Publication
Frequency-agile lasers that can simultaneously feature low noise characteristics and fast mode-hop-free frequency tuning are keystone components for applications ranging from LiDAR and distributed sensing to communication and quantum information processing. Hybrid integrated lasers have recently demonstrated faster tuning and lower phase noise than the best legacy systems, including fibre lasers, offering new avenues for compact and scalable frequency-agile lasers. In particular, Pockels-tunable lasers based on self-injection locking to high-Q optical microresonators fabricated from lithium niobate on insulator have achieved ultrafast tuning rates reaching the petahertz per second. However, the impact of these lasers is still hampered by the dynamics of self-injection locking, which limits the maximum tuning range, output power and dictates high operational complexity. Here we overcome these limitations and demonstrate a turn-key-operable hybrid integrated Pockels laser featuring a mode-hop-free tuning range of over 10 GHz, a tuning efficiency of over 550 MHz V–1, tuning rates reaching the exahertz per second and a high output power of 15 mW. We achieve this drastic improvement of hybrid integrated laser performance with an elegant and compact external distributed Bragg reflector architecture that combines an inexpensive reflective semiconductor optical amplifier with an electro-optically-actuated distributed Bragg reflector manufactured at the wafer scale. The excellent linearity and coherence of the external distributed Bragg reflector Pockels laser, together with its unprecedented tuning bandwidth and range—a combination unmet by legacy bulk lasers—make it an ideal candidate for applications in frequency-modulated continuous-wave LiDAR, distributed fibre sensing and atmospheric gas metrology. We demonstrate this performance and flexibility in a proof-of-concept frequency-modulated continuous-wave LiDAR experiment, achieving a 4 cm distance resolution over a 20,000 voxel acquisition in 100 ms, as well as in a hydrogen cyanide spectroscopy experiment. The compact and rugged Pockels laser assembly has been packaged in a commercial butterfly package, improving its resilience to environmental noise and demonstrating long-term stability with a frequency fluctuation of the free-running laser of below 25 MHz over 2.5 h.