Precise Determination of the Refractive Index of Samples Showing Low Transmission Bands by THz Time-Domain Spectroscopy

In this paper, we propose a method to determine the refractive index and the absorption coefficient of samples showing spectral bands of very low transmission. The method, takes advantages of both transmission and reflection terahertz time-domain spectroscopy (THz-TDS) to obtain more precise optical constants than when only reflection measurement is used. It has been then validated using pellets made of maltose, which exhibits resonant lines within the THz spectral range.