Efficient second-harmonic generation in silicon nitride resonant waveguide gratings.

We demonstrate a thousand-fold enhancement of second-harmonic generation in an all-dielectric silicon nitride (SiN) resonant waveguide grating compared to a flat SiN film. The strong second-harmonic output measured at 532 nm results from the combination of the enhanced local fields in the nanostructure and the large second-order susceptibility of SiN. The second-harmonic conversion efficiency in the resonant structure is found to be of the order of 10(-8), which is significantly larger than that typically observed from plasmonic metal nanostructures.