Doppler cooling with coherent trains of laser pulses and tunable "velocity comb"

TL;DR

This paper investigates Doppler cooling of two-level atoms using coherent pulse trains, revealing that the resulting optical force creates a velocity space 'comb' of narrow cooling peaks, with dynamics depending on atomic and pulse parameters.

Contribution

It introduces an analytical model for atom-light interaction with pulse trains, demonstrating the formation of a velocity comb in Doppler cooling, a novel approach in laser cooling techniques.

Findings

The effective scattering force mimics the frequency comb structure.

The force pattern depends on atomic lifetime, pulse repetition, and pulse area.

Cooling results in a velocity space 'comb' of narrow peaks.

Abstract

We explore the possibility of decelerating and Doppler cooling of an ensemble of two-level atoms by a coherent train of short, non-overlapping laser pulses. We develop a simple analytical model for dynamics of a two-level system driven by the resulting frequency comb field. We find that the effective scattering force mimics the underlying frequency comb structure. The force pattern depends strongly on the ratio of the atomic lifetime to the repetition time and pulse area. For example, in the limit of short lifetimes, the frequency peaks of the optical force wash out. We show that laser cooling with pulse trains results in a "velocity comb", a series of narrow peaks in the velocity space.