Enhancement of second-harmonic generation with phase-matching on periodic sub-wavelength structured metal film

We propose a sub-wavelength structured metal film with two sets of grooves with different periods. It can enhance the second harmonic generation (SHG) based on phase-matching. Meanwhile, we reduce the thickness of metal film to excite long-range surface plasma wave for improving the interaction length of SHG. The numerical study shows that this structure greatly improves the conversion efficiency of SHG for about 106 times, and that the SHG light is emitted in a direction perpendicular to the metal surface. This new type of structure could contribute to high conversion efficiency of SHG for the virtues of low loss and extremely compact structure.