Colloquium: Philippe Jacquod

Abstract(s):
Unlike conventional lasers, random lasers have no resonator to trap light and are instead based on a disordered gain medium where photons undergo random multiple scattering. It is this multiple scattering that determines the lasing modes. Random lasers are usually highly multimode, with potentially strong modal interactions. Interference effects notoriously modify the propagation of waves in such highly scattering random media, but their fate in the presence of nonlinearity, such as those generated by modal interactions, is poorly understood.

In this talk, I will discuss the fate of wave interference effects in nonlinear random lasers. A brief introduction to laser physics will be followed by a historico-physical survey of random lasers, discussing what they are, why they are interesting and what the current states of the arts in both theory and experiments on random lasers are. I will then move on to discuss wave interference effects in such nonlinear systems, focusing on Anderson localization — the localization of waves by destructive interference effects in strongly scattering media. In that particular limit, I will show analytically that lasing modes are not affected by nonlinearities [1]. This is one of the very few analytical results ever obtained in this highly nonlinear problem, and I will close my presentation with proposals to extend this theory to more interesting, more weakly scattering regimes.

[1] P. Stano and Ph. Jacquod, Nature Photonics 7, 66 (2013).