Disorder as a Playground for the Coexistence of Optical Nonlinear Effects: Competition between Random Lasing and Stimulated Raman Scattering in Complex Porous Materials

Abstract

We predict the coexistence and competition of random lasing and stimulated Raman scattering (SRS) in active disordered random media. We develop a simple model that includes both mechanisms coupled to diffusion equation. We find that the prevalence of a nonlinear mechanism over the other is determined by the degree of scattering. This is confirmed experimentally in dye-infiltrated three-dimensional porous silica-based disordered samples, with controllable pore size and transport properties. Experimentally, random lasing dominates in a sample with a large transport mean free path, lt ≈ 100 μm, while it gives way to SRS for lt ≈ 25 μm. The competition is explained in terms of disorder-dependent pump depletion and fluorescence saturation.