Optimizing the excitation of surface plasmon polaritons by difference-frequency generation on a gold surface

We investigate theoretically the excitation of surface plasmon polaritons (SPPs) by difference-frequency generation on a planar air-gold interface. Calculations are presented for three SPP wavelengths: 1.55 mu m, 1.00 mu m, and 750 nm (free-space values). The predicted conversion efficiency, optimized with respect to the angles of incidence of the two p-polarized laser pumps, increases by two orders of magnitude, from 3.5 x 10(-8) at the telecom wavelength to 3.4 x 10(-6) at 750 nm. The latter value is four orders of magnitude larger than the recently reported experimental value for SPP excitation at 633 nm by four-wave mixing. Higher conversion efficiency is expected at shorter SPP wavelengths before the efficiency will drop in the reflection edge of gold.