Hybrid optical pumping of optically dense alkali-metal vapor without quenching gas

TL;DR

This paper demonstrates a novel optical pumping method for dense alkali-metal vapor that achieves high polarization without the need for quenching gases by using spin-exchange transfer from trace Rb contamination.

Contribution

It introduces a hybrid optical pumping technique leveraging trace Rb to polarize K vapor effectively without quenching gases, enhancing applications in quantum measurements and magnetometry.

Findings

Achieved 4.5 times higher K polarization using trace Rb.

Demonstrated effective spin-exchange transfer in optically dense vapor.

Eliminated need for quenching gas in optical pumping of dense alkali vapors.

Abstract

Optical pumping of an optically thick atomic vapor typically requires a quenching buffer gas, such as N$_{2}$, to prevent radiation trapping of unpolarized photons which would depolarize the atoms. We show that optical pumping of a trace contamination of Rb present in K metal results in a 4.5 times higher polarization of K than direct optical pumping of K in the absence of N$_{2}$. Such spin-exchange polarization transfer from optically-thin species is useful in a variety of areas, including spin-polarized nuclear scattering targets and electron beams, quantum-non-demolition spin measurements, and ultra-sensitive magnetometry.