THz media characterization by means of coherent homodyne detection, results and potential applications

This paper describes the performance of a coherent homodyne spectrometer to preserve phase information of the THz electric field. Thereby, optical constants of a high resistive silicon sample are presented between 200 GHz and 1.2 THz. The phase shift introduced by such a thick sample is much greater than 2 pi, and the manner of solving the ambiguity of the modulo 2 pi is discussed and can be used to surround the refractive index mainly at high frequency where the signal to noise ratio decreases. The analysis of the coherent homodyne signal as a function as the frequency at a fixed delay line permits deduction of sample thickness or measurement of distance without any mechanical displacement, and so facilitates potential ranging and tomography studies.