A hybrid integrated high-precision tunable semiconductor laser

Thin-film lithium niobate has become a promising platform for integrated photonics due to its outstanding electro-optic and nonlinear properties. However, the development of on-chip tunable lasers, which is essential for a plethora of applications ranging from optical communications and sensing to metrology and quantum technology, remains limited. Current solutions fall short in either wavelength tuning range or precision, and frequently relies on complex control strategy. Here, we demonstrate an integrated electro-optically tunable narrow-linewidth III-V laser, achieving a tuning range of ~51.8 nm, an intrinsic linewidth of ~1.21 MHz, and high tuning precision of ~0.03 nm. Specifically, our external cavity uniquely combines highly reflective Sagnac mirrors and a series of unbalanced interferometers which together offer a spectral response in favor of single-longitudinal-mode narrow-linewidth lasing operation, evidenced by not only experimental demonstration but also insightful theoretical analysis.