Role of spontaneously generated coherence (SGC) in laser cooling of atoms

TL;DR

This paper investigates how spontaneously generated coherence (SGC) influences laser cooling in atoms, demonstrating experimentally and theoretically that blue-detuned cooling occurs for both type-I and type-II transitions in rubidium-87, highlighting the role of SGC.

Contribution

It provides the first combined experimental and theoretical analysis of SGC's role in enabling blue-detuned cooling across different atomic transition types.

Findings

Blue-detuned cooling observed for both transition types in rubidium-87.

Comparison of temperatures across various configurations.

Confirmation of SGC's critical role in sub-Doppler cooling mechanisms.

Abstract

The well-known sub-Doppler polarization gradient cooling in type-I transition ($F_e=F_g+1$) is caused by red-detuned lasers. On the other hand, in type-II transition ($F_e\le F_g$), sub-Doppler cooling takes place through blue-detuned lasers. This opposite behavior for the two types of transitions is due to SGC. In the absence of SGC, both types of transitions show blue-detuned cooling. In this work, we experimentally and theoretically demonstrate blue-detuned cooling for both types of transitions in $^{\textrm{87}}$Rb. For completeness, we compare the temperatures in various configurations.