Homodyne Quadrature Displacement Interferometer. Experimental Results

Abstract

In the previous work [1], the results of mathematical modeling of the optical scheme of a single-pass homodyne displacement interferometer with the quadrature principle of phase recording have been presented. The interferometer has been built according to the Michelson scheme and polarization optical elements have been used to obtain quadrature signals. The interferometer has been 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. This paper presents experimental studies of the operation of a homodyne quadrature displacement interferometer model. In this work, a conventional (non-polarization) beam splitter and two polarizers have been used in the optical scheme of a homodyne interferometer in the recording unit instead of a polarization beam splitter. This added additional degrees of freedom when aligning the optical channels for recording interference channels and has made it possible to achieve the required signal shift of 90° with an accuracy of 0.1°. As a result, a displacement measurement error of 0.2 nm has been experimentally achieved. Generalized expressions have been obtained for quadrature signals for arbitrary azimuths of polarizers in three channels of recording of interference signals. An assessment of the accuracy of displacement measurements using a quadrature homodyne interferometer has been carried out and it has been found that the extended uncertainty of such measurements does not exceed 0.3 nm.