<b>High Efficiency Si</b>_{<strong>3</strong>}<b>N</b>_{<strong>4</strong>}<b> Grating Couplers with Hybrid Al</b><b>₂</b><b>O</b><b>₃</b><b>/Metal-Mirror Structure for Back-Reflection Suppression</b>

We present a high-performance one-dimensional silicon nitride grating coupler optimized via chirped duty cycle and period engineering for superior mode matching. A tailored multilayer dielectric stack above the grating suppresses back reflection and enhances index matching, while a metal reflector beneath redirects leakage light to boost coupling efficiency. Three-dimensional finite-difference time-domain simulations yield a record 95% peak efficiency and a 57 nm 1 dB bandwidth, combining high performance with broadband operation. This approach provides a compact, fabrication-ready optical interface for silicon photonic integrated circuits, advancing the performance frontier of one-dimensional silicon nitride grating couplers.我们提出一款高性能一维氮化硅光栅耦合器（one-dimensional silicon nitride grating coupler），通过啁啾占空比与周期优化设计实现了优异的模式匹配。光栅上方的定制化多层介质膜堆可抑制背向反射并优化折射率匹配，而光栅下方的金属反射镜则可将泄漏光重新导向，以提升耦合效率。经三维时域有限差分法（three-dimensional finite-difference time-domain）仿真验证，该耦合器实现了创纪录的95%峰值效率与57纳米的1dB带宽，兼顾高性能与宽带工作特性。本方案为硅基光子集成电路（silicon photonic integrated circuits）提供了紧凑且可直接制备的光学接口，推动了一维氮化硅光栅耦合器的性能前沿发展。