Generation of High Harmonics in Silicon Metasurfaces Boosted by Bound States in the Continuum

Bound states in the continuum (BICs) are lossless states predicted in quantum mechanics in 1929, and for the last decade, received special attention in optics and photonics as a versatile tool to achieve giant quality factors (Q factors) [1] . For ordered arrays of subwavelength meta-atoms, metasurfaces, with broken in-plane symmetry, it was shown that Q factor of quasi-BICs can be unambiguously controlled by variation of the unit cell asymmetry parameter [2] .