Measurement Method of Polarization Properties of Protected Aluminum Coating on Astronomical Mirror

The instrument polarization effect of the telescope, which is mainly caused by the reflection polarization effect of metal coatings on mirrors, is the principal technical problem facing the current high-precision astronomical polarimetry. It is essential to perform accurate and comprehensive measurements and research on the polarization properties of metal coating materials in the laboratory in order to eliminate the influence of instrument polarization on the accuracy of polarimetry. This paper proposes a polarization properties measurement method for the protected aluminum coating. This method can directly measure the key elements of the Mueller matrix of the protected aluminum coating by two photoelectric modulations at a multiple-angle-of-incidence spectrum. This method also retrieves the optical parameters based on the double-layer model without dispersion model and parameter assumptions. The retrieval results of the method in this paper are consistent with those obtained by traditional methods, and the method in this paper can fully characterize the polarization properties.