All-optical spin locking in alkali-metal-vapor magnetometers

Abstract

The nonlinear Zeeman effect can induce splittings and asymmetries of magnetic-resonance lines in the geophysical magnetic-field range. We demonstrate an all-optical scheme, based on spin locking, to suppress the nonlinear Zeeman effect. This scheme achieves spin locking via an effective oscillating magnetic field in the form of AC Stark shifts induced by an intensity-and polarization-modulated laser beam. This results in the collapse of the multi-component asymmetric magnetic-resonance line with ∼100 Hz width in the Earth-field range into a peak with a central component width of 25 Hz. The technique is expected to be broadly applicable in practical magnetometry, potentially boosting the sensitivity and accuracy of Earth-surveying magnetometers by increasing the magnetic-resonance amplitude and decreasing its width. An advantage of the all-optical approach is the absence of crosstalk between nearby sensors when they are used in a gradiometric or array arrangement.

Recent Progress of Atomic Magnetometers for Geomagnetic Applications

“…For example, based on the measured magnetic field parameters, magnetometers can be divided into scalar and vector ones [39][40][41]. According to the modulation method, the atomic magnetometers can be divided into magnetic-field-modulation magnetometers and all-optical ones [42,43]. Among them, magnetometers that can work under geomagnetic conditions mainly include the alkali-metal-or helium-based optically pumped magnetometers and the coherent population-trapping (CPT) magnetometers [44][45][46].…”

The suppression of the probe laser pumping effect in SERF atomic magnetometer

“…In SERF atomic magnetometers, a circularly polarized laser is used to pump the alkali metal atoms in a glass cell and the alkali metal atoms are sensitive to the magnetic field at this pumping state [11,12]. Furthermore, a linearly polarized probe laser is utilized to detect the magnetic field signal based on the optical rotation effect [13]. Linear polarization devices are used to produce the linearly polarized laser in a SERF Atomic magnetometer [14].…”