Spectroscopic and laser cooling results on Yb3+-doped BaY2F8 single crystal

Abstract

Anti-Stokes cooling has been observed in an Yb3+-doped BaY2F8 single crystal. Single crystals have been grown by the Czochralski technique. The absorption spectra and the emission properties have been measured at room temperature and at 10K. The energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and separated from the vibronic substructure. The intrinsic decay time of the F5∕22 level has been measured taking care of avoiding the effect of multiple reabsorption processes. The theoretical and experimental cooling efficiencies of Yb:BaY2F8 are evaluated and compared with respect to those of the most frequently investigated materials for laser cooling. A temperature drop of almost 4K was measured by pumping the crystal with 3W of laser radiation at ∼1025nm in single pass configuration with a cooling efficiency of ∼3%.