Nonlinear plasmonics at planar metal surfaces

Abstract

We investigate the nonlinear optical response of a noble metal surface. We derive the components of the third-order nonlinear susceptibility and determine an absolute value of χ (3) ≈0.2 nm 2   V −2 , a value that is more than two orders of magnitude larger than the values found for typical nonlinear laser crystals. Using nonlinear four-wave mixing (4WM) with incident laser pulses of frequencies ω 1 and ω 2 , we generate fields oscillating at the nonlinear frequency ω 4WM =2 ω 1 − ω 2 . We identify and discuss three distinct regimes: (i) a regime where the 4WM field is propagating, (ii) a regime where it is evanescent, and (iii) a regime where the nonlinear response couples to surface plasmon polaritons.