  Metasurfaces control optical wavefronts via arrays of nanoscale resonators
laid out across a surface. When combined with III-V semiconductors with strong
optical nonlinearities, a variety of nonlinear effects such as harmonic
generation and all optical modulation can be enabled and enhanced at the
nanoscale. This review presents our research on engineering and boosting
nonlinear effects in ultrafast and nonlinear semiconductor metasurfaces
fabricated at the Center for Integrated Nanotechnologies (CINT). We cover our
recent works on parametric generation of harmonic light via direct and cascaded
processes in GaAs-metasurfaces using Mie-like optical resonances or
symmetric-protected Bound State in the Continuum, and then describe the recent
advances on harmonic generation in all-dielectric metasurfaces coupled to
intersubband transitions in III-V semiconductor heterostructures. The review
concludes on the potential of metasurfaces to serve as the next platform for
on-chip quantum light generation.
