Dependence of random laser emission on silver nanoparticle density in PMMA films containing rhodamine 6G

We report experiments on random lasers based on films of poly(methyl methacrylate) containing rhodamine 6G and silver nanoparticles (NPs). The films were deposited on an aluminum-coated substrate that provides reinjection of leaking photons. The results show strong dependence of the emission on the silver NPs' density and smaller linewidth and threshold due to the feedback provided by the aluminum film. For comparison purposes, samples with TiO(2) NPs were also prepared, and no evidence of random lasers was obtained for the same experimental conditions. This demonstrates that higher optical gain for lasing is obtained using silver NPs mainly due to the contribution of localized surface plasmons in the NPs. (C) 2011 Optical Society of America