Robust and broadband UV laser utilizing Čerenkov phase matching on a hybrid photonic chip.

We present a detailed characterization of a hybrid photonic platform for robust and broadly tunable ultraviolet (UV) laser generation using Čerenkov nonlinear frequency conversion (CNFC). By integrating silicon nitride waveguides with barium borate (BBO) cladding, the platform achieves UV emission across an unprecedented wavelength range of 204-319 nm. Compared to state-of-the-art UV photonic devices, our approach addresses longstanding challenges in spectral range, tunability, and integration. Theoretical modeling and experimental validation demonstrate remarkable fabrication tolerance, maintaining phase matching over a 1500 nm waveguide width variation. Angle-resolved far-field mapping reveals key trade-offs in waveguide design and emission profile. These findings offer a compact, scalable solution addressing critical needs in disinfection, quantum technologies, and free-space optical communication.