Properties of a Three-Level $\Lambda$-Type Atom Driven by Coherent and Stochastic Fields

TL;DR

This paper theoretically investigates a three-level atom driven by both coherent and stochastic fields, revealing how noise can be used as a control parameter to manipulate atomic populations and emission spectra.

Contribution

It introduces a model incorporating realistic laser noise into the atom's dynamics and demonstrates noise's role as a control tool in quantum systems.

Findings

Stochastic drive influences atomic decoherence and control.

Detuning stochastic fields alters emission spectra significantly.

Noise can enhance or suppress specific fluorescence features.

Abstract

We present a theoretical investigation of a three-level $\Lambda$-type atom driven by a strong coherent laser and a weak stochastic field exhibiting amplitude and phase fluctuations. The stochastic field is modeled as a complex Gaussian-Markovian random process with finite bandwidth to describe realistic laser noise. Using the Born-Markov and rotating-wave approximations, we derive a Lindblad-form master equation that incorporates spontaneous emission and noise-induced terms, and we solve for the steady-state regime. We examine level populations in both the bare and dressed bases and compute the incoherent resonance-fluorescence spectrum. Our analysis shows that the stochastic drive is not merely a source of decoherence but a versatile control parameter. By detuning the stochastic-field central frequency relative to the coherent drive (especially for narrow bandwidths), we observe pronounced changes in emission characteristics, including selective enhancement or suppression, and reshaping of the multi-peaked fluorescence spectrum when the detuning matches the generalized Rabi frequency. Numerical results reveal nontrivial steady-state modifications distinct from purely coherent driving, enabling precise control of populations and suggesting applications in quantum control, quantum technologies, spectroscopy, and noise-assisted manipulation of atomic systems.