Disorder Supression with a Pulsed Laser

Quantum gas microscopy enables site-resolved detection and control of ultracold atoms in optical lattices, allowing remarkably clean study of strongly correlated quantum phenomena. However, trace amounts of disorder can still limit the observation of certain delicate and exotic phases of matter. Here we present a technique to overcome disorder originating from stray light by utilizing a pulsed laser as the light source for a low disorder optical lattice. One prevalent source of disorder in a continuous-wave lattice configuration comes from stray light interfering with the primary lattice beams. Seemingly negligible quantities of light from higher-order reflections or scatter from optical surfaces can interfere and produce substantial disorder. By creating an interfering lattice from two time-delayed pulses of a femto-second laser, we avoid detrimental interference that arises from other stray light beams. Higher order reflections and stray beams acquire optical path length differences that exceed the coherence length of the light, preventing interference in the atom-lattice plane. Tuning the time delay between these two pulses allows us to choose the location of the interfering plane that forms the lattice to stay within the focus of our microscope objective. This configuration allows us to reach a residual Hz-level RMS in lattice depth variations and can easily be implemented into existing and planned experiments with little overhead.