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Tesi etd-09122018-121530


Tipo di tesi
Tesi di dottorato di ricerca
Autore
CITTADINO, GIOVANNI
URN
etd-09122018-121530
Titolo
An increasing cooling efficiency in fluoride crystals co-doped Yb-Tm
Settore scientifico disciplinare
FIS/03
Corso di studi
FISICA
Relatori
tutor Prof. Tonelli, Mauro
controrelatore Prof. Fuso, Francesco
controrelatore Prof. Agnesi, Antoniangelo
controrelatore Prof. Nogues, Gilles
Parole chiave
  • codoping ytterbium-thulium
  • cooling efficiency
  • Czochralski technique
  • optical refrigeration
  • Rare Earths
Data inizio appello
18/09/2018
Consultabilità
Completa
Riassunto
Anti-Stokes shift, provided by embedded rare earth (RE) ions in fluoride crystal host, is used to obtain a net cooling of a solid system. Yb3+ is currently the RE ion that presents the best cooling performance when inserted into a suitable host, like yttrium lithium fluoride (YLF). Recently, a new approach to laser cooling has been proposed, in which an enhancement of the cooling efficiency is reached by co-doping with Yb3+ and Tm3+. In this work, we compare, in terms of cooling efficiency, several samples doped with Yb and co-doped Yb-Tm. They were grown by employing the Czochralski technique. This specific technique allows to fabricating defect-free and large samples for such application. Samples possessing the same chemical composition of impurity and defect-free were compared denoting the goodness of the Tm-enrichment for the optical refrigeration. We demonstrate that the presence of a small concentration of Tm ions permits to decrease the background absorption and to increase the cooling efficiency. So far, a sample reached the important results of 4.2% in cooling efficiency overcoming the 3% barrier.
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