The Svenja and Regal research groups are collaboratively advancing the development of scalar and vector magnetometers, including integrated vector-scalar systems. This thesis focuses on designing a compact optically pumped vector magnetometer (COPVM) that measures the orientation of the magnetic field through Rabi frequencymeasurements driven by a microwave field, serving as an electromagnetic vector reference, across multiple atomic transitions. We transformed a large optical table setup for the vector magnetometer, designed by Cindy's group, into a 20 cm by 10 cm rectangular optical breadboard, designing and fabricating essential components like optical mounts, a microwave cavity, a thermal oven, Kapton heaters, and photodiode electronics to meet the dimensional constraints of COPVMs. To improve temperature uniformity in the vapor cell, we propose a novel cylindrical oven design supported by thermal simulations and in-situ experimental measurements of the vapor cell's heating temperature. We also designed a low-magnetic polyimide heater to mitigate magnetic field interference caused by conventional electrical heating elements. Additionally, we developed a compact cubic dielectric cavity (15 x 15 x 15 mm) with feeding loop antennas as a microwave source to drive various hyperfine 87Rb transitions (σ± and π). This project analyzes miniaturization challenges for the compact physics package (CPP) and its impact on size, weight, and power (SWaP), aiming to maintain optimal functionality. Components like optics mounts and microwave cavities are fabricated from nonmetallic materials using advanced techniques such as selective laser sintering (SLS) and CNC machining, which reduce magnetic interference and enhance structural alignment. This approach also allows for customization and rapid adjustments, supporting flexible prototyping and optimization. This thesis provides a roadmap for designing a compact optically pumped vector magnetometer, addressing key challenges and laying the foundation for future advancements in miniaturized atomic sensors.
The Svenja and Regal research groups are collaboratively advancing the development of scalar and vector magnetometers, including integrated vector-scalar systems. This thesis focuses on designing a compact optically pumped vector magnetometer (COPVM) that measures the orientation of the magnetic field through Rabi frequencymeasurements driven by a microwave field, serving as an electromagnetic vector reference, across multiple atomic transitions. We transformed a large optical table setup for the vector magnetometer, designed by Cindy's group, into a 20 cm by 10 cm rectangular optical breadboard, designing and fabricating essential components like optical mounts, a microwave cavity, a thermal oven, Kapton heaters, and photodiode electronics to meet the dimensional constraints of COPVMs. To improve temperature uniformity in the vapor cell, we propose a novel cylindrical oven design supported by thermal simulations and in-situ experimental measurements of the vapor cell's heating temperature. We also designed a low-magnetic polyimide heater to mitigate magnetic field interference caused by conventional electrical heating elements. Additionally, we developed a compact cubic dielectric cavity (15 x 15 x 15 mm) with feeding loop antennas as a microwave source to drive various hyperfine 87Rb transitions (σ± and π). This project analyzes miniaturization challenges for the compact physics package (CPP) and its impact on size, weight, and power (SWaP), aiming to maintain optimal functionality. Components like optics mounts and microwave cavities are fabricated from nonmetallic materials using advanced techniques such as selective laser sintering (SLS) and CNC machining, which reduce magnetic interference and enhance structural alignment. This approach also allows for customization and rapid adjustments, supporting flexible prototyping and optimization. This thesis provides a roadmap for designing a compact optically pumped vector magnetometer, addressing key challenges and laying the foundation for future advancements in miniaturized atomic sensors.
Quantum optical sensing is a maturing field that offers the capability to achieve extraor- dinary sensitivity. Atomic magnetometers, for example, now have the capability to detect brain signals and to precisely measure Earth’s gravity field. In optical atomic magnetome- ters, the electronic spins of the atoms in vapor form are aligned in the same direction by “pumping” the ensemble using laser light at a select frequency. Any magnetic field alters the spin states, which changes the optical properties of the vapor, such as the transmission of the laser light, providing a way to measure magnetic fields. After reviewing the theory of atomic structure and atom-light interactions relevant to the research presented here, I describe in the first part of this thesis a vector magnetometry method using microwave-assisted optical pumping, in which a microwave field resonant to the ground state hyperfine splitting of 87Rb pumps an ensemble of warm rubidium vapor, in addition to a strong optical pump beam, and a weaker optical probe beam. I present theoretical details as well as preliminary data demonstrating magnetic field measurements of a DC magnetic field. The measurements were taken when the DC field was aligned at various angles relative to the microwave magnetic field alignment. I compare theoretical and experimental differences in the measurements. With new methods for quantum devices comes the need for portability. In the second part of this thesis, we demonstrate the fabrication of millimeter-sized rubidium vapor cells using silicon micro-machining techniques. This method is relatively inexpensive compared to glass-blowing methods and allows rapid, large-scale production. I describe our process flow and demonstrate the presence of rubidium atoms inside our vapor cells. To conclude, suggestions for improvement are discussed.
Robust calibration of vector optically pumped magnetometers (OPMs) is a nontrivial task, but increasingly important for applications requiring high-accuracy such as magnetic navigation, geophysics research, and space exploration. Here, we showcase a vector OPM that utilizes Rabi oscillations driven between the hyperfine manifolds of 87 Rb to measure the direction of a DC magnetic field against the polarization ellipse structure of a microwave field. By relying solely on atomic measurements—free-induction decay (FID) signals and Rabi measurements across multiple atomic transitions—this sensor can detect drift in the microwave vector reference and compensate for systematic shifts caused by off-resonant driving, nonlinear Zeeman (NLZ) effects, and buffer gas collisions. To facilitate deadzone-free operation, we also introduce a Rabi measurement that utilizes dressed-state resonances that appear during simultaneous Larmor precession and Rabi driving (SPaR). These measurements, performed within a microfabricated vapor cell platform, achieve an average vector accuracy of 0.46 mrad and vector sensitivities down to 11µrad/Hz for geomagnetic field strengths near 50 µT. This performance surpasses the challenging 1-deg (17 mrad) accuracy threshold of several contemporary OPM methods utilizing atomic vapors with an electromagnetic vector reference.
Sensitive and accurate magnetic-field measurements are essential in many applications, including geophysical studies, biomagnetic signal detection, navigation, event monitoring, and magnetic anomaly detection. In this context, atomic magnetometers are a particularly promising approach, combining high sensitivity and accuracy, and able to rival superconducting quantum interference devices (SQUIDs) without requiring cryogenic cooling. While the best sensitivity levels are achieved in the zero-field regime within magnetic shielding, scalar magnetometers operating in ambient fields also demonstrated remarkable sensitivities. Initiated in the 2000s, the miniaturization of atomic devices, and in particular alkali-vapor cells, paves the way for magnetometers that are both sensitive and compact, well suited to embedded measurements and field applications.This thesis contributes to the development of microfabricated vapor cells for atomic magnetometry. We propose a new filling and sealing method that overcomes some limitations of conventional approaches and could enable the fabrication of purer cells compatible with a wider range of chemical species. This strategy could also facilitate the integration of anti-relaxation coatings, which reduce relaxation caused by collisions with the cell walls. To date, no long-lasting anti-relaxation effects have been demonstrated in microfabricated cells, as traditional methods rely on high temperatures that are incompatible with these coatings.A cell design suited to the deposition of anti-relaxation coatings is presented. We then describe the fabrication and characterization of a multi-axis microfabricated cell, designed for compact atomic devices using multiple optical beams. This multi-axis cell was experimentally validated in a dual-beam magnetometry configuration using an experimental setup developed as part of this thesis.
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.
A miniature wide-range three-axis vector atomic magnetometer under spin-exchange relaxation-free regime has been developed. With a cylindrical vapor cell of size 10 mm in diameter and length, we have constructed a single-beam configuration through a polarization-maintaining fiber carrying the laser beam to the sensor and a multimode fiber guiding the transmitted light field to the photodiode. A rotating field on the plane perpendicular to the direction of propagation of the laser and another modulation field in the pump direction, which are generated in the field programmable gate array using direct digital synthesis to measure the three components of the magnetic field simultaneously. The spin-exchange relaxation is suppressed in zero field controlled by a feedback system, thus a wide range and excellent accuracy of three-axis vector atomic magnetometer response is obtained. Consequently, the transverse magnetic field sensitivity of 350 fT/Hz1/2and longitudinal field sensitivity of 3pT/Hz1/2are achieved with a dynamic range of 60000 nT. This sensor with compact size, wide range and high sensitivity is particularly suitable for geomagnetic observatory and space exploration.
An optically pumped magnetometer was drastically miniaturized, by taking advantage of MEMS techniques, producing the chip-scale atomic magnetometers (CSAM) physics package. The key component of the package is an alkali vapor cell. To probe the magnetic field experienced by the atoms, the injection current to the VCSEL was modulated at 3.4 GHz near half the hyperfine frequency of87Rb. Lock-in detection is used to determine the center of the resonance, and the magnetic field is determined by counting the modulation frequency, which is related to the Larmor precession frequency under these locked conditions. The ITO heaters create a large magnetic field gradient, which broadens the resonance and reduces the sensitivity.