4 - High-Order Nonlinearities of Metal-Dielectric Nanocomposites

Abstract

When metal nanoparticles (NPs) are embedded in a dielectric host, the mismatch between the dielectric functions of the NPs and the host may originate large local fields that contribute to enhance high-order optical nonlinearities (HON) of the composite sample. Such behavior has motivated many investigations aiming the application of metal-dielectric nanocomposites (MDNCs) in photonic devices. In this chapter, we briefly review recent works on the origin, characteristics, and measurements of HON in MDNCs and on the management of the nonlinear light propagation through the samples. The MDNCs selected to exemplify the nonlinearity management (NM) procedure were diluted metal nanocolloids, and the generalized Maxwell-Garnett model was used as a guide to engineer the effective nonlinear susceptibilities of the samples. The high-order response of the MDNCs was controlled by changing the NPs volume fraction and the light intensity in order to build the conditions for propagation of stable spatial solitons. As application of the NM procedure, various silver nanocolloids were investigated experimentally in the picosecond regime, and the conditions were identified to observe soliton propagation in two different circumstances: bright solitons in quintic-septimal (focusing-defocusing) media and vortex solitons in cubic-quintic (defocusing-focusing) media. The management of the HON was essential to observe both phenomena. Numerical simulations corroborate all experimental results. The NM procedure reviewed in this chapter provides a powerful method to design experiments related to high-order optical phenomena in MDNCs and opens new routes for investigation of the large amount of theoretical proposals already existing in the literature.