Second harmonic generation from GaP metasurfaces using quasi-bound-states-in-the-continuum

We demonstrate highly efficient second harmonic generation from dielectric meta-surfaces based on gallium phosphide platform, utilizing quasi-bound-state-in-the-continuum resonances. In particular, we demonstrate an efficiency of 0.1 %/W using pulsed laser at an intensity of 10 MW/cm
²
and 5e-5 %/W using continuous wave laser at an intensity of 1 kW/cm
²
.