A Digital Alkali Spin Maser

TL;DR

This paper introduces a digital signal processing-enhanced atomic magnetometer that achieves high sensitivity and bandwidth in a portable, chip-scale device suitable for geophysical magnetic field measurements.

Contribution

It integrates digital signal processing into a spin maser feedback loop, enabling a compact, high-performance atomic magnetometer with improved resolution and bandwidth.

Findings

Achieved 50 fT resolution at 1 s sampling

Operates effectively in a 50 microtesla magnetic field

Provides a 10 kHz sensor bandwidth

Abstract

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 microtesla field, making it a suitable technology for portable measurements of the geophysical magnetic field. We demonstrate a Cramer-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.