Authors:	Li, Wenbing Wolf, Sebastian Klein, Lukas Budker, Dmitry Düllmann, Christoph E. Schmidt-Kaler, Ferdinand
Title:	Robust polarization gradient cooling of trapped ions
Online publication date:	6-Feb-2024
Year of first publication:	2022
Language:	english
Abstract:	We implement three-dimensional polarization gradient cooling (PGC) of trapped ions. Counter-propagating laser beams near 393 nm impinge in lin ⊥ lin configuration, at a frequency below the S1/2 to P3/2 resonance in 40Ca+. Our measurements demonstrate that cooling with laser beams detuned to lower frequencies from the resonance is robust against an elevated phonon occupation number and works continuously in the crossover from regular Doppler cooling to detunings of tens of linewidths. It is thus robust against heating events and also works well for an initial ion motion far out of the Lamb–Dicke regime. We show that PGC performance strongly depends on residual micromotion (MM) and find PGC working for a MM modulation index β ⩽ 0.1. Still, we find that the spectral impurity of the laser field affects both, cooling rates and cooling limits. Thus, a Fabry–Pérot cavity filter is employed to efficiently suppress amplified spontaneous emission of the diode laser. We demonstrate mean phonon numbers for a single ion of 5.4(4) at a trap frequency of 2π × 285 kHz and 3.3(4) at 2π × 480 kHz, in the axial and radial directions, respectively.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik Helmholtz Institut Mainz
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-10060
Version:	Published version
Publication type:	Zeitschriftenaufsatz
Document type specification:	Scientific article
License:	CC BY
Information on rights of use:	https://creativecommons.org/licenses/by/4.0/
Journal:	New journal of physics 24 4
Pages or article number:	043028
Publisher:	IOP
Publisher place:	London
Issue date:	2022
ISSN:	1367-2630
Publisher DOI:	10.1088/1367-2630/ac6233
Appears in collections:	DFG-491381577-G