Observation of anti-Stokes fluorescence 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 mum < < 1-97 m. At a pump wavelength of 1.9 mum and incident average power of similar to3 W, a Tm3+:ZBLANP (ZrF4-BaF2-LaF3-AlF3-NaF-PbF2) sample cooled to -1.2 degreesC from room temperature for a single pass of the pump beam. This corresponds to an absorbed pump power of similar to 40 mW and a peak temperature change per absorbed power of similar to -30 degreesC/W from room temperature.