Abstract
Nonlinear metasurfaces and photonic crystals provide a significant way to generate and manipulate nonlinear signals owing to the resonance-and symmetry-based light-matter interactions supported by the artificial structures.However,the nonlinear conversion efficiency is generally limited by the angular dispersion of optical resonances especially in nonparaxial photonics.Here,we propose a metagrating realizing a quasi-bound-state in the continuum in a flat band to dramatically improve the third harmonic generation(THG)efficiency.A superior operating angular range is achieved based on the interlayer and intralayer couplings,which are introduced by breaking the mirror symmetry of the metagrating.We demonstrate the relation of angular dispersion between the nonlinear and linear responses at different incident angles.We also elucidate the mechanism of these off-axis flat-band-based nonlinear conversions through different mode decomposition.Our scheme provides a robust and analytical way for nonparaxial nonlinear generation and paves the way for further applications such as wide-angle nonlinear information transmission and enhanced nonlinear generation under tight focusing.
基金项目
国家重点研发计划(2021YFA1400601)
国家重点研发计划(2022YFA1404501)
National Natural Science Fund for Dislinguished Young Scholar(11925403)
国家自然科学基金(12122406)
国家自然科学基金(12192253)
国家自然科学基金(12274239)
国家自然科学基金(12274237)
国家自然科学基金(U22A20258)
维普
万方数据