Lan Yang, Liu Siwei, Cheng Chuang, Chen Xiuzhi, Fu Xin, Yang Lin
Opt Express. 2025 Mar 24;33(6):13133-13144. doi: 10.1364/OE.555795.
Achieving compact waveguide routing with arbitrary configurations is essential for on-chip mode-division multiplexing (MDM) systems to enable higher integration density and more flexible layouts. However, current multimode waveguide bends (MWBs) are limited to 90°, restricting design flexibility. In this paper, we propose, for the first time to our knowledge, ultra-compact MWBs with arbitrary bending angles. As a proof of concept, we design and experimentally demonstrate four different MWBs with bending angles of 15°, 30°, 45°, and 60° on a standard silicon-on-insulator (SOI) platform, supporting the first three TE modes. Dual Bezier contours are employed for the MWBs' trajectory optimization. For all MWBs, the largest footprint is only 7.5 × 5.1 µm. Measurement results show insertion losses below 0.417 dB and inter-mode crosstalks below -16.6 dB within the wide wavelength range of 1500-1600 nm for all three modes. Furthermore, these MWBs can serve as building blocks for arbitrary-angle MWBs and S-bends with various displacements, paving the way for ultra-compact on-chip MDM systems.
实现具有任意配置的紧凑型波导路由对于片上模式分割复用（MDM）系统至关重要，以实现更高的集成密度和更灵活的布局。然而，当前的多模波导弯曲（MWB）仅限于90°，限制了设计灵活性。在本文中，据我们所知首次提出了具有任意弯曲角度的超紧凑型MWB。作为概念验证，我们在标准绝缘体上硅（SOI）平台上设计并通过实验演示了四种不同的MWB，弯曲角度分别为15°、30°、45°和60°，支持前三个TE模式。采用双贝塞尔曲线轮廓对MWB的轨迹进行优化。对于所有MWB，最大尺寸仅为7.5×5.1 µm。测量结果表明，在1500 - 1600 nm的宽波长范围内，所有三种模式的插入损耗均低于0.417 dB，模式间串扰低于 -16.6 dB。此外，这些MWB可作为具有各种位移的任意角度MWB和S形弯曲的构建模块，为超紧凑型片上MDM系统铺平了道路。
