Fang Shaobo, Hong Binzhou, Liu Shuyuan, Lao Yinan, Cai Haiwen, Chu Wei
Opt Express. 2025 Apr 21;33(8):18467-18476. doi: 10.1364/OE.561741.
We propose a broadband, polarization-insensitive, and fabrication-friendly edge coupler (EC) optimized for efficient coupling between a 600-nm X-cut thin-film lithium niobate (TFLN) platform and a standard 9.2-μm single-mode fiber at 1550 nm. A single-layer silicon nitride (SiN) waveguide structure and a three-stage adiabatic taper are employed to enhance mode-field matching and minimize propagation losses. The optimized EC achieves coupling losses of -0.546/-0.501 dB (TE/TM), polarization-dependent loss (PDL) of 0.035 dB, a 1-dB bandwidth exceeding 100 nm, and robust alignment tolerances (±2.0 μm/±2.2 μm laterally and ±1.7 μm/±1.9 μm vertically for TE/TM modes), making it highly suitable for scalable TFLN photonic integration.
我们提出了一种宽带、偏振不敏感且易于制造的边缘耦合器（EC），该耦合器针对600纳米X切薄膜铌酸锂（TFLN）平台与标准9.2微米单模光纤在1550纳米处的高效耦合进行了优化。采用单层氮化硅（SiN）波导结构和三级绝热锥度来增强模场匹配并最小化传播损耗。优化后的EC实现了-0.546/-0.501 dB（TE/TM）的耦合损耗、0.035 dB的偏振相关损耗（PDL）、超过100纳米的1分贝带宽以及强大的对准容差（TE/TM模式横向为±2.0微米/±2.2微米，纵向为±1.7微米/±1.9微米），使其非常适合可扩展的TFLN光子集成。
