Laser action at the critical regime of localization

Abstract

This paper studies the random lasing at the critical regime of localization. A strongly disordered optical medium composed of core-shell nanoparticles (TiO2@Silica) suspended in ethanol solution of Rhodamine 6G conform the random laser material. Narrow peaks of approximately equal intensity are observed on top of the classical super-fluorescence band of random laser, indicating suppression of the interaction between the peaks modes (localized modes). The linewidth of these peaks is lower than that of the passive modes of the scattering medium. The classical super-fluorescence band of the random laser was measured separately by collecting the emission at the back of the samples, showing a linear dependence with pumping fluence without gain depletion. However, frontal emission of the random laser showed saturation.