Ultracold atoms in an optical lattice one millimeter from air

Over the past decade, ultracold atoms in optical lattices have shown to be versatile systems able to realize canonical Hamiltonians of condensed matter. High-resolution in-situ imaging of ultracold clouds has furthermore enabled thermometry, equation of state measurements, direct measurement of fluctuations, and unprecedented control. We report on microscopy of ultracold bosons and fermions in a novel configuration where the atoms are harmonically trapped 800 microns away from a 200 micron-thick vacuum window. This window also serves as a retro-reflecting mirror for an optical lattice, into which the atoms can be loaded. Two additional transverse standing waves complete the three-dimensional lattice setup. In free space, we have shown that laser cooling with 405 nm light, on the open 4S$_{1/2}$-5P$_{3/2}$ transition, allows for temperatures below the Doppler temperature of the 4S$_{1/2}$-4P$_{3/2}$ cycling transition at 767 nm. Microscopy with 405 nm light furthermore reduces the diffraction limit of in-situ imaging.