Highly birefringent, low-loss liquid crystals for terahertz applications

Abstract

With growing interest in switchable devices for the THz frequency range, there is a strong demand for liquid crystals (LC) exhibiting both a high birefringence and a low absorption. We present the refractive index and absorption coefficient of the liquid crystal mixtures 1852 and 1825 in the frequency range between 0.2 and 2.5 THz. Both mixtures are designed specifically for high birefringence Δn of 0.32 and 0.38, respectively, in the THz region. In addition, they show low absorption coefficients for both ordinary and extraordinary polarization. This low absorbance in combination with the high birefringence makes these LCs particularly well suited for applications in switchable devices for THz optics

High Birefringence Liquid Crystals

“…Properties of the mixture 1825 are at this moment the best recognized. It was tested in different photonic devices working in infrared as well as GHz and THz range with a good performance [52,129,130]. It shows the strong dispersion of birefringence in a visible range and the small birefringence in the infrared region and THz region (see Figure 14), as is predicted by the Cauchy model and experimentally verified by Wu et al [131,132].…”

Distinguishing Gasoline Engine Oils of Different Viscosities Using Terahertz Time-Domain Spectroscopy

“…Using this scheme many substances haven been characterized. This includes gases [44][45], liquids [46], liquid crystals [47][48], and different types of solids [49][50][51][52][53]. But also artwork [54] and plants [55][56] have been investigated by THz-TDS.…”

Using Terahertz Time-Domain Spectroscopy to Discriminate among Water Contamination Levels in Diesel Engine Oil

“…THz-TDS uses ultrashort laser pulses and photoconductive antennas (Hunsche et al, 1998;Moreno et al, 2014;Tani et al, 1997) or nonlinear crystals (Moreno et al, 2014). THz-TDS has been used to characterize solids (Jiang et al, 2014;LloydHughes et al, 2006;Misochko et al, 1998;Nickel et al, 2014;Wietzke et al, 2011), liquids (Wang et al, 2014), liquid crystals (Reuter et al, 2013;Vieweg et al, 2010), gases (Harde et al, 1995;Mittleman et al, 1998), and plants (Born et al, 2014;Castro-Camus et al, 2013).…”