Selective Pumping of Localized States in a Disordered Active Medium

TL;DR

This paper demonstrates a method to selectively excite and image localized lasing modes in a disordered active medium using pump shaping, advancing control over Anderson localized states in random lasers.

Contribution

It introduces a technique to individually select and image localized modes in a strongly scattering random laser through pump shaping, revealing insights into non-Hermiticity and nonlinear effects.

Findings

Successful selection of localized lasing modes via pump shaping

Direct imaging confirms the confined nature of selected modes

Provides insights into non-Hermiticity and nonlinearities in active scattering media

Abstract

Light scattering and localization in strongly scattering disordered systems is governed by the nature of the underlying eigenmodes, specially their spatial extension within the system. One of the main challenges in studying experimentally Anderson like localized states resides in the difficulty to excite these states independently and observe them individually anywhere in the sample. The modes mutual interaction and their coupling to the sample boundaries makes it extremely challenging to isolate them spectrally and image them alone. In the presence of gain, random lasing occurs above threshold and lasing modes are excited. It was shown recently that shaping the intensity profile of the optical pump is a very effective way to control and force random lasing in singlemode regime at any desired emission wavelength. Active random media therefore offer a unique platform to select modes individually. By using pump shaping technique in a strongly scattering random laser, we successfully select localized lasing modes individually. Direct imaging of the light distribution within the random laser confirms the confined nature of the modes and enables us to elucidate long standing questions on the role of non-Hermiticity in active scattering media and the influence of nonlinearities on Anderson wave localization.