Combining Lithium‐Niobate and Silicon‐Nitride Integrated Photonics in Ultrafast Tunable, Low‐Noise Lasers

Narrow‐linewidth lasers, the heart of precision‐driven commercial and scientific applications, are poised to transition from bench‐top devices to photonic integrated circuits. Despite wide exploration and great progress, an integrated laser that simultaneously meets all desired performance aspects in linewidth, tunability, and agility remains elusive, primarily due to the non‐ideal properties of individual integration platforms. This work proposes a family of tri‐material integrated lasers to address these problems. Utilizing a dual‐external‐cavity structure, the lasers leverage complementary low‐loss silicon‐nitride photonics and ultrafast thin‐film lithium‐niobate (TFLN) photonics via hybrid integration alone. The demonstrated laser enables wavelength tunability of 40 nm within the S‐and C‐bands, with an intrinsic linewidth of 106 Hz. Through further laser structural optimization, a record intrinsic linewidth below 20 Hz is achieved, surpassing previous TFLN‐based integrated lasers. Exploiting TFLN‐enabled electro‐optic dynamics under the dual‐cavity synergy, high‐speed laser switching and electro‐optic frequency stabilization are demonstrated in one single laser, achieving sub‐50‐ns switching time over a wavelength range of 12 nm, and a stabilized integral linewidth of 1.7 kHz @ 10 ms, respectively. Unifying high coherence, wide tunability, and high‐speed operation, the proposed lasers unlock new opportunities in interconnects, metrology, quantum computing, and beyond.