Superior optical limiting, stabilization, and spatio-temporal reshaping of ultrashort laser pulses in an opto-stable intrinsic polymer film

A chemically modified poly(fluorene-alt-benzothiadiazole) (PFBT) polymer film is reported to exhibit high two-photon absorbing capability and chemical/physical stability upon the action of high-power laser pulses of similar to 780 nm wavelength and similar to 160 fs duration. A nonlinear transmission measurement is conducted by varying the input intensity from similar to 20 to similar to 600 GW/cm(2), the corresponding nonlinear transmission of a similar to 70 mu m thick film is reduced from similar to 0.8 to 0.18, indicating a superior optical limiting behavior. In the meantime, intensity fluctuation of laser pulses can be significantly reduced after passing through the same film sample. Based on the intensity-dependent nonlinear attenuation mechanism, a straightforward optical reshaping effect on spatio-temporal profiles of the laser pulses has also been demonstrated. (C) 2011 Optical Society of America