Ultrafast optical nonlinearities in aluminum phthalocyanine organic thin films and a picosecond all-optical organic etalon switch.

Abstract

The history of femtosecond laser pulse generation is summarized and a current state-of-the-art femtosecond laser system described. The femtosecond pulses are used to observe coherent coupling effects in a fluoro-aluminum phthalocyanine thin film. The polarization dependency of the coherent coupling indicates that orthogonal polarization states in the phthalocyanine ring are effectively uncoupled. The coherent coupling effect evolves into a nonequilibrium exciton population spectrally coincident with the pump pulse. This population rapidly decays to the bottom of the π- π* absorption band. These singlet excitons exhibit rapid bimolecular decay characteristics. In addition, some singlet excitons relax into the triplet manifold by intersystem crossing. Excited-state triplet-triplet absorption is then observed. The triplet excitons relax to the ground state, apparently via nonradiative decay mechanisms. Femtosecond techniques are also employed to demonstrate a picosecond all-optical organic NOR gate. A dye-doped polymer is used as the nonlinear material inside a Fabry-Perot etalon.