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 &mgr;m<lambda<1.97 &mgr;m. At a pump wavelength of 1.9 &mgr;m and incident average power of approximately 3 W, a Tm3+:ZBLANP ( ZrF4-BaF2-LaF3-AlF3-NaF-PbF2) sample cooled to -1.2 degrees C from room temperature for a single pass of the pump beam. This corresponds to an absorbed pump power of approximately 40 mW and a peak temperature change per absorbed power of approximately -30 degrees C/W from room temperature.