Abstract
We investigated the operation of an all-optical rubidium-87 atomic magnetometer with amplitude-modulated light. To study the suppression of spin-exchange relaxation, three schemes of pumping were implemented with room-temperature and heated paraffin coated vacuum cells. Efficient pumping and accumulation of atoms in the F=2 ground state were obtained. However, the sought-for narrowing of the resonance lines has not been achieved. A theoretical analysis of the polarization degree is presented to illustrate the absence of light narrowing due to radiation trapping at high temperature.
Highlights
Magnetometry is an important branch of modern metrology
Though the Spin Exchange Relaxation Free (SERF) atomic magnetometers reach a sensitivity of sub-fT level,[6] they typically require high temperature of the cells and magnetic field of no more than ∼100 nT, much less than the Earth field of ∼50 μT
At Earth field, atomic magnetometers usually operate in the regime where the Larmor precession rate is much higher than the spin-exchange collision rate
Summary
Magnetometry is an important branch of modern metrology. In order to detect magnetic fields, a variety of devices are utilized, including fluxgates, proton-precession magnetometers and superconducting quantum interference devices (SQUIDs).[1]. When an atomic magnetometer is limited by photon shot noise, theoretical and experimental results show that its sensitivity improves as the slope of the dispersive part of the magnetic resonance, from σS−E1 to σS−E3/4σS−D1/4 where the spin-exchange cross-section σSE far surpasses the spin-destruction cross-section σSD.[20] In a miniaturized cesium cell with 170 mbar nitrogen buffer gas and volume of only 9.9 mm[3], a shot noise limited sensitivity of 42 fT/Hz1/2 at μT-level magnetic field was achieved by preparing 95% of the atoms in the stretched state and optimizing pump power, cell temperature, and magnetic fields.[21] The same research group operated in the light-narrowing regime at 50 μT magnetic field and eliminated the side effect of light shift by averaging two magnetometers with oppositely circularly polarized channels.[22] A sequence of coupled pump pulses repeated at the Larmor frequency suppressed spin-exchange collisions at nearEarth field (0.1 G) in 267 mbar nitrogen buffer gas rubidium-87 cells.[23] Both spin orientation up to. A theoretical analysis suggests that the underlying cause is radiation trapping, i.e. reabsorption of spontaneously emitted pump photons in the vapor, which results in depolarization
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