Nature 377, 500 - 503 (12 October 2002); doi:10.1038/377500a0

Observation of laser-induced fluorescent cooling of a solid

Richard I. Epstein^*, Melvin I. Buchwald^*, Bradley C. Edwards^*, Timothy R. Gosnell^† & Carl E. Mungan^†

^*Astrophysics and Radiation Measurement Group, NIS-2, Mail Stop D436
^†Condensed Matter and Thermal Physics Group, MST-10, Mail Stop E543, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

THE possibility that an object might cool through its interaction with radiation was suggested as early as 1929 by Pringsheim¹. After Landau² established the basic thermodynamic consistency of such a process, certain aspects of fluorescent cooling were vigorously pursued^3á¤-11. In particular, laser 'Doppler' cooling of gas-phase atoms and ions has today grown into a robust research area^12á¤-15. In contrast, attempts to cool solids with light have met with limited success; non-radiative heating effects tend to dominate, and fluorescent cooling has at best resulted in a reduction in overall heating rates⁶. Here we report the experimental realization of net cooling of a solid with radiation. The cooling efficiencies achieved (up to 2%) are more than 10⁴ times those observed in Doppler cooling of gases. By pumping a fluorescent cooling element with a high-efficiency diode laser, it may be possible to construct a compact, solid-state optical cryocooler, thereby allowing widespread deployment of cryogenic electronics and detectors in space and elsewhere¹⁶.

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