High performance mode (de)multiplexer assisted with a microring resonator on the lithium niobate-on-insulator platform

The high extinction ratio mode (de)multiplexer is a pivotal component in high capacity mode-division multiplexing data communication and nascent on-chip intermodal acousto-optic modulators. Up to now, high performance on-chip mode (de)multiplexers are still lacking for integrated AOMs on the lithium niobate-on-insulator platform. In this paper, we propose and demonstrate an innovative scheme to achieve high extinction ratio signal routing for acousto-optic modulation, by leveraging a two-mode (de)multiplexer in conjunction with a high-Q racetrack microring resonator. The integrated devices are fabricated with one-step electron beam lithography and dry etching processes. The demonstrated two-mode (de)multiplexer boasts the excellent intermodal crosstalk below −20 dB and the on-chip insertion loss of less than 1.92 dB within the wavelength range of 1,514–1,580 nm. With the reinforcement of the microring resonator filter, the carrier signal can be suppressed thoroughly and the measured extinction ratio attains over 30 dB. Our proof-of-principle investigations have provided a feasible and compact solution to implement practical intermodal AOMs in LNOI for photonic and quantum information process, microwave photonics, and LiDAR.