Mode-selective edge coupler with cladding grating for a lithium-niobate-on-insulator waveguide  

作　　者：Pengfei Fan Xiaotian Zhang Chi Zhang Shanshan Cheng Xiao-Hui Tian Kunpeng Jia Hua-Ying Liu Shining Zhu Zhenda Xie 范鹏飞;张啸天;张弛;成珊珊;田晓慧;贾琨鹏;刘华颖;祝世宁;谢臻达

机构地区：[1]National Laboratory of Solid State Microstructures,College of Engineering and Applied Sciences,School of Electronic Science and Engineering,School of Physics,and Collaborative Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210093,China

出　　处：《Chinese Optics Letters》2025年第1期140-144,共5页中国光学快报(英文版)

基　　金：supported by the National Key R&D Program of China(Nos.2022YFA1205100 and 2019YFA0705000);the National Natural Science Foundation of China(Nos.62293523,12304421,and 62305156);the Jiangsu Natural Science Foundation(No.BK20232033);the Leading-edge Technology Program of Jiangsu Natural Science Foundation(No.BK20192001);the Zhangjiang Laboratory(No.ZJSP21A001);the Jiangsu Funding Program for Excellent Postdoctoral Talent。

摘　　要：Lithium-niobate-on-insulator(LNOI)chips have shown outstanding performance in various photonic devices including modulators,lasers,nonlinear converters,and quantum sources.LNOI-based edge couplers are quite important for further promotion of the above devices in practical applications,especially for large-scale multiport photonic uses,where efficient and mode-selective coupling between chips and fibers is of necessity.Previously,several LNOI edge couplers have been demonstrated,but they mainly focus on achieving high coupling efficiency of the fundamental mode,and sub-wavelength etched lithium-niobate(LN)structures are normally needed,which increases fabrication complexity.Here we propose a new type of edge coupler with direct mode-selective excitation ability,using only Si ON cladding grating structures without additional etching of LN.By introducing a cladding waveguide with periodic structures on the uniform LNOI waveguide,highefficiency excitation of multiple modes can be realized directly with easier fabrication.For a specific simulation here,TE00,TM00,and TE10core modes can be excited,respectively,at optimized periods and grating lengths with a tunable central wavelength,at the launch of the TM cladding mode.The periods of the needed Si ON gratings are all over 2μm,which is feasible with i-line UV lithography.Our results provide a low-cost edge coupler for LNOI photonic circuits with the ability of flexible spatial mode selectivity,which may promote LNOI devices in large-scale multiport photonic integrated circuits in the future.

关 键 词：lithium-niobate-on-insulator chip edge coupler mode selectivity 

分 类 号：TN256[电子电信—物理电子学]