Laser Cooling and Trapping of Neutral Mercury Atoms Using an Optically-Pumped External-Cavity Semiconductor Laser

The level structure of the Hg atom is similar to other alkaline earth-like atoms, offering the possibility to realize an extremely high quality resonance factor (Q) on the ``clock'' transition ($^{1}$S$_{0}$- $^{3}$P$_{0})$ when confined in an optical lattice at the Stark-shift free wavelength. A key feature of the Hg system is the reduced uncertainty due to black-body induced Stark shifts, making it an interesting candidate as an optical frequency standard. One challenge to laser-cooling neutral Hg atoms is finding a reliable source for cooling on the $^{1}$S$_{0}-^{3}$P$_{1}$ transition at 253.7 nm. We employ an optically pumped semiconductor laser (OPSEL) operating at 1015 nm, whose frequency is quadrupled in two external-cavity doubling stages to generate over 120 mW at 253.7 nm. With this new laser source we have trapped Hg$^{199}$ from a background vapor in a standard MOT. We trap up to 2 x 10$^{6}$ atoms with a 1/e$^{2}$ radius of our MOT of $\sim $310 microns, corresponding to a density of 1.28 x 10$^{10}$ atoms/cm$^{3}$. We report on the progress of our Hg system and plans for precision lattice-based spectroscopy of the clock transition.