Measurements of optical refrigeration in ytterbium-doped crystals

We measured anti-Stokes fluorescence cooling (optical refrigeration) in ytt erbium-doped yttrium aluminum garnet (YAG). Pumping the 2.3% Yb3+:YAG cryst al with 1.8 W of 1030 nm laser light produced a temperature drop of 8.9 deg reesC from room temperature. The high thermal conductivity and ruggedness o f this crystal make it an attractive material for use in optical refrigerat ors. Our spectral studies show that pure crystals of this material could be efficient for optical refrigeration at temperatures above similar to 100 K . Photothermal deflection measurements show that our current crystals can c ool at similar to 250 K. Additionally, we measured optical refrigeration in a 5% Yb3+:Y2SiO5 crystal when pumped at 1050 nm. (C) 2001 American Institu te of Physics.