Cooling effect on fluoride crystals

In this work various Yb-doped fluoride single crystals have been investigated as active media for optical refrigeration. For each material, samples with varying doping levels have been grown by means of the Czochralski technique, optically charaterized through absorption, static and dynamic fluorescence measurements and tested for anti-Stokes cooling. The optical cooling efficiency has been measured by measuring the heating/cooling temperature change of samples as a function of pumping wavelength. A preliminary investigation of impurities by elemental analyses has been also carried out.