Passively Tunable Terahertz Filters Using Liquid Crystal Cells Coated with Metamaterials

Abstract

Liquid crystal (LC) cells that are coated with metamaterials are fabricated in this work. The LC directors in the cells are aligned by rubbed polyimide layers, and make angles θ of 0°, 45°, and 90° with respect to the gaps of the split-ring resonators (SRRs) of the metamaterials. Experimental results display that the resonance frequencies of the metamaterials in these cells increase with an increase in θ, and the cells have a maximum frequency shifting region of 18 GHz. Simulated results reveal that the increase in the resonance frequencies arises from the birefringence of the LC, and the LC has a birefringence of 0.15 in the terahertz region. The resonance frequencies of the metamaterials are shifted by the rubbing directions of the polyimide layers, so the LC cells coated with the metamaterials are passively tunable terahertz filters. The passively tunable terahertz filters exhibit promising applications on terahertz communication, terahertz sensing, and terahertz imaging.

Metamaterial Absorbers: From Tunable Surface to Structural Transformation

“…[ 24,32,90–93 ] Some materials, such as ferrite materials (FMs) and liquid crystals (LCs), are capable of varying μ r and ε r under the magnetic force and electric field, providing the ability to manipulate the EM properties of MAs. [ 60,92,94,95 ] Alternatively, dynamically controlling dielectric thickness is a novel tuning technique to realize tunable/reconfigurable MAs, as illustrated in Figure 2h. With this technique, resonant frequency can be shifted when thickness of the dielectric spacer varies.…”

Difunctional terahertz metasurface with switchable polarization conversion and absorption by VO2 and photosensitive silicon

“…6 Metasurface is a two-dimensional status of metamaterials. 7 In the THz region, metasurfaces can exhibit many unique properties that can be applied to design various functional devices, such as beam splitters, 8 biosensors, 9 filters, 10 polarization converters, 11 and absorbers. 12 Especially, polarization converters and absorbers have attracted increasing attention.…”

Effect of Thicknesses of Liquid Crystal Layers on Shift of Resonance Frequencies of Metamaterials

“…Metamaterials have attracted considerable interest thanks to their unusual electromagnetic resonance [1][2][3][4][5][6][7]. The resonance frequencies of metamaterials are determined by their geometrical structures [1][2][3] and the refractive indices of the media that surround the metamaterials [4][5][6][7][8][9][10][11]. As a result, metamaterials have the potential to develop sensors, intensity modulators, and frequency filters.…”

“…As a result, metamaterials have the potential to develop sensors, intensity modulators, and frequency filters. The resonance frequencies of terahertz metamaterials can be tuned using liquid crystals (LCs) owing to their large birefringences [6][7][8][9][10][11]. Chen et.…”