Raman Imaging of Atoms Inside a High-bandwidth Cavity

TL;DR

This paper demonstrates a method to image atoms inside a high-bandwidth fiber cavity by detecting repumper fluorescence during Raman cooling, overcoming fluorescence suppression due to the Purcell effect.

Contribution

It introduces a novel imaging technique using repumper fluorescence in strongly coupled atom-cavity systems, enabling atom position control in high-bandwidth cavities.

Findings

Successful imaging of $^{87}$Rb atoms via repumper fluorescence.

Detailed analysis of light shifts affecting Raman resonance.

Identification of an optimal regime balancing signal quality and atom survival.

Abstract

High-bandwidth, fiber-based optical cavities are a promising building block for future quantum networks. They are used to resonantly couple stationary qubits such as single or multiple atoms with photons routing quantum information into a fiber network at high rates. In high-bandwidth cavities, standard fluorescence imaging on the atom-cavity resonance line for controlling atom positions is impaired since the Purcell effect strongly suppresses all-directional fluorescence. Here, we restore imaging of $^{87}$Rb atoms strongly coupled to such a fiber Fabry-P\'erot cavity by detecting the repumper fluorescence which is generated by continuous and three-dimensional Raman sideband cooling. We have carried out a detailed spectroscopic investigation of the repumper-induced differential light shifts affecting the Raman resonance, dependent on intensity and detuning. Our analysis identifies a compromise regime between imaging signal-to-noise ratio and survival rate, where physical insight into the role of dipole-force fluctuations in the heating dynamics of trapped atoms is gained.