A tunable UV spectrometer for Doppler broadening thermometry of mercury

We realised a tunable UV laser source at 253 nm for Doppler-broadening thermometry on the 1S0-3P1 intercombination line in mercury vapors. Our setup is based on the two-stage second harmonic generation of a 1015 nm diode laser in a fiber-coupled periodically-poled lithium niobate waveguide crystal and a beta-barium borate crystal in enhancement cavity, and we exploit injection locking of a 507 nm diode laser to boost the available optical power after the first duplication. The realized source has 1x10-4 relative intensity stability, Gaussian shape and over 10 GHz mode-hop-free tunable range. These features are necessary for retrieving the thermodynamic temperature of the atomic sample from the absorption profile with 10-6 accuracy. This will make Doppler broadening thermometry a viable technique for the practical realization of the kelvin in the new International System of Units.