Laser Polarization State Measurement in Heterodyne Interferometry

In heterodyne interferometry the accuracy is partly limited by non-linearity errors. These errors are caused by laser polarization state errors and errors of optical components, including alignment. In this paper we present two independent methods to measure the actual polarization state properties of the laser beam. Uncertainties and differences between the methods are discussed. Measurement of a commercially available laser source show ellipticity up to 1:170 in the E-fields and 0.3° deviation of orthogonality. This may cause a non-linearity calculated in a heterodyne interferometer of 0.6 nm.