Opt Lett. 2023 Jul 1;48(13):3367-3370. doi: 10.1364/OL.492372.
Lithium niobate-on-insulator (LNOI) is a promising integration platform for various applications, such as optical communication, microwave photonics, and nonlinear optics. To make Lithium niobate (LN) photonic integrated circuits (PICs) more practical, low-loss fiber-chip coupling is essential. In this Letter, we propose and experimentally demonstrate a silicon nitride (SiN) assisted tri-layer edge coupler on LNOI platform. The edge coupler consists of a bilayer LN taper and an interlayer coupling structure composed of an 80 nm-thick SiN waveguide and an LN strip waveguide. The measured fiber-chip coupling loss for the TE mode is 0.75 dB/facet at 1550 nm. Transition loss between the SiN waveguide and LN strip waveguide is ∼0.15 dB. In addition, the fabrication tolerance of the SiN waveguide in the tri-layer edge coupler is high.
铌酸锂-绝缘体（LNOI）是一种很有前途的集成平台，适用于各种应用，如光通信、微波光子学和非线性光学。为了使铌酸锂（LN）光子集成电路（PIC）更实用，低损耗的光纤-芯片耦合是必不可少的。在本信中，我们提出并实验演示了一种基于 LNOI 平台的氮化硅（SiN）辅助三层边缘耦合器。边缘耦合器由双层 LN 锥形和由 80nm 厚的 SiN 波导和 LN 条形波导组成的层间耦合结构组成。在 1550nm 处，TE 模式的光纤-芯片耦合损耗为 0.75dB/面。SiN 波导和 LN 条形波导之间的转换损耗约为 0.15dB。此外，三层边缘耦合器中 SiN 波导的制造容差较高。
