Bichromatic Slowing of Metastable Helium

TL;DR

This paper explores methods to extend the velocity range of the optical bichromatic force for laser deceleration, demonstrating experimental results with metastable helium and proposing a chirped BCF approach for improved atomic slowing.

Contribution

It introduces a chirped BCF technique with a small velocity range to effectively slow atoms, showing experimental success with helium and potential for efficient atomic deceleration.

Findings

Helium atoms were slowed by approximately 370 m/s.

A BCF profile with a velocity width of less than 125 m/s was used.

Scaling suggests the method can produce a MOT-loading brightness comparable to larger Zeeman slowers.

Abstract

We examine two approaches for significantly extending the velocity range of the optical bichromatic force (BCF), to make it useful for laser deceleration of atomic and molecular beams. First, we present experimental results and calculations for BCF deceleration of metastable helium using very large BCF detunings, and discuss the limitations of this approach. We consider in detail the constraints, both inherent and practical, that set the usable upper limit of the BCF. We then show that a more promising approach is to utilize a BCF profile with a relatively small velocity range in conjunction with chirped Doppler shifts, to keep the force resonant with the atoms as they are slowed. In an initial experimental test of this chirped BCF method, helium atoms are slowed by $\sim 370$ m/s using a BCF profile with a velocity width of $\lesssim 125$ m/s. Straightforward scaling of the present results indicates that a decelerator for He* capable of loading a magneto-optical trap (MOT) can yield a brightness comparable to a much larger Zeeman slower.