http://physicsworld.com/cws/article/news/2015/may/15/polariton-refrigerator-could-chill-tiny-semiconductor-devices
A new method for using light to cool solids has been created by physicists in France and Germany. The technique uses quasiparticles called "polaritons" to remove vibrational heat from a tiny piece of semiconductor, and unlike previous optical cooling schemes it works at very low temperatures. The scheme could provide a new way of cooling very small electronic devices, as well as giving physicists an alternative approach to studying heat transport.
Developed by Maxime Richard of the University of Grenoble and colleagues, the new cooling technique is based on "anti-Stokes fluorescence" (ASF), which has already been used with limited success to cool solids. In the case of a semiconductor, this involves laser light being used to create an electron–hole pair, or "exciton", in the material, which can then absorb one or more thermal vibrations (phonons). The exciton will go on to decay into a photon that carries with it the thermal energy.
Physicists have been able to use ASF to cool a semiconductor from room temperature to 260 K – a difference of about 30 K. Achieving more cooling power is difficult because defects in the semiconductor cause some excitons to decay and return heat to the material via multiple phonons. Some of the laser light therefore heats the material, rather than cooling it.