Interferometric ellipsometer.

We describe an interferometric ellipsometer that, in contrast to previous designs, requires a single reflection from a sample surface so that tanpsi and Delta are measured directly. A reference beam is created in one arm of a modified Mach-Zehnder interferometer such that the p and s polarizations have a common phase and fixed relative amplitude, irrespective of the sample. This beam is combined interferometrically with the measurement beam. The output beam is spatially separated into its polarization components and temporal fringes created at the photodetectors via mechanical scanning of one of the mirrors. Measurements made on a reference SiO(2) film are in excellent agreement with the calibration certificate while those made on a glass surface demonstrate measurement capabilities for low reflectivity samples. Estimates of the noise performance indicate a precision, in air, of approximately 41 pm.