NONDESTRUCTIVE OPTICAL INSPECTION OF EVAPORATED FLUORIDE GLASS LAYERS

Fluoride PZG (PbF2, ZnF2, GaF3) glass layers have been successfully gr own on metal, glass, and semiconductor substrates by co-evaporation un der vacuum conditions. When doped with a suitably chosen rare earth el ement, the layer becomes an active medium which can be used for making integrated optical components. In this paper, the surface quality of the layers is inspected by means of a new non-destructive optical tech nique: phase stepping microscopy (PSM). Interferograms from a reflecti on microscope are automatically interpreted using computer assisted im age processing to give synthesized images of the relief of the film su rface and the substrate surface buried below the film. The resolution is 1 nm in the vertical direction and 0.6 mum laterally. Results are p resented of the analysis of the quality of a PZG glass layer grown on a gold-plated brass substrate. Preliminary results on ZBLAN, GaAs and InP substrates are also discussed.