Enhanced wide-angle third-harmonic generation in flat-band-engineered quasi-BIC metagratings  

作　　者：Yijia Zang Ruoheng Chai Wenwei Liu Zhancheng Li Hua Cheng Jianguo Tian Shuqi Chen 

机构地区：[1]The Key Laboratory of Weak Light Nonlinear Photonics,Ministry of Education,School of Physics and TEDA Institute of Applied Physics,Nankai University,Tianjin 300071,China [2]School of Materials Science and Engineering,Smart Sensing Interdisciplinary Science Center,Nankai University,Tianjin 300350,China [3]The Collaborative Innovation Center of Extreme Optics,Shanxi University,Taiyuan 030006,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2024年第4期81-87,共7页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1400601,and 2022YFA1404501);the National Natural Science Fund for Distinguished Young Scholar(Grant No.11925403);the National Natural Science Foundation of China(Grant Nos.12122406,12192253,12274239,12274237,and U22A20258)。

摘　　要：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 offaxis 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.

关 键 词：nonlinear metasurfaces quasi-bound-state in the continuum angular dispersion third harmonic generation efficiency 

分 类 号：O43[机械工程—光学工程]