Time-resolved stimulated emission in an α-sexithienyl thin film

We have investigated the stimulated emission of an evaporated thin film of α-sexithienyl at 20 K. We have performed femtosecond differential transmission measurements with excitation energies around 2.35 eV and probing the spectral region from 2 to 2.65 eV. The results are compared to time-resolved photoluminescence spectra. We observe amplification of the probe light at the spectral position of a sharp peak measured in time-resolved photoluminescence. The stimulated emission decays with a time constant of 2.5 ps.