Generation of Bragg Spectroscopy Potentials with a DMD

Gloria Clausen - ETH Zurich / University of Oxford
2020 - MSc thesis

This thesis describes the design and installation of a Bragg spectroscopy setup using a digital micromirror device (DMD). The conducted work involves the generation of translating sinusoidal lattice potentials for erbium atoms via spatial modulation of a laserbeam’s intensity profile, and the subsequent projection of the sinusoidal pattern using a suitable imaging setup. For this, we employ the direct projection method using a two-stage demagnification setup, where a custom objective is introduced to account for multiple types of aberrations. The lower resolution bound of our imaging setup is given by the objective’s resolution objective = 2.18 ± 0.19 µm, with the average resolution of the setup being measured at r = 2.55±0.12 µm over the extent of the atomic cloud. The quality of the sinusoidal patterns created by the imaging setup was tested and improved using an iterative correction process to account for beam inhomogeneities and aberrations. Additionally, the switching dynamics of the DMD were investigated. Clean switching between consecutive frames with refresh rates up to 10.3 kHz en abled a smooth spatial translation. The performed calibrations and measurements are crucial for the successful probing of the dispersion relation of dipolar quantum gases in the roton regime via Bragg spectroscopy.