LiNbO3 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
_π
· L of ~3 V · cm and a 3-dB bandwidth of ~8 GHz.