Ultrafast studies of laser-action in poly(p-phenylene vinylene) films

Summary form only given. The recent demonstration of emission spectral narrowing in /spl pi/-conjugated polymer films, has stirred widespread interest to the phenomenon of laser-action in these materials. It is now generally believed that spectral narrowing in superior polymer films is caused by amplified spontaneous emission (i.e. single pars stimulated emission (SE)) enhanced by the optical waveguiding in the film. However, the femtosecond exciton dynamics under SE conditions, and the effects of exciton inhomogeneity in the films on the properties of the SE and its dynamics have not been investigated. In this study we have used the gated frequency up-conversion technique with 300 fs time resolution to fully resolve the emission dynamics in thin films of 2,5-dioctyloxy poly(p-phenylene vinylene) (DOO-PPV) an excitation power, below and above the threshold power for spectral narrowing.