Enhanced quadrupolar second-harmonic generation from rough gold films

The nonlinear optical response of gold films of different thicknesses is investigated by two-beam second-harmonic generation to address the role of surface and bulk effects in their second-order nonlinear optical response. Preliminary results suggest that both types of effects contribute to the measured second-harmonic signals. Furthermore, both effects are found to be enhanced for the thin film with a higher level of nanoscale surface roughness.