Probe-assisted Depopulation Pumping in Low-pressure Alkali-metal Vapor Cells for Magnetometry

TL;DR

This paper demonstrates high-sensitivity atomic magnetometry using low-pressure alkali vapor cells with probe-assisted depopulation, achieving sensitivities comparable to or better than traditional high-pressure cells.

Contribution

It introduces a novel probe-assisted depopulation technique in low-pressure alkali vapor cells for enhanced magnetometer performance.

Findings

Achieved 18 fT/√Hz sensitivity for Earth's field magnetometry.

Demonstrated RF magnetometry sensitivity of 12 fT/√Hz at 110 kHz.

Used a 25 Torr, 0.5 cc cell for high-performance measurements.

Abstract

For precision atomic magnetometry, inert buffer gas is included in alkali-metal vapor cells to significantly broaden hyperfine transitions, which facilitates optical pumping and reduces diffusive relaxation, while also providing non-radiative excited state quenching. We show low-buffer gas pressure (below 50 Torr) alkali vapor cells with resolved hyperfine manifolds can also yield high-performance magnetometers. For high polarization in $^{87}$Rb, we optically pump $F=2$ states with narrow linewidth $\sigma_+$ light, while tuning a probe beam to depopulate $F=1$ states ($\Delta\nu = 6.8$ GHz from $F=2$). The probe tuning then also provides $F=2$ detection with high optical rotation and low probe broadening; we demonstrate top-bottom gradiometry, within a single 25 Torr, 0.5 cc cell, that yields an Earth's field free-precession magnetometer sensitivity of 18 fT/$\sqrt{\text{Hz}}$ with a 1 kHz bandwidth, as well as RF magnetometer sensitivity of 12 fT/$\sqrt{\text{Hz}}$ in a small band about 110 kHz.