In this thesis, I present a novel technique enabling three-dimensional localization of single atoms in an optical lattice up to sub-micrometer precision over an enhanced depth of field from a single experimental image. It consists of changing the microscope’s response to a point source, the so-called point spread function (PSF), such that it has an azimuthally structured shape, performing a rigid rotation along the observation axis, the angle of which provides information about the axial position. This is done by imposing on the collected fluorescence light a phase modulation built up from a superposition of Laguerre-Gauss modes in the pupil plane by a spatial light modulator (SLM). I demonstrate this method using the DQSIM quantum gas microscope with an engineered double-helix-shaped PSF. As I show, this enables axial resolution at the level of the vertical lattice separation of 532 nm even at lower numerical apertures while preserving the lateral resolution, overcoming the limitations of retrieving the axial position through the defocus alone.
In Chapter 1, I present the experimental setup of the DQSIM experiment in Chapter 2. I particularly address the aspects necessary for the understanding of the subsequent measurements, as well as my contributions to the setup. Chapter 3 is about my contributions to a deep horizontal lattice. In Chapter 4, I present the three-dimensional imaging of single atoms. I describe the technique of preparing atoms in a single plane, the concept of PSF, and the resolution limit. I then discuss existing methods of three-dimensional imaging, in particular the rotating PSFs. Finally, I present the experimental realization and the measurements performed. Chapter 5 draws a conclusion and gives an outlook to this thesis.
}, Author = {Legrand, T.}, Journal = {}, Pages = {}, Title = {{Three-Dimensional Imaging of Single Atoms in an Optical Lattice via Helical Point-Spread-Function Engineering}}, Volume = {}, Year = {2022} }