Broadband thin-film lithium niobate waveguide modulator with high-order mode suppression

A high-frequency phase modulator based on a multimode optical waveguide made of thin-film lithium niobate was designed and studied. The modulator was fabricated in a topology with metal electrodes placed near the edges of the waveguide to suppress higher-order waveguide modes and provide quasi-single-mode light propagation. Efficient modulation with a voltage-length product $V_{\pi} L \approx 4 \mathrm{~V} \cdot \mathrm{cm}$ and a bandwidth of more than 30 GHz have been successfully demonstrated.