Cr$^{3+}$-doped crystals as promising materials for laser cooling of solids

The fluorescence of some dielectric crystals doped with Cr$^{3+}$ ions is studied upon laser excitation in the range of the long wavelength tail of the absorption spectrum (cooling mode). Although no actual optical cooling was observed, spectroscopic results and temperature measurements of the samples indicate that electron-phonon bands of Cr$^{3+}$ ions are of interest for obtaining laser cooling