Emission waveguiding in organic thin films supported by metal

On silver thin film, an organic semiconductor rubrene layer consisting of a planar waveguide exhibits spectrally narrowing photoluminescence (PL) spectra with an increasing emission angle, which are compared with those of rubrene thin films on glass. The PL spectra of rubrene on Ag have a polarization characteristic. In the side direction of the multilayer structure, spectrally very sharp PL was observed. The PL characteristics are discussed from the viewpoint of waveguided modes allowed only for a phase-matching condition. The narrowed PL spectra are attributable to generation of a leaked waveguided mode in the rubrene layer, which is supported by the underlying Ag thin film.