Photocurrent autocorrelation of femtosecond laser pulses in poly(p-phenylenevinylene)

Photoconductive thin-film cells made from a pi-conjugated polymer, poly-(p-phenylenevinylene) (PPV) can be used for diagnostics of femtosecond laser pulses utilizing the phenomenon of photocurrent autocorrelation. In general, the autocorrelation photocurrent signal can be due to the nonlinearity of the primary photogeneration step or to the influence of the existing photogenerated charge carriers on the efficiency of production of further amounts of charges. Experiments with 150 femtosecond pulses from a Ti-sapphire laser at 800 nm show that two-photon induced photocarrier generation is the nonlinear process leading to the autocorrelation in PPV photoconductive cells. There is no indication of the presence of any photogeneration intermediates with picosecond range lifetimes.