Intrinsic atomic calibration of oscillating magnetic fields in ULF and VLF bands

TL;DR

This paper introduces a novel calibration method for ultra low and very low frequency magnetic fields using an RF optically pumped magnetometer, enabling accurate measurements without geometric or electrostatic distortions.

Contribution

The paper presents a frequency-based calibration technique for RF magnetic fields using an RF-OPM, improving accuracy over traditional inductive sensors in ULF and VLF ranges.

Findings

Calibration achieved in 300 Hz - 20 kHz range

Sensor noise floor of 15 fT/Hz^{1/2}

Method avoids geometric and electrostatic response issues

Abstract

We present a method for absolute calibration of received radio-frequency in the ultra low frequency (ULF), and very low frequency (VLF) range. This is achieved with the use of a radio frequency optically pumped magnetometer (RF-OPM). We describe a method using an optically pumped sample where the RF broadening of the Cs magnetic resonance allows the magnitude of the received field to be calibrated against the ground-state gyromagnetic ratio of the Cs atoms. This frequency-based calibration avoids the geometric and electrostatic response functions that affect inductive sensors, such as fluxgates, search coils, and SQUID magnetometers. We demonstrate calibration of magnetic measurement using oscillating magnetic fields in the 300 Hz - 20 kHz range and a sensor noise floor of 15 fT.Hz-1/2. This radio-frequency sensor may be used as a widely tunable narrowband receiver for communication, ranging, or penetrative conductivity imaging.