Mesure de la réflectance de miroirs métalliques dans l'infrarouge

The performance of high power CO(2) lasers depends directly on the quality of the metallic mirrors used. The mirrors are therefore the key elements of these lasers and must have a reflectance as near as possible to unity. Thus, we have to characterize these mirrors precisely, that is to say, to use suitable measurement methods to determine their optical properties with enough accuracy. In this paper we describe a reflectance measurement system based on the use of a classical spectrophotometer. This method gives relative measurements, but with the help of a known standard reflectance, we can obtain the absolute value. Experimental results show that the accuracy is ~1-2.5 x 10(-4) provided that many measurements are made and precautions are taken. We propose here to study these conditions and in particular to give the reflectances of metallic mirrors at 10.6 microm.