Optimization of optical refrigaration in Yb3+:YAG samples

The laser cooling process with anti-Stokes fluorescence in Yb3+:YAG samples with different ion concentrations, shapes and sizes ranging from cm- to the nm-scale is compared. The temperature dependence of parameters of the system is taken into account. The impact of cooperative effects such as re-absorption, energy migration in the dipole-dipole approximation and cooperative luminescence on the cooling process are considered and analyzed for the first time to our knowledge. The preferred ion concentrations for the different sample sizes are determined. The shapes of the samples for different sample size ranges are also suggested.