Master Thesis Defense by Benjamin Krogh

Investigation of Three-Level Spectroscopy for Single Atom Imaging

This thesis investigates the applications of a laser-driven electric quadrupole transition in atomic cesium for the purpose of single atom imaging. A theoretical survey of the atom-field coupling in a spherical tensor approach critically examines the required properties of radiation fields to drive this transition, including spatially structured light and optical orbital momentum. Experimentally, an ensemble of neutral cesium atoms are imaged by their fluorescent light via a quadrupole excitation with a 685 nm laser, and the $5^2D_{5/2}$ hyperfine spectrum is resolved. To provide a stable frequency-lock of the laser, two separate Doppler-free spectroscopic methods are employed. The laser is locked to the atomic resonance using polarization rotation spectroscopy and a novel scheme for single atom imaging is presented. The findings in this thesis provide a foundation for the applications of the cesium quadrupole transition along with a systematic study of the experimental parameters required to drive the atoms on this narrow line.