Anti-Stokes Fluorescence as a Cooling Process

Christoph Zander, Karl Heinz Drexhage

Weiping Qin, Shihua Huang, Guotong Du +6 more

M. S. Chang, S. Elliott, T. Kenneth Gustafson +2 more

Wayne T. Whitney, Nicholas Djeu

P. R. Eastham, Conor N. Murphy, Luísa Toledo Tude

The established approach to laser cooling of solids relies on anti-Stokes fluorescence, for example from rare earth impurities in glass. Although successful, there is a minimum temperature to which such a process can cool set by the electronic level spacing in the impurity. We propose an alternative method which does not suffer from this limitation. Our approach relies on the formation of dressed states under strong laser driving, which generates a spectrum in which the gaps can be tuned to optimize the heat absorption. This allows for a cooling cycle which operates at any temperature with a power comparable to the maximum dictated by thermodynamic principles. While this cooling cycle will compete with heating due to non-radiative decay and other mechanisms, it could in principle allow laser cooling to temperatures which are unachievable with anti-Stokes fluorescence.

Jing Dai, Li Li, Xinlu Zhang

We present a physical scheme of upconversion-assisted anti-Stokes fluorescence cooling in Tm doped low phonon materials. The upconversion pumping from the metastable level to the upconversion excited level is introduced to produce extra anti-Stokes cooling cycles which can improve the laser cooling performance. Both the limitation of the cooling cryogenic temperature and the range of the cooling wavelength can be extended notably in contrast to the traditional anti-Stokes cooling.