Anti-Stokes laser cooling in Yb^3+-doped KPb_2Cl_5 crystal

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 ∼5 × 1019 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. © 2002 Optical Society of America.