We investigate the effect of different gain media and different scattering media in random lasers. We demonstrate an increase in the emission intensity and efficiency of random lasing by incorporating gold rather than dielectric alumina nanoparticles. There is a trade-off between enhancing the random laser performance due to the localised surface plasmon resonance field effects and reduction in performance due to fluorescence quenching by the gold nanoparticles. We use fluorescence resonant energy transfer between dye molecules to extend the wavelength range of emission. � Copyright 2016 by SCITEPRESS-Science and Technology Publications, Lda. All rights reserved.

We investigated the spectral and coherence signatures of threshold in random lasers with incoherent feedback consisting of alumina colloidal nanoparticles suspended in rhodamine 6G methanol solution under nanosecond-pulsewidth pumping, based on measurement of temporal and spatial coherence properties and comparison with emission spectra. Feedback in this random laser was provided by multiple scattering from the alumina particles, and the effects of particle concentration and scattering length were studied for the weakly scattering and diffusive scattering regimes. At threshold, in each regime, the visibility of the interference fringes jumped abruptly, coinciding with a substantial increase in peak emission intensity and decrease in the linewidth of a single dominant emission peak. � 2014 IOP Publishing Ltd.