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The non-specular reflection scenario is considered important for many practical applications of gratings because this regime corresponds to the maximum efficiency of diffraction. Retroreflection is a particular case of a non-specular scenario when a grating returns a large portion of the incident light back to its source. We propose a detailed quasi-optic (microwave) experimental study of the retroreflection phenomenon in dielectric metasurfaces. Our study is supplemented by an analytical description and full-wave numerical simulation. The experimental sample of the metasurface is constructed as an array of disk-shaped low-loss ceramic resonators inserted in a host with air-like material properties. To ensure efficient reflection, the metasurface is coated on one side with a metallic foil. The conditions of retroreflection for any direction and polarization of an incident wave are demonstrated in both far-field and near-field experiments. The main contribution to the non-specular reflection of the Mie-type (HE 11) mode of the disk-shaped resonators forming the metasurface is revealed. The high efficiency of retroreflection in both TE (transverse electric) and TM (transverse magnetic) polarizations allows us to consider our metasurface as a prototype of planar grating rulers for high-precision displacement measurements.

The problem of electromagnetic wave diffraction by the metallic bar grating with inhomogeneous dielectric filling of each slit between bars has been investigated by using the mode matching technique. The transmission and the inner field distribution have been analyzed for the structure which has a single defect in the periodic filling of slits. Such periodic structures are of particular interest for applications in optics, as they have the ability to concentrate a strong inner electromagnetic field and are characterized by high-Q transmission resonances. We use a simple approach to control the width and location of the stopband of the structure by placing a defect in the periodic filling of the grating slits. As a result, we observe the narrow resonance of transmission in terms of stopband width of the defect-free grating and confinement of strong inner electromagnetic field. By changing the permittivity of the defect layer we can shift the frequency of the resonant transmission.

This article provides examples that illustrate the search for different two-layer metamaterials that provide rotation of the polarization plane (“optical activity”). Selected objects show a twenty-year history of the search for a new principle of creation of polarization rotators based on planar metamaterials that were implemented in the form of thin-layered periodic structures. The manifestation of optical activity, presence or absence of satisfactory or perfect matching, the possibility of a multiband phenomena, the role of high spatial harmonics in “electromagnetics” of this effect are explained by the features of the eigen-oscillations that are excited in the gap of the multilayer structure.

PACS numbers: 81.05.Xj, 78.67.Pt Subject and purpose: The resonant properties are studied of the dielectric metalayer in a form of a doubly periodic structure consisting of silicon parallelepipeds placed on a flat quartz substrate. Design/methodology/approach: Using the pseudospectral timedomain method, numerical simulations of electromagnetic plane wave scattering on the metalayer are made. Resonant properties of the metalayer were experimentally investigated by measuring frequency characteristics of a transmitted electromagnetic wave in a quasi-optical measuring waveguide within 52 to73 GHz. For experimental study, a sample of metalayer was made with the method of mechanical cutting of a layered silicon-quartz structure by a diamond disk. A peculiarity of the studied structure is a double-layer character of the array elements. Each element has a form of a parallelepiped and includes an upper silicon part and a bottom quartz part. A height of the upper part of parallelepiped was changed during the experimental study (the patterned silicon side of the metalayer was polished). Findings: A new technological design of metalayers providing an excitation of high-Q resonances is proposed. The resonances were found to be associated with forming of longitudinal electric or magnetic dipoles in elements of the array and in the substrate. The properties of these kinds of resonances depend on the height of the elements in different ways that allows to control the resonant properties of the structure by selecting the height of the silicon parts. Experimental studies have confirmed the properties of the magnetic dipole resonances predicted theoretically. Conclusions: Performed theoretical and experimental research efforts have demonstrated the opportunity to design all-dielectric resonant metalayers for terahertz applications. Key words: dielectric metalayer, periodic structure, silicon, quartz, transmission resonance, absorption resonance Manuscript submitted 22.12.2015 Radio phys. radio astron. 2016, 21(1): 65-76 REFERENCES 1. AYDIN, K., BULU, I., GUVEN, K., KAFESAKI, M., SOUKOULIS, C. M. and OZBAY, E., 2005. Investigation of magnetic resonances for different split-ring resonator parameters and designs. New J. Phys . vol. 7, id. 168. DOI: 10.1088/1367-630/7/1/168 2. FALCONE, F., LOPETEGI, T., LASO, M. A. G., BAENA, J. D., BONACHE, J., BERUETE, M., MARQUES, R., MARTIN, F. and SOROLLA, M., 2004. Babinet principle applied to the design of metasurfaces and metamaterials. Phys. Rev. Lett . vol. 93, no. 19, id. 197401. DOI: https://doi.org/10.1103/PhysRevLett.93.197401 3. KHARDIKOV, V.V., IARKO, E. O. and PROSVIRNIN, S. L., 2012. Agiant red shift and enhancement of the light confinement in a planar array of dielectric bars. J. Opt . vol. 14, no. 3, id. 035103. DOI: https://doi.org/10.1088/2040-8978/14/3/035103 4. KHARDIKOV, V. V., IARKO, E. O. and PROSVIRNIN, S. L., 2008, Using of transmission matrixes and pseudospectral method in time domain to investigate light diffraction on planar periodic structures. Radio Phys. Radio Astron . vol. 13, no. 2, pp. 146–158 (in Russian). 5. ZHAO, Q., ZHOU, J., ZHANG, F. and LIPPENS, D., 2009. Mie resonance-based dielectric metamaterials. Materials Today . vol. 12, is. 12, pp. 60–69. DOI: https://doi.org/10.1016/S1369-7021(09)70318-9 6. VAN DE GROEP, J. and POLMAN, A., 2013. Designing dielectric resonators on substrates: Combining magnetic and electric resonances. Opt. Express. vol. 21, is. 22, pp. 26285–26302. DOI: https://doi.org/10.1364/OE.21.026285 7. LAMB, J. W., 1996. Miscellaneous data on materials for millimeter and submillimetre optics. Int. J. Infrared Millimeter Waves . vol. 17, no. 12, pp. 1997–2034. DOI: https://doi.org/10.1007/BF02069487 8. KULESHOV, Y. M., 1986. Chapter 8. Measurements in sub-mm wavelength band. In: A. Y. USIKOV, ed. Electronics and Radio Physics of Millimeter and Sub-millimeter Waves . Kyiv: Naukova Dumka Publ., pp. 140–157 (in Russian). 9. The A.Y. Usikov Institute of Radio-Physics and Electronics of National Academy of Sciences of Ukraine, 2008. Quasi-optical radio measuring devices on the basis of a circular hollow dielectric beamguide of submillimeters and millimeters waves [online]. Available from: http://www.ire.kharkov.ua/depquasi/HDB.html

We develop a group-theoretical method for analysis of metamaterials which includes both longitudinal and transversal components of currents in different parts of molecules. In comparison with the existing approach which takes into account only longitudinal components, our method allows one to obtain more information about the properties of metamaterials. As an example of the method application, we suggest and analyze an electromagnetic graphene array for terahertz region. Depending on the parameters of the structure, different types of the absorption resonances can exist in the structure which are discussed from the point of view of symmetry.

УДК 537.774.6 Исследуется резонансное увеличение коэффициента прохождения плоской электромагнитной волны через многослойный трехмерный полностью диэлектрический фотонный кристалл, в котором для получения высокой плотности моды специально создан дефектный слой с включениями активной среды. Проведено сравнение значений коэффициента прохождения для структур с разными толщинами ефектного слоя и с разными значениями мнимой части диэлектрической проницаемости активной среды. Ключевые слова: трехмерная периодическая структура, запрещенная зона, дефектный слой, резонанс прохождения Статья поступила в редакцию 22.04.2015 Radio phys. radio astron. 2015, 20(3): 216-222 СПИСОК ЛИТЕРАТУРЫ 1. Barnes W. L. Topical review. Fluorescence near interfaces: the role of photonic mode density // J. Mod. Opt. – 1998. – Vol. 45, No. 4. – P. 661–699. 2. Dowling J. P. and Bowden C. M. Atomic emission rates in inhomogeneous media with applications to photonic band structures // Phys. Rev. A. – 1992. – Vol. 46, No. 1. – P. 612 622. DOI: 10.1103/PhysRevA.46.612 3. Bendickson J. M. and Dowling J. P. Analytic expressions for the electromagnetic mode density in finite, one-dimensional, photonic band-gap structures // Phys. Rev. E. – 1996. – Vol. 53, No. 4. – P. 4107–4121. DOI: 10.1109/QELS.1996.865760 4. Sukhoivanov I. A. and Guryev I. V. Photonic Crystals. – Berlin–Heidelberg: Springer, 2009. – 242 p. 5. Lourtioz J.-M., Benisty H., Berger V., Gerard J.-M., Maystre D., and Tchelnokov A. Photonic Crystals: Towards Nanoscale Photonic Devices. – Berlin–Heidelberg: Springer, 2008. – 514 p. 6. Киттель Ч. Введение в физику твердого тела. – М.: Наука, 1978. – 791 с. 7. Сидорчук Н. В. Резонансное рассеяние волн плоскими периодическими структурами, расположенными между двумя однородными средами // Радиофизика и радиоастрономия. – 2008. – Т. 13, № 4. – С. 250–262. 8. Savelev R. S., Shadrivov I. V., Belov P. A., Rosanov N. N., Fedorov S. V., Sukhorukov A. A., and Kivshar Y. S. Loss compensation in metal-dielectric layered metamaterials // Phys. Rev. B. – 2013. – Vol. 87, Is. 11. – id.115139. DOI: 10.1103/PhysRevB.87.115139

We report on a progress in development of an idea that a proper arrangement of dielectric particles with a particular structural asymmetry which are made from a low-loss high-refractive-index material allows to reach high-Q trapped-mode resonant conditions in planar metamaterials in the microwave, infrared and visible parts of spectrum. In these metamaterials an electromagnetic coupling between the displacement currents in adjacent particles or within a single particle per unit cell induces the field concentration inside the system which can enforce a number of phenomena like luminescence, nonlinear scattering, and lasing.

We numerically investigate the resonance properties of the reflective metasurface, which is a planar, two-direction lattice of pairs of dielectric bars placed on a metal substrate. The structure is designed in such a way and with such sizes that in its subwavelength mode the first few lowest frequency resonances fall within the far infrared wavelength range. To study the physical processes in the metasurface, spectral characteristics, 3D vector plots and maps for electromagnetic fields in the structure are presented.

We demonstrate results of a simulation of nonlinear reflection of intensive terahertz radiation from a silicon-on-metal metasurface involving an excitation of a high-Q trapped mode resonance. Conditions are presented to observe effects of bistability and hysteresis of nonlinear reflection.

Optical properties of a one-dimensional photonic structure consisting of Kerr-type nonlinear and magnetic layers under the action of an external static magnetic field in the Faraday geometry are investigated. The structure is a periodic arrangement of alternating nonlinear and magnetic layers (a one-dimensional photonic crystal) with one of the layers doubled to create a defect where periodicity is violated. Strong enhancement of nonreciprocity is observed at the frequencies of the defect modes, where linearly polarized light incident from one side of the structure undergoes 90 deg polarization rotation upon reflection, while light reflected from the other side has its polarization unchanged. Using the nonlinear transfer matrix calculations in the frequency domain, it is demonstrated that defect resonances in the nonlinear reflection spectra undergo bending, resulting in polarization bistability of reflected light. This bistability is shown to result in abrupt switching between linear polarization of the output reflected light when the input intensity is varied. This switching is confirmed in finite-difference time-domain simulations, and its hysteresis character is established., Comment: 12 pages, 7 figures

An approximate self-consistent solution of the problem of plane electromagnetic wave difiraction on a thick grating of metallic bars with slits between the bars fllled a Kerr-type nonlinear dielectric is solved. The bistable operating regime of wave transmission through the grating is studied.

Using the transfer-matrix approach and solving time-domain differential equations, we analyze the loss compensation mechanism in multilayer systems composed of an absorbing transparent conductive oxide and dielectric doped with an active material. We reveal also another regime with the possibility of enhanced transmission with suppressed reflection originating from the resonant properties of the multilayers. For obliquely incident and evanescent waves, such enhanced transmission under suppressed reflection turns into the reflectionless regime, which is similar to that observed in the PT-symmetric structures, but does not require PT symmetry. We infer that the reflectionless transmission is due to the full loss compensation at the resonant wavelengths of the multilayers., Comment: 12 pages, 10 figures

We report resonant features of electrically controllable reflect array consisting of continues wavy-shaped graphene strips placed on a thin metal-backed dielectric substrate.

The resonance properties of the metasurface were obtained using the pseudo-spectral time domain method. The frequency dependence of transmission and absorption of sub-THz waves passed through metasurface have been measured.

The most interesting examples of various double-layer metamaterials that provide “optical activity” are presented to reveal the motivation of use of different cell topologies. The phenomena of the giant “optical activity”, existence or lack of perfect matching, multi-band phenomena, the role of higher space harmonics, and influence of space spectrum rarefying are considered and explained based on the spectral theory of opened structures.

Electromagnetic wave scattering by a PEC rectangular bars grating with a piecewise homogeneous dielectric filling slits between bars has been studied by the mode matching technique. The frequency selective properties of transmission and inner field distribution of the grating with regular periodic filling of the slits and the grating with a broken periodicity of dielectric filling are investigated.

We report on recent developments of the conception of all-dielectric planar metamaterials that are capable to support high-Q trapped-mode resonant excitations. A set of new designs of metamaterials are proposed and configurations of the unit cell allowing trapped-mode resonances are discussed. Advantages of the proposed designs to manifest high-Q resonant regime providing a concision choice of the degree of structural asymmetry within the unit cell are revealed.

We propose a novel design of a true 3D chiral metasurface behaving as a spatial polarization converter with asymmetric transmission. The metasurface is made of a lattice of metallic sesquialteral (one and a half pitch) helical particles. Each particle contains six rectangular bars arranged in a series one above the another creating a helix The proposed metasurface exhibits a dual-band asymmetric transmission accompanied by the effect of a complete polarization conversion in the response on the particular distributions of currents induced in the particle's bars by an incident wave. Regarding circularly polarized waves the metasurface demonstrates a strong circular dichroism. A prototype of the metasurface is manufactured for the microwave experiment by using 3D-printing technique utilizing Cobalt-Chromium alloy, which exhibits good performances against thermal fatigue and corrosion at high temperatures. Our work paves the way to find an industrial solution on fabricating communication components with efficient polarization conversion for extreme environments., Comment: 5 pages, 4 figures

The dispersion relation for propagation and attenuation constants of electromagnetic waves which are supported by a metal film placed on a substrate and covered by a thin dielectric layer is studied numerically in visible and infrared wavelength ranges.

Analysis of frequency selective surfaces with high Q-factor resonance and polarization insensitivity is the aim of this work. Two new array configurations are suggested, which support the trapped-mode regime. The arrays were optimized in order to obtain the highest Q-factor by varying some of their geometrical and physical parameters. Theoretical results are presented and discussed.

We report on a bistable wave transmission through a narrow slit with Kerr nonlinear dielectric filling which is perforated on a perfectly conducting metal screen. The approximate analytical expressions for calculation of both the inner intensity inside the slit and the transmission coefficient are presented.

We demonstrate for the first time a nanostructured planar photonic metamaterial transmitting light differently in forward and backward directions.

In 2003 Bergman and Stockman introduced the spaser, a quantum amplifier of surface plasmons by stimulated emission of radiation. They argued that, by exploiting a metal/dielectric composite medium, it should be possible to construct a nano-device, where a strong coherent field is built up in a spatial region much smaller than the wavelength. It was suggested that V-shaped metallic inclusions, combined with a collection of semiconductor quantum dots could lead to a realization of the spaser. Here we introduce a further development of the spaser concept. We show that by combining the metamaterial and spaser ideas one can create a planar narrow-diversion coherent source of electromagnetic radiation that is fuelled by plasmonic oscillations. We argue that two-dimensional arrays of a certain class of plasmonic resonators supporting high-Q current excitations belong to a new category of coherent metamaterials that provide an intriguing opportunity to create a spatially and temporally coherent laser source, the Lasing Spaser.

We show that in the visible to near-IR part of the spectrum, normal incidence transmission of circularly polarized light through a nanostructured anisotropic planar chiral metamaterial is asymmetric in the opposite directions. The new effect is fundamentally different from the conventional gyrotropy of bulk chiral media and the Faraday effect. It has a resonance nature associated with a new type of excitation in the metal nanostructure: the enantiomerically sensitive plasmon.

We investigate the resonant enhancement of transmission and reflection of a plane electromagnetic wave incident on a multilayer three-dimensional fully dielectric photonic crystal in which a defect layer with excited medium inclusions has been designed specifically to obtain a high-density mode. The numerical investigation is performed for a near infrared wavelength range. Comparison of transmission and reflection coefficient values for structures with different thicknesses of a defect layer and values of an imaginary part of an active medium permittivity is presented.

Frequency dependence of phase reflection coefficient of a microstrip periodic gratingof undulated strips is numerically investigated by means of the method of moments. The possibility of using of such structure as a high-impedance surface is shown. The influence of change in shape of the strips and in the parameters of dielectric substrate on the frequency characteristics of the grating is analyzed for the case on normal incidence of a plane electromagnetic wave. The possibility of electronic control of the grating characteristics is demonstrated. INTRODUCTION As is known, at normal reflection of a plane electromagnetic wave by perfectly conductive metal plane the vectors of the incident and reflected electric field strength have the same values but opposite directions on this plane owing to equality to zero of the strength of the total electric field E G in a perfect conductor. Therefore the reflection coefficient of such plane (which is called also “electric wall”) is equal to –1, and the surface impedance, as follows from its definition

Electromagnetic Wave Diffraction by Two-Periodic Grating of Continuous Curvilinear Metal Strips

An analytical model of reflection and transmission of plane waves in double regular arrays of bianisotropic particles is developed. A method to correct approximate values of the particle polarizabilities so that the energy conservation requirements are exactly satisfied is proposed. Double arrays of planar omega particles are studied in detail, and it is shown that very sharp Bragg resonances exist in such arrays. The theory is verified by comparison with numerical simulations based on the method of moments.

Numerical solution of electromagnetic wave diffraction by a two-periodic grating of wavy metal strips placed on a dielectric substrate is obtained. The solution is verified for a particular case of straight strips by comparison with the rigorous solution. Analytical expressions for the reflection coefficients from wavy gratings in free space are obtained in the low frequency range. Frequency dependencies of the reflection coefficients are analyzed. Differences in reflection from classical one-periodic gratings of straight strips are discussed.

We discuss the similarity between the nature of resonant oscillations in two nonlinear systems, namely, a chain of coupled Duffing oscillators and a bilayer fish-scale metamaterial. In such systems two different resonant states arise which differ in their spectral lines. The spectral line of the first resonant state has a Lorentzian form, while the second one has a Fano form. This difference leads to a specific nonlinear response of the systems which manifests itself in appearance of closed loops in spectral lines and bending and overlapping of resonant curves. Conditions of achieving bistability and multistability are found out., 14 pages, 6 figures

A numerical analysis of reflecting and transmitting properties of multi-layered structures composed of doubly pe- riodic arrays of metallic strips is presented in this paper. Array elements have been selected having the shape of the capital letters C, S and Ω. The metallic strips of arrays are placed on a thin dielectric substrate. These strips may include a con- centrated impedance loading. The interferences in the multi- layered array systems, due to multiple reflections of waves between the layers, combined with the resonance properties of single layers lead the structure to acquire typical properties of the photonic band gap (PBG) crystals.

Results of research of resonant phenomena in planar periodic structures consisted of dielectric elements are presented. An existence of high Q-factor trapped mode resonances is revealed in structure which a periodic cell is composed of two dielectric bars with different lengths or width. Besides higher Q-factor essential difference of studied structures in contrast to the planar structure with a single dielectric bar in the unit cell is appearing of a great red shift of a trapped mode resonant wavelength. This property is very attractive to design a new type high-Q dielectric metamaterials for THz and Infrared.

The results of the study of the electromagnetic waves resonant reflection from and transmission through planar metamaterials based on periodic structures, which are composed of some elements consisted of nonlinear materials are presented.

The possibility of achievement of the reflected field amplification by the metamaterial made of microstrip grating placed on the layer of an optically gain dielectric is shown. The comparison of obtained results with ones known for the metamaterial with a lossy substrate is curried out.

In this paper we present some recent results of our theoretical investigations of electromagnetically controllable surfaces. These surfaces are designed on the basis of periodic arrays made of metallic inclusions of special form which are placed on a thin substrate of active material (magnetized ferrite or optically active semiconductor). The main peculiarity of the studied structures is their capability to support the trapped-mode resonance which is a result of the antiphase current oscillations in the elements of a periodic cell. Several effects, namely: tuning the position of passband and the linear and nonlinear (bistable) transmission switching are considered when an external static magnetic field or optical excitation are applied. Our numerical calculations are fulfilled in both microwave and optical regions.

A one-dimensional magnetophotonic crystal with a nonlinear defect placed either symmetrically or asymmetrically inside the structure is considered. Simultaneous effects of time-reversal nonreciprocity and nonlinear spatial asymmetry in the structure are studied. Bistable response is demonstrated in a such system, accompanied by abrupt polarization switching between two circular or elliptical polarizations for transmitted and reflected waves. The effect is explained in terms of field localization at defect-mode spectral resonances and can be used in the design of thin-film optical isolators and polarization transformation devices., 20 pages, 8 figures

It is shown that a one-dimensional magnetophotonic crystal with a nonlinear cavity layer exhibits bistable optical response accompanied by abrupt polarization switching between two circular or elliptical polarizations for transmitted and reflected waves. The effect is explained in terms of field localization at cavity-mode spectral resonances and can be used in the design of thin-film tunable optical isolators and polarization transformation devices.

We report on a bistable light transmission through two-layered structure which consists of two gratings of planar perfectly conducting infinite strips placed on the both sides of a dielectric slab. It is demonstrated that a switching may be achieved nearly the frequency of the high-quality-factor Fano-shape trapped-mode resonance excitation.

We report on a bistable light transmission through a planar metamaterial consisted of a metal pattern of weakly asymmetric elements placed on a nonlinear substrate which enables sharp resonance response by excitation of a trapped mode. A feedback required for bistability is provided by the coupling between strong trapped mode resonance antiphased currents exited on the metal elements and an intensity of inner field in the nonlinear substrate.