This paper reports, for the first time to the best of our knowledge, the design of a compact three-mode converter/(de)multiplexer (DE/MUX) based on a 3 × 3 subwavelength grating (SWG) multimode interference (MMI) coupler. The device uses a π/2 phase shifter and an asymmetric tri-junction coupler built in a silicon/silicon-on-insulator (SOI) platform. The inherent dispersion and anisotropy properties of the SWG structure are employed to increase the traditional MMI coupler operation bandwidth and reduce the overall dimensions of the DE/MUX. The proposed device can realize mode order converting and (de)multiplexing of the fundamental transverse electric mode TE₀, the first-order transverse electric mode TE₁, and the second-order transverse electric mode TE₂ to three uniform TE₀ with good performance and compact size compared with the conventional ones. The designed device's overall area is 4.5 × 120 µm², and its performance is simulated using Rsoft photonics CAD suit 3D-BPM. The simulation results show that the device exhibits a maximum insertion loss of 1.3 dB, maximum crosstalk of − 15 dB, and 120 nm (3 dB-bandwidth) over the entire C-band.

据我们所知，本文首次报道了基于 3 × 3 亚波长光栅 (SWG) 多模干扰 (MMI) 的紧凑型三模转换器/（解）复用器（DE/MUX）的设计耦合器。该器件使用一个 π/2 移相器和一个内置在硅/绝缘体上硅 (SOI) 平台中的非对称三结耦合器。SWG 结构的固有色散和各向异性特性被用来增加传统的 MMI 耦合器操作带宽并减小 DE/MUX 的整体尺寸。该器件可以实现基本横电模TE ₀、一阶横电模TE ₁和二阶横电模TE _{2 的}模阶转换和（解）复用。到三个均匀的 TE ₀与传统的相比，具有良好的性能和紧凑的尺寸。设计的器件总面积为 4.5 × 120 µm ²，其性能使用 Rsoft photonics CAD 套件 3D-BPM 进行模拟。仿真结果表明，该器件在整个 C 波段上的最大插入损耗为 1.3 dB，最大串扰为 − 15 dB，并且为 120 nm（3 dB 带宽）。