The status of optical refrigeration of rare-earth-doped solids is reviewed, and the various factors that limit the performance of current laser-cooling materials are discussed. Efficient optical refrigeration is possible in materials for which hω_max < E_p/8, where h&omega;_max is the maximum phonon energy of the host material and E_p is the pump energy for the rare-earth dopant. Transition-metal and OH- impurities at levels >100 ppb are believed to be the main reason for the limited laser-cooling performance in current materials. The many components of doped ZBLAN glass pose particular processing challenges. Binary fluoride glasses such as YF3-LiF are considered as alternatives to ZBLAN, and the crystalline system KPb₂Cl₅ :Dy³⁺ is identified as a prime candidate for high-efficiency laser cooling.

Date Published: 12 February 2009
PDF: 8 pages
Proc. SPIE 7228, Laser Refrigeration of Solids II, 72280E (12 February 2009); doi: 10.1117/12.809091

Published in SPIE Proceedings Vol. 7228:
Laser Refrigeration of Solids II
Richard I. Epstein; Mansoor Sheik-Bahae, Editor(s)