Calibration of achromatic Fresnel rhombs with an elliptical retarder model in Mueller matrix ellipsometers

Abstract

Fresnel rhombs are the most achromatic form of retarders available and they are suitable compensating elements for spectroscopic Mueller matrix ellipsometers. However, the small stress in the rhomb caused by the mount or produced during the fabrication can affect the ellipsometry measurements with non-negligible systematic errors, due to the relatively long path length of light inside the rhomb. This work describes a calibration method that considers the non-ideal response of the Fresnel rhomb, and that it is especially well suited for calibrating Mueller matrix ellipsometers. The method describes each rhomb as the most general form of an elliptical retarder with a small ellipticity, instead of simply assuming that they behave as linear retarders. After this calibration, we show that the systematic errors of measurements are significantly decreased.