A compact silicon-based TM₀-to-TM₂ mode-order converter using shallowly-etched slots

Abstract

Mode-order converter is a pivotal component in the on-chip multimode optical transmissions with different mode orders. In this work, we propose a compact and highly-efficient TM 0 -to-TM 2 modeorder converter using shallowly-etched rectangular slots on the silicon-on-insulator platform. The proposed device consists of four same shallowly-etched slots in symmetrical arrangements (two by two) along the light propagation direction and a smaller one between them, which can change the refractive index distribution of the silicon waveguide and add accumulated phase difference through light propagation. With detailed optimizations, we realize the efficient mode conversion from input TM 0 mode to output TM 2 mode, which is different from some reported TE-polarized mode-order converters, and the insertion loss and conversion efficiency of the present device are 0.21 dB and 94.3%, respectively, in a total device length of only 8.97 μm. Meanwhile, the modal crosstalk is lower than −15 dB and the bandwidth can be extended to ∼100 nm. We believe this device could be applied in the on-chip multimode optical transmission systems with different mode orders to further improve the link capacity.

Silicon-Based TM0-to-TM3 Mode-Order Converter Using On-Chip Shallowly Etched Slot Metasurface

“…First, the input single-wavelength laser was coupled to the input waveguide and then separated into N waveguide channels through splitter, where the input and output waveguide modes were kept as fundamental modes. Second, the N waveguide channels were connected with different mode-order converters to generate higher-order modes, where only the TM 0 -to-TM 3 mode-order converter was analyzed in here and other TM 0 -to-TM 1 /-TM 2 ones were also studied in our previous work [25,36] and they could also be added in such an MDM system. Other more higher-order converters could also be realized using the shallowly etched scheme due to its scalability in controlling the mode-order conversion.…”