An ultrafast spectroscopy study of stimulated emission in poly(9,9-dioctylfluorene) films and microcavities

We report measurements of stimulated emission in poly(9,9-dioctylfluorene). We find a gain coefficient of ${\text{1.2×10}}^4 {\mathrm{cm}}^{\mathrm{-1}}$ for 100 nm-thick films at an excitation energy density of 9.9 mJ/cm². Using ultrafast pump–probe measurements, we have studied the effect of cavity optical confinement. A strong shift of the cavity resonance due to nonlinear refraction is observed.