High-efficiency multi-beams output from diffraction optical element (DOE) with equal energy in parallel is of intense interest because high-performance multiple output beams can improve transmission rate of some key optical signals. Herein, we design a novel sandwiched fused-silica diffraction grating, which can operate at the high-efficiency nine-port beam splitting output with good uniformity. By performing rigorous coupled-wave analysis (RCWA) method, grating parameters and fabrication errors are optimized and discussed for TE and TM-polarized modes. A theoretical simplified modal method (SMM) can insight into an explicit light-matter coupling mechanism in grating area. In addition, for better evaluating real performances of the grating, incident spectral bandwidth of the grating can be fully investigated based on RCWA approach and finite-element method (FEM). Thus, this work can open up a possible way for optimizing more high-performance polarization-independent or polarization-dependent higher-order-port diffraction gratings.

平行等能量衍射光学元件（DOE）的高效多光束输出引起了人们的强烈兴趣，因为高性能的多输出光束可以提高一些关键光信号的传输速率。在此，我们设计了一种新型夹层熔融石英衍射光栅，它可以在高效率的九端口分束输出下工作，具有良好的均匀性。通过执行严格的耦合波分析 (RCWA) 方法，针对 TE 和 TM 偏振模式优化和讨论了光栅参数和制造误差。理论上的简化模态方法 (SMM) 可以深入了解光栅区域中的显式光物质耦合机制。此外，为了更好地评估光栅的真实性能，基于RCWA方法和有限元方法（FEM）可以充分研究光栅的入射光谱带宽。因此，这项工作可以为优化更高性能的偏振无关或偏振相关的高阶端口衍射光栅开辟一条可能的途径。