Determination of fast axis and phase retardation of wave plates using polarization common-path vortex interferometry

This Letter introduces a method for identifying the fast axis and phase retardation of wave plates by means of polarization common-path vortex interferometry. The technique utilizes a composite polarized vortex beam interacting with the wave plate under test. By analyzing the azimuth angle of the dark fringe in the interference pattern, the wave plate's characteristics are accurately extracted. The method involves rotating the wave plate to align its principal axes, followed by determining the fast-axis orientation and the phase retardation based on the direction of the dark fringe. The measurement theory is presented, and the feasibility of the technique is substantiated through experimental demonstration.