Spin-resolved Holography in Ultracold Sodium Gases: Providing an insight into the magical world of spinor physics

In this thesis, we develop, validate and apply a non-destructive, spin-sensitive probing method for ultracold gases of sodium. By exploiting the polarization dependence of the atom-light interaction, the method combines optical hardware with computational reconstruction to access spin-resolved density and magnetization distributions from a single, minimally destructive exposure. The thesis is structured in three parts; firstly, we describe the experimental platform for making, probing and manipulating sodium spinor Bose–Einstein condensates, including laser cooling, optical and magnetic trapping, and radio-frequency techniques for coherent spin preparation. In the second part, we develop the core measurement technique of spin-dependent off-axis holography is developed, and evaluate its robustness to technical noise and the magnetic field variations. The reconstruction and analysis pipeline is presented in detail, with special emphasis on the background noise suppression using an inpainting technique based on principal component analysis. In the final part, the method is applied to investigate dynamics in spin-1 ultracold atomic sodium. To that end, we introduce the theory of three-level spin systems and propose magnetization-preparation and precise Zeeman-sublevel readout schemes, which are experimentally verified. These tools are then used to investigate spin diffusion and spin mixing dynamics, and the formation and evolution of spin domains. This work establishes spin-dependent off-axis holography as a powerful tool for probing spinor quantum gases. The techniques developed here enable efficient and minimally destructive imaging of spin dynamics, and provide new opportunities for studying non-equilibrium spin phenomena and magnetism in ultracold atomic systems.