Optical magnetometer: Quantum resonances at pumping repetition rate of 1/n of the Larmor frequency

Abstract

The response of a spin exchange relaxation free atomic magnetometer to a repetitive short-pulsed pump was investigated. Quantum sub-resonances at a repetition rate of 1/n of the Larmor frequency of the magnetic field inside the shield are experimentally observed and theoretically explained. This is a type of synchronization phenomenon. Investigations in single alkali atom cells and mixed alkali atoms of K and Rb are presented. In the latter, one species is pumped while the probe is on the other species polarized by spin exchange. The effect of spin destruction, spin exchange, and collisions is studied in order to account for the width of the resonances. Quantum calculations of a three-level Λ model for this phenomenon exhibit a dip at the resonance frequency in the absorption spectrum for both cases of pulsed and cw pump modes and an evidence for electromagnetically induced transparency.

Quantum Applications of an Atomic Ensemble Inside a Laser Cavity

“…The latter, called "pulsed magnetometer", offers a direct measurement of the Larmor frequency, independent to the first order on temperature and temperature gradients over the cell, an important and favorable feature in many practical applications. This method also avoids possible complications with the Electromagnetically Induced Transparency process (EIT) when using polarization intensity changes as a method for magnetometry [14]. Just recently, an unshielded, portable gradiometer with a sensitivity of 16 fT/cm/ √ Hz in open space with reduced size and lower power consumption based on multipass cells pulsed magnetometers has been demonstrated [15,16].…”

Quantum Applications of an Atomic Ensemble Inside a Laser Cavity

“…Over the last ten years, less sensitive but unshielded magnetometers, based on the Bell-Bloom method (cw lasers) or based on measuring the Larmor frequency changes of the Free Induction Decay (FID) of the atomic polarization indued by pulsed lasers, have been developed. These devices open the way for many applications requiring a sensitivity of several pico-Tesla (pT)/√Hz at 1 Hz in measuring minute changes in ambient earth magnetic field [5][6][7]. The latter, called "pulsed magnetometer", offers a direct measurement of the Larmor frequency, independent to first order on temperature and temperature gradients over the cell, an important and favorable feature in many practical applications.…”

“…The latter, called "pulsed magnetometer", offers a direct measurement of the Larmor frequency, independent to first order on temperature and temperature gradients over the cell, an important and favorable feature in many practical applications. This method also avoids possible complications with the Electromagnetically Induced Transparency process (EIT), when using polarization intensity changes as a method for magnetometry [8]. Just recently, an unshielded, portable gradiometer with a sensitivity of 16 fT/cm/√Hz in open space with reduced size and lower power consumption, based on multipass cells pulsed magnetometers has been demonstrated [9].…”