Evanescent-wave-excited quasi-two-dimensional random lasing

Abstract

We report on random lasing from a dye-scatterer system directly excited by evanescent modes formed over a dielectric-dielectric interface. The system is quasi-two-dimensional because of the subwavelength exponential decay of the excitation energy. Spectral narrowing by a factor of $\sim 13$ was obtained under diffusive scattering conditions. The peak intensity exhibited a unique dual-saturation behavior due to the localized nature of the excitation. We observed a reduction of threshold for samples with a higher dye concentration because of a larger excitation-state occupation number within the same interaction volume