Spatial dependent spontaneous emission of an atom in a semi-infinite waveguide of rectangular cross section

TL;DR

This paper investigates how the position of an atom near a semi-infinite rectangular waveguide affects its spontaneous emission, revealing conditions for suppression, enhancement, and revival of emission due to mode interactions and retardation effects.

Contribution

It introduces a detailed model of atom-waveguide interaction considering spatial dependence and retardation, providing new insights into controlling atomic emission in waveguide QED systems.

Findings

Atomic emission can be suppressed or enhanced by adjusting atom position.

Retardation effects lead to partial revivals and collapses in emission.

Multiple transverse modes influence the emission dynamics significantly.

Abstract

We study a quantum electrodynamics (QED) system made of an two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emission has been included in the coupling strength relevant to the eigenmodes of the waveguide. The role of retardation is studied for the atomic transition frequency far away from the cutoff frequencies. The atom-mirror distance introduces different phases and retardation times into the dynamics of the atom interacting resonantly with the corresponding transverse modes. It is found that the upper state population decreases from its initial as long as the atom-mirror distance does not vanish, and is lowered and lowered when more and more transverse modes are resonant with the atom. The atomic spontaneous emission can be either suppressed or enhanced by adjusting the atomic location for short retardation time. There are partial revivals and collapses due to the photon reabsorbed and re-emitted by the atom for long retardation time.