Vector AC Stark shift in 133Cs atomic magnetometers with antirelaraxion coated cells
The main focus of this dissertation is investigation of vector AC Stark shifts (light shifts) in evacuated 133Cs paraffin-coated cells. Although light shifts in alkali atoms have been investigated since 1960s, the effect of laser-induced vector light shifts (VLS) in paraffin-coated cells is little explored in literature. The works considering light shift effects primarily focus on transitions relevant for atomic clocks, or magnetometers using buffer gas cells, or magnetometers using broad-spectrum alkali metal lamps. This work, on the other hand, focuses on light shifts in a setup shared by finite-field optical magnetometers that use paraffin-coated sensor cells, as well as on their impact on sensitivity and accuracy of these devices.
Along with describing the light shifts, this work presents several techniques that take advantage of the VLS to improve atomic magnetometers as a tool. The proposed techniques eliminate the need for oscillating radio-frequency magnetic fields and replace them with well contained laser beams. This can benefit applications where non-magnetic sensors are needed and stray fields are highly undesirable, such as the search for a permanent electric dipole moment of the neutron.
This dissertation includes two such projects, the all-optical vector magnetometer and the rf magnetometer driven by a fictitious magnetic field. In the first project a finite-field optical magnetometer, which is normally a scalar sensor, is augmented with two power-modulated orthogonal laser beams that provide the directional sensitivity. The sensor exhibits a demonstrated rms noise floor of 50 fT/√Hz in measurement of the field magnitude and 0.5 mrad/√Hz in the field direction. Elimination of technical noise would improve these sensitivities to 12 fT/√Hz and 5 μrad/√Hz, respectively. In the second project, the atomic precession in a scalar 133Cs magnetometer is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. The demonstrated sensitivity of this magnetometer is 40 fT/√Hz rms, which is equivalent to the conventional coil-driven scalar magnetometer we built sharing the same setup.
The Appendix includes documentation on the custom-built polarimeter used in the experiments and the frequency response of the magnetic sensor head.