A NEW AND HIGH-PRECISION ACHROMATIC ELLIPSOMETER - A 2-CHANNEL AND POLARIZATION ROTATOR METHOD

We present a new ellipsometric method that does not use a quarter-wave plate, an optical compensator, or a polarizing component rotating at a fixed velocity. The implemented set-up is very sensitive, even if reflected light is either circular or quasi-circular, i.e. when the apparatus works in the best conditions of accuracy (angle of incidence approximately equal to principal angle). Furthermore, the adjustment is made by rotating the polarizer only (maximum angle of rotation is less than a few tens of degrees), all other polarizing components being fixed. In the automatic set-up, the polarizer azimuth angle is locked on the ellipsometric angle PSI = arctan\r(p)/r(s)\. This ellipsometer uses a Wollaston or Foster prism and a highly efficient Faraday modulator, with water multipassed (visible region) or ferrofluid material (near-IR).