Ellipsometry in the terahertz range for liquid identification

We present a method to determine the optical constants of a liquid at a given frequency in the terahertz range, by using a backward-wave oscillator as a continuous-wave source and an ellipsometric measurement setup consisting of two wire-grid polarizers. The liquid sample is placed on the total internal reflection surface of a silicon prism, thus changing the polarization state of the wave. By rotating the analyzer, useful information can be gathered about the optical properties of the liquid. We expect that this will ultimately allow the liquid identification or analysis.