First Demonstration of Differential-Drive Push-Pull Modulators on Thin-Film Lithium Niobate

Thin-film lithium niobate (TFLN) based electro-optic (EO) Mach–Zehnder modulators (MZMs) have shown their potential for next generation high-speed optical transmission modules and systems. Unlike modulators on other platforms, most of TFLN based EO MZMs adopt single-drive push-pull configuration. It is more attractive to design a differential-drive and push-pull compatible MZM, which would not only improve the modulation bandwidth, but also facilitate interfacing with electronic drivers. Here, we demonstrate, to the best of our knowledge, the first differential-drive push-pull EO modulator on TFLN using a two-segment MZM structure. By compensating the delay mismatch between optical and microwave signals, the fabricated differential-drive modulator features an ultra-low V_π of 670 mV and a large extrapolated EO bandwidth of ≈109 GHz. This corresponds to, so far, the best voltage-bandwidth-ratio performance of ≈243 GHz/V² for TFLN modulators. Both intensity and coherent modulators are built using the proposed structure, and high-speed data transmissions are also demonstrated. This differential-drive MZM structure could promote co-packaging of TFLN based modulators with electronic chips.