The Characterization and Application of Two Liquid Crystal Mixtures in the Low THz Region

Andong Zheng,Hongbo Lu,Xiujun Chu,Guangsheng Deng,Jun Yang,Sheng Gao,Pengjun Wang,Peng Wang,Zhiping Yin

doi:10.3390/cryst10020099

Abstract

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 (Δn) characteristics of the two LC nematic mixtures E7-2 (Δn = 0.260) and S200-2 (Δn = 0.298) are greater than those of the commercial LC E7 (Δn = 0.224) and S200 (Δn = 0.266). The properties (TN-I, ε//, Δɛ, K11, and K33) 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.

Highlights

In recent years, terahertz (THz) technologies have been used for THz wireless communications [1], THz imaging [2], biomedical research [3], and environmental monitoring [4]
The experimental results show that the results show that the metrics ΔT, insertion loss (IL) ofLC
The nematic liquid crystal (NLC) mixture of E7-2 and S200-2 were composed of Shijiangzhuang, Hebei province, China.)

Summary

Introduction

Terahertz (THz) technologies have been used for THz wireless communications [1], THz imaging [2], biomedical research [3], and environmental monitoring [4]. THz functional devices have gradually become a major research topic [5]. There are many kinds of modulation mechanisms in the relevant materials that have been reported, such as graphene [6,7], VO2 [8], electron gas [9], and liquid crystals (LCs) [10]. In 2014, the nematic liquid crystal (NLC)-based metamaterial was designed, fabricated, and used in THz tunable devices [11]. In 2015, Kowerdziej et al proposed a tunable LC THz MM device. As the applied voltage increased to 200 V, a maximum tuning value of 22% occurred at 0.82 THz. the modulation depth of the LC-based metamaterial is still very narrow and the bias voltage is too high

Methods

Results

Conclusion