Measuring the Laser Polarization State and PBS Transmission Coefficients in a Heterodyne Laser Interferometer

By placing a polarizer between a dual-frequency laser source (DFLS) and a polarizing beam splitter (PBS), two optical beat signals are formed; then, the transmission coefficients of the PBS and the polarization state parameters of the DFLS can be simultaneously measured without coupling while achieving high accuracy. We obtained explicit equations for the ellipticity angles of the laser beam components and explained the relationship between the extreme values of the beat amplitude and the laser polarization state parameters, which obtain less uncertainties than the existing work. The method is validated experimentally. Measuring these parameters is important to compensate for nonlinearity errors in heterodyne laser interferometers and assess the quality of devices.