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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Effective Microwave Electromagnetic Response of the Infinite Chain of Dielectric Coated Circular Metal Cylinders
摘要： Microwave approximations for effective electric and magnetic responses of the infinite chain have been obtained in this study. This infinite chain is comprised of long dielectric coated circular metal cylinders infinitely periodically space. The obtained approximations have been derived on the basis of the long wave approximation for the diffraction problem of a plane electromagnetic wave on the cylindrical chain using the Effective Medium Theory. Comparisons of the analytically obtained results with the numerically calculated ones have made in the study.
关键词： Artificial Dielectrics,Effective Medium Theory,Plane Wave Diffraction,Infinite Grating
更新于2025-09-23 15:21:21
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Design of 2 to 18?GHz balanced antipodal Vivaldi antennas using substrate-integrated lenses
摘要： Conventional balanced antipodal Vivaldi antennas (BAVAs) normally have deep ripple levels in E-plane mainlobe region and significant H-plane beamwidth variation over upper frequency band, which are drawbacks for ultra-wideband (UWB) applications. To overcome these issues, this paper introduces two types of lens configurations in front of BAVA. A gradient-index semi-cylindrical lens and a cylindrical lens are employed to improve ripples depth of E-plane mainlobe and broaden H-plane beamwidth, respectively. Both these lenses and BAVA are integrated on the same substrate and the desired refractive indexes of lenses are realized by a combination of a set of air-filled holes in the substrate. Prototypes of the modified BAVA with lenses (BAVA-Ls) are designed, fabricated, and experimentally investigated as well. Measured results show close agreement with simulation. The proposed BAVA-Ls exhibit promising performances such as smaller ripple levels in E-plane mainlobe, wider H-plane beamwidth, higher aperture efficiency, and excellent group delay, while maintaining good bandwidth characteristics over 2 to 18 GHz.
关键词： effective medium theory,dielectric lens,ultra-wideband (UWB),Balanced antipodal Vivaldi antenna (BAVA)
更新于2025-09-23 15:21:01
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Extraction of the terahertz constitutive tensors of multilayer graphene-dielectric stacks
摘要： In this paper, we present a reliable method to extract the electromagnetic constitutive tensors of complex synthesized multilayer graphene-dielectric stacks in the terahertz band. This macroscopic electromagnetic characterization method uses the transmission and reflection coefficients of a normal-incident circularly polarized electromagnetic wave on the material structure. The employment of circularly polarized waves has the advantage of overcoming the ambiguity at high frequencies attributed to the multi-branching discontinuities in the extracted permeability and permittivity tensors of natural or synthesized materials. The retrieved permeability and permittivity tensors are validated by the data obtained from analytical and numerical solutions of the original electromagnetic problem for the case of circularly polarized wave incidence.
关键词： Graphene-dielectric,Terahertz,Tensor extraction,Effective medium theory,Circular polarization
更新于2025-09-23 15:19:57
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Effective medium theory to the description of plasmonic resonances: Role of Au and Ti nanoparticles embedded in MoO3 thin films
摘要： The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments. This article presents a new theoretical methodology to characterize molybdenum trioxide (MoO3) thin films doped with resonant gold – nanoparticles (Au – NPs) and non-resonant titanium – nanoparticles (Ti – NPs). The modulation of surface plasmon resonance (SPR) and the implications in the MoO3 transmittance spectrum is described by applying an effective medium theory. The transmittance modulation was modified by variating three parameters, the radius of the NPs, the concentration of the NPs as well as the variation of the MoO3 thin films thickness. It was found that the nanoparticles concentration is the most important parameter in the transmittance modulation. Additionally, the orthorhombic and monoclinic structure of MoO3 was studied, from which it was obtained that the monoclinic structure of the MoO3 doped with Au – NPs favors the reduction in the transmittance values in the visible region which is associated with the increase of the SPR signal. Similar analyses are performed for non-resonant nanoparticles such as Ti, where it was found that optical modulation is not as marked as the case of gold nanoparticles.
关键词： optical modulation,plasmonic resonances,Au and Ti nanoparticles,surface plasmon resonance,MoO3 thin films,effective medium theory
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optimisation of Dispersion Flatness in Nanostructured Core Fibres
摘要： Nanostructured optical fibres allow to obtain an arbitrary profile of refraction index in the core. These fibres are composed of several thousands of rods with diameter smaller than incident wavelength. Their optical performance is described with the Maxwell-Garnett effective medium theory. A modification of nanorods distribution or doping level in nanorods allow controlling of chromatic dispersion, polarization and modal properties of the nanostructured fibres. We study an influence of additional microrings in the core on fibre dispersion characteristics. We consider a fibre composed of pure silica nanorods and silica nanorods highly doped with Ge (concentration of GeO2 equals 20% mol). Modification of core internal structure affects electric field distribution in the fundamental mode, and consequently results in changes of its dispersion characteristics. We show that flat, all-normal dispersion characteristics (≈ 2.5 ps/nm/km) in wavelength range from 1.3 up to 2.15 μm can be achieved in the optimized structure. Moreover, within these limits, 1.5 μm to 1.9 μm range was revealed to be ultra-flat (≈ 0.2 ps/nm/km). In contrast to already reported in the literature similar fibres, proposed design is based on fused silica glasses, exhibits spectrally broader and more flat dispersion profile, it is an all-solid construction and it has the effective mode area equal 13μm2 for λ=1.55μm wavelength. Thanks to such characteristics, the fiber allows free from higher order distortions light propagation of highly confined broadband optical pulses, what might find applications in ultrafast optics, or dispersion management systems.
关键词： ultrafast optics,Maxwell-Garnett effective medium theory,chromatic dispersion,nanostructured optical fibres,all-normal dispersion
更新于2025-09-16 10:30:52
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The improved performance of BHJ organic solar cells by random dispersed metal nanoparticles through the active layer
摘要： In this paper, the performance of bulk heterojunction (BHJ) organic solar cells (OSCs) in the presence of random dispersed Ag nanoparticles (NPs) into the active layer is investigated. By the well-known Maxwell-Garnett effective medium theory, we have analyzed the optical absorption of P3HT:PCBM and PCDTBT:PCBM photoactive blends when spherical Ag NPs are randomly embedded in them. The photocurrent enhancement of OSCs based on the blend:AgNP composites has been examined by an analytical drift-diffusion method. Our theoretical analysis demonstrates a considerable enhancement in the optical absorption of the blends with Ag NPs resulted in the power conversion efficiency (PCE) improvement of the devices up to 65.6% in comparison with the reference blends. In addition, the spectrally correlation of simulated external quantum efficiency (EQE) and the absorption coefficient enhancements proves the influence of localized surface plasmon resonance (LSPR) of the Ag NPs in boosting the performance of the OSC devices.
关键词： plasmonic enhancement,drift-diffusion model,Organic solar cells,effective medium theory,Random distribution
更新于2025-09-16 10:30:52
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The IR plasmonic properties of sub-wavelength ITO rod arrays predicted by anisotropic effective medium theory
摘要： Simple three-layer Fresnel equations combined with Maxwell-Garnett approximation were applied to study the IR plasmonic properties of ITO nanorods. By treating the anisotropic nanorod layer as a layer with an effective dielectric constant, and using anisotropic effective medium theory, we were able to accurately predict the surface plasmon resonance behavior of ITO nanorods with different nanorod length, spacing, and tilt angle. This model allows a fast and computationally inexpensive calculation to predict the plasmonic properties of arrayed nanorods.
关键词： IR plasmonic properties,ITO nanorods,anisotropic effective medium theory
更新于2025-09-12 10:27:22
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Arbitrarily shaped homogeneous concentrator and its layered realization
摘要： Arbitrary shaped N-sided polygonal electromagnetic concentrators with homogeneous properties are proposed and designed based on coordinate transformation approach. In comparison with the reported concentrators, material parameters of the concentrators developed here are homogeneous and non-negative, which make the devices applicable to practical fabrication. The constitutive parameters equations reported here are effective for concentrators of regular and irregular shape, which provide the flexibility for device design. Furthermore, to remove the anisotropic of material parameters, layered structure concentrator composed of only homogenous, isotropic materials are presented based on effective medium theory. Space compressing ratio and concentrating efficiency are calculated to quantitatively investigate the efficiency of the proposed device. The feasibility of concentrator design with ordinary isotropic materials instead of metamaterials would dramatically reduce the fabrication difficulties and move the device a step further towards the practical use.
关键词： Electromagnetic concentrator,Metamaterials,Transformation optics,Effective medium theory
更新于2025-09-09 09:28:46
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Linear Optical Properties of Gold Colloid
摘要： Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG) effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.
关键词： gold nanoparticle,aqueous-phase reduction,Maxwell-Garnett effective medium theory,Drude dispersion model
更新于2025-09-09 09:28:46
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POLARIZATION TRANSFORMATION BY A HYPERBOLIC METAMATERIAL ON A METAL SUBSTRATE
摘要： In the present paper we focus on the study of polarization properties of biaxial metamaterial, which consist of alternate ferrite and semiconductor layers, located on an ideally conducted metal substrate. The system is placed into an external magnetic field along the boundaries of the layers. The effective medium theory is applied. Effective linear-to-elliptic polarization conversion has been shown, by means of physical and geometrical parameters of the system under consideration.
关键词： biaxial metamaterial,ferrite,linear-to-elliptic polarization conversion,metal substrate,polarization properties,semiconductor layers,external magnetic field,effective medium theory
更新于2025-09-04 15:30:14