Ultra-compact multimode waveguide bends with arbitrary bending angles
Yang Lan, Siwei Liu, Chuang Cheng, Xiuzhi Chen, Xin Fu, Lin Yang
Abstract
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 2 . 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.