An electrically tuned phase shifter based on the single slot unit cell and liquid crystal for a reconfigurable reflectarray antenna was presented. The simulation and measured results obtained at the F-band were used to demonstrate that the dielectric properties of a nematic state liquid crystal could be exploited to realize a slot unit cell phase shifter for the reconfigurable reflectarrays antennas. By reducing the inhomogeneous of the external electric field in the liquid crystal layer, a lower control voltage and improved model accuracy was obtained. In the experiments test, the achieved saturation bias voltage (10 V) was smaller than the previously reported structure, and the phase shift of the reflectarray greater than 300° was achieved in the frequency range 121.5–126 GHz. The maximum phase shift of 306° occurred at 124.5 GHz.

This paper introduces a tunable metamaterial absorber (MA) based on polymer network liquid crystal (PNLC) in the terahertz (THz) frequency band. Under the optimal polymerization condition, through electrical control of the orientation of the PNLC embedded in the frequency selective surface, the resonant frequency of the absorber can be tuned from 416.5 to 405.0 GHz, corresponding to fractional frequency bandwidth of 2.8%. The experimental results show that the proposed MA based on the PNLC offers an adjustment time of 10 ms and recovery time of 85 ms, which is significantly faster than the tunable metamaterial devices based on conventional nematic liquid crystal (LC).

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In the previous work, two new nematic liquid crystal (NLC) mixtures, E7-2 and S200-2, were produced by adding eight LC monomers to two commercial LCs S200 and E7, respectively. At λ = 589 nm, the birefringence (∆n) characteristics of the two LC nematic mixtures E7-2 (∆n = 0.260) and S200-2 (∆n = 0.298) are greater than those of the commercial LC E7 (∆n = 0.224) and S200 (∆n = 0.266). The properties (T N-I , ε // , ∆ , K 11 , and K 33 ) of these four NLCs were measured. A double-layer metal loop arrays modulation structure based on metamaterial (MM) metal-dielectric-metal (MDM) was designed and fabricated for use in the THz frequency range. The results show that the LC mixtures E7-2 and S200-2 have greater modulation depth (MD) and less modulation insertion loss (IL) than E7 and S200 at THz frequencies. The results show that LC mixtures have significant potential for designing active tunable LC-based devices in the THz and visible light range.there has been increasing interest in characterizing LC materials as a tunable materials unit for THz applications, such as modulators [15], filters [16], phase shifters [17,18], switches [19], and absorbers [20]. High birefringence nematic liquid crystals have been broadly researched to satisfy the needs of the extensive variety of optical infrared range photonics devices [21]. Compared to NLCs for use in the visible region, these NLCs show weak birefringence in THz regions. Some papers demonstrated that the birefringence exhibited by LCs is relatively low in the THz band [22,23]. The relatively low birefringence can lead to performance limitations for THz electronically tunable devices. An effective way to solve these problems is to synthesize high birefringence LC compound materials. Recently, Vieweg et al. reported the birefringence of the LC mixture BL037, from ∆n = 0.16 at 0.5 THz to ∆n = 0.2 at 2.5 THz [24]. Wang et al. proposed a new LC mixture, called NJU-LDn-4, with a large birefringence of 0.306 from 0.4 to 1.6 THz [25]. Reuter et al. proposed the high birefringence LC mixtures 1852 (∆n = 0.33 at 0.5 THz) and 1825 (∆n = 0.38 at 0.5 THz) [26].In the previous work, two new NLCs mixtures (E7-2 and S200-2) were proposed [27], which can be used to construct tunable THz devices due to tunable dielectric properties. In this paper, the more physical properties of these mixture LCs were measured and analyzed. Currently, to develop effective terahertz modulators and switches, electromagnetic metamaterials, an artificial composite material, are essential components. They consist of two-or three-dimensional arrays of tailored metallic unit cells [28]. In order to directly manipulate THz waves, we demonstrated THz LC modulators based on electromagnetic metamaterials and E7-2, S200-2 LC mixtures. The experimental results show that the metrics ∆T, MD, and IL of these mixture-based LCs can be significantly higher than those of commercial LCs in their working frequency band. This suggests that two high birefringence NLCs can also be used to fabricate highly efficient and functional...