Giant enhancement of third harmonic generation via guided mode resonances in notched silicon waveguides

We report a giant enhancement of the third harmonic generation (THG) at 343 nm by periodically notched silicon waveguide arrays supporting guided mode resonances (GMRs) at 1030 nm. Maximum efficiency of the third harmonic generation η = 7.71 × 10−5 is achieved with a peak pump power density of 5.31 GW/cm2. The enhancement factor of the THG from the GMR metasurface reaches up to 1.3 × 107 compared to a flat silicon film with the same thickness. This observation demonstrates a promising approach to design high-efficiency nonlinear optical metasurfaces.