Low temperature laser cooling with a rare-earth doped glass

A theoretical study of laser cooling at low temperature by anti-Stokes luminescence in a rare-earth doped glass is performed. A model is developed to evaluate the absorption and emission spectra of rare-earth ions in a glass matrix. This model allows the evaluation of the inhomogeneously broadened spectra at any temperature. It takes into account the saturation effects that occur at high excitation. The model is used to evaluate the cooling capability at low temperature of a ytterbium-doped fluorozirconate glass, the latter having been proposed in the literature as a good candidate for the cooling element of a cryocooler. Results are compared with previous estimations, confirming that one could expect a useful cooling efficiency from this material, but with smaller performances than previously estimated. Limitations to the cooling process are discussed. The reabsorption of luminescence is identified as one of the main limitations to the performance of a potential cryocooler.