Monostatic microwave ellipsometry for material characterization

Abstract

We propose Microwave ellipsometry based on monostatic measurements in which the transmitter and receiver are located in the same location. The traditional ellipsometry technique is based on bi-static measurements in which the polarization state of the reflected wave from a sample is analyzed to estimate its electromagnetic properties. Initially, the ellipsometric methods had been applied in the optical spectrum since the wavelengths and the constituent atomic structure are comparable leading to the strong matter-wave interaction and polarization changes. Thanks to the recent advancements in metasurfaces, chiral sensing can now be potentially applied to characterize materials at the microwave frequencies in a compact laboratory environment. In this paper, we lay down the fundamentals of microwave monostatic elliposmetry method. We demonstrate the permittivity detection by a numerically simulated monostatic sensing set-up composed of L-shaped unit chiral unit cells etched on the dielectric sample and illuminated by a monochromatic linearly polarized electromagnetic source. We construct the Jones matrix to extract the polarization states from the reflection coefficients. The determination of the reflection coefficients is greatly simplified by using a cross-dipole antenna receiver which provides the ratio of the two corresponding orthogonal complex currents.