Thermal radiation of semitransparent plane-parallel objects

Based on the analysis of absorptances of plane-parallel objects, distinctive features of their thermal radiation caused by multibeam interference are investigated. Using a semiconductor as an example, thermal radiation spectra for plane-parallel and identical non-plane-parallel plates in the spectral region beyond the fundamental absorption edge are calculated, and a comparison of the parameters of these spectra was carried out. It is shown that, in spectral regions corresponding to interference maxima, the radiant emittance of a plane-parallel plate can exceed many times over that of non-plane-parallel plate. For very small values of the absorption coefficient of a plane-parallel plate, its radiant emittance can attain the value of 0.5 of that of a blackbody in these spectral regions. It is proved that the results obtained can be used for creation of new controllable thermal radiation sources. (C) 2002 Elsevier Science B.V. All rights reserved.