薄膜铌酸锂反向锥形端面耦合器  

Inverse Taper Edge Coupler Based on LiNbO_(3)Thin Film

作　　者：向美华 于硕 李德阳 杨登才[1] XIANG Meihua;YU Shuo;LI Deyang;YANG Dengcai(Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学材料与制造学部,北京100124

出　　处：《北京工业大学学报》2023年第7期737-745,共9页Journal of Beijing University of Technology

基　　金：北京市自然科学基金资助项目(1212009)。

摘　　要：薄膜铌酸锂波导与单模光纤在模场尺寸上存在很大差异,模场失配严重,导致两者直接耦合的效率低下。针对薄膜铌酸锂波导与超高数值孔径(ultra-high numerical aperture, UHNA)光纤的端面耦合问题,基于时域有限差分(finite difference time domain, FDTD)法优化设计了反向锥形端面耦合器的结构参数,仿真实现了薄膜铌酸锂矩形波导与UHNA光纤的高效耦合。利用电子束曝光、电感耦合等离子体刻蚀等工艺,制备了反向锥形耦合器,设计并建立了端面耦合测试平台,完成了反向锥形耦合器的性能测试。实验结果表明,反向锥形耦合器近场输出光斑在水平和垂直方向的模场直径分别为3.3和3.6μm,水平和垂直方向的3 dB对准容差分别为3.0和3.2μm,单端插入损耗为6.24 dB/面,表明设计制作的反向锥形耦合器具有较好的耦合性能。该研究为大容量、高速率的集成光子器件与光纤之间的耦合提供了高耦合效率的光接口方案。The modal field size of lithium niobate on insulator(LNOI)-based waveguides and single-mode fibers has a huge difference,and the direct coupling efficiency is low due to the modal field mismatch.For the edge coupling between the LNOI waveguide and ultra-high numerical aperture(UHNA)optical fiber,an inverse-taper edge coupler was optimized based on finite difference time domain(FDTD)method.The simulation realizes the efficient coupling of lithium niobate rectangular waveguide and UHNA fiber.The designed inverse taper coupler was fabricated by electron beam lithography,and inductively coupled plasma etching.The test system of edge coupling was established to evaluate the performance of inverse taper coupler.The test results show that at the wavelength of 1550 nm,the mode field diameters of the near-field output spot of the inverse taper coupler in the horizontal and vertical directions are 3.3μm and 3.6μm,respectively.The 3 dB alignment tolerance with the UHNA fiber in horizontal and vertical directions are 3.0μm and 3.2μm,respectively.The insertion loss of single end reaches 6.24 dB/facet,and this verifies that the designed inverse taper reduces the direct coupling loss between the LNOI waveguide and single-mode fiber effectively,and has the fine coupling performance.This study provides a high-coupling-efficiency optical interface scheme for the coupling between high-capacity,high-rate integrated photonic devices and optical fibers.

关 键 词：光波导 超高数值孔径光纤 薄膜铌酸锂 时域有限差分法(FDTD) 端面耦合 反向锥形耦合器 

分 类 号：TN252[电子电信—物理电子学]