Absorption measurement of layer or material: how to calibrate?

The knowledge of the absorption in the materials is important because it can generate problematic phenomena (deformations, depolarization, damage...) when one uses power lasers. Often it is neglected because we use glasses "transparent" and it is difficult to measure it. For low absorptions, the photothermal deflection (P.D.) was developed at the end of the 1980s by Boccara's team. It measures the deflection of a probe beam caused by the propagation inside a material of a pump laser. The deflection depends on the thermomechanical parameters and needs to be calibrated. The purpose of this paper is to provide a method for measuring the absorption of material with a low extinction coefficient and to establish simple ratios for estimating the absorption of materials or thin layers.