Study On Nonlinear Optical Properties Of A Novel Asymmetrical Indium Porphyrin-polymer

More and more nonlinear optical materials are widely used in the fields of industry and information over past decades. Compared with other materials, organic materials have attracted widespread attention with better optical nonlinearity and plasticity.Here, the nonlinear optical properties of a porphyrin derivative named asymmetrical Indium Porphyrin-Polymer(In Cl Por-MMA26) are investigated by means of nanosecond(ns) and picosecond(ps) Z-scan at 532 nm. In the two cases, reverse saturation absorption and nonlinear positive refraction are observed. It suggests In Cl Por-MMA26 can be a potential optical limiter as the normalized transmittances of open-aperture Z-scan decrease rapidly with the increase of incident energy in the two time-domains. The optical nonlinearity dynamics of In Cl Por-MMA26 are studied via time-resolved pump-probe technique with phase object at 532 nm in picosecond domain. In Cl Por-MMA26 may have lager nonlinear refraction at nanosecond domain owing to its closed-aperture normalized transmittance increasing gradually. Based on five-level model and with the help of ns Z-scan, a series of nonlinear optical parameters are calculated out. The results shows intersystem crossing time is shorter than the lifetime of first excited singlet state, the majority of electrons in first excited singlet state transfer to excited triplet state quickly. And the absorption cross-section of excited triplet state is close to first excited singlet state’s. These factors guarantee In Cl Por-MMA26 has good performance in reverse saturation absorption both at nanosecond and picosecond domain.Results of femtosecond(fs) transient absorption spectra between 475 nm and 780 nm reveal In Cl Por-MMA26 has better nonlinear absorption between B-band and Q-band. And the absorption cross-section of excited triplet state shows stronger dependence on wavelength than first excited singlet state’s. Lifetime of higher excited-singlet-state is determined by fs Z-scan at 532 nm. According to fs Z-scan experiments and transient absorption spectra, absorption cross-sections at different selected wavelength are acquired. The strongest nonlinear absorption appears at 484 nm in our detection range. Ratios of first excited singlet state’ and excited triplet state’ absorption cross-section with ground state’s reach 9.9 and 19, respectively. It implies In Cl Por-MMA26 can be a good optical limiter.