Nonlinear nanophotonics based on surface plasmon polaritons

Abstract

Surface plasmon polaritons (SPPs), elementary excitation of the hybrid states between collective motion of electrons and photons, are associated with strong local field enhancement and deep subwavelength mode confinement. The use of SPPs in nonlinear optics can amplify intrinsically weak nonlinear processes and shrink down the size of nonlinear optic devices to a nanometer scale. In this Perspective, we review the nonlinear optic processes using SPPs in the plasmonic waveguides and foresee their potential in developing compact nonlinear integrated circuits. We discuss the key factors to enhance the conversion efficiency from the plasmonic waveguide, including the spatial overlap between the interacting modes and the nonlinear materials, and the momentum conservation that allows the coherent constructive superposition. Strategies toward this goal include shrinking the effective mode area through adjusting the geometry of the plasmonic waveguide, proper incorporation of the nonlinear susceptibilities to the plasmonic near field, and the use of counter-propagating configurations or phase compensation techniques. We also forecast the future developments of nonlinear plasmonics based on propagating SPPs in active nonlinear devices.