Azimuthal alignments in ellipsometry: a high-precision method using a polarization modulator

An original (to the best of our knowledge) method to achieve azimuthal alignments of all polarizing components in ellipsometry is presented. It is an accurate nulling method, and it is easy to implement and can be used with any isotropic reflecting layer. It also allows one to check the eventual presence of surface anisotropy. The ferrofluid modulator used in this setup is briefly described. Measurements made for three reflecting surfaces (fused silica, silicon, and germanium) are presented.