ABSORPTION MAPPING FOR CHARACTERIZATION OF GLASS SURFACES

The surface quality of bare substrates and preparation procedures take on an important role in optical coating performances. The most common ly used techniques of characterization generally give information abou t roughness and local defects. A photothermal deflection technique is used for mapping surface absorption of fused-silica and glass substrat es. We show that absorption mapping gives specific information on surf ace contamination of bare substrates. We present experimental results concerning substrates prepared by different cleaning and polishing tec hniques. We show that highly polished surfaces lead to the lowest valu es of residual surface absorption. Moreover the cleaning behavior of s urfaces of multicomponent glasses and their optical performance in ter ms of absorption are proved to be different from those of fused silica .