Theory of atoms in twisted light

doi:10.1017/CBO9780511795213.012

11 - Theory of atoms in twisted light

Published online by Cambridge University Press: 05 December 2012

M. Babiker ,

D. L. Andrews and

V. E. Lembessis

Edited by

David L. Andrews and

Mohamed Babiker

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M. Babiker: Affiliation:
University of York
D. L. Andrews: Affiliation:
University of East Anglia
V. E. Lembessis: Affiliation:
King Saud University
David L. Andrews: Affiliation:
University of East Anglia
Mohamed Babiker: Affiliation:
University of York

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Summary

Introduction

The theoretical foundations for describing the influence of twisted light on atoms, ions and molecules are essentially the same as those leading to their cooling and trapping by ordinary plane wave laser light [1–4]. A third of a century has passed since the Doppler mechanism was first put forward by Wineland and Dehmelt as a mechanism for cooling ions [5], and then by Hänsch and Schawlaw for neutral atoms [6]. The key role played by the Doppler mechanism is best illustrated by the simplest case of one-dimensional optical molasses, where a two-level atom is subject to two identical counter-propagating plane waves of a frequency near to resonance with the atomic transition frequency. In terms of a classical description, at small velocities the atom experiences a friction force F= −αv, where v is the velocity vector of the atomic centre of mass parallel to the common axis of the light beams, and α is a friction coefficient. The friction force gradually cools the atoms to progressively smaller, albeit limited, velocities and can be made to operate in all three dimensions by use of multiple beams. The cooling technique based on the Doppler mechanism has been superseded by more effective cooling mechanisms, especially evaporative and Sisyphus cooling mechanisms, culminating, with the achievement of super-cooling, in the realisation of Bose-Einstein condensates (BECs) [7]. Nevertheless, the Doppler mechanism remains important as a mechanism for the early stages of cooling and still plays a key role in the interaction of atomic systems with laser light.

Type: Chapter
Information: The Angular Momentum of Light , pp. 284 - 313

DOI: https://doi.org/10.1017/CBO9780511795213.012 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2012

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