基于超表面结构的紧凑型铌酸锂波导模式转换器  

Compact Lithium Niobate Waveguide Mode Converter Employing Metasurface Structure

作　　者：王琳 高阳 石昊 张磊 尹坤 Wang Lin;Gao Yang;Shi Hao;Zhang Lei;Yin Kun(Research Institute of Intelligent Networks,Zhejiang Lab,Hangzhou 311121,Zhejiang,China)

机构地区：[1]之江实验室智能网络研究院,浙江杭州311121

出　　处：《光学学报》2023年第16期312-319,共8页Acta Optica Sinica

基　　金：之江实验室科研项目(2020LC0AD02,2022QA0AL01)。

摘　　要：模式转换器是片上模式复用(MDM)系统的关键器件。为在绝缘体上铌酸锂(LNOI)中实现结构紧凑的模式转换,本文提出了一种基于超表面结构的模式转换器。该模式转换器可以实现TE0-TE1、TE0-TE2的转换。为了在模式之间实现高效转换,采用逆向设计方法,结合3D电磁场仿真,优化器件倾斜周期性亚波长条形蚀刻结构参数,以同时符合沿传播方向的相位匹配要求,以及符合短耦合长度的横向方向折射率分布要求。仿真结果表明,器件在1400~1700 nm波段内,TE0-TE1转换的插入损耗<0.8 dB,模间串扰<-10 dB,模式转换区长度~20μm。且该器件具有较好的高阶模式转换扩展性以及工艺容差性,是未来LNOI的高密度集成MDM系统中模式转换器的良好备选方案。Objective With the development of informatization,there is a growing demand for information transmission and processing.In this situation,it becomes urgent to increase the channel capacity.Currently,there are multiple multiplexing techniques available to enhance channel capacity,such as wavelength division multiplexing,polarization multiplexing,and mode division multiplexing(MDM).Among them,MDM utilizes different modes and polarizations of light to carry data and parallelly transmits multiple data channels in optical waveguides or fibers using only a single wavelength laser source,which can be seen as a new dimension to expand the capacity of optical fiber communication.The lithium niobate-oninsulator(LNOI)platform,with its strong electro-optic effect,low material loss,and wide transparent window,can achieve high-speed electro-optic modulators and optical nonlinear devices while providing high refractive index contrast waveguides,which thus makes it capable of manufacturing high-speed and high-density on-chip optical devices.However,there are few reports on MDM devices on LNOI platforms,and they mainly focus on the principle of phase matching of directional couplers loaded with LNOI platforms with silicon nitride.Although the mode converter based on the principle of phase matching of directional couplers has low processing difficulty and good scalability,it may have the problem of a relatively large footprint,which is not conducive to large-scale on-chip integration.Methods According to the coupled mode theory,when light propagates in a medium,the energy of the light field can be coupled from one mode to another mode by designing the appropriate medium structure.In this process,the perturbation of the medium structure not only satisfies the phase matching requirement of the two converting modes along the propagation direction of the z-axis but also has an appropriate refractive index distribution in the lateral direction to obtain an appropriate coupling coefficient and achieve a shorter coupling length.Metasurfa

关 键 词：光学器件 模式转换器 集成光子器件 铌酸锂 

分 类 号：TN256[电子电信—物理电子学]