Two-photon-induced excited-state absorption: Theory and experiment

We develop an open-aperture (OA) Z scan and nonlinear transmission theory of two-photon-induced excited-state absorption, under the excitation of spatial Gaussian laser pulses with temporal Gaussian and hyperbolic secant profiles. The found analytic expressions allow us to straightforwardly fit the OA Z-scan trace and the nonlinear transmission curve, for convenient extraction of the nonlinear absorption coefficients. As a test, the two-photon-induced excited-state absorption in a chalcone derivative of 3,4-dimethoxy-4(')-fluorochalcone is explored by performing femtosecond Z-scan measurement and is analyzed by our theory. (C) 2008 American Institute of Physics.