycle. From the analysis of the degree of polarization in the glass sample, we observed that polarization memory has been partially lost due to the ESIPT process in the molecule. The single crystal exhibited much larger transient optical gain than the glass sample. (c) 2007 Elsevier B.V All rights reserved.