Fluorescence control through vacuum induced coherences

TL;DR

This paper investigates how vacuum-induced coherences affect the resonance fluorescence spectrum of a four-level atom driven by two coherent fields, revealing phase-dependent control of spectral peaks through polarization detection.

Contribution

It provides an analytical framework and numerical analysis demonstrating vacuum-induced coherence effects on fluorescence spectra, including phase-dependent peak enhancement or suppression.

Findings

Vacuum-induced coherence influences fluorescence spectral peaks.

Phase control enables modulation of spectral features.

Polarization detection scheme affects observed coherence effects.

Abstract

The resonance fluorescence of a four-level atom in J = 1/2 to J = 1/2 transition driven by two coherent fields is studied. We find that the incoherent fluorescence spectrum shows a direct indication of vacuum-induced coherence in the atomic system. We show that such coherence manifests itself via an enhancement or suppression of the spectral peaks in the $\pi$-polarized fluorescence. The effect of the relative phase of the driving fields on the spectral features is also investigated. We show that phase-dependent enhancement or suppression of the fluorescence peaks appears in the incoherent spectrum emitted along the $\sigma$ transitions. It is found that this phase dependence occurs because of the polarization-detection scheme employed for the observation of the fluorescence light. We present an analytical explanation, based on dressed-states of the atom-field system, to interpret the numerical results.