Optimization of wavefront measurement method for polarization modulators

Polarization modulators are core components in polarimetric imaging, and measuring their wavefront aberration is a prerequisite for achieving high-resolution polarimetric imaging observations. However, when using a Fizeau interferometer for measuring the wavefront aberration of a polarization modulator, the polarization modulator under test may significantly affect the contrast of interference fringes due to additional polarization effects, thereby degrading the accuracy of wavefront aberration measurement. In this study, a polarization model for the Fizeau interferometer-tailored for wavefront testing of polarization-sensitive components-was developed, and its measurement limitations were systematically analyzed. An optimization method employing a standard quarter-wave plate is presented, which improves fringe contrast compared to traditional interferometric configurations, and its efficacy is experimentally verified. Results demonstrate that this method enables accurate wavefront measurement of Stokes parameter-based polarization modulators under arbitrary configurations. Furthermore, the approach can be extended to general polarization optical components and systems, thereby broadening the applicability of Fizeau laser interferometers in polarization-sensitive optical systems and improving both the versatility and accuracy of measurements.