Nonlinear plasmonics

When light interacts with metal nanostructures, it can couple to free-electron excitations near the metal surface. The electromagnetic resonances associated with these surface plasmons depend on the details of the nanostructure, opening up opportunities for controlling light confinement on the nanoscale. The resulting strong electromagnetic fields allow weak nonlinear processes, which depend superlinearly on the local field, to be significantly enhanced. In addition to providing enhanced nonlinear effects with ultrafast response times, plasmonic nanostructures allow nonlinear optical components to be scaled down in size. In this Review, we discuss the principles of nonlinear plasmonic effects and present an overview of their main applications, including frequency conversion, switching and modulation of optical signals, and soliton effects.