Integrated nonlinear conversion of visible diode laser to UV light

Far-UVC light (200–230nm) is emerging as a uniquely powerful spectral window: it inactivates airborne pathogens while remaining safe for human exposure, enables background-free molecular spectroscopy and offers untapped bandwidth for free-space optical links. However, its promise has been limited by the absence of compact and scalable light sources. We present an integrated photonic platform for compact and scalable far-UVC generation via nonlinear frequency conversion of visible laser diodes. Leveraging advances in visible light photonic integrated circuits (PICs), our architecture achieves high local visible-light intensities in low-loss waveguides. The heterogeneous integration of nonlinear crystals enables robust frequency conversion across hundreds of nanometers. This wide tunability is achieved through a geometric phase-matching mechanism at the waveguide–crystal interface, called Cherenkov phase-matching, and enables demonstration of UV emission spanning 203 to 319nm. This approach supports both second-harmonic and sum-frequency generation along the propagation length, drastically reducing pump-source requirements through cross-mode interaction in multimode lasers, enabling continuous-wave operation using low-cost diode lasers. We present theoretical modeling, device design, and experimental validation of Cherenkov-style frequency conversion. To optimize performance, we investigate visible-wavelength loss mechanisms in low-loss PIC platforms and explore on-chip integration of visible laser diodes. This work establishes a pathway to compact, chip-scale far-UVC sources, extending integrated photonics deep into the ultraviolet, offering a practical alternative to excimer lamps and far-UVC LEDs. With continued refinement, Cherenkov phase matching could enable a new class of ultraviolet photonic systems, opening applications previously inaccessible to integrated platforms across healthcare, life sciences, and spectroscopy.