Measurement of refractive indices and absorption coefficients for glass materials and nematic liquid crystals in THz frequency band

Many optical devices that can be used in terahertz (THz) systems are continuously being researched and developed. Among them, liquid crystal (LC)-based polarizers and phase-shifting devices have been developed. The LC devices used in the THz systems are fabricated in the form of a cell. The substrate of the cell should be transparent and non-birefringent with low absorption in the THz frequency range. In this paper, we report the refractive indices and birefringence measurement results for glass materials, such as slide glass, cover glass, A-cut quartz, and Z-cut quartz in the THz band. Among them, 5CB and E7 nematic LC (NLC) cells are prepared using Z-cut quartz as a substrate. We report the results of the refractive indices, absorption coefficients, and birefringence measurements of each NLC cell in the THz band. It is expected that this result can be used as a LC-based optical device in the THz band in future.