On the new potentials of ellipsometry arising from the null optical circuit. Ellipsometry of real surface structures. 11. Problem of improving accuracy in the null ellipsometry measurements. Definition of the role of the instrument metering configuration

The paper considers the instrument metering configurations dependent on the position of the ellipsometer phase compensator fast axis. We have shown that they play a very important role in increasing the accuracy of experimental estimation of polarization angles Δ and Ψ. Particular cases (Δ = 0, π, π/2, 3π/2) permitting complete analytical consideration have been studied. For those cases, relations for second derivatives of the light beam intensity at the instrument output by the polarizer and analyzer angular positions have been constructed. As a result, metering configurations providing maximum derivatives of the mentioned type, which ensure sufficient pronouncement of the intensity minimum and, therefore, the necessary accuracy of experimental estimation of the Δ and Ψ angles, have been revealed. A conclusion was made that, in certain situations when angle Ψ is small, the process of measuring angles Δ and Ψ can be subdivided. At the same time, we have noticed that in many cases it is necessary to make efforts to select some general optimal metering configuration ensuring sufficient resolution by both polarization angles. Based on the results obtained in particular cases, the metering situation in the vicinity of the Brewster angle has been analyzed. The paper considers a general case of arbitrary polarization angles Δ and Ψ. In addition, the paper discusses questions that need further analysis of the instrument metering configurations. Particularly, a conclusion has been made that it is necessary to thoroughly study the role of metering configurations in ellipsometry of anisotropic media.