Coherent random lasing in the deep blue from self-assembled organic nanofibers

We report on the morphological and nonlinear optical properties of highly ordered para-sexiphenyl nanofibers grown by hot-wall epitaxy on muscovite mica. For suitable substrate temperatures and deposition times, needle-shaped aggregates are obtained. These nanoaggregates, which are formed by regrouping of small islands of the material, can support optical waveguiding and amplification of the deep-blue emission of para-sexiphenyl. We show evidence of low-threshold coherent random lasing in ensembles of nanofibers and study the dependence of lasing on the nanofibers’ film thickness. We also present spatially resolved lasing measurements on individual nanofiber segments. The achievement of isolated nanofibers with suitable morphology and low optical losses could open the route to unprecedented photonic and optoelectronic devices at the submicrometric scale.