Effect of axial substitution on the ultrafast dynamics and third-order optical nonlinearity of metallophthalocyanines films

摘要

The ultrafast dynamics of the excited excitons of three axially substituted amorphous metallophthalocyanine (MPc) films were investigated by the femtosecond pump-probe technique at λ = 800 and 400 nm. By considering the exciton-exciton annihilation, the internal conversion and the inter-system crossing, the ultrafast dynamics of the excitons can be well simulated with a three-level model. The third-order optical nonlinearities of these films were measured by Z-scan technique at wavelength of 800 nm. In order to illuminate the axial substitution effect on the samples, we carried out the geometry determination calculation base on the Hartree-Fock theory with basis-set of 3-21 G for the three molecules. The real and imaginary parts of the molecular nonlinear hyperpolarizability γ, were evaluated with the equation of sum-over-states from the quantum theory. The results showed the axial substitution has great effect on the optical nonlinearity of the MPcs.