Laser stabilization using saturated absorption in a cavity QED system

TL;DR

This paper demonstrates that saturated absorption features in a cavity QED system with cooled atoms can significantly enhance laser phase stability, overcoming Doppler broadening effects and enabling new regimes for high-precision stabilization.

Contribution

It introduces a method for laser stabilization using narrow saturated absorption features in a cavity QED system with moving atoms, surpassing Doppler broadening limitations.

Findings

Achieved high phase stabilization comparable to state-of-the-art.

Doppler broadening effects can be mitigated by cavity-induced saturated absorption.

Optical bistability disappears with atomic velocity inhomogeneity, enabling stable operation.

Abstract

We consider the phase stability of a local oscillator (or laser) locked to a cavity QED system comprised of atoms with an ultra-narrow optical transition. The atoms are cooled to millikelvin temperatures and then released into the optical cavity. Although the atomic motion introduces Doppler broadening, the standing wave nature of the cavity causes saturated absorption features to appear, which are much narrower than the Doppler width. These features can be used to achieve an extremely high degree of phase stabilization, competitive with the current state-of-the-art. Furthermore, the inhomogeneity introduced by finite atomic velocities can cause optical bistability to disappear, resulting in no regions of dynamic instability and thus enabling a new regime accessible to experiments where optimum stabilization may be achieved.