Radiative Cooling Of Bulk Si By Optical Down-Conversion

We report on the radiative cooling of an indirect band gap semiconductor through its absorption of interband incoherent light and subsequent spontaneous emission of multiple longer-wavelength photons (optical down-conversion) in conditions when the energy deficit of the process is covered by the thermal energy. The 10 x 10 x 5 mm(3) Si slab kept at 473 K in an evacuated up to 10(-3) torr chamber was cooled by 3.8 K when pumped with light of 1.06 mu m wavelength. First-principles estimates and several advantages of the down-conversion approach over possible cooling of direct band gap semiconductors through the optical upconversion and negative luminescence are discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3485831]