Combined Nonlinear Effects in Two-Photon Absorption Chromophores at High Intensities (Preprint)

摘要

Large two-photon and excited state absorption have been reported in donor-acceptor-substituted pi-conjugated molecules. We have performed detailed nonlinear absorption and photophysical measurements on a system of AFX chromophores and calculate the nonlinear transmission based on an effective three-level model. A numerical model that includes far wing linear absorption has been developed and compared with an analytical three-photon absorption model. The models are in accordance and yield excellent agreement with experimental nonlinear transmission date of 0.02-M AFX solutions up to laser intensities approximately 1GW/cm2. Concentration effects at this intensity become increasingly evident. We have extended our modeling efforts to include some new effects that may be anticipated in this regime, such as stimulated scattering are included. We report on our experimental observations of various materials and discuss results with respect to our extended theoretical models.