Mechanism of refrigeration cycle on laser cooling of solids

A simple model is developed to study the laser cooling of solids.The condition of laser cooling of a solid is developed.By using some parameters of the Yb 3+ ion,which is most widely used in laser cooling,we then calculate the cooling power and the cooling efficiency.In order to make a more precise analysis, the effect of fluorescent reabsorption,which is unavoidable in the cooling process,is discussed using the random walk model.Taking Tm 3+ ion as an example,we derive the average number of absorption events and determine the change in quantum efficiency due to reabsorption.Finally,we obtain the red-shift of the fluorescent wavelength and the requirement of sample dimension.