Interference phenomena in modulation spectroscopy

Interference phenomena in light reflected or transmitted through a sample can be clearly observed either in a transparency region or in very thin samples. In the case of modulation experiments carried out on such samples the interference is superimposed on a differential spectrum that makes its interpretation more complicated. This is a disturbing aspect of interference. As a rule, one tries to eliminate interference influence (if it is not of special interest). Because this is not always possible, it is useful to know its manifestation in various modulation experiments. Some of the examples of interference manifestation are considered in the present report. However the interference can be used as a source of additional information. This is a useful aspect of interference. Several cases are considered in which interference in modulation spectroscopy is used for determination of the some constants of solids, particularly the electrointerference application for determination of the electro-optical effect constant. A brief review is given of work in this direction. A new method is given for the determination of the refraction coefficient and its variation from the usual interference and modulation interference data. The method provides the determination of these quantities even in the presence of noticeable dispersion, when other methods guarantee the needed accuracy. The imperfectness of the system, which leads to considerable errors in the determination of parameters by usual formulas, is also considered. The results are presented.