Resonator-enhanced distributed Bragg reflector lasers

Narrow-linewidth lasers are pivotal components for advanced optical communications, precision metrology, and microwave photonics. The drive towards low-cost, high-volume manufacturing has fueled intense interest in integrated platforms for high-coherence optical sources. However, state-of-the-art integrated low-noise lasers are fundamentally constrained by trade-offs between linewidth, tunability, and operational robustness, often sacrificing one to achieve the others. Here, we introduce and experimentally demonstrate a new class of integrated lasers-resonator-enhanced distributed Bragg reflector (RE-DBR) lasers-that overcome these limitations, simultaneously achieving ultra-narrow linewidths, wide mode-hop-free tunability, and universal turnkey operation. The RE-DBR laser architecture incorporates a grating-assisted ring resonator that serves as a compact external cavity, providing narrow-band optical feedback to enable single-wavelength lasing. Importantly, the resonator enhancement enables RE-DBR lasers to circumvent the traditional linewidth-tunability trade-off inherent to conventional DBR lasers. Furthermore, unlike self-injection-locked lasers, RE-DBR lasers maintain high optical coherence and stable operation across a broad current tuning range, enabling robust, turnkey performance. As a proof of concept, we demonstrate a RE-DBR laser with a 24 Hz Lorentzian linewidth, 34 GHz mode-hop-free tuning range, and universal turnkey operability, all realized with an external cavity of only 0.56 million loaded Q and a sub-4 mm² footprint. These results establish RE-DBR lasers as a cost-effective, high-performance integrated alternative to bulky, expensive benchtop lasers, enabling advancement in a wide variety of applications including telecommunications, sensing, and metrology.