Perturbative approach in the frequency domain for the intensity correlation spectrum at electromagnetically induced transparency

TL;DR

This paper introduces a perturbative frequency domain method to analyze intensity correlation spectra in electromagnetically induced transparency, revealing how absorption and dispersion influence correlation linewidth and sideband resonances.

Contribution

It presents an analytical perturbative framework connecting intensity correlations with optical properties in EIT, enhancing understanding of frequency domain correlation spectroscopy.

Findings

First-order perturbation suffices for coherent light correlation analysis.

Analytical expression links correlation spectrum to absorption and dispersion.

Sideband resonances observed, indicating complex frequency domain behavior.

Abstract

Correlation spectroscopy has been proposed as a spectroscopic technique for measuring the coherence between the ground states in electromagnetically induced transparency (EIT). While in time domain the steep dispersion in EIT condition accounts for the robustness of the correlation linewidth against power broadening, such physical insight was not directly established in the frequency domain. We propose a perturbative approach to describe the correlation spectroscopy of two noisy lasers coupled to a $\Lambda$-transition in cold atoms, leading to EIT. Such approach leads to an analytical expression that maps the intensity correlation directly in terms of the absorption and dispersion of the light fields. Low and high perturbative regimes are investigated and demonstrate that, for coherent light sources, the first oder term in perturbation expansion represents a sufficient description for the correlation. Sidebands resonances are also observed, showing the richness of the frequency domain approach.