The optics of the Mach-Zehnder interferometer

Abstract

The paper is intended to give a complete optical theory of the Mach-Zehnder interferometer, without using difficult mathematical methods or complicated three-dimensional diagrams. The topics covered include the effect of tile spectral distribution of the source, with and without dispersion. The effect on the fringe contrast of the size and shape of the source are considered. These effects are related to the fringe pattern which is produced near the usual source position if a source is placed in what is normally the emergent beam. This fringe pattern is related to the displacement of the two images of a co-ordinate system in the emergent beam, as seen through the four-mirror system. The effects of all such displacements are discussed and illustrated. The effect of mirror movements on these displacements is analysed, to show the number of fine adjustments required, and the effect of each. A section on the imperfections of the optical elements includes discussions of the effects of differences of thickness, incidence and refractive index, wedge angles, surface flatness and refractive index variation. Except for the permissible wedge angles, the limits found necessary are less strict than those usually given. Aberration of the collimating lens has practically no effect. A review of methods of adjustment of the interferometer includes descriptions of some of the well-known methods and of two which do not appear to have been described previously. Of these, one is a method for obtaining a parallelogram arrangement, which was used by K. J. Habell, and the other is an accurate method for final adjustment based on the source-plane fringe pattern.