We report internal laser cooling in Yb<sup>3+</sup> -doped KPb<sub>2</sub>Cl<sub>5</sub> . 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 ~5×10<sup>19</sup>ions/cm<sup>3</sup> . 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
A. Mendioroz, J. Fernández, M. Voda, M. Al-Saleh, R. Balda, and A. J. García-Adeva, "Anti-Stokes laser cooling in Yb3+-doped KPb2 Cl5 crystal," Opt. Lett. 27, 1525-1527 (2002)