  Dielectric metasurfaces have shown prominent applications in nonlinear optics
due to strong field enhancement and low dissipation losses at the nanoscale.
Chalcogenide glasses are one of the promising materials for the observation of
nonlinear effects due to their high intrinsic nonlinearities. Here, we
demonstrate, experimentally and theoretically, that significant second harmonic
generation can be obtained within amorphous chalcogenide based metasurfaces by
relying on the coupling between lattice and particle resonances. We further
show that the high quality factor resonance at the origin of the second
harmonic generation can be tuned over a wide wavelength range using a simple
and versatile fabrication approach. The measured second harmonic intensity is
orders of magnitude higher than that from a deposited chalcogenide film, and
more than three orders of magnitude higher than conventional plasmonic and
Silicon-based structures. Fabricated via a simple and scalable technique, these
all-dielectric architectures are ideal candidates for the design of flat
non-linear optical components on flexible substrates.
