Strong enhancement of second-harmonic generation in all-dielectric resonant waveguide grating

The authors demonstrate that a dielectric resonant waveguide grating can enhance optical second-harmonic generation by a factor of 550 compared to a similar flat surface. Their structure, which consists of purely dielectric and thereby transparent materials, has a low index silicon dioxide grating covered by a high index titanium dioxide layer and it is optimized for the fundamental wavelength of 1064 nm. Polarization dependence of the second-harmonic response suggests that the enhancement arises from the favorable interaction of the resonant waveguide mode and its strong local field with the inherent surface nonlinearity of the dielectric materials.