Abstract
We report internal laser cooling in Yb3+-doped KPb2Cl5. From the quantum efficiency values measured in the heating and cooling regions by use of the photothermal deflection technique, we have obtained a room-temperature cooling efficiency of 0.2% in a sample doped with similar to5 X 10(19) ions/cm(3). Excitation spectra obtained under high irradiation fluences show an excess of fluorescence with regard to those obtained at low fluences, which agrees with the prediction of a model based on photon-ion-phonon interaction. (C) 2002 Optical Society of America.