Enhancement of reflective second harmonic generation using periodically arrayed silver-island films

The characteristics of angle-resolved optical second harmonic generation (SHG) reflectance from periodically arrayed silver-island films were investigated. The silver-island films were fabricated using micro-spherical lithography. The SHG intensity from these arrays was more than one order of magnitude greater than that of flat silver films for some angles of incidence. This enhancement arises from the excitation of surface plasmon resonance at the pumping frequency. We found this resonance by analyzing the reciprocal lattice phase-matching condition for the silver-island films. The predicted surface plasmon wave vectors are in good agreement with those obtained using three-dimensional finite-difference time-domain numerical simulations.