Random Lasing at Localization Transition in a Colloidal Suspension (TiO@Silica).

Anderson localization of light and random lasing in this critical regime is an open research frontier, which besides being a basic research topic could also lead to important applications. This article investigates the random laser action at the localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO@Silica) in ethanol solution of Rhodamine 6G. The classical superfluorescence 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.

Anderson localization of light in a colloidal suspension (TiO2@silica).

In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition.