Two-photon induced excited-state absorption and optical limiting properties in a chiral polymer

The nonlinear absorption and optical limiting properties of a chiral polymer were investigated by employing Z-scan technique in femtosecond regime. Reverse saturable absorption was observed in the polymer at 800 nm and the nonlinear absorption coefficient of 5.97 cm/GW was obtained at the irradiance of 2.75 GW/cm(2). The nonlinear absorption coefficient versus the input irradiance was measured to meet a linear increasing function, giving evidence of two-photon induced excited-state absorption existing. Particularly, the chiral polymer was shown to possess a large ratio (similar to 251) of excited-state to ground-state absorption cross-section and a remarkable optical limiting behavior was achieved in it. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790391]