Enhanced sum-frequency generation from etchless lithium niobate empowered by dual quasi-bound states in the continuum  

作　　者：Siqi Feng Tingting Liu Wenya Chen Feng Wu Shuyuan Xiao 

机构地区：[1]Institute for Advanced Study,Nanchang University,Nanchang 330031,China [2]Jiangxi Key Laboratory for Microscale Interdisciplinary Study,Nanchang University,Nanchang 330031,China [3]School of Optoelectronic Engineering,Guangdong Polytechnic Normal University,Guangzhou 510665,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2023年第12期119-128,共10页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.12104105,12264028,12304420,and 12364045);the Natural Science Foundation of Jiangxi Province(Grant Nos.20232BAB201040,and 20232BAB211025);the Chenguang Program of Shanghai Education Development Foundation;Shanghai Municipal Education Commission(Grant No.21CGA55);the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011024);the Science and Technology Program of Guangzhou(Grant No.202201011176);the Interdisciplinary Innovation Fund of Nanchang University(Grant No.2019-9166-27060003);the Start-up Funding of Guangdong Polytechnic Normal University(Grant No.2021SDKYA033);the China Scholarship Council(Grant No.202008420045)。

摘　　要：The miniaturization of nonlinear light sources is central to the integrated photonic platform,driving a quest for high-efficiency frequency generation and mixing at the nanoscale.In this quest,the high-quality(Q)resonant dielectric nanostructures hold great promise,as they enhance nonlinear effects through the resonantly local electromagnetic fields overlapping the chosen nonlinear materials.Here,we propose a method for the enhanced sum-frequency generation(SFG)from etcheless lithium niobate(LiNbO_(3))by utilizing the dual quasi-bound states in the continuum(quasi-BICs)in a one-dimensional resonant grating waveguide structure.Two high-Q guided mode resonances corresponding to the dual quasi-BICs are respectively excited by two near-infrared input beams,generating a strong visible SFG signal with a remarkably high conversion efficiency of 3.66×10^(-2)(five orders of magnitude higher than that of LiNbO_(3)films of the same thickness)and a small full-width at half-maximum less than 0.2 nm.The SFG efficiency can be tuned via adjusting the grating geometry parameter or choosing the input beam polarization combination.Furthermore,the generated SFG signal can be maintained at a fixed wavelength without the appreciable loss of efficiency by selectively exciting the angle-dependent quasi-BICs,even if the wavelengths of input beams are tuned within a broad spectral range.Our results provide a simple but robust paradigm of high-efficiency frequency conversion on an easy-fabricated platform,which may find applications in nonlinear light sources and quantum photonics.

关 键 词：resonant grating waveguide structure bound states in the continuum sum-frequency generation lithium niobate 

分 类 号：TN252[电子电信—物理电子学]