Deconvolution and measurement of bulk and surface optical absorptions in Ti:Al2O3 crystals using photopyroelectric interferometry

Abstract

The extension of our earlier single-layer ͑monolithic͒ photopyroelectric ͑PPE͒ interferometric theory to include surface and bulk optical absorptions has allowed the measurement of both bulk absorption coefficient and surface absorptance in one single experiment. Based on purely thermal-wave interferometry, the thermal-wave cavity lengths of a PPE interferometer were scanned using pairs of Ti: sapphire crystals with appropriate combinations of figure of merit, surface polish, and thickness. In the conventional single-ended ͑noninterferometric͒ PPE technique, the surface reflectivity, surface absorptance, and bulk absorption coefficient are always coupled together. However, PPE destructive interferometry provides a method for extracting highly precise values of one of these optical parameters, without the requirement of equally precise knowledge of the values of the others.