Novel ellipsometry based on the manipulation of vectorial optical field and digital image processing

摘要

Ellipsometry is a kind of measuring techique to research the optical properties of materials by utilizing the polarization characteristics of light. The key of the optical ellipsometry is to utilize the polarization transformation that occurs as a beam of polarized light is reflected or transmitted through the dielectric film, and the characteristic parameters of this film can be obtained by measuring this transformation. In this paper, we present a novel scheme of ellipsometry that can extract the ellipsometric parameters of the reflected light from a single shot, which is achieved by using the vectorial optical field and digital image processing technique. In order to obtain the ellipsometric parameters of the reflected light, a zero-order vortex half-wave retarder is placed after the thin film to transfer the reflected elliptically polarized light to a vectorial optical field. When this vectorial optical field is analyzed by a linear polarizer, the transmitted light pattern with an hourglass-shaped intensity distribution can be obtained, and two gradual dark and bright areas show alternately. The azimuth angles and the intensity values of the central lines of dark and bright areas are related to the ellipsometric parameters, which can be obtained by processing the hourglass-shaped intensity image with our specially designed image processing algorithm. The theoretical model of our presented ellipsometer system is established firstly by using the Jones matrix theory, and the simulating and analyzing formulas are obtained based on the model. Some numerical analyzing studies have been carried out to validate the feasibility of our scheme, and the results of the simulated research indicate that the retrieved values of the ellipsometric parameters are consistent with the preset values.