Collective emission of an atomic beam into an off-resonant cavity mode

TL;DR

This paper investigates how a beam of atomic dipoles collectively emits into an off-resonant optical cavity, analyzing the effects of detuning, cavity linewidth, and stability, revealing superradiant and polychromatic emission regimes.

Contribution

It provides a theoretical framework for understanding collective atomic emission into off-resonant cavities, including analytical formulas and stability analysis of various emission phases.

Findings

Small cavity pulling when cavity linewidth exceeds atomic linewidth

Identification of superradiant and polychromatic emission regimes

Theoretical predictions align with numerical simulations

Abstract

We study the collective emission of a beam of atomic dipoles into an optical cavity. Our focus lies on the effect of a finite detuning between the atomic transition frequency and the cavity resonance frequency. By developing a theoretical description of the coupled atom-cavity dynamics we analyze the stationary atomic configurations including a superradiant phase where the atoms undergo continuous monochromatic collective emission. In addition, we derive an analytical formula for the cavity pulling coefficient which characterizes the displacement of the emission frequency towards the cavity frequency. We find that the pulling is small if the cavity linewidth is much larger than the collective linewidth of the atomic beam. This regime is desired for building stable lasers because the emission frequency is robust against cavity length fluctuations. Furthermore, we investigate the stability of the atomic phases and compare our theoretical predictions with numerical results. Remarkably, we also find polychromatic emission regimes, where the spectrum has several frequency components while the light output is still superradiant.