Detection of Weak Optical Anisotropy in Strontium Tetraborate Activated by Ytterbium Ions

A technique for detecting and measuring the weak optical anisotropy has been proposed and experimentally implemented. The strontium tetraborate activated by ytterbium ions, which is considered to be an amorphous glass, has been investigated and its anisotropy comparable with the instrumental errors of ellipsometer goniometers has been found and measured. The proposed approach is based on a previously developed effective and relatively simple method, in which the contribution of the surface (transition) layer to the formation of the resulting beam is essentially smaller than the contribution of the bulk material. The relations between the ellipsometer measuring zones have been used. Some important aspects of the optical and mechanical alignment of the ellipsometers have been described as applied to the weak anisotropy investigations.