Mode‐division multiplexing (MDM) introduces a new dimension to on‐chip optical interconnection, where the multimode optical switch is one of the core components. However, researchers are still struggling to reduce the chip size and response time, despite great efforts being made. Here, a compact, scalable, fast‐response multimode 2 × 2 switch supporting four modes is demonstrated based on the specific inverse design. The device consists of two multimode 2 × 2 CB couplers (including mode converters, multimode interference couplers, and crossings) and a thermo‐optic (TO) phase shifter. It achieves extinction ratios exceeding 15 dB for all modes at the central wavelength of 1.55 µm. All the fundamental components are designed by an improved general shape optimization method, realizing a compact size and a larger manufacturing tolerance (±20 nm). Besides, a hydrogen‐doped indium oxide microheater is introduced as a TO phase shifter to achieve a fast response (≈3.5 µs in average) for all modes. This solution provides an effective avenue toward large‐scale multimode optical switch matrices for the future MDM systems.

中文翻译：

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基于逆向设计的紧凑、可扩展、快速响应的多模 2 × 2 光开关

模分复用（MDM）为片上光互连引入了新的维度，其中多模光开关是核心组件之一。然而，尽管研究人员付出了巨大的努力，但仍在努力缩小芯片尺寸并缩短响应时间。这里，基于特定的逆向设计，展示了一种紧凑、可扩展、快速响应的多模2×2开关，支持四种模式。该器件由两个多模 2 × 2 CB 耦合器（包括模式转换器、多模干涉耦合器和交叉点）和一个热光 (TO) 移相器组成。它在 1.55 µm 中心波长处实现了所有模式超过 15 dB 的消光比。所有基本部件均采用改进的通用形状优化方法设计，实现了紧凑的尺寸和更大的制造公差（±20 nm）。此外，引入氢掺杂氧化铟微加热器作为 TO 移相器，以实现所有模式的快速响应（平均约 3.5 µs）。该解决方案为未来 MDM 系统提供了实现大规模多模光开关矩阵的有效途径。