Dual-mode 1 × 2 optical switch with simultaneous modulation based on inverse design devices

Abstract Mode division multiplexing (MDM) technology, based on the parallelism inherent in mode dimensions, provides an advancement in enhancing on-chip optical communication channel capacity. In MDM communication systems, the routing and switching of optical signals are of essential importance. However, conventional multimode optical switches typically follow the demultiplexing-processing-multiplexing technological route, leading to an unavoidable increase in device size. In scenarios where multiple modes need to be routed synchronously, the implementation of simultaneous modulation optical switches offers a more efficient and feasible solution. Here, we propose two 1 × 2 dual-mode optical switches with simultaneous modulation on a silicon-on-insulator platform in the 1525–1565 nm wavelength range, utilizing two optical phase modulation techniques: mode transformation and waveguide widening. Simultaneously, we employ inverse design methodologies based on the adjoint variable method and level-set method to create the compact single-connected devices, which are compatible with complementary metal-oxide semiconductor fabrication processes. The experimental results show that the insertion losses for both TE 0 and TE 1 modes are less than 1.6 dB (2.5 dB), with the worst modal crosstalk at most −13.5 dB (−12.7 dB) for the switch based on mode transformation (waveguide widening) strategy at the wavelength of 1550 nm. The extinction ratio of the two proposed optical switches exceeds 25 dB at the same wavelength. Furthermore, the switches exhibit a 10%–90% rise time of 15.2 μ s and a 90%–10% fall time of 19.5 μ s at 1550 nm, indicating the switching speed can be up to kilohertz. Our proposed 1 × 2 optical switches hold potential as a fundamental unit for optical signal switching in high-integration multimode optical communication systems.