Homodyne quadrature displacement interferometer. Experimental results

In the previous work, the results of mathematical modeling of the optical scheme of a single-pass homodyne interferometer of displacements with the quadrature principle of phase registration are presented. The interferometer is built according to the Michelson scheme, and polarizing optical elements are used to obtain quadrature signals. The interferometer is supposed to be used as part of a new national standard of the kilogram based on watt balance method for precision measurements of the displacement and speed of the coil in the vertical direction. In this paper, experimental studies of the operation of a model of a homodyne quadrature displacement interferometer are presented. In this work, instead of a polarization beam splitter, a conventional (non-polarization) beam splitter and two polarizers are used in the optical scheme of a homodyne interferometer in the registration units. This added additional degrees of freedom when aligning optical channels for recording interference channels and made it possible to achieve the required signal shift by 90$^\circ$ with an accuracy of 0.1$^\circ$. As a result, a displacement measurement error of 02. nm was experimentally achieved. Generalized expressions are obtained for quadrature signals for arbitrary azimuths of polarizers in three channels of recording interference signals. An assessment of the accuracy of displacement measurements using a quadrature homodyne interferometer was carried out and it was obtained that the expanded uncertainty of such measurements does not exceed 0.3 nm.