Abstract-Terahertz Time-Domain Polarimetry for Principal Optical Axes of Anisotropic Crystals

 

Alexander Mamrashev, Fedor Minakov, Nazar Nikolaev, Valery Antsygin, 

https://www.mdpi.com/2304-6732/8/6/213/pdf

We propose a method for measuring the terahertz properties for two principal optical axes of anisotropic crystals without optical activity using terahertz time-domain spectroscopy (THzTDS). The method put forward in this paper utilizes the inherent polarization sensitivity of the THz-TDS electro-optic detection system. We demonstrate the practical application of the method by measuring the temperature dependence of the refractive index and the absorption coefficient of a lithium triborate crystal for three optical axes.

Abstract-Simulations of some physical parameters of homologous series of nBT and nCHBT at 0.3–20.0 THz

K. Sielezin,  Polan R. Kowerdziej,  J. Parka,

https://www.tandfonline.com/doi/abs/10.1080/02678292.2018.1563918?journalCode=tlct20

In this work, the terahertz (THz) absorption of homologous series of isothiocyanobiphenyls (nBT) and 4-(trans-4ʹ-n-alkylcyclohexyl)isothiocyanato-benzene (nCHBT) are simulated by using the density functional theory (DFT) method. Numerical results show that absorption of the tested nematic liquid crystals (NLCs) varies up to 0.04 in the broad range of 0.3–20.0 THz and takes maximum value in the range of 9–14 THz.

In addition, the values of molecular polarisabilities (αo, αe) increase with the increase in the number of carbon atoms in the alkyl chain, while refractive indices (no, ne) decreases. The calculated birefringence (Δn) values for nCHBT are approximately twice as large as the birefringence value for nBT. It is crucial to examine these series of nematic liquid crystals at THz frequencies due to the role of soft matter in various switchable THz components.