Single-drive electro-optic frequency comb source on a photonic-wire-bonded thin-film lithium niobate platform

Stable pulse and flat-top frequency comb generation are an indispensable component of many photonic applications, from ranging to communications. Lithium niobate on insulator is an excellent electro-optic platform, exhibiting high modulation efficiency and low optical loss, making it a fitting candidate for pulse generation through electro-optic modulation of continuous-wave light, a commonly utilized method for generating ultrashort pulses. Here, we demonstrate an on-chip electro-optic comb generation module on thin-film lithium niobate consisting of a Mach-Zehnder interferometer (MZI) amplitude modulator and cascaded phase modulator system driven by a single electrode drive. We show that when operated in the correct regime, the lithium niobate chips can generate frequency combs with excellent spectral power flatness. In addition, we optically package one of the pulse generator chips via photonic wire bonding. The pulses generated by the photonic wire bonded device are compressed to 840 fs pulse duration using optical fiber and show extremely stable operation.