The role of the polarization in ATIR proximity sensing

The proximity sensing based on the attenuated total internal reflection (ATIR) is a technique that allows us to control the separation between two planes—the attenuating media surface and dielectric boundary, in the neighborhood of which the total internal reflection (TIR) takes place. This measurement supposes known optical constants of all media. An effect of lateral fringe shift and variations in intensity distribution of the interferometrical signal were observed during the measurements by an angular sheering polarization interferometer. The simple theory here proposed explains these effects. For that reason the relationship between the polarization effects, accompanying the ATIR and the output interferometrical signal had to be taken into account. To explain the variations of interference fringes intensity topography, the evolution of the Stokes parameters as a function of the gap width for Si attenuator is studied numerically.