Broadband optical mode switch with ultra-fast switching speed and high extinction ratio on lithium niobate on insulator platform

Mode-division multiplexing (MDM) is a promising technology for enhancing data transmission capacity in next-generation optical interconnects. Optical mode switches are critical components in MDM systems, enabling the routing of different mode channels. However, achieving optical mode switches with both ultra-broad operation bandwidth and ultra-fast switching speeds remains a major challenge. In this work, we present an optical mode switch based on a 600 nm X-cut lithium niobate on insulator (LNOI) platform, integrating a dual-mode Y-branch and a multi-mode interference mode demultiplexer. The proposed mode switch demonstrates an ultra-fast switching time of <87 ps and an operational bandwidth exceeding 100 nm. Furthermore, it features a low VπL (<1.95 V cm), high extinction ratio (>24 dB), low insertion loss (<3.0 dB), and low crosstalk (<15 dB) across the 100 nm wavelength range, by employing a well-engineered push–pull electrode design and high-precision LNOI structure fabrication methods. This device, in combination with other on-chip MDM components, paves the way for future high-speed and high-capacity optical interconnects.