Far-UVC light in the wavelength range of 200-230 nm has attracted renewed
interest because of its safety for human exposure and effectiveness in
inactivating pathogens. Here we present a compact solid-state far-UVC laser
source based on second-harmonic generation (SHG) using a low-cost
commercially-available blue laser diode pump. Leveraging the high intensity of
light in a nanophotonic waveguide and heterogeneous integration, our approach
achieves Cherenkov phase-matching across a bonded interface consisting of a
silicon nitride (SiN) waveguide and a beta barium borate (BBO) nonlinear
crystal. Through systematic investigations of waveguide dimensions and pump
power, we analyze the dependencies of Cherenkov emission angle, conversion
efficiency, and output power. Experimental results confirm the feasibility of
generating far-UVC, paving the way for mass production in a compact form
factor. This solid-state far-UVC laser source shows significant potential for
applications in human-safe disinfection, non-line-of-sight free-space
communication, and deep-UV Raman spectroscopy