Subvolt electro-optical modulator on thin-film lithium niobate and silicon nitride hybrid platform

A low voltage operation electro-optic modulator is critical for applications ranging from optical communications to an analog photonic link. This paper reports a hybrid silicon nitride and lithium niobate electro-optic Mach-Zehnder modulator that employs 3 dB multimode interference couplers for splitting and combining light. The presented amplitude modulator with an interaction region length of 2.4 cm demonstrates a DC half-wave voltage of only 0.875 V, which corresponds to a modulation efficiency per unit length of 2.11 V cm. The power extinction ratio of the fabricated device is approximately 30 dB, and the on-chip optical loss is about 5.4 dB.