Laser cooling of solids

Article By:

Epstein, Richard I. Santa Fe, New Mexico.

Sheik-Bahae, Mansoor Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico.

Last reviewed:2011

DOI:https://doi.org/10.1036/1097-8542.YB110089

The term “laser cooling” most often is associated with cooling dilute gases of atoms or ions to extremely low temperatures by employing the Doppler effect to reduce their thermal translational energy. This area of science has progressed immensely. However, it is not widely know that in 1929, some 46 years before Doppler cooling of atoms was even contemplated, the physicist Peter Pringsheim suggested the possibility of cooling solids by optical means. In the solid phase, atoms do not possess relative translational motion; their thermal energy is largely contained in the vibrational modes of the lattice. Laser cooling of solids (or optical refrigeration) is similar to atom cooling: Light quanta in the red tail of the absorption spectrum are absorbed from a monochromatic source followed by spontaneous emission of more energetic (blue-shifted) photons, a process known as fluorescence up-conversion. In the case of solids, the extra energy is extracted from lattice phonons, the quanta of vibrational energy in which heat is contained. The removal of these phonons cools the solid.

The content above is only an excerpt.