Bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphineplatinum(II): a promising material for broadband optical limiting in the visible

This work reports the results of nonlinear absorption and nonlinear fluorescence studies carried out on a 0.8 M solution of the complex in THG in the spectral range 450 to 700 nm. Nonlinear absorption results demonstrate that this material exhibits optical limiting behavior over this entire spectral band when excited with nanosecond pulses. Results of nonlinear fluorescence and excite probe studies show that at wavelengths longer than 530 nm, the nonlinear absorption is a consequence of the pathway: two-photon absorption from the S/sub 0/ to the S/sub 1/ state, fast intersystem crossing in less than 300 ps from S/sub 2/ to T/sub 1/, followed by excited state absorption from T/sub 1/ to T*. Fluorescence studies as a function of the excite wavelength show that the two-photon absorption coefficient has little variation with wavelength in the region 550 to 700 nm. Detailed studies of the nonlinear absorption behavior at 595 nm reveal that the nonlinear absorption has a significant contribution from the triplet excited state absorption, resulting in an optical limiting performance that is not strongly dependent on pulse length.