Liquid crystals have been employed for several decades in devices such as phase shifters, Fabry-Perot filters, polarizers, phase gratings, and Bragg switches at optical frequencies. However it is only recently that such devices have been demonstrated at terahertz frequencies. This is because of several fundamental frequency dependent relationships between device properties and frequency of operation. When designing liquid crystal devices, we need to find liquid crystals with high birefringence, low viscosity and low absorption at terahertz frequencies. In this paper we will present some measurements and simulations of potentially suitable liquid crystal mixtures.
New terahertz (THz) optical devices which can control the optical properties of THz waves are needed to broaden the
application area of THz technology. Liquid crystals (LCs) are very attractive materials for developing such devices
because they have outstanding properties such as sensitivity to applied electric fields, chemical stability, relatively large
birefringence and moderate absorption in the THz range. LCs need to be optimized to have a large birefringence and
small absorption in the THz range. In this paper, we have investigated optical properties of a set of LCs in the THz range:
E7, BL037, and RDP-97304. Optical parameters for the ordinary and extraordinary axis of LCs were acquired using THz
time-domain spectroscopy and THz air-biased coherent detection system. We found that RDP-97304 has the largest
birefringence and smallest absorption compared to E7 and BL037 in the THz range. It is thus a good candidate to design
fast and efficient THz optical devices.