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A Bi-layered Chiral Metamaterial with High-Performance Broadband Asymmetric Transmission of Linearly Polarized Wave
摘要： In this paper, a novel bi-layered chiral metamaterial (CMM) is presented to realize high–efficiency broadband asymmetric transmission (AT) of linearly polarized electromagnetic wave (EM) in the microwave region from 10.1GHz to 15.1GHz. For this purpose, a pair of modified resonators is employed on two sides of a thin dielectric substrate. The simulated and measured results confirm that linearly polarized wave in the form of x-polarized or y-polarized could be nearly converted into the orthogonal polarization after transmission through the introduced prototype which is affirmed by the polarization rotation azimuth angle . The polarization conversion ratio (PCR) is more than 92% at the mentioned frequency range. Full parametric simulation of modified resonators, azimuth rotation angle, and chirality parameter variable with frequency are discussed in detail. In addition, the surface current distributions of the structure have been demonstrated to investigate the physical mechanism of the cross-polarization and corresponding polarization conversion.
关键词： Metamaterials,chiral metamaterial,linearly polarized wave,asymmetric transmission
更新于2025-09-23 15:21:01
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Tunable infrared asymmetric light transmission and absorption via graphene-hBN metamaterials
摘要： We theoretically prove in this paper that using planar multilayer graphene-hexagonal boron nitride (hBN) metamaterials (GhMMs) can yield ultrabroadband and high-contrast asymmetric transmission (AT) and asymmetric absorption (AA) of light. The AA and AT features are obtained in the far-infrared (FIR) and mid-infrared (MIR) regions for normally incident light with transverse magnetic polarization. Here, the GhMMs are integrated with two asymmetric gratings of Ge and are composed of alternating multilayers of graphene (11 multi-layers) and hBN layers (10 layers). Moreover, the total subwavelength thickness of the hybrid structures is about 3 μm, being less than half of the free-space wavelength up to nearly 50 THz. This approach—which is similar to the one introduced by Xu and Lezec [Nat. Commun. 5, 4141 (2014)] for a passive hyperbolic metamaterial operating in the visible range—is based on the excitation of high-β modes of the GhMM with di?erent transmission characteristics. In addition to being ultrabroadband and high-contrast, AT and AA features of the proposed GhMMs can be actively tuned by varying the chemical potential of graphene. Furthermore, it is shown that an on-o? switching of AT factor at FIR and selective tunability at MIR frequencies can be obtained via varying μ. Due to its subwavelength and planar con?guration and active operation, these multilayer graphene-hBN metamaterials with AT and AA characteristics hold promise for integration with compact optical systems operating in the MIR and FIR ranges and are suitable for applications such as optical diodes, sensors, and thermal emitters.
关键词： asymmetric absorption,asymmetric transmission,mid-infrared,graphene-hBN metamaterials,tunable optical properties,far-infrared
更新于2025-09-16 10:30:52
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Folded W-Band Waveguide Filters with Resonant Coupling Apertures for the Generation of Additional Transmission Zeros
摘要： In this paper the realization of multiple additional transmission zeros in folded W-band waveguide filters is discussed. The transmission zeros (TZs) can be placed symmetrically as well as asymmetrically in the near passband region of the filter and arise due to a resonant coupling between source and / or load. Third and fourth order filter set-ups are presented, showing in total between three and six TZs. These zeros can be used to improve the selectivity of the filter without increasing the overall order. The filter design and realization process is discussed. Subsequently, the measurement results are compared with simulation, showing good agreement. As the filters are designed for the W-band, the manufacturing process is connected with some difficulties which are addressed within this paper as well.
关键词： asymmetric transmission zeros,fully canonical waveguide filter,W-band,folded filter structure,resonant TZs
更新于2025-09-16 10:30:52
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Dual-band asymmetric optical transmission of both linearly and circularly polarized waves using bilayer coupled complementary chiral metasurface
摘要： It is highly desirable to develop asymmetric transmission (AT) devices for both linearly and circularly polarized light. However, currently existing metamaterial-based AT devices require multi-step micro-nano fabrication processes and usually realize AT responses only for linearly or circularly polarized waves, not simultaneously for both. We here propose a dual-band AT device for both linearly and circularly polarized waves in the near-infrared region by using a bilayer coupled complementary chiral metasurface, which includes a half-gammadion-shape gold (Au) structural layer and its Babinet’s complimentary copy. Unlike other multilayer AT devices working at optical frequencies, it takes less micro-nano fabrication steps. Besides, with the help of chirality and the inherent near-?eld coupling e?ect between the two complementary Au layers, the maximal AT parameters for linearly and circularly polarized waves can reach up to 0.45 and 0.56, respectively. The underlying mechanisms of dual-band AT responses are also investigated in depth from the perspectives of chirality and coupling e?ect. Our work o?ers a new and simple approach to high-performance AT devices, helps to better understand near-?led coupling e?ect in coupled complementary metasurfaces, and also expands their application ?elds.
关键词： chiral metasurface,asymmetric transmission,polarization conversion,coupling effect,near-infrared
更新于2025-09-11 14:15:04