Ultrafast laser action dynamics in Dooppv thin films

We have investigated the femtosecond transient photoinduced absorption (PA) dynamics of excitons in DOO-PPV thin films as a function of the excitation intensity, studied simultaneously with stimulated emission measurements. We observed both fast and slow PA components, which depend on the excitation intensity. At low excitation intensity only the slow PA component was measured with a life time of240 ps. However, for intensities above the threshold for spectral-narrowing, a fast PA dynamics dominate the decay for times less then 10 ps.