  Laser cooling of solids keeps attracting attention owing to abroad range of
its applications that extends from cm-sized all-optical cryocoolers for
airborne and space-based applications to cooling on nanoparticles for
biological and mesoscopic physics. Laser cooling of nanoparticles is a
challenging task. We propose to use Mie resonances to enhance anti-Stokes
fluorescence laser cooling in rare-earth (RE) doped nanoparticles made of
low-phonon glasses or crystals. As an example, we consider an Yb3+:YAG
nanosphere pumped at the long wavelength tail of the Yb3+ absorption spectrum
at 1030 nm. We show that if the radius of the nanosphere is adjusted to the
pump wavelength in such a manner that the pump excites some of its Mie resonant
modes, the cooling power density generated in the sample is considerably
enhanced and the temperature of the sample is consequently considerably (~ 63%)
decreased. This concept can be extended to nanoparticles of different shapes
and made from different low-phonon RE doped materials suitable for laser
cooling by anti-Stokes fluorescence.
