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 $3.5\times {10}^{-8}$ at the telecom wavelength to $3.4\times {10}^{-6}$ 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.

• Received 16 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.155442