Calibration of elliptical retarders in Mueller matrix spectroscopic polarimetry and ellipsometry

The dual-rotating compensator Mueller matrix ellipsometer is a well-established and commercially mature instrument, with its compensators typically modeled as linear retarders. However, in many practical implementations, these compensators behave as elliptical retarders rather than purely linear ones. Accurate calibration of the compensators is essential to ensure proper instrument functionality, but calibrating elliptical retarders is considerably more complex than calibrating linear ones. This work describes a method for calibrating elliptical retarders by utilizing the motion reciprocity symmetry observed when polarized light is transmitted through a homogeneous depolarizing sample. The method enables simultaneous calibration of the six ellipsometric parameters of dual rotating elliptical retarders, and its accuracy has been experimentally validated.