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

Abstract

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.

Impact of titanium dioxide nanoparticles on purification and contamination of nematic liquid crystals

“…The area of LCs for non-display applications is also rapidly growing. The application of LCs includes metamaterials [4], photonic crystals [5], plasmonic structures [6], THz devices [7], sensors [8], diffractive optics [9], adaptive lens technologies [10] and vision correction [11], as well as tunable filters [12] and dispersion for imaging [13]. In addition, nanoparticles can induce other new functions in liquid crystals, including improved response time [14–15], surface plasmon resonance [16], and improvements in alignment [17].…”

A Review of THz Modulators with Dynamic Tunable Metasurfaces

“…Due to the dielectric and optical anisotropy, liquid crystal materials have great application potential. The direction of liquid crystal molecules can be adjusted through an external field to effectively regulate the intensity, phase, and polarization of electromagnetic waves in various frequency bands [18,28,144,145,146,147,148]. In the terahertz range, although the large absorption loss and scattering are problems, the birefringence characteristics of liquid crystals is much larger than that of ordinary anisotropic materials.…”

Active metamaterial nearly perfect light absorbers: a review [Invited]

“…LCs have several phases such as nematic, smectic, cholesteric, and isotropic. These phases can be tuned by external stimuli (e.g., gate voltage and heating) [102][103][104][105][106] and can be employed to achieve active MPAs [150][151][152][153]. As an example of the phase transformation, we can refer to nematic LCs.…”