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Application of metasurfaces in the design of performance-enhanced low-profile antennas
摘要： This paper presents a review of metasurface-based antennas conducted at the Microwave Communication Laboratory (MCL) of Ajou University in the Republic of Korea. In this paper, pro?le miniaturization, bandwidth enhancement, multiband operation, and radiation pattern control of metasurface-based antennas are considered. The paper ?rst presents metasurface-based antennas implemented by placing various radiators on top of the metasurface. It then presents antennas implemented by placing the radiators below the metasurface with and without the ground plane. Metasurface-based antennas are not only able to achieve high ef?ciency with a low pro?le but they are also able to generate extra resonances from the metasurface structures, which signi?cantly enhances the overall performance of the antennas. These additional resonances were utilized in multiband and/or wideband operations. In addition, the design of a planar compact wide-gain-bandwidth metasurface-based antenna and its radiation characteristics are presented at a terahertz (THz) frequency range. The THz antennas were designed with metasurfaces and a planar leaky-wave feeding structure. Finally, the outlook on future research at the MCL for antenna-related work and their applications using metasurfaces is provided.
关键词： surface wave resonance,sequential rotation,crossed dipole,arti?cial magnetic conductor,metamaterial,wideband,circular polarization,leaky-wave,Antenna,array,metasurface
更新于2025-09-23 15:23:52
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Optical diffraction radiation from a dielectric and a metal nanowire excited by a modulated electron beam
摘要： The optical diffraction radiation that accompanies the motion of a modulated beam of electrons near a dielectric and silver nanowire scatterers is investigated in the two-dimensional formulation. Our goal is to compute the field in the near and far zones and analyze how it depends on electron beam parameters. We demonstrate the excitation of internal resonances of such a scatterer that can be useful in the design of nanoscale non-invasive beam position monitors.
关键词： Plasmon resonance,Diffraction radiation,Nanowire scatterers,Total scattering cross-section,Absorption cross-section,Smith–Purcell effect,Surface wave
更新于2025-09-23 15:22:29
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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21
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Pumping Systems for Compton Free-Electron Lasers: Microwave Undulators and Powering Sources
摘要： The concept of Compton-type free-electron lasers (FELs) operating in short wavelength ranges with a high e?ciency and power level is currently underway at the IAP RAS (Nizhny Novgorod). This concept is aimed at reducing the energy of a driving relativistic electron beam and thereby increasing the e?ciency of the electron–wave interaction in FELs, as well as making the oscillator relatively compact. The basis of this concept is microwave undulators of a new type — the so-called “?ying” undulators. This paper is devoted to the results of the current studies of these undulators, their simulation, and “cold” electrodynamic tests in the Ka band. For powering microwave undulators, a spatially extended narrow-band ˇCerenkov surface-wave oscillators (SWOs) are developed in the speci?ed frequency range driven by Sinus-6, a high-current accelerator, with a particle energy of 0.5 MeV, a current of 5 kA, and a pulse duration of 25 ns. The required sub-gigawatt power level of output radiation combined with a high stability of the narrow-band oscillation regime is achieved under conditions of a strongly oversized oscillator by using two-dimensional distributed feedback provided in a 2D doubly-periodic slow-wave structure. The design parameters of a 32 GHz/0.5 GW SWO intended for powering microwave undulators are presented and the results of its simulation and reported.
关键词： flying undulators,Ka band,Cerenkov surface-wave oscillators,Sinus-6 accelerator,microwave undulators,Compton-type free-electron lasers
更新于2025-09-23 15:21:01
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Nonlinear surface waves propagating along the composite waveguide consisting of self-focusing slab between defocusing media separated by interfaces with nonlinear response
摘要： The model of the composite symmetric waveguide consisting of self-focusing slab between defocusing nonlinear media separated by interfaces characterized by own nonlinearity response is proposed. Two new types of nonlinear surface waves propagating along it with anti-phase amplitude oscillations at interface planes are found. The frequencies of the nonlinear surface waves existing near the interfaces with the nonlinear response only are calculated analytically. The conditions of the surface wave existence are found. The frequencies and localization distances of the surface waves in dependence on nonlinearity waveguide parameters, slab width and interface characteristics are analyzed.
关键词： interface,nonlinear Schr€odinger equation,surface wave,Layered structure,waveguide
更新于2025-09-23 15:19:57
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Azimuthal illumination enabled ultra-high polar angle sensitivity by Bloch surface wave resonance refractive index sensor
摘要： The scheme of polar angle space refractive index (RI) sensor based on grating coupled Bloch surface wave (BSW) resonance excited by azimuthal illuminations is studied. It is shown that, for any polar angle, one can always find a case of BSW resonance with the tangential wave vector of the BSW mode perpendicular to that of the incident electromagnetic wave. When the sensor is designed to work around this resonance, ultra-high polar angle sensitivity can be expected. The numerical simulated polar angle sensitivity reaches as large as 1786 degree per RI unit (Deg/RIU), which is almost one order higher than that can be found in literatures.
关键词： Bloch surface wave,azimuthal illumination,polar angle sensitivity,refractive index sensor
更新于2025-09-23 15:19:57
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Design and Analysis of Wideband Low-Scattering Endfire Antenna Using Moth Tail-Inspired Metamaterial Absorber and Surface Waveguide
摘要： This paper presents a wideband endfire antenna co-designed with broadband low-scattering characteristics. The wideband reflection and endfire radiation attribute the success to the supported dual-resonance surface waves, and the broadband low scattering owes to the combination of a metamaterial absorber (MA) absorption and an incident penetration of a frequency selective surface (FSS). Based on the transmission line model, a surface waveguide (SWG) which can support dual-resonance surface waves is adopted and analyzed to realize the wideband reflection response (4.95 ~ 6.83 GHz) and endfire radiation. Also, the SWG can be seen as an FSS for the normal incidence. In addition, a wideband MA, which is inspired by the luna moth's escape from bat attack, is designed and integrated with the SWG to realize low back radar cross section (RCS) in the frequency range from 0.5 to 12.5 GHz. The reflection, radiation and scattering performance are validated by the full-wave simulation and experimental verification.
关键词： Frequency selective surface (FSS),radar cross section (RCS),surface wave,moth tail-inspired metamaterial absorber (MA)
更新于2025-09-16 10:30:52
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Experimental investigation on a new hybrid laser process for surface structuring by vapor pressure on Ti6Al4V
摘要： Besides conventional structuring processes such as turning, milling or photo-chemical etching, laser processes are increasingly being used for surface structuring of metals. These laser processes differ fundamentally in that structuring is carried out either by material removal or by material redistribution. In this study, a new hybrid process of material ablation by means of pulsed laser radiation and material redistribution based on a remelting process by means of cw laser radiation is experimentally investigated. Besides an introduction to this new hybrid process, we give a detailed description of the equipment and methods used as well as surface structures produced on Ti6Al4V. A melt pool was generated on a prepared Ti6Al4V surface using cw laser radiation with a laser beam diameter of 520 μm, laser power of 220 W, and a scanning velocity of 100 mm/s. In order to create surface structures, simultaneously, superimposed pulsed laser radiation with a laser beam diameter of 65 μm, pulse duration of 60 ns, a maximum pulse energy of 0.35 mJ, and a pulse frequency of 50 kHz was used to evaporate small amounts of molten material from the melt pool. This localized evaporation of molten material is assumed to create vapor pressure that deforms the melt pool surface and therefore leads to surface structures. Our results indicate that by pulsed laser radiation capillary surface waves with a wavelength of the doubled laser beam diameter are excited on the melt pool surface. This forced excitation of capillary surface waves result in surface structures that are analyzed after solidification by means of white light interferometry. Based on this analysis we derived an oscillation frequency of ν = 2.27 (± 0.16) kHz for the excited capillary surface wave as well as an effective kinematic viscosity of μ = 0.1328 cm2 s-1 for the damping of this surface oscillation during solidification. In terms of structural features, we achieved surface structures with heights of up to 100 μm. Furthermore, structure height controllably scales in dependence on pulse energy and number of laser pulses as long as no ejection of molten material takes place. Finally, a comparison of the redistributed material volume per time shows that we achieved a volume redistribution rate of 28.37 mm3/min, which is significantly bigger than has been achieved with other laser texturing techniques so far and demonstrates the high potential of this new hybrid technique not only for surface structuring purposes.
关键词： surface structuring,melt pool,material redistribution,capillary surface wave,Ti6Al4V,remelting
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Improving Multicast Routing Performance in Surface Wave Optical Network-on-Chip
摘要： Considering the broadcasting communication feature of surface wave, we construct a two-layer hybrid ONoC architecture, and a multicast routing strategy suitable for this architecture is also proposed.
关键词： Surface wave communication,ONoC,Multicast routing on chip
更新于2025-09-16 10:30:52
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Visible light from modulated electron beam moving between twin circular silver nanowires forming plasmonic photonic molecule
摘要： The visible-range diffraction radiation of harmonically modulated electron beam, which moves between twin circular silver nanowires is considered. The electromagnetic field of such a two-dimensional beam is a surface wave propagating along its trajectory with the phase velocity equal to the beam velocity. This wave induces currents on the nanowires and hence radiation occurs even if the beam does not touch the wires. If the wires are tuned to a resonance, the radiated power displays a peak proportional to the resonant mode Q-factor. Sub-wavelength in radius silver nanowires are famous as nanoresonators due to the localized surface-plasmon modes. In our analysis, we use the field expansions in the azimuthal Fourier series and the addition theorems for the cylindrical functions. This enables us to reduce the wave scattering problem to a Fredholm second kind infinite-matrix equation that guarantees convergence of numerical solutions. Truncating this matrix, we compute the near and far field patterns of the wires as optically coupled plasmonic resonators and analyse dependence of the far-field spectral characteristics on the wavelength and electron beam parameters.
关键词： absorption cross-section,optical diffraction radiation,total scattering cross-section,plasmon resonance,surface wave,silver nanowires
更新于2025-09-12 10:27:22