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Self-ordering and cavity cooling using a train of ultrashort pulses

Authors :
Valentin Torggler
Ivor Krešić
Ticijana Ban
Helmut Ritsch
Source :
New Journal of Physics, Vol 22, Iss 6, p 063003 (2020)
Publication Year :
2020
Publisher :
IOP Publishing, 2020.

Abstract

A dilute atomic gas in an optical resonator exhibits a phase transition from a homogeneous density to crystalline order when laser illuminated orthogonal to the resonator axis. We study this well-known self-organization phenomenon for a generalized pumping scheme using a femtosecond pulse train with a frequency spectrum spanning a large bandwidth covering many cavity modes. We show that due to simultaneous scattering into adjacent longitudinal cavity modes the induced light forces and the atomic dynamics becomes nearly translation-invariant along the cavity axis. In addition the laser bandwidth introduces a new correlation length scale within which clustering of the atoms is energetically favorable. Numerical simulations allow us to determine the self-consistent ordering threshold power as function of bandwidth and atomic cloud size. We find strong evidence for a change from a second order to a first order self-ordering phase transition with growing laser bandwidth when the size of the atomic cloud gets bigger than the clustering length. An analysis of the cavity output reveals a corresponding transition from a single to a double pulse traveling within the cavity. This doubles the output pulse repetition rate and creates extra substructures in close analogy to a time crystal formation in the cavity output. Simulations also show that multi-mode operation significantly improves cavity cooling generating lower kinetic temperatures at a much faster cooling rate.

Details

Language :
English
ISSN :
13672630
Volume :
22
Issue :
6
Database :
Directory of Open Access Journals
Journal :
New Journal of Physics
Publication Type :
Academic Journal
Accession number :
edsdoj.6295c336704e4b2695e5b297cde4c7a1
Document Type :
article
Full Text :
https://doi.org/10.1088/1367-2630/ab85a8