THE COMBINED ELLIPSOMETRIC METHOD OF COMPLETE OPTICAL CHARACTERIZATION OF CRYSTALS. I. DETERMINATION OF THE ORIENTATION OF THE OPTICAL INDICATRIX

Viktor Belyukh, B. Pavlyk

Abstract


The first part of the article describes in detail the method of determining the orientation of the optical indicatrix in crystals. The experimental basis of the method was the careful ellipsometric measurements of the dependence of the effective refractive index on the angle of rotation of the crystal around the normal to the investigated surface, neff = f(α). The measurements were carried out on crystals cadmium tungstate (CdWO4) and lithium niobate (LiNbO3). Note that neff is the real part of the complex refractive index of the crystal, Neff = neff - i∙keff, calculated on the basis of the model “optically isotropic homogeneous medium – optically isotropic homogeneous substrate”. It is experimentally proved that the extrema of the dependence neff = f(α) determine the orientation of the optical indicatrix. It is especially important that knowledge of the crystallographic orientation of the investigated samples is completely unnecessary for the practical implementation of the method. The proposed method is applicable to crystals of any crystallographic system. This method of determining the orientation of the optical indicatrix became the basis for the combined ellipsometric method of the complete optical characterization of crystals and is its first stage.

Key words: ellipsometry, optical indicatrix, principal refractive indexes, uniaxial and biaxial crystals.


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DOI: http://dx.doi.org/10.30970/eli.15.11

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