Fluorescence during Doppler cooling of a single trapped atom

TL;DR

This paper presents an analytical model and experimental method for estimating the initial energy and temperature of a single trapped atom during Doppler cooling, offering a simpler alternative to traditional techniques.

Contribution

The authors develop a semiclassical analytical model for Doppler cooling dynamics and demonstrate a practical fluorescence-based temperature measurement method.

Findings

The fluorescence rate during cooling can estimate the atom's initial energy.

The fluorescence method agrees reasonably with sideband detection.

The approach simplifies temperature measurement in trapped atom experiments.

Abstract

We investigate the temporal dynamics of Doppler cooling of an initially hot single trapped atom in the weak binding regime using a semiclassical approach. We develop an analytical model for the simplest case of a single vibrational mode for a harmonic trap, and show how this model allows us to estimate the initial energy of the trapped particle by observing the fluorescence rate during the cooling process. The experimental implementation of this temperature measurement provides a way to measure atom heating rates by observing the temperature rise in the absence of cooling. This method is technically relatively simple compared to conventional sideband detection methods, and the two methods are in reasonable agreement. We also discuss the effects of RF micromotion, relevant for a trapped atomic ion, and the effect of coupling between the vibrational modes on the cooling dynamics.