Beyond third-order optical nonlinearities in liquid suspensions of metal-nanoparticles and metal-nanoclusters

Abstract

Abstract Various nonlinear optical (NLO) phenomena observed in liquid suspensions of metal nanoparticles (NPs) and metal nanoclusters (NCs) have received considerable attention in the past few years. For example, multiphoton absorption, modulational instability, optical solitons, and parametric processes, benefit from research on soft-matter systems. Thus, many results are still being published providing support for earlier theoretical predictions and new discoveries. In particular, colloids containing NPs and NCs of noble-metal atoms present outstanding NLO responses and have been exploited to study for studying various phenomena and applications. Indeed, when illuminated with intense optical fields, such colloids can exhibit effective high-order nonlinearities (HONs) with large magnitudes which can dominate their NLO behavior. In this article, we review experiments with liquid suspensions of noble-metal NPs and noble-metal NCs, in which an appropriate methodology has been applied to study effective HONs for different sizes and morphologies of metal-nanostructures. In addition, a nonlinearity management procedure is discussed as a valuable tool to control for controlling the NLO response of metal-colloids through constructive and destructive interference among the nonlinearities of different orders. Because of the strong NLO behavior of metal-colloids, various phenomena associated to effective HONs were investigated such as: self-action effects, saturated multiphoton absorption, NLO scattering, bright and vortex spatial solitons, and operation of Random Lasers. Perspectives for further studies and photonic applications of metal-colloids exploring their effective nonlinearities are also discussed.