High-bandwidth electro-optic modulator on a hybrid silicon–nitride–lithium-tantalate platform

Integrated electro-optic modulators are key components in modern communication networks and various applications, with lithium tantalate currently being one of the most promising crystalline thin-film materials. However, direct etching of thin-film lithium tantalate (TFLT) presents challenges, particularly in achieving vertical sidewalls. In contrast, the silicon nitride (SiN) etching process has seen substantial advancements, enabling more precise vertical etching. In this study, we propose an integrated electro-optic modulator based on a TFLT and SiN heterogeneous platform, utilizing a Mach-Zehnder modulator structure. Thanks to the optimization of the optical field structure and electrode design in our device, the modulation efficiency has been improved, achieving a half-wave voltage-length product of 2.75 V·cm. Furthermore, a noteworthy achievement is the successful measurement of a 67 GHz EO bandwidth for the modulator.