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Ultra high-sensitivity and tunable dual-band perfect absorber as a plasmonic sensor
摘要： In this paper, we demonstrate a dual-band tunable absorber coupled with a nanoscale metal-dielectric-metal (MDM) structure for sensing applications in the near-infrared spectral region. This structure exhibits a dipole resonance mode in absorbance and reflectance spectra which results in the enhancement of absorbance over a wide range of incident angles for TE polarization. Using a numerical and analytical study, the performance parameters of the structure including sensitivity (SS), the figure of merit (FoM) and quality factor (Q) are investigated by changing the incident polarization, geometrical parameters, filling dielectric and plasmonic metasurface material. Moreover, we study the dependence of the sensitivity as a function of plasmonic metasurface shape to demonstrate a better response compared with other methods. Results show that, in terms of the refractive index unit (RIU), an ultra-high sensitivity and tunable sensor can be designed with a maximum sensitivity of 1240.8 nm/RIU for a refractive index change of Δn = 0.0458. In the optimum design of the proposed dual-band absorber, a Q-factor and FoM equal to 123.45 and 44.5 are obtained. Furthermore, the proposed structure can be utilized for controlling the light propagation. By considering silver as a plasmonic metasurface, a slow down factor as high as 680 is obtained. Our work will be applied to future sensors capable of ultra-high sensitivity.
关键词： Absorber,Nanoscale Structure,Plasmonics Sensor,Slow down factor,Metasurface
更新于2025-09-19 17:13:59
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Ultra-Wideband Low-Loss Control of Terahertz Scatterings via an All-Dielectric Coding Metasurface
摘要： Despite the growing interests for controlling of terahertz (THz) scatterings via metallic metasurfaces, the avoidance of Ohmic loss resulting from the interaction between light and phonons or free electrons remains an arduous task. Herein, we propose a new approach of ultra-wideband low-loss control of THz-scatterings via all-dielectric coding metasurface (DCMF). In our experiments, the DCMFs manipulate THz waves remarkably in an ultra-wideband of 900 GHz. When a THz wave enters into the DCMFs, it emerges split into two Bessel-beams with a higher amplitude of transmission up to 60%, and the lower amplitude about 30%. In our simulations the high amplitude of transmission even may achieve 99%. Besides, the variation of coding sequence enables diversification of manipulation for THz-scatterings. Notably, the DCMF with the sequence of ‘101010…’ refracts a beam of 1.3THz in two directions. The energy of the main beam seems to dissipate at all. We also fins that, as a beam of 1.63 THz passes through the DCMFs consisting of the sequence of ‘110110…’, its energy may scatter in multiple directions, demonstrating an unprecedented control of THz-scatterings. Our results not only enriches the strategy of THz modulation but also guides the superior design for THz devices.
关键词： modulation,Terahertz,coding metasurface,metamaterial,phase sensitivity
更新于2025-09-19 17:13:59
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Resonant Metagratings for Spectral and Angular Control of Light for Colored Rooftop Photovoltaics
摘要： We design semi-transparent metagrating supercells that enable control over the spectrum and directivity of incident light for applications in photovoltaics with tailored angular appearance. The building block of the supercells is a 110-120 nm wide and 175 nm tall silicon nanowire that shows a strong Mie resonance around λ= 650 nm. By arranging the resonant Mie scatterers into metagratings of increasing pitch (675-1300 nm) we create a Lambertian-like scattering distribution over an angular range of choice. The millimeter-sized metasurfaces were fabricated using electron beam lithography and reactive ion etching. The fabricated metasurface nearly fully suppress specular reflection on resonance while 10% of the incoming light around the resonance is scattered into the angular range between 30-75°, creating a bright red appearance over this specific range of angles. Off-resonant light in the blue, green and near-infrared is efficiently transmitted through the metasurface and absorbed in the underlying photovoltaic cell. The implemented silicon heterojunction solar cells with integrated metagrating supercells show a reduction in external quantum efficiency matching the resonant scattering spectral range. The short circuit current is reduced by 13% due to the combined effects of resonant scattering, reflection from the high-index substrate and absorption in the Si nanowires. In addition, to efficient colorful photovoltaics with tailored angular appearance, the metagrating concept can find application in many other light management designs for photovoltaics and other opto-electronic devices.
关键词： light management,metasurface,Mie resonators,BIPV,silicon nanoparticles,colored photovoltaics,transparent metagratings,solar cells
更新于2025-09-19 17:13:59
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Plasmonic ommatidia for lensless compound-eye vision
摘要： The vision system of arthropods such as insects and crustaceans is based on the compound-eye architecture, consisting of a dense array of individual imaging elements (ommatidia) pointing along different directions. This arrangement is particularly attractive for imaging applications requiring extreme size miniaturization, wide-angle fields of view, and high sensitivity to motion. However, the implementation of cameras directly mimicking the eyes of common arthropods is complicated by their curved geometry. Here, we describe a lensless planar architecture, where each pixel of a standard image-sensor array is coated with an ensemble of metallic plasmonic nanostructures that only transmits light incident along a small geometrically-tunable distribution of angles. A set of near-infrared devices providing directional photodetection peaked at different angles is designed, fabricated, and tested. Computational imaging techniques are then employed to demonstrate the ability of these devices to reconstruct high-quality images of relatively complex objects.
关键词： metasurface,computational imaging,lensless compound-eye vision,Plasmonic ommatidia,directional photodetection
更新于2025-09-19 17:13:59
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Numerical and Theoretical Study of Tunable Plasmonically Induced Transparency Effect Based on Brighta??Dark Mode Coupling in Graphene Metasurface
摘要： In this paper, we numerically and theoretically study the tunable plasmonically induced transparency (PIT) effect based on the graphene metasurface structure consisting of a graphene cut wire (CW) resonator and double split-ring resonators (SRRs) in the middle infrared region (MIR). Both the theoretical calculations according to the coupled harmonic oscillator model and simulation results indicate that the realization of the PIT effect significantly depends on the coupling distance and the coupling strength between the CW resonator and SRRs. In addition, the geometrical parameters of the CW resonator and the number of the graphene layers can alter the optical response of the graphene structure. Particularly, compared with the metal-based metamaterial, the PIT effect realized in the proposed metasurface can be flexibly modulated without adding other actively controlled materials and reconstructing the structure by taking advantage of the tunable complex surface conductivity of the graphene. These results could find significant applications in ultrafast variable optical attenuators, sensors and slow light devices.
关键词： plasmonically induced transparency effect,metasurface,mid-infrared region,graphene split-ring resonators,graphene cut wire resonator
更新于2025-09-19 17:13:59
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Infrared subwavelength focusing metasurfaces for harvesting heat from the Eartha??s back radiation
摘要： In this paper, we introduce two different metasurfaces that can achieve subwavelength focusing of the electromagnetic radiation in the infrared range with transmission ef?ciencies reaching 46% and 74.33% in silicon and thus they can be integrated in heat harvesting applications. We made our designs at the wavelength of 10 μm which is the peak of the back radiation of the Earth. In designing our metasurfaces in the infrared range, we used the phase modulation techniques that proved to be useful in the visible domain. The best focusing resolution achieved in our metasurfaces is 0.26λ (super-focusing). In addition to heat harvesting, the two proposed metasurfaces can be useful in other compact applications that require manipulating the mid-infrared radiation on a very small scale. We used copper and silicon in our metasurfaces which are speci?cally suitable for the mid-infrared range besides being CMOS compatible. In this paper, we also explained how heat can be harvested from the introduced metasurfaces using the Seebeck effect.
关键词： plasmonics,subwavelength focusing,planar lens,phase modulation,heat harvesting,metasurface,mid-infrared focusing
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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Guided‐Mode Resonances in All‐Dielectric Terahertz Metasurfaces
摘要： Coupling of diffracted waves in gratings with the waveguide modes gives rise to the guided mode resonances (GMRs). The GMRs provide designer linewidth and resonance intensity amidst a broad background, and thus have been widely used for numerous applications in visible and infrared spectral regions. Here, terahertz GMRs are demonstrated in low-loss, all-dielectric metasurfaces, which are periodic square lattices of silicon cuboids on quartz substrates. The silicon cuboid lattice simultaneously acts as a diffraction grating and an in-plane slab waveguide, thereby resulting in the formation of terahertz GMRs. At oblique incidence, two distinct frequency detuned GMRs are observed. The frequency difference between these two GMRs increases at larger angle of incidence. However, extremely small angle of incidence causes destructive interference between these counter-propagating GMRs that leads to a nonradiative symmetry-protected bound state in the continuum. GMRs in all-dielectric silicon metasurfaces can have potential applications in the realization of efficient terahertz devices such as high-Q transmission filters with angular spectral selectivity, ultrafast modulators, and free-space couplers.
关键词： guided-mode resonance,bound states in the continuum,all-dielectric metasurface,terahertz
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - A terahertz microfluidic sensor based on metasurface
摘要： We present a microfluidic sensor integrated with metasurface and a terahertz measuring system used for it. To obtain better sensing sensitivity, numerical simulations were conducted to determine the structure and excitation mode for metasurface. A method to obtain the concentration of sample solution was given as an application of the sensor. Asymmetry metasurface are discussed with figure of merit. A new tradeoff index FD is defined to assess the performance of microfluidic sensor and the best metasurface for our microfluidic sensor is selected through FD.
关键词： Fano resonance,microfluidic sensor,metasurface
更新于2025-09-19 17:13:59
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Optical properties of 2D photonic structures fabricated by direct laser writing
摘要： This paper presents the results of fabrication and investigation of different 2D photonic structures with the square C4v, hexagonal C6v, and pentagonal local C5v symmetry. The samples were created using the direct laser writing technique. The number of submicron scatterers varied from 25 to 10,000, and the lattice parameters varied in different samples in the range of 0.5 μm ≤ a ≤ 8.0 μm. Our experimental and theoretical studies demonstrate that 2D photonic structures reveal many remarkable optical effects. Created ordered and disordered photonic structures demonstrate a great variety of optical phenomena observed on a far-field screen placed behind the sample. When the random fluctuations of the orientation for individual rods were introduced to the perfect fishnet photonic structure, a crossover from Laue diffraction to speckle patterns was observed and investigated.
关键词： Laue diffraction,Light scattering,Photonic structure,Direct laser writing,SEM images,Metasurface
更新于2025-09-19 17:13:59