Characterization of noise sources in a microfabricated single-beam zero-field optically-pumped magnetometer

Abstract

We present an experimental noise characterization of a miniature single-beam absorption-based optically-pumped magnetometer with a noise floor of 7 fT/Hz 1/2 operating in the spin-exchange relaxation-free regime. We experimentally evaluate noise arising from the laser intensity, laser frequency, laser polarization, cell temperature, and magnetic field coils used for the phase-sensitive detection of the magnetometer signal. We find that noise in the range between DC and 30 Hz is a result of noise sources coupling to the atoms in a manner similar to a magnetic field, while the noise at frequencies above 30 Hz is mainly due to laser intensity noise. Our results place an upper limit on the noise sources for our system that matches well with the noise spectrum of the magnetometer at frequencies above 5 Hz.

A conformal array of microfabricated optically-pumped first-order gradiometers for magnetoencephalography

“…It can also be seen that the gradiometers all have noise floors of 7 fT/cm/Hz 1/2 × 2 cm = 14 fT/Hz 1/2 of lower, some as low as 10 fT/Hz 1/2 . This implies that the individual magnetometers support a sensitivity of 7 fT/Hz 1/2 (since the noise of both magnetometers add in quadrature) in a small sensitive volume of 3 × 3 × 2 mm 3 , which is consistent with our previous results [26].…”

Single-beam double-pass miniaturized atomic magnetometer for bio-magnetic imaging systems

“…In the SERF regime, we define a coordinate system with the direction of laser beam propagation along z and the external magnetic field along y. The behavior of the spin polarization S can be described phenomenologically using the Bloch equations as [19,25,28]…”

VCSEL frequency stabilization for optically pumped magnetometers

“…Conversely, it appears that the VCSEL noise is not reduced under the single-closed-loop system. Therefore, the OPM noise from the VCSEL is reduced under the double-closed-loop mode [30] .…”