Chiral Harmonic Generation by Quasi-Bound States in the Continuum

Abstract

Quasi-bound states in the continuum (quasi-BICs) of dielectric metasurfaces, selectively coupled to circularly polarized waves, provide maximum linear-optical chirality. We consider how they can empower chiral nonlinear-optical processes. We demonstrate that using arbitrarily polarized pumping wave one can generate circularly polarized harmonics at the chiral quasi-BIC wavelength. Conversely, pumping at such a wavelength results in giant harmonic circular dichroism. We design maximum-chiral metasurfaces based on different semiconductor materials and simulate generation of second and third harmonics. We compare various scenarios and reveal feasible limits of generation enhancement and chirality. Show more