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Laser cooling of ytterbium-doped silica glass

: Mobini, E.; Rostami, S.; Peysokhan, M.; Albrecht, A.; Kuhn, S.; Hein, S.; Hupel, C.; Nold, J.; Haarlammert, N.; Schreiber, T.; Eberhardt, R.; Tünnermann, A.; Sheik-Bahae, M.; Mafi, A.

Volltext ()

Communications Physics 3 (2020), Art. 134, 6 S.
ISSN: 2399-3650
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IOF ()
laser cooling; refrigeration; cryocooler; absorption spectroscopy; Ytterbium

Laser cooling of a solid is achieved when a coherent laser illuminates the material in the red tail of its absorption spectrum, and the heat is carried out by anti-Stokes fluorescence of the blue-shifted photons. Solid-state laser cooling has been successfully demonstrated in several materials, including rare-earth-doped crystals and glasses. Silica glass, being the most widely used optical material, has so far evaded all laser cooling attempts. Here we show the net cooling of high-purity Yb-doped silica glass samples that are fabricated with low impurities to reduce their parasitic background loss for fiber laser applications. The non-radiative decay rate of the excited state in Yb ions is very small in these glasses due to the low level of impurities, resulting in near-unity quantum efficiency. We report the measurement of the cooling efficiency as a function of the laser wavelength, from which the quantum efficiency of the Yb-doped silica is calculated.