大曲率低损耗弯曲波导的飞秒激光直写  

Femtosecond Laser Direct Writing of Bent Waveguides with High Curvature and Low Loss

作　　者：李义春 肖凯恒 李中天 刘畅 于颜豪[1] 田振男 Li Yichun;Xiao Kaiheng;Li Zhongtian;Liu Chang;Yu Yanhao;Tian Zhennan(College of Electronic Science and Engineering,Jilin University,Jilin 130012,China)

机构地区：[1]吉林大学电子科学与工程学院,吉林长春130012

出　　处：《中国激光》2024年第16期268-276,共9页Chinese Journal of Lasers

基　　金：国家自然科学基金(62131018,61805098);中国博士后基金(2019M651200);吉林省科技发展计划(20220301002GX,20230508110RC)。

摘　　要：飞秒激光直写光波导是实现三维光子集成芯片(PIC)的重要技术手段。PIC集成度的提升受弯曲波导曲率半径的限制。为了实现大曲率低损耗弯曲波导的飞秒激光直写,提出多次激光修饰增强波导芯层与包层折射率对比度的方法来优化芯层的横截面折射率分布。在20 mm曲率半径下,实现S型弯曲波导低至0.64 dB/cm的弯曲损耗。该方法在降低弯曲波导损耗方面拥有巨大潜力,对于提升PIC的集成度具有重要意义。Objective Femtosecond laser direct writing(FLDW)has been widely used in material processing to improve material performance due to its high flexibility,true three-dimensional capability,and wide applicability to various materials.Photonic integrated circuits(PICs)constructed by FLDW are advantageous in terms of high stability and strong resistance to interference,making them suitable for applications in optical interconnects,biosensing,quantum communication,and quantum simulation.With the continuous expansion and enrichment of these applications,miniaturization of photonic devices has become an inevitable trend.However,the integration density of PICs is significantly limited by the loss caused by large curvature waveguides(including 90°bending,180°bending,and S-shaped bending)due to the low refractive index contrast of waveguides produced by single-shot FLDW.Although various methods have been reported to optimize the bending loss of large curvature waveguides,none of them can simultaneously meet the requirements of high integration density and wide applicability range.In this work,we employ a method of multiple laser modifications to enhance the refractive index contrast between the core and cladding of waveguides,optimize the cross-sectional refractive index distribution of the core,and achieve a bending loss as low as 0.64 dB/cm for S-shaped bent waveguides with a radius of 20 mm.Since the modification lines are written inside the waveguide and completely consistent with the bending shape and formation of the waveguide,this method possesses the characteristics of high integration density and wide applicability range,providing an important basis for the miniaturization of PICs.Methods This paper analyzes the causes of bending loss in waveguides and proposes a method of multiple laser modifications to enhance the refractive index contrast between the core and cladding of waveguides,optimizing the cross-sectional refractive index distribution of the core.Then,the mode field distribution within the bent waveguide

关 键 词：光学制造 光波导 飞秒激光直写 大曲率 弯曲损耗 截面控制 

分 类 号：TN252[电子电信—物理电子学]