Methods for drift stabilization and photomultiplier linearization for photometric ellipsometers and polarimeters.

We describe simple modifications to photometric polarimeter and ellipsometer systems that greatly reduce nonlinearity, component drift, and digital noise effects. A photomultiplier feedback circuit is described and analyzed that varies the effective system linearity by means of a single control. Linearity to 5 x 10(-4) over more than three orders of magnitude of incident light intensity is obtained.

High precision scanning ellipsometer.

We describe the design, construction, alignment, and calibration of a photometric ellipsometer of the rotating-analyzer type. Data are obtained by digital sampling of the transmitted flux with an analog-to-digital converter, followed by Fourier transforming of the accumulated data with a dedicated minicomputer. With an operating mechanical rotation frequency of 74 Hz, a data acquisition cycle requires less than 7 msec.

Geometrically exact ellipsometer alignment.

A procedure is outlined in which the symmetry of the ellipsometer is used to provide the information needed for its own alignment. Alignment is based upon four null measurements taken on a transparent reflecting surface. These are related to the tilt angles of the polarizer and analyzer telescope arms, and reference angles for which the transmitted polarization vectors of the analyzer and polarizer prisms lie in the plane of incidence.