Transmittance of CsI, AgCl, KRS-5, and KRS-6 crystals in the terahertz range

The spectral dependences of the transmittance of CsI, AgCl, KRS-5 and KRS-6 single crystals in the infrared (IR) and terahertz (THz) ranges have been measured. The spectral dependences of the absorption (attenuation) coefficient of these crystals were calculated in the spectral range of 200–3000 $\mu$m. It was found, that these crystals are transparent in the millimeter range, which makes it possible to use materials when working with THz radiation. It should be noted that, in contrast to the IR spectral region, the optical quality of the surface of the crystal samples practically does not affect the transmission in the millimeter range.