A 760 mW stable continuous-wave narrow-linewidth 253.7 nm deep-ultraviolet laser is developed for laser cooling of mercury atoms. It is based on a high-power 1014.8 nm room-temperature fiber laser amplifier and two cascaded efficient frequency-doubling stages. The saturated absorption spectrum of Hg202 on the 6S1-6P3 transition is demonstrated with a high signal-to-noise ratio. This deep-ultraviolet laser has significant applications in quantum optics and laser cooling of mercury atoms in 2D and 3D magneto-optical traps.

Mercury is a promising candidate for the optical lattice clock, due to its low sensitivity to the blackbody radiation.We develop a single folded beam magneto-optical trap for the neutral mercury optical lattice clock, with a 253.7 nm frequency quadrupled laser. Up to 1.7 × 10 6 ( 202 Hg) or 1.5 × 10 6 ( 199 Hg) atoms can be captured, and the atom temperature is lowered to 170 𝜇K ( 202 Hg) or 50 𝜇K ( 199 Hg). The cold atom signals of all six rich abundant isotopes are observed in this system.

We experimentally observe polarization spectroscopy (PS) of the 1 S 0-3 P 1 transition of mercury atom gases at 253.7 nm. The PS signal can be observed in all six richly abundant isotopes and the PS signal of six transitions for laser cooling are all clear and of a dispersive line shape. The optimized pump power and probe power are found for the PS of 202 Hg. We find the linearly polarized component in the pump beam will distort the original PS signal due to the use of linear PS. Consequently, the purity of the pump beam is crucial to laser frequency stabilization by PS.