Mode converters (MCs) play an essential role in mode-division multiplexing (MDM) systems. Numerous schemes have been developed on the silicon-on-insulator (SOI) platform, yet most of them focus solely on the conversion of fundamental mode to one or two specific higher-order modes. In this study, we introduce a hybrid shape optimization (HSO) method that combines particle swarm optimization (PSO) with adjoint methods to optimize the shape of the S-bend waveguide, facilitating the design of arbitrary-order MCs featuring compactness and high performance. Our approach was validated by designing a series of 13 μm-long MCs, enabling efficient conversion between various TE modes, ranging from TE0 to TE3. These devices can be fabricated in a single lithography step and exhibit robust fabrication tolerances. Experiment results indicate that these converters achieve low insertion losses under 1 dB and crosstalks below −15 dB across bandwidths of 80 nm (TE0–TE1), 62 nm (TE0–TE2), 70 nm (TE0–TE3), 80 nm (TE1–TE2), 55 nm (TE1–TE3), and 75 nm (TE2–TE3). This advancement paves the way for flexible mode conversion, significantly enhancing the versatility of on-chip MDM technologies.

中文翻译：

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基于混合形状优化的低损耗、紧凑型任意阶硅模式转换器


模式转换器 (MC) 在模分复用 (MDM) 系统中发挥着重要作用。人们在绝缘体上硅 (SOI) 平台上开发了许多方案，但大多数方案仅专注于将基模转换为一种或两种特定的高阶模。在本研究中，我们引入了一种混合形状优化（HSO）方法，该方法将粒子群优化（PSO）与伴随方法相结合来优化S弯曲波导的形状，促进具有紧凑性和高性能的任意阶MC的设计。我们的方法通过设计一系列 13 μm 长的 MC 得到验证，能够实现从 TE0 到 TE3 的各种 TE 模式之间的高效转换。这些器件可以在单个光刻步骤中制造，并表现出强大的制造公差。实验结果表明，这些转换器在 80 nm (TE0–TE1)、62 nm (TE0–TE2)、70 nm (TE0–TE3)、80 nm (TE1) 带宽内实现了低于 1 dB 的低插入损耗和低于 -15 dB 的串扰–TE2)、55 nm (TE1–TE3) 和 75 nm (TE2–TE3)。这一进步为灵活的模式转换铺平了道路，显着增强了片上 MDM 技术的多功能性。