Observation of anti-stokes fluorescent cooling in thulium-doped glass

We report the first observation of anti-Stokes fluorescence cooling in a thulium-doped solid with pump excitation at 1.82 mm , l , 1.97 mm. At a pump wavelength of 1.9 mm and incident average power of 3 W, a Tm31:ZBLANP (ZrF4-BaF2-LaF3-AlF3-NaF-PbF2) sample cooled to 21.2 ±C from room temperature for a single pass of the pump beam. This corresponds to an absorbed pump power of 40 mW and a peak temperature change per absorbed power of 230 ±C W from room temperature.