Quasi-continuous-wave operation of an organic thin-film distributed feedback laser

The operation of organic thin-film distributed feedback lasers at repetition rates up to 5 MHz is studied. The active organic medium consists of a highly efficient, modified poly(9,9-dioctylfluorene) derivative containing 12% of statistical intrachain 6,6(') -(2,2(')-octyloxy-1,1(')-binaphthalene) binaphthyl spacer groups. The threshold energy density of these pulsed optically pumped lasers remains virtually unaltered at elevated repetition rates up to 5 MHz. Therefore, we conclude that on this time scale photoinduced absorption which might affect the waveguide loss or the overall quantum efficiency is negligible in our active polymer. These results state an organic solid-state laser operating at repetition rates in the megahertz range which for many applications can be considered as quasi-cw.