Efficient polarization of high-angular-momentum systems

TL;DR

This paper introduces novel optical pumping techniques for high-angular-momentum systems that significantly reduce population loss by minimizing spontaneous emissions needed to achieve a stretched state.

Contribution

The authors develop methods using coherent population transfer to efficiently polarize high-angular-momentum atoms and molecules, outperforming conventional optical pumping.

Findings

Reduction of spontaneous decays from 2J to log2(2J)

Achieving polarization with approximately one spontaneous decay

Methods applicable to open, high-angular-momentum transitions

Abstract

We propose methods of optical pumping that are applicable to open, high-angular-momentum transitions in atoms and molecules, for which conventional optical pumping would lead to significant population loss. Instead of applying circularly polarized cw light, as in conventional optical pumping, we propose to use techniques for coherent population transfer (e.g., adiabatic fast passage) to arrange the atoms so as to increase the entropy removed from the system with each spontaneous decay from the upper state. This minimizes the number of spontaneous-emission events required to produce a stretched state, thus reducing the population loss due to decay to other states. To produce a stretched state in a manifold with angular momentum J, conventional optical pumping requires about 2J spontaneous decays per atom, one of our proposed methods reduces this to about log_2(2J), while another of the methods reduces it to about one spontaneous decay, independent of J.