Wave-Kinetic Approach to Collective Atomic Emission

José Tito Mendonça,Antonio P B Serbêto

doi:10.3390/atoms8030042

José Tito Mendonça, Antonio P B Serbêto

Open Access

https://doi.org/10.3390/atoms8030042

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Journal: Atoms	Publication Date: Aug 10, 2020
Citations: 1	License type: CC BY 4.0

Affiliation: University of Lisbon, Universidade Federal Fluminense

Abstract

We study the collective scattering of radiation by a large ensemble of Na≫1 atoms, in the presence of a pump field. We use the wave-kinetic approach where the center-of-mass position of the moving atoms is described by a microscopic discrete distribution, or alternatively, by a Wigner distribution. This approach can include thermal effects and quantum recoil in a natural way, and even consider atomic ensembles out of equilibrium. We assume two-level atoms with atomic transition frequency ωa very different from the frequency ω0 of the pump field. We consider both the quasi-classical and quantum descriptions of the center-of-mass motion. In both cases, we establish the unstable regimes where coherent emission of radiation can take place.

Highlights

Collective atomic processes between atoms and radiation are of fundamental importance in several areas of physics, with relevance for laser cooling [1], Bose–Einstein condensation [2], free-electron lasers [3], or super-radiant photon emission and scattering [4,5]
They first used a quasi-classical description, which was extended to include the quantum recoil associated with photon emission and absorption [8,9]
We start with the equations describing the evolution of an ensemble of two-level atoms coupled with radiation, when the atoms are submitted to an intense pump field

Summary

Introduction

Collective atomic processes between atoms and radiation are of fundamental importance in several areas of physics, with relevance for laser cooling [1], Bose–Einstein condensation [2], free-electron lasers [3], or super-radiant photon emission and scattering [4,5]. Bonifacio and collaborators in 1994 [6,7], as the atomic physics equivalent of a free-electron laser, where the electron beams are replaced by moving atoms They first used a quasi-classical description, which was extended to include the quantum recoil associated with photon emission and absorption [8,9]. The wave-kinetic approach followed here can partly be considered an extension of our previous kinetic model for the free-electron laser [11], when electrons in a relativistic beam are replaced by slowly moving atoms.

Basic Equations

Radiation Instability

Quantum Recoil

Conclusions