Experimental study on terahertz metamaterial embedded in nematic liquid crystal

Kowerdziej, Rafał; Jaroszewicz, Leszek R.; Olifierczuk, Marek; Parka, Janusz

doi:10.1063/1.4914032

Cited by 39 publications

(22 citation statements)

References 10 publications

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“…Various types of active metasurfaces employ different mechanisms for tuning the liquid crystal, i.e. applying electric field 99,100,108,[197][198][199][200][201][202][203][204][205][206][207][208][209][210][211][212][213] , magnetic field 67,68 , optical pumping 101,214 , or thermal heating 102,103,109,215,216 . New types of light-driven plasmonic color filters by (e, f) ref.…”

Section: Liquid Crystals (Lcs)mentioning

confidence: 99%

Tunable and reconfigurable metasurfaces and metadevices

Nemati

Wang

Hong

et al. 2018

Opto-Electronic Advances

320

205

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Metasurfaces, two-dimensional equivalents of metamaterials, are engineered surfaces consisting of deep subwavelength features that have full control of the electromagnetic waves. Metasurfaces are not only being applied to the current devices throughout the electromagnetic spectrum from microwave to optics but also inspiring many new thrilling applications such as programmable on-demand optics and photonics in future. In order to overcome the limits imposed by passive metasurfaces, extensive researches have been put on utilizing different materials and mechanisms to design active metasurfaces. In this paper, we review the recent progress in tunable and reconfigurable metasurfaces and metadevices through the different active materials deployed together with the different control mechanisms including electrical, thermal, optical, mechanical, and magnetic, and provide the perspective for their future development for applications.

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Section: Liquid Crystals (Lcs)mentioning

confidence: 99%

Tunable and reconfigurable metasurfaces and metadevices

Nemati

Wang

Hong

et al. 2018

Opto-Electronic Advances

320

205

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“…Liquid crystals, in which the anisotropy can be changed by electric or magnetic means, have been successful at controlling and propagating electromagnetic waves. Wavelengths have included millimeter waves, visible light, and THz waves [12][13][14]. High birefringence values are especially important for devices working in the millimeter or THz ranges of electromagnetic waves.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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...

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“…[23][24][25][26] Several LC tunable THz metamaterial filters were realized by embedding metamaterials inside LC cells where either two Indium Tin Oxide layers or the metamaterial structure made of noble metal along with a conductive wire were used as two electrodes to apply a bias voltage on LC cell and thereby to align LC molecules in the direction of created bias electric field. [25][26][27][28][29] However, these approaches usually necessitate applying a large bias voltage to fully utilize birefringent characteristic of LCs due to the creation of non-uniform and omnidirectional bias electric filed inside LC. To better employ LC birefringent properties, two conductive but THz-transparent electrodes are required such that a uniform and unidirectional bias electric field is created between electrodes.…”

mentioning

confidence: 99%

Investigation of tunable terahertz metamaterial perfect absorber with anisotropic dielectric liquid crystal

et al. 2017

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In this letter, we report the unique design, simulation and experimental verification of an electrically tunable THz metamaterial perfect absorber consisting of complementary split ring resonator (CSRR) arrays integrated with liquid crystal as the subwavelength spacer in between. We observe a shift in resonance frequency of about 5.0 GHz at 0.567 THz with a 5 V bias voltage at 1KHz between the CSRR and the metal backplane, while the absorbance and full width at half maximum bandwidth are maintained at 90% and 0.025 THz, respectively. Simulated absorption spectrum by using a uniaxial model of LC matches perfectly the experiment data and demonstrates that the effective refractive index of LC changes between 1.5 and 1.7 by sweeping a 1 kHz bias voltage from 0 V to 5 V. By matching simulation and experiment for different bias voltages, we also estimate the angle of LC molecules versus the bias voltage. Additionally, we study the created THz fields inside the spacer to gain a better insight of the characteristics of tunable response of this device. This structure and associated study can support the design of liquid crystal based tunable terahertz detectors and sensors for various applications.

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Experimental study on terahertz metamaterial embedded in nematic liquid crystal

Cited by 39 publications

References 10 publications

Tunable and reconfigurable metasurfaces and metadevices

Tunable and reconfigurable metasurfaces and metadevices

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

Investigation of tunable terahertz metamaterial perfect absorber with anisotropic dielectric liquid crystal

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