Chiral harmonic generation studies from partially etched amorphous silicon nanodisk arrays

In this work, partially etched amorphous silicon (a-Si) metasurface is designed and fabricated to enhance chiral THG from the a-Si nanodisks and SHG from integrated multilayer GaSe overlayers with spectrally tunable chirality. The metasurfaces are designed to support guided mode resonance in the 1500-1600 nm wavelength range. A minimum degree of circular polarization (DOCP) of -0.6 is obtained experimentally on-resonance for the inherent THG process from the silicon nanodisks with resonant enhancement of more than 5 orders. A spectrally tunable DOCP of -0.5 to 0.5 is obtained for the generated SHG from the GaSe layer on top of the silicon metasurface with resonant enhancement of more than 5 orders.