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Terahertz MEMS metamaterials
Published in Guangya Zhou, Chengkuo Lee, Optical MEMS, Nanophotonics, and Their Applications, 2017
Prakash Pitchappa, Chengkuo Lee
Electrostatic actuation was also reported for active tuning of wavelength selective THz absorption. The metamaterial absorber is a trilayer structure, consisting of a continuous bottom metal and top metamaterial pattern with a dielectric layer. The bottom metal acts as the reflector and prevents any transmission through the device. The dielectric layer acts as the spacer between the two layers. Hence, by releasing the metamaterial patterns, an out-of-plane air gap can be achieved in between the bottom reflector and the metamaterial layers that act as the spacer layer. Through electrostatic actuation, the air gap, and hence the effective spacer thickness, along with angle of incidence can be actively altered. As the air gap was reduced with increasing voltage, the peak absorption frequency red shifted accordingly. [68].
Textile-based 3D metamaterial absorber design for X-band application
Published in Waves in Random and Complex Media, 2022
Ediz Erdem, Ahmet Hayrettin Yuzer
A metamaterial absorber (MMA) is obtained by combining a periodic resonator, a dielectric layer, and a conductive layer. In this study, two different types of textile fabrics were used in the designed textile-based MMA structure. One of them was a weft-knitted fabric and the other one was plain weave fabric. For periodic layer, 3D structure and its size corresponds to the X-band sub-wavelengths the weft-knitted fabric was preferred. Similarly, the reason for choosing the plain weave was it acts as a conductive surface due to the narrow loop gap and could be used as the conductive layer. Flexible double-sided bonding tape was used as the dielectric layer to hold these two surfaces together. As well as perfect absorption, washable, wearable, low weight, ease of production, applicability, low weight, cost, and flexible textile-based MMA was obtained by combining three layers.
Tunable dual-band liquid crystal based near-infrared perfect metamaterial absorber with high-loss metal
Published in Liquid Crystals, 2019
Rafał Kowerdziej, Leszek Jaroszewicz
In summary, a tunable dual-band near-infrared metamaterial absorber is proposed using a combination of highly birefringent liquid crystal and high-loss metal. The numerical analysis demonstrates that absorbance can be self-regulated both in terms of its magnitude (up to 26.3%) and wavelength (up to 8 THz) by simply switching of liquid crystal alignment. Owing to the high optical loss of Ti, perfect absorbance exceeding 99.4% may by achieved at 328 THz and 364 THz. Furthermore, by fusing the low-Q LSP resonance and the generated PSP resonance on Ti-LC interface the absorption bandwidth is extended., i.e. absorbance exceeding 70% is observed over a wide spectrum ranging from 318 THz to 372 THz. Modelled controllable absorber offers better absorption performance than any previously reported metamaterial absorber employing soft-matter [26,27]. Particularly, combination of a highly birefringent nematic liquid crystal with a high-loss metal is first proved to realize tunable dual-band perfect absorbance. All of the above indicates that the designed soft-matter-based metamaterial absorber is a promising alternative for use in various active systems.
Broadband metamaterial absorber on a single-layer ultrathin substrate
Published in Waves in Random and Complex Media, 2019
Gobinda Sen, Mukesh Kumar, Sk Nurul Islam, Santanu Das
The periodic/non-periodic random metallic structures on metal-backed dielectrics have convened adequate research interest for the design of low-profile metamaterial absorber over the decades owing to their exquisite properties and performances, along with their simple fabrication techniques [1]. Over the past few decades, metamaterial absorber found potential applications on radar cross-section reduction, sensors, energy harvesting from microwaves, solar cell and emitters [2–4] and unveiling a sector of boundless opportunities. In the first near-perfect metamaterial absorber as proposed by Landy et al. [1] in the year of 2008, simultaneously excited electric and magnetic resonances are responsible for absorption of the incident wave almost without reflections.