Group Seminar via Zoom: Potential Shaping Using a DMD and High-Resolution Imaging of Cesium Atoms in Optical Lattices

March 28, 2023

Scott Hubele, University of Hamburg
Group Seminar via Zoom: Potential Shaping Using a DMD and High-Resolution Imaging of Cesium Atoms in Optical Lattices
Tuesday, March 28th, 9:00am (MEZ)



In this seminar presentation, the results of my recent Master’s thesis are summarized, describing two proposed additions to the Cesium quantum gas microscope: the addition of a blue fluorescence imaging scheme on the 6S1/2 - 7P3/2 transition of Cesium at 456 nm with additional repumping on the 5D3/2 - 7P3/2 and 5D5/2 - 7P3/2 transitions, and the addition of a high-resolution imaging system to project light from a digital micromirror device (DMD) onto the atoms in order to tune the potential energy landscape on the atom plane.

Because the resolution of fluorescence imaging is limited by the wavelength of light, we consider blue fluorescence imaging as an alternative to imaging on the D2 line, at 852 nm. However, during the application of blue imaging light, atoms that decay to the 5D3/2 and 5D5/2 states would be heated, and so a repumping scheme is proposed which, according to numerical simulations of the optical Bloch equations, can lower the populations of the two states from 6% and 49% in the non-repumped case to 4% and 24% in the repumped case. Since the repumping lasers do not address the ground state directly, traditional modulation spectroscopy on the Doppler-free resonance signal cannot be used to lock the lasers on resonance. Instead, a proposal is presented for frequency locking the repumping lasers on an atomic signal by measuring transmission of the 456nm beam (6S1/2-7P3/2 transition) through a warm vapour cell.

The imaging system used to project the DMD onto the atoms is first tested in a low magnification test setup before it is implemented in the experiment to apply a box potential with homogeneous interior, created by applying compensation to the harmonic potentials in the trap. Here, methods for coherence reduction are presented as well as an iterative procedure for generating homogeneous potentials in the image plane are presented. Using this iterative procedure, we can generate a flat potential on the atom plane such that the average atomic density of a superfluid prepared in the flattened region has a relative standard deviation of 20%. This generation of flat potentials enables future investigations of topological systems.

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