*Introductory Lecture for Students*

Noble-metal nanostructures support collective electron resonances, known as plasmons, that can concentrate optical fields down to nanometer-scale volumes, well below the conventional diffraction limit. The strong localization of electromagnetic fields greatly enhances nonlinear optical processes, both in the metal nanostructure itself and in adjacent optical materials. Because the processes occur entirely within a sub-wavelength volume, the usual phase-matching conditions for these processes are lifted. Observable signals have thus been produced even from single nanostructures. When the strength of coupling between the plasmons in the metal nanostructures and resonant materials (such molecules, molecular aggregates, quantum dots) exceeds decay rates in the coupled system, new phenomena appear. In particular, mixed light-matter systems known as polaritons are formed in this "strong-coupling" regime. These quasiparticles synergistically combine the nonlinear properties of the plasmonic and excitonic constituents and are thus ideal for the development of efficient nonlinear photonic devices. Ensembles of quantum emitters optically coupled to plasmonic nanocavities, have recently emerged as new platforms for strong light-matter interactions. This talk overviews recent advances in the research field of polaritonic systems discussing both linear and nonlinear optical phenomena.

Host: Andrei Piryatinski (T-4)