Nonlinear absorption of tetrathiafulvalene radical cation (TTF⁺) based charge transfer (CT) aggregates in PMMA

Nolinear Absorption of CT TTF+ -based aggregates in PMMA matrix was studied with resonant excitation around 800 nm in the femtoseconds regime with the Z-Scan technique with 100 Hz pulse repetition rate. The saturated absorption profiles were fitted with a prepared formula based on steady state rate equations for a homogeneous ensemble of two levels systems, thin samples and quasi monochromatic field without the usual assumption of low saturation regime. The lifetime of the CT state, with the use of this model was estimated in hundred of fs, of the same order of magnitude of the exciting pulse.