Metrology of complex refractive index for solids in the terahertz regime using frequency domain spectroscopy

We present a metrological study of a new technique for measuring the complex refractive indices of solids in the THz regime. The technique is widely applicable thanks to requiring only frequency-domain spectroscopy, and is shown to be capable of high accuracy reconstruction of the complex refractive index (RI) spectrum. We quantify the sensitivity to experimental imperfections such as noise, showing that the new technique is more robust than previous methods. We demonstrate the extraction of RI of crystalline Si between 2–20 THz using this method, and comment on the capability to discriminate between absorption and scattering using only a power-transmission measurement.