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Perfect Dual-Band Absorber Based on Plasmonic Effect with the Cross-Hair/Nanorod Combination
摘要： Plasmonic e?ect using a cross-hair can convey strongly localized surface plasmon modes among the separated composite nanostructures. Compared to its counterpart without the cross-hair, this characteristic has the remarkable merit of enhancing absorptance at resonance and can make the structure carry out a dual-band plasmonic perfect absorber (PPA). In this paper, we propose and design a novel dual-band PPA with a gathering of four metal-shell nanorods using a cross-hair operating at visible and near-infrared regions. Two absorptance peaks at 1050 nm and 750 nm with maximal absorptance of 99.59% and 99.89% for modes 1 and 2, respectively, are detected. High sensitivity of 1200 nm refractive unit (1/RIU), ?gure of merit of 26.67 and Q factor of 23.33 are acquired, which are very remarkable compared with the other PPAs. In addition, the absorptance in mode 1 is about nine times compared to its counterpart without the cross-hair. The proposed structure gives a novel inspiration for the design of a tunable dual-band PPA, which can be exploited for plasmonic sensor and other nanophotonic devices.
关键词： plasmonic e?ect,localized plasmon modes,plasmonic sensor,dual-band plasmonic perfect absorber,absorptance peaks
更新于2025-09-23 15:19:57
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Implementing infrared metamaterial perfect absorbers using dispersive dielectric spacers
摘要： A typical metamaterial perfect absorber (MPA) is comprised of a metamaterial layer, a dielectric spacer, and a ground plane. The conventional spacer material is usually a lossy dielectric with little-dispersion for the purpose of easing the design and optimization procedure of the MPA. In this paper, we present the design, fabrication, and characterization of metamaterial perfect absorbers with a highly dispersive spacer, which is compatible with functional microelectromechanical systems. The measured dispersive permittivity of a silicon nitride thin film is used in modeling the absorption response of MPAs with rigorous coupled wave analysis. Different designs of MPA structures are fabricated and characterized. Spectroscopy data shows two perfect absorption peaks in wavelengths ranging from 8 μm to 20 μm, which supports the theoretical calculation and numerical simulation. The dispersion of silicon nitride enables the shared resonant modes of the two peak wavelengths and decreases the wavelength shift led by variations in structural parameters. We demonstrate that the use of dispersive dielectric materials in MPAs potentiates various functional devices.
关键词： rigorous coupled wave analysis,metamaterial perfect absorber,infrared,silicon nitride,fabrication,characterization,dispersive dielectric
更新于2025-09-19 17:15:36
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Ultrahigh Q-factor dual-band terahertz perfect absorber with dielectric grating slit waveguide for sensing
摘要： Terahertz (THz) perfect absorber with ultra-narrow bandwidth at near-unity absorbance has been a challenging issue due to mutual restriction of elemental requirements in design. Here, we propose an extremely sharp dual-band THz perfect absorber with ultrahigh Q-factor and near-unity absorbance by incorporating a Fabry-Perot micro-cavity into dielectric grating slit waveguide. Full-wave simulation demonstrates that the proposed structure not only achieves ultra-narrow band perfect absorption with an ultrahigh Q-factor of 4600 in THz regime, but also shows extraordinary sensing performance with a record figure of merit (FOM) of 2415 at THz frequencies. The optimized guided mode resonance leads to the ultrahigh Q-factor through suppressing the absorption and radiation losses. The enhanced interaction between the cavity localized fields and the analytes significantly improves THz sensing capability. Our design approach shows a promising future in simple and inexpensive THz biochemical sensors.
关键词： THz sensing,Terahertz wave,perfect absorber,ultrahigh Q-factor
更新于2025-09-19 17:13:59
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Narrowband Perfect Terahertz Absorber Based on Polar-dielectrics Metasurface
摘要： We theoretically propose a narrowband perfect absorber metasurface (PAMS) based on a silver surface phonon polaritons in the terahertz range. The PAMS has biarc on the top, a thin polar-dielectric in the middle and a silver layer at the bottom. The phonon polaritons have excited at the interface between the silver biarc and the polar dielectric and have enhanced the absorption of the PAMS. The absorption peak is at 36.813μm and the full width half maximum (FWHM) near 36nm and is independent of the polarization and incidence angle. The electric fields are located at the split of the biarc silver layer and the quality factor (Q) is 1150. The FWHM decreases with the decreasing of split width. When the thickness of bottom layer larger than 50nm, the narrow band and high absorption are insensitive of the thickness of those layer. The designed absorber may have useful applications in terahertz spectrum such as energy harvesting, thermal emitter, and sensing.
关键词： Polar-dielectrics,Terahertz,Metasurface,Narrowband Perfect Absorber
更新于2025-09-19 17:13:59
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Broadband terahertz metamaterial absorber enabled by using high-loss dielectric materials
摘要： Metamaterial absorbers consisted of two metallic layers separated by low-loss dielectric materials have been extensively presented and studied. However, these absorbers using low-loss dielectric materials usually exhibit narrow bandwidth, which are not conductive to the practical applications. Here, we demonstrate a novel terahertz meta-device that can obviously widen the absorption bandwidth of metamaterial absorber. This meta-device is composed of a high-loss dielectric material sandwiched by a metallic strip and an opaque metallic mirror. Absorption of greater than 80% of the meta-device can cover a continuous frequency range of 2.43 THz, and its relative absorption bandwidth can reach 89.17%. These two indexes are both much larger than those of previous absorption devices using low-loss dielectric materials. Physical mechanism of the meta-device originates from the superposition of two different resonant modes. More importantly, the variation of meta-device parameters can provide considerable degree of freedom to regulate the absorption bandwidth and relative absorption bandwidth of the device.
关键词： broadband absorption,metamaterials,perfect absorber,high-loss dielectric material
更新于2025-09-19 17:13:59
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An ultrathin MoSe<sub>2</sub> photodetector with near-perfect absorption
摘要： An ultrathin near-perfect MoSe2 absorber working in the visible regime is demonstrated theoretically and experimentally, and it consists of a MoSe2/Au bi-layer film. The polymer-assisted deposition method is used to synthesize MoSe2 films, which can reduce the roughness and thus improve the film absorption. Simulation results show that the absorption of the absorber with 22 nm MoSe2 reaches to larger than 90% between 628.5 nm and 718 nm with a peak value up to 99.5% at 686 nm. Moreover, the measured absorption also shows near-perfect absorption of this simple absorber. Finally, an ultrathin photodetector is fabricated based on this perfect absorber and shows on/off reproducibility and remarkable photocurrent, which is three orders of magnitude higher than the dark current.
关键词： FDTD,near perfect absorber,photodetector
更新于2025-09-19 17:13:59
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Design principles for sensitivity optimization in plasmonic hydrogen sensors
摘要： Palladium nanoparticles have proven to be an exceptionally suitable material for the optical detection of hydrogen gas, due to the dielectric function that changes with the hydrogen concentration. The development of a reliable, low-cost, and widely applicable hydrogen detector requires a simple optical read-out mechanism and an optimization of the lowest detectable hydrogen concentration. So-called ‘perfect absorber’-type structures, consisting of a layer of plasmonic palladium nanoantennas suspended above a metallic mirror layer, are a promising approach to realizing such sensors. The absorption of hydrogen by palladium leads to a shift of the plasmon resonance and thus to a change in the far-?eld re?ectance spectrum. The spectral change can be analyzed in detail using spectroscopic measurements, while the re?ectance change at a speci?c wavelength can be detected with a simple photometric system of a photodiode and a monochromatic light source. Here, we systematically investigate the geometry of cavity-coupled palladium nanostructures as well as the optical system concept, which enables us to formulate a set of design rules for optimizing the hydrogen sensitivity. Employing these principles, we demonstrate the robust detection of hydrogen at concentrations down to 100 ppm. Our results are not limited to hydrogen sensing, but can be applied to any type of plasmonic sensor.
关键词： Hydrogen detection,Palladium,Tailored disorder,Plasmonic sensing,Microspectroscopy,Metasurface,Perfect absorber,Fourier-plane spectroscopy
更新于2025-09-16 10:30:52
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Independently tunable perfect absorber based on the plasmonic in double-layer graphene structure
摘要： Graphene can be utilized in designing tunable photonic devices due to its unique properties such as high optical transparency and tunable conductivity. In this paper, a tunable triple-band perfect absorber is designed and numerically demonstrated, which is composed of a stacked graphene nanodisk, L-shape graphene layer and a gold ground plane spaced by insulator layers. The results show that there are three higher than 99% absorption peaks in the infrared range with a wide incident angle range up to 50°, and the absorber is insensitive for TE and TM polarized incident light. Moreover, the perfect absorption peak wavelength can be tuned by changing Fermi levels or geometric parameters of graphene layers. The findings above indicate that the designed perfect absorber can be used in the field of photodetectors, thermal emitters and photovoltaics.
关键词： Perfect absorber,Graphene,Tunable,Plasmonic,Infrared
更新于2025-09-16 10:30:52
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Dynamically Tunable Dual-Frequency Terahertz Absorber Based on Graphene Rings
摘要： A dual-frequency absorber with periodic double-layer graphene ring arrays separated by dielectric spacer is proposed. Coupled-mode theory and finite difference time domain method are used to analyze the perfect absorption and the absorption mechanism. Moreover, the influences of structural parameters and chemical potential of graphene on the peak positions have been investigated. Benefiting from chemical potential can be controlled by external bias voltage, thus the proposed structure can be used as a dynamically tunable absorber. Such simple absorber has potential applications in optical storage devices and frequency-selective detectors for terahertz regime.
关键词： Dynamically tunable,perfect absorber,graphene
更新于2025-09-12 10:27:22
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Tunable mid-infrared perfect absorber based on the critical coupling of graphene and black phosphorus nanoribbons
摘要： We demonstrate theoretically a wide-angle and tunable mid-infrared perfect absorber by coupling the graphene and black phosphorus plasmonics and utilizing the concept of critical coupling. With the black phosphorus nanoribbons alone, the localized surface plasmon resonances (LSPR) can be excited, while the absorption is small due to its single-layer thickness. A Fabry-Perot cavity is formed by adding an Au mirror as the substrate, which is separated from the black phosphorus by a dielectric spacer, hence the absorption is enhanced markedly due to critical coupling. In order to further enhance the absorption, a graphene grating is introduced on the top of black phosphorus and is separated by a dielectric slab. It is shown that the perfect absorption can be obtained due to the critical coupling of LSPR of black phosphorus and graphene. Based on these result, it is further demonstrated that the perfect absorption can work in large incident angle range, and the working wavelengths can be adjusted by the Fermi level of graphene. Our results provide a new avenue to achieve wide-angle and adjustable perfect absorption, and it may be beneficial for a variety of mid-infrared plasmonic applications.
关键词： plasmonics,mid-infrared,perfect absorber,graphene,black phosphorus,critical coupling
更新于2025-09-12 10:27:22