THEORETICAL-ANALYSIS OF THE PICOSECOND, INDUCED ABSORPTION EXHIBITED BY CHLOROALUMINUM PHTHALOCYANINE

Picosecond measurements of the optical response of chloroaluminum phth alocyanine in solutions are presented. The observed nonlinearities are modeled and interpreted theoretically by rate-equation and density-ma trix techniques within a three-level model. Single-pulse power limitin g is observed at 532 nm, and the absorption cross section of the first excited state is determined to be 15 times that of the ground state. From time-resolved excitation-probe measurements we determine an excit ed-state recombination time of 7 ns and a reorientational time of 7 ps . Further, the observation of the associated optical coherence effects , which are manifested as a negative coherent artifact, allow us to ob tain an 8ps coherence time. (C) 1997 Optical Society of America.