High-efficiency optical frequency mixing in an all-dielectric metasurface enabled by multiple bound states in the continuum

We present nonlinear optical four-wave mixing in a silicon nanodisk dimer metasurface. Under the oblique incident plane waves, designed metasurface exhibits multiresonant feature with simultaneous excitations of three quasi-bound states continuum (BIC). Through employing these quasi-BICs maximizing electric field energy at input bump wavelengths, significant enhancement third-order processes including third-harmonic generation, degenerate and nondegenerate are demonstrated, giving rise to ten frequencies visible wavelengths. This work may lead new frontier ultracompact mixer for applications circuitry, ultrasensitive sensing, quantum nanophotonics.