Subradiance with saturated atoms: population enhancement of the long-lived states

TL;DR

This paper demonstrates a significant increase in population of long-lived subradiant atomic states by saturating the atoms, revealing a mechanism akin to optical pumping that enhances these states without affecting their lifetimes.

Contribution

It presents the first experimental evidence of population enhancement in subradiant states through saturation, extending understanding beyond linear optics.

Findings

Two hundred-fold increase in subradiant state population

Enhancement mechanism similar to optical pumping

Lifetimes remain unaffected by pump strength

Abstract

Dipole-dipole interactions are at the origin of long-lived collective atomic states, often called subradiant, which are explored for their potential use in novel photonic devices or in quantum protocols. Here, we study subradiance beyond linear optics and experimentally demonstrate a two hundred-fold increase in the population of these modes, as the saturation parameter of the driving field is increased. We attribute this enhancement to a mechanism similar to optical pumping through the well-coupled superradiant states. The lifetimes are unaffected by the pump strength, as the system is ultimately driven toward the single-excitation sector.