Third-order optical nonlinearities and femtosecond responses in metallophthalocyanine thin films made by vacuum deposition molecular beam epitaxy and spin coating

摘要

Abstract: The molecular design and assembly of metallophthalocyanine systems that have the enhanced macroscopic third-order nonlinear susceptibility $chi$+(3)$/ijkl(- approximately ega$-4$/; approximately ega$-1$/, approximately ega$-2$/, approximately ega$-3$/) and show ultrafast responses are described. Enhancement of the third harmonic susceptibility $chi$+(3)$/1111(-3 approximately ega@; approximately ega@, approximately ega@, approximately ega@) was observed in vanadyl phthalocyanine vacuum-deposited film with the staggered stacking arrangement induced by thermal treatment. Processable polymeric system based on tert-butyl mono-substituted rich vanadyl phthalocyanine was developed and the favorable staggered stacking arrangement was induced in a polymer matrix to enhance $chi$+(3)$/1111(-3 approximately ega@; approximately ega@, approximately ega@, approximately ega@). Femtosecond-time-resolved spectroscopy was performed on vanadyl phthalocyanine thin films with different morphological forms in order to elucidate the exciton dynamics. The exciton decay kinetics consists of three processes: exciton-exciton annihilation, exciton-phonon coupling, and much slower triplet state formation. The decay rate of the exciton population via exciton-exciton annihilation was found to have a time dependence of t$+$MIN$HLF$/. The vacuum-deposited film and spin-coated film of vanadyl phthalocyanine derivatives showed similar decay behavior, whereas molecular beam epitaxy film showed a faster decay with a time constant of several hundreds of femtoseconds. !15