High-efficiency lithium niobate modulator for K band operation

This paper reports a hybrid silicon nitride–lithium niobate electro-optic Mach–Zehnder-interferometer modulator that demonstrates overall improvements in terms of half-wave voltage, optical insertion loss, extinction ratio, and operational bandwidth. The fabricated device exhibits a DC half-wave voltage of ∼1.3 V, a static extinction ratio of ∼27 dB, an on-chip optical loss of ∼1.53 dB, and a 3 dB electro-optic bandwidth of 29 GHz. In addition, this device operates beyond the 3 dB bandwidth, where a half-wave voltage of 3 V is extracted at 40 GHz when the device is biased at quadrature. The modulator is realized by strip-loading thin-film lithium niobate with low-pressure chemical vapor deposited silicon nitride; this enables reduced on-chip losses and allows for a lengthened 2.4 cm long interaction region that is specifically engineered for broadband performance.