Progress Towards Single-site Imaging of Fermions in an Optical Lattice

We discuss progress towards in-situ imaging of a single plane of fermionic $^{40}$K atoms in an optical lattice. Spin-sensitive in- situ imaging will allow for local measurements of occupation, spin ordering, and domain structure of interesting many-body phases, including band insulators, Mott insulators, Neel antiferromagnets, superfluid states, and striped or other structured ordering. We are currently testing a design that collects light from the 405 nm $\mathit{4S}\rightarrow\mathit{5P}$ transition of $^{40}$K through a thin (200 micron) vacuum window and have demonstrated a resolution of better than 550 nm. We have also used saturation spectroscopy to lock a laser to the $\mathit{4S}\rightarrow\mathit{5P}$ transition, allowing for narrow-line Doppler cooling.