Ultrafast resonant optical switching in isolated polyfluorenes chains

Using ultrafast spectroscopy, we report evidence of monodimensional photophysics coming fromisolated chains of poly(9,9-dioctylfluorene) dispersed in a polymethylmethacrylate matrix. Weidentify intrachain charge carriers dynamics, the decay taking place in about 1 ps. Using athree-pulse experiment we bring evidence for charges generation from higher lying states and wereport an ultrafast optical gain switching in the stimulated emission region over a broad wavelengthrange saround 100 nmd. Our experiments suggest that the expected maximum rate of on–offswitching in such a molecular device can be as high as 300 GHz.