Thin Metallic Screen Research Articles

Analytical approach to the problem of electromagnetic wave scattering by a cylindrical hole in a thin metal screen

A method of analytical study of a metal film perforated by cylindrical nanoholes as the basis of a metasurface has been proposed. The formulas deduced completely determine the electromagnetic field of a wave scattered by the hole at any distance from the surface. The calculation of the transmission and absorption spectra of the studied structure, as well as the dependence of the phase of the scattered wave on the radius of the hole, is carried out using analytical formulas. The calculation results are consistent with the literature data for calculating the efficiency of a quantum photodetector and the phase change interval of light scattered by meta-atoms required for lens design.

The problem of electromagnetic wave transmission in a circular waveguide

The article deals with the problem of transmission in a circular waveguide, in the cross section of which there is a thin metal screen. The waveguide is bounded by a perfectly conducting surface. The transmission problem is an auxiliary problem that arose when solving inverse diffraction problems. In the transmission problem, it is required to find the electromagnetic field in the waveguide on one side of the screen by a given field on the other side of the screen: both by given waves incident on the screen and by given waves leaving the screen to infinity. It is shown how the transmission problem can be reduced to an infinite system of linear algebraic equations. To solve the resulting system, it is proposed to use the truncation method. We study under what conditions the numerical solution of the transmission problem will be stable to small perturbations of the input data.

Opaque pixel mask with a broadband absorbing metasurface: application to infrared detectors.

We present an imager architecture comprising dark and active pixels allowing the simultaneous measurement of photonic and dark current, which is of particular interest for low-photon-flux astronomical applications. The principle of operation relies on both the total opacity of a thin metallic screen of sufficient area and the anti-reflective properties of well-designed resonant metal-dielectric gratings made on the same screen. The concept is exemplified in the context of cooled HgCdTe hybrid detectors, at short- and long-wave infrared ranges.

Analytical Evaluation of the Low-Frequency Magnetic Shielding of Thin Planar Magnetic and Conductive Screens

A recent analytical formulation for the low-frequency magnetic shielding effectiveness of a thin metal screen against a circular loop source is extended to the case of a screen exhibiting both magnetic and conductive properties. The presence of magnetic properties introduces a series impedance in the equivalent network of the structure, in addition to the shunt admittance associated with the screen conductivity. However, the fields scattered by the two elements do not interact and hence can be treated independently; furthermore, the series impedance gives rise to integrals akin to those stemming from the shunt admittance. A generalized analytical formulation for a combined magnetic and conductive screen is thus obtained, that is favorably compared with both classical approximate formulations and exact results.

Light Transmission of a Thin Metal Screen with an Infinite Array of Periodic Nanoslits

A rational method for calculating the transmission of light by a thin metal screen with an infinite periodic array of subwavelength slits is proposed. The calculation results agree well with available experimental and theoretical data.

Пропускание света тонким металлическим экраном с бесконечным массивом периодических нанощелей

AbstractA rational method for calculating the transmission of light by a thin metal screen with an infinite periodic array of subwavelength slits is proposed. The calculation results agree well with available experimental and theoretical data.

Исследование температурного режима элементов конструкции вакуумной электропечи сопротивления методом структурного математического моделирования

The article demonstrates the importance of developing a structural mathematical model of a high-temperature vacuum electrical resistance furnace (ERF) for studying the thermal processes in it with determining the temperature of each furnace element, predicting the service life of heating elements, screens, and other furnace structural elements, selecting the temperature sensor installation place, and making relevant adjustment of the temperature control system. The commonly used model, in which the furnace is represented by a first-order inertial section, does not provide such possibility, because the furnace average temperature is calculated in that case. Therefore, it is necessary to construct a model based on the energy balance equations for macro elements (heater, each of the screens, loading, etc.) taking into account radiant heat transfer between the macro elements. A mathematical structural model of a Tamman vacuum high-temperature electric furnace equipped with a heater in the form of a coal or graphite pipe and thermal insulation in the form of graphite cylinders-screens has been developed and implemented in the Simulink software package. The thermal resistance of graphite screens thermal conductivity, which is commonly neglected in design calculations of widely used thin metal screens, was taken into account in simulating the thermal processes. The temperature operating conditions of individual structural elements (heaters, screens, etc.) are analyzed, both at constant power supply voltage of the heaters and in using a closed-loop temperature control system. The effect the temperature sensor installation place has on the automatic temperature control quality is shown. The advisability of using the developed model for adjusting the proportional-integral-differential controller to ensure the required control quality is substantiated.

PHOTON FLOW DENSITY DISTRIBUTION IN THE DIFFRACTION PATTERN OF SINGLE- AND TWO PARALLEL SLITS

The paper proposes a quantum mechanical model of the phenomenon of light diffraction by one and two slits in an infinitely thin metal screen. Based on the assumption that the photons passing through the slits interact with the electrons of the matter through elastic collisions, the resulting distribution of light intensity in the diffraction pattern for the cases of diffraction of particles on one and two cracks was obtained.

Sound energy harvesting using an acoustic grating

A sound energy harvester with an acoustic grating and a piezoelectric plate has been demonstrated. The acoustic grating consists of a metal slit grating and a thin flat metal screen. The metal slit grating can squeeze an incident acoustic wave into the air gap between the slit grating and metal screen, thus giving rise to high sound pressure and causing the metal screen to vibrate. Using the direct piezoelectric effect, the “squeezed” acoustic energy is harvested efficiently by a piezoelectric component that is mounted on the back of the metal screen.

Microscopic theory of diffraction of light from a small hole

On the basis of the Maxwell-Lorentz local-field equations and nonlocal linear response theory, a self-consistent microscopic Green function theory of diffraction of light from a single hole in a thin and plane metallic screen is established. By subtracting the scattering of identical incident fields from screens with and without a hole, a causal effective optical aperture response tensor is introduced. An approximate expression is derived for the aperture response tensor in the limit where the screen behaves like an electric-dipole absorber and radiator. In this limit the internal electron dynamics is that of a quantum well. For a screen so thin that its bound electron motion can be described by a single quantum level, a approach for a quantum mechanical calculation of the aperture response tensor is presented. When the linear dimensions of the hole become sufficiently small the so-called aperture field, defined as the difference between the prevailing electric field with and that without a hole, becomes identical to the field from an incident-field-induced electric dipole with anisotropic linear polarizability. Our theory is formulated in such a manner that preknowledge only of (i) the incident electromagnetic field and (ii) the light-unperturbed optical electron properties (the microscopic conductivity tensor) of the screen with the geometrically given hole is needed. Since the microscopic theory allows for the presence of an (oscillating) component of the sheet current density perpendicular to the plane of the screen, a generalization of (i) the standard jump conditions of the field across the sheet and (ii) the reflection symmetries of the various fields in the plane of the screen is worked out. As our theory deviates radically from the approach of all classical diffraction theories, which are based on the macroscopic Maxwell equations and some kind of pheno-menological expression for the screen conductivity $\ensuremath{\sigma}$ (often just $\ensuremath{\sigma}\ensuremath{\rightarrow}\ensuremath{\infty})$, we give a brief review of classical diffraction theory, formulated in such a manner that a comparison to the microscopic theory is made easier. In particular, the Bethe-Bouwkamp theory of classical diffraction from a small hole in an infinitely thin and perfectly conducting $(\ensuremath{\sigma}\ensuremath{\rightarrow}\ensuremath{\infty})$ screen is our focus. We suggest that experimental frequency and angular resolved studies of the interference of the diffracted fields from quantum wells with and without holes are undertaken to obtain detailed insight into the microscopic aperture response functions, not least in the optical near-field domain.

Controlled bandpass frequency-selective surfaces

Bandpass frequency-selective surfaces (FSSs) controlled by varactors and representing biperiodic lattices formed from slotted squares in a thin metallic screen are considered. Main factors affecting the FSS tuning range with different circuits for connection of control varactors are experimentally evaluated. Experimental results obtained by the waveguide method of measuring the transmission coefficient through samples of both individual FSS elements loaded with varactors of various types and lattices consisting of these elements at microwave frequencies are presented. Based on the measured data, attainable values of the relative tuning of the FSS resonance frequency are evaluated: fmax/fmin = 1.4 for control circuits with two MA46N120 low-capacitance varactors in each FSS element and fmax/fmin = 1.5 for control circuits with one VV857 medium-capacitance varactor.

Analytical Wideband Model for Strip/Slit Gratings Loaded With Dielectric Slabs

This paper presents a fully analytical model to determine the transmission and reflection properties of planar 1-D distributions of metal strips or slits made in thin metal screens. In contrast with other analytical or quasi-analytical approaches, the formulation incorporates the presence of dielectric slabs and is valid over a wide frequency band, from the long wavelength limit to the grating lobes operation. The model has been adapted to the case where two 1-D planar grids are stacked or a single grid is printed on a grounded substrate. In these cases, the model rigorously takes into account higher order mode interaction between the two stacked arrays of strips/slits or with the ground plane. Oblique incidence and both TE and TM polarizations have been considered. The analytical results show a good agreement with those computed by high-performance numerical methods, accounting for very fine details of extremely complicated transmission/reflection spectra. These results are of straightforward application to a variety of practical situations from microwaves to the terahertz regime. The present methodology can still be useful at higher frequencies provided that adequate models of the planar conductors are incorporated. In general, the model provides physical insight on the nature of the expected spectra and facilitates the design of devices based on planar metallic gratings.

Resonant Power Transmission Through Coupled Subwavelength Ridged Circular Apertures

The enhanced electromagnetic power transmission through single and coupled subwavelength ridged circular apertures in a thin metal screen is analyzed. The optimum distance between the apertures for the maximum transmission cross section (TCS), corresponding to the resonance condition, is identified with different relative arrangements. Based on an analysis of the TCS at resonance and a duality analogy with small dipole antennas, equivalent circuits for the resonant transmission are drawn that allow the self and mutual conductances to be quantitatively extracted, thereby providing a deeper comprehension of the enhanced power transmission mechanism.

Experimental evidence of cut-wire-induced enhanced transmission of transverse-electric fields through sub-wavelength slits in a thin metallic screen

Recent numerical studies have demonstrated the possibility of achieving substantial enhancements in the transmission of transverse-electric-polarized electromagnetic fields through subwavelength slits in a thin metallic screen by placing single or paired metallic cut-wire arrays at a close distance from the screen. In this paper, we report on the first experimental evidence of such extraordinary transmission phenomena, via microwave (X/Ku-band) measurements on printed-circuit-board prototypes. Experimental results agree very well with full-wave numerical predictions, and indicate an intrinsic robustness of the enhanced transmission phenomena with respect to fabrication tolerances and experimental imperfections.

Backscattering of electromagnetic waves by the vertex area of a thin conducting screen

The backscattering of the electromagnetic waves by the vertex area of a thin metal screen is investigated. A special case when the magnetic field of the incident wave is perpendicular to the diagonal of the vertex area is considered. The dependence of the vertex-scattered signal on the grazing angle is experimentally found. At a certain angle, an extremum in the radar scattering is discovered. At the extremum, good agreement between the results predicted by the asymptotic theory and the experimental results is observed.

Paired Cut-Wire Arrays for Enhanced Transmission of Transverse-Electric Fields Through Subwavelength Slits in a Thin Metallic Screen

It has recently been shown that the transmission of electromagnetic fields through sub-wavelength slits (parallel to the electric field direction) in a thin metallic screen can be greatly enhanced by covering one side of the screen with a metallic cut-wire array laid on a dielectric layer. In this Letter, we show that a richer phenomenology (which involves both electric- and magnetic-type resonances) can be attained by pairing a second cut-wire array at the other side of the screen. Via a full-wave comprehensive parametric study, we illustrate the underlying mechanisms and explore the additional degrees of freedom endowed, as well as their possible implications in the engineering of enhanced transmission phenomena.

A spline approximation applied for solving the problem of diffraction by a periodic grating located over a chiral half-space

The method of extended boundary conditions is modified for solving the problem of scattering a plane wave by a periodic grating consisting of thin metal screens. The grating is located over a chiral half-space. The method is tested for the case of scattering by a strip structure and for the parabolic and circular shapes of the grating’s elements.

Total optical transmission through a small hole in a metal waveguide screen

We present the theory of total optical transmission through a small hole in metal waveguide screen. Unlike past works on extraordinary optical transmission using arrays, there is only a single hole; yet, the theory predicts total transmission for a perfect electric conductor (not normalized to the hole size) 100% transmission, regardless of how small the hole. This is very surprising considering the usual application of Bethe's theory to waveguide apertures. Comprehensive numerical simulations agree well with the theory and their modal-analysis supports the proposed evanescent-mode mechanism for total transmission. These simulations are extended to show the influence of realistic material response (including loss) at microwave and visible-infrared frequencies. Due to the strong resonant field localization and transmission from only a thin metal screen with a single hole, many promising applications arise for this phenomenon including filtering, sensing, plasma generation, nonlinear optics, spectroscopy, heating, optical trapping, near-field microscopy and cavity quantum electrodynamics.

Use of a spline approximation to solve the problem of diffraction by an unclosed screen located in a planar waveguide

A new method is developed for solving the problem of scattering by a thin metal screen placed in a planar waveguide. The method can be applied for a screen of an arbitrary geometry and extended to problems of scattering by bodies and unclosed screens located in complex layered structures.

An analytic formalism for the emission of coherent transition radiation from an oblique finite thin metallic target screen

Long-wavelength coherent transition radiation is commonly used in electron beam diagnostics for the determination of bunch lengths. Typically the spectrum of coherent transition radiation for a short bunch accelerator is settled in the low or sub-THz regime. Hereby, we present a theoretical model based on physical optical techniques in order to calculate emission characteristics for transition radiation, for both the radiating near-field and the far-field. This approach yields analytic solutions for the emitted electromagnetic fields without the need to solve integral equations. The simulated intensity distribution is compared with measurements showing good agreement.