Exploring Disordered Light Transport in Scattering Media to Optimize Random Lasers

Abstract

Disordered light has recently been introduced as a novel and efficient approach for pumping random lasers (RLs), resulting in a reduced lasing threshold and enhanced emission intensity. Here, we investigate the photon propagation, coming from both homogeneous and disordered light patterns, within scattering media to understand the influence of disorder in the spatial intensity and wavevector distributions of the pump light on RL optimization. For this purpose, an adapted coherent backscattering (CBS) technique was employed to measure the residence time and total distance traveled by coherently backscattered photons within a scattering sample. The experimental measurements reveal that in media with low scatterer density, disordered light facilitates longer photon travel distances because the random wavevector distribution favors coupling with the different modes defined by the scattering media. Consequently, in a gain-scattering medium, disordered light showcases efficient amplification of stimulated emission due to multiple scattering. However, as the scatterer density increases, the difference in travel distances between photons coming from homogeneous and disordered light diminishes, potentially impacting RL optimization. RL experiments using TiO 2 @SiO 2 suspended in rhodamine 6G colloids corroborate these findings, revealing that optimizing the distance traveled by photons from disordered light influences increased RL emission intensity, and the disordered distribution of intensity hot spots, which concentrate a larger number of excitation photons in small volumes, significantly reduces the RL threshold. Therefore, this study contributes to the understanding and consolidation of disordered light as an important tool for enhancing RL performance and efficiency.