Calculations of second harmonic generation by nano-particles or holes

We are setting up finite-difference time-domain (fdtd) calculations of second harmonic generation (shg) by metallic nano-particles or at nano-holes in metallic films. This generation is driven by first order fields at the metal surfaces, using the phenomenological a and b parameters that have been used to describe shg at planar jellium-metal surfaces. Our interest is in locating and understanding the occurrence of resonances and hot-spots for shg.