Alkali-Metal Spin Maser

Different Configurations of Radio-Frequency Atomic Magnetometers-A Comparative Study

We comprehensively explore different optical configurations of a radio-frequency atomic magnetometer in the context of sensor miniaturisation. Similarities and differences in operation principles of the magnetometer arrangements are discussed. Through analysis of the radio-frequency and noise spectra, we demonstrate that all configurations provide the same level of atomic polarisation and signal-to-noise ratio, but the optimum performance is achieved for significantly different laser powers and frequencies. We conclude with possible strategies for system miniaturisation.

A digital alkali spin maser

Self-oscillating atomic magnetometers, in which the precession of atomic spins in a magnetic field is driven by resonant modulation, offer high sensitivity and dynamic range. Phase-coherent feedback from the detected signal to the applied modulation creates a resonant spin maser system, highly responsive to changes in the background magnetic field. Here we show a system in which the phase condition for resonant precession is met by digital signal processing integrated into the maser feedback loop. This system uses a modest chip-scale laser and mass-produced dual-pass caesium vapour cell and operates in a 50 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu $$\end{document}μT field, making it a suitable technology for portable measurements of the geophysical magnetic field. We demonstrate a Cramér-Rao lower bound-limited resolution of 50 fT at 1 s sampling cadence, and a sensor bandwidth of 10 kHz. This device also represents an important class of atomic system in which low-latency digital processing forms an integral part of a coherently-driven quantum system.

Role of the probe beam in a radio-frequency atomic magnetometer

We explore the role of the linearly polarized probe beam in the radio-frequency atomic magnetometer. Two regimes of coupling of the linearly polarized light to the atomic ensemble, near and off-resonant, are demonstrated and discussed. Our studies cover three types of interaction between the atomic spin system and the linearly polarized beam, i.e., absorptive production of spin polarization, dispersive spin state readout, and nonlinear spin couplings. The work is performed with the outlook of optimization and simplification of magnetometer operation. Operation of a magnetometer with a single beam, generating and probing the atomic orientation, is presented. This single-beam configuration, which combines optical pumping, nonlinear spin couplings, and spin-exchange collisions, creates the option for a portable device with simple instrumentation.