LiNbO 3 Thin-Film Modulators Using Silicon Nitride Surface Ridge Waveguides

Lithium niobate (LiNbO 3 ) is an excellent electrooptic material due to its low loss, large electrooptic coefficient, linear modulation response, and large modulation bandwidth. In this letter, we present the first LiNbO 3 thin-film Mach–Zehnder optical modulator that employs silicon nitride surface ridge optical waveguides. The modulator contains a 1.2-cm-long push–pull phase modulation section and a pair of multimode interferometric 3-dB couplers. It demonstrated $V_{{\pi }} \cdot {L}$ of $\sim 3\text {V}\cdot \text {cm}$ and a 3-dB bandwidth of $\sim 8$ GHz.