Interferometer for measurement of phase changes in recording media

A description is given of a method for automatic measurement of local phase changes in materials intended for optical data storage. The use of a two-frequency He–Ne laser (λ = 0.63 μ) makes it possible to increase the precision of measurements and to determine the behavior of the refractive index of a material during exposure. The method was used in an investigation of photoinduced structural transformations in glassy chalcogenide semiconductors.