Ultrafast tunable lasers using lithium niobate integrated photonics.

Early works and recent advances in thin-film lithium niobate (LiNbO) on insulator have enabled low-loss photonic integrated circuits, modulators with improved half-wave voltage, electro-optic frequency combs and on-chip electro-optic devices, with applications ranging from microwave photonics to microwave-to-optical quantum interfaces. Although recent advances have demonstrated tunable integrated lasers based on LiNbO (refs. ), the full potential of this platform to demonstrate frequency-agile, narrow-linewidth integrated lasers has not been achieved. Here we report such a laser with a fast tuning rate based on a hybrid silicon nitride (SiN)-LiNbO photonic platform and demonstrate its use for coherent laser ranging. Our platform is based on heterogeneous integration of ultralow-loss SiN photonic integrated circuits with thin-film LiNbO through direct bonding at the wafer level, in contrast to previously demonstrated chiplet-level integration, featuring low propagation loss of 8.5 decibels per metre, enabling narrow-linewidth lasing (intrinsic linewidth of 3 kilohertz) by self-injection locking to a laser diode. The hybrid mode of the resonator allows electro-optic laser frequency tuning at a speed of 12 × 10 hertz per second with high linearity and low hysteresis while retaining the narrow linewidth. Using a hybrid integrated laser, we perform a proof-of-concept coherent optical ranging (FMCW LiDAR) experiment. Endowing SiN photonic integrated circuits with LiNbO creates a platform that combines the individual advantages of thin-film LiNbO with those of SiN, which show precise lithographic control, mature manufacturing and ultralow loss.