Weak optical anisotropy and its detection on the example of strontium tetraborate activated by ytterbium ions

The method that makes it possible to detect and measure weak optical anisotropy has been proposed and experimentally implemented. Strontium tetraborate, which is considered amorphous glass, activated by ytterbium ions was investigated. The presence of anisotropy, which is comparable to the instrumental errors of ellipsometer goniometers, was found and measured in it. The proposed approach is based on the previously developed effective and relatively simple method, for which the contribution to the formation of the resultant beam from the surface (transition) layer is substantially less than the material volume. The ratios of the ellipsometer measuring zones are also used. Some important aspects of the optical and mechanical alignment of ellipsometers, as applied to the investigation of weak anisotropy, are formulated.