Power-Broadening-Free Correlation Spectroscopy in Cold Atoms

TL;DR

This paper investigates correlation spectra in cold atoms under EIT, revealing a power-broadening-independent transition from correlation to anti-correlation that directly measures ground-state coherence time.

Contribution

It introduces a novel method to extract real-time correlation spectra and demonstrates its effectiveness in cold cesium and rubidium atoms.

Findings

Transition from correlation to anti-correlation occurs at EIT resonance.

Transition point is independent of power broadening.

Method accurately measures ground-state coherence time.

Abstract

We report a detailed investigation on the properties of correlation spectra for cold atoms under the condition of Electromagnetically Induced Transparency (EIT). We describe the transition in the system from correlation to anti-correlation as the intensity of the fields increases. Such transition occurs for laser frequencies around the EIT resonance, which is characterized by a correlation peak. The transition point between correlation and anti-correlation is independent of power broadening and provides directly the ground-state coherence time. We introduce a method to extract in real time the correlation spectra of the system. The experiments were done in two distinct magneto-optical traps (MOT), one for cesium and the other for rubidium atoms, employing different detection schemes. A simplified theory is introduced assuming three-level atoms in $\Lambda$ configuration interacting with a laser with stochastic phase fluctuations, providing a good agreement with the experimental observations.