Resonant Chiral Effects in Nonlinear Dielectric Metasurfaces

We study the resonant enhancement of linear and nonlinear chiroptical effects in planar silicon metasurfaces with an in-plane asymmetry supporting multipolar Mie resonances quasi-bound states continuum (quasi-BICs). demonstrate theoretically observe experiment pronounced circular dichroism at quasi-BIC originating from interaction modes substrate. further find that both local field third-harmonic signal are large for some due to critical coupling. experimentally a strong response associated high efficiency generation varying +0.918 ± 0.049 −0.771 0.004 samples different asymmetries. reveal nonreciprocal nature chirality governed by microscopic symmetry nonlinearities macroscopic symmetries meta-atom metasurface lattice. believe our results suggest general strategy engineering dielectric metasurfaces.