薄膜铌酸锂片上倒装激光芯片的结构设计与优化  

Structural Design and Optimization for Hybrid Integration of Laser on TFLN by Flip-Chip

作　　者：卢金龙 郝婷 李志浩 周赤 吉贵军 王兴龙 Lu Jinlong;Hao Ting;Li Zhihao;Zhou Dennis;Ji Guijun;Wang Xinglong(School of Precision Instruments and Opto-Electronics Engineering,Tianjin University,Tianjin 300072,China;Advanced Fiber Resources(Zhuhai)Ltd.,Zhuhai 519080,Guangdong,China)

机构地区：[1]天津大学精密仪器与光电子工程学院,天津300072 [2]珠海光库科技股份有限公司,广东珠海519080

出　　处：《光学学报》2023年第23期302-309,共8页Acta Optica Sinica

基　　金：国家重点研发计划(SQ2021YFB2800064);珠海市产学研合作项目(ZH22017001210108PWC)。

摘　　要：基于薄膜铌酸锂干法刻蚀工艺不能获得高垂直度截面的特点,设计了一种基于折射率相近的填充材料作为模斑转换结构。所设计结构可兼容不同尺寸的输出光斑且整体结构的转换效率大于-0.28 dB。所提方案避免了薄膜铌酸锂干法刻蚀后的大倾角断面直接作为耦合端面时性能低的劣势,可提升薄膜铌酸锂电光调制器件在片上集成激光芯片的性能。三维模拟结果显示该结构对工艺误差不敏感、加工可行性高,为减小集成器件体积、降低成本及高密度集成提供可行方案。Objective Thin film lithium niobate(TFLN)electro-optic modulation devices feature large bandwidth,low loss,and small half-wave-voltage length.However,lithium niobate materials cannot be directly applied to light source fabrication,and current integrated electro-optic modulation systems still require an external III-V laser chip.Three main methods for integrating light sources on the wafer level include flip-chip,micro-transfer printing,and heterogeneous integration.The micro-transfer printing and heterogeneous integration both involve fabricating structures of the laser devices,and the on-chip output power in most reports is less than 10 mW,which is difficult to meet practical applications.In contrast,flip-chip integration based on butt coupling with a high-power laser chip that has passed a stability test can not only achieve high-level integration on the TFLN chip but also has been verified to obtain an on-chip output power larger than 60 mW.However,most TFLN devices are based on the ridge waveguide due to the difficult fabrication,and dry etching of TFLN always results in an end facet with an angle between 40°and 80°,which drastically decreases the coupling efficiency of integrating photonic dies on the chip.On the other hand,low-loss coupling among devices with different mode sizes is still a problem for TFLN.To this end,we propose a spot size converter(SSC)design and prove its effectiveness.Methods As shown in Fig.1,the proposed SSC is divided into two parts.Part 1 is the SiN ridge waveguide that is directly connected to the inclined section of the TFLN waveguide,and part 2 is designed to convert the mode distribution similar to the target device through a SiN core waveguide and two thin layers of SiON,with the entire mode converter cladding of SiO_(2). This structure reduces the crucial requirements for dry etching of lithium niobate materials as SiN fabrication is more mature. Based on the structure in Fig. 1, we first improve the conversion efficiency between the SSC and the TFLN (part 1) by optimizing

关 键 词：薄膜 铌酸锂 片上集成 倒装焊 模斑转换 

分 类 号：O436[机械工程—光学工程]