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Ever since their discovery, Maxwell’s equations have been vigorously applied in a large plethora of complex material configurations to characterize their radiation and scattering properties, and to provide explanations of and insights into their physics and potential applications. Many advances have been facilitated by material science and engineering. New materials lead to new physics and to the consequent engineering of new devices. In particular, efforts in the field of and metasurfaces have not only furnished functional material platforms that have revealed truly novel and rather exotic properties, but they have also revived and extended the traditional scattering analysis methods. While most initial efforts exploited metals in the proposed platforms, the obvious desire to move the operation to higher frequencies made use of low-loss dielectrics. With respect to the latter, a very appealing avenue has recently turned out to be use of nothing more than water as the main ingredient in platforms for tailoring of microwaves at will. Among the advantages of water are its price, availability, biofriendly nature and high and easily tunable permittivity. Our talk reviews mostly our own analytical, numerical and experimental efforts on how water can be used to design simple microwave platforms like e.g., metasurface reflect-arrays, dielectric resonator antennas and Huygens antennas, and water-based structures supporting the socalledbound-states in the continuum with huge application potential. While the reviewed water-based devices are truly simple, they facilitate a revival, perhaps a necessary one, of our field by placing mature theories in the context of modern applications.

Hydrogen sensing is crucial in a wide variety of areas, such as industrial, environmental, energy and biomedical applications. However, engineering a practical, reliable, fast, sensitive and cost-effective hydrogen sensor, is a persistent challenge. Here we demonstrate hydrogen sensing using aluminum-doped zinc oxide (AZO) metasurfaces based on optical read-out. The proposed sensing system consists of highly ordered AZO nanotubes (hollow pillars) standing on a SiO2 layer deposited on a Si wafer. Upon exposure to hydrogen gas, the AZO nanotube system shows a wavelength shift in the minimum reflectance by 13 nm within 10 minutes for a hydrogen concentration of 4%. These AZO nanotubes can also sense the presence of a low concentration (0.7 %) of hydrogen gas within 10 minutes. Its rapid response time even for low concentration, the possibility of large sensing area fabrication with good precision, and high sensitivity at room temperature make these highly ordered nanotube structures a promising miniaturized H2 gas sensor., Comment: 15 pages, 6 figures

Due to military events started in 2014 in the east of Ukraine, the number of gunshot injuries because of the use of large-caliber firearms has significantly increased. Consequently, the study of damage by largescale weapons is a relevant forensic medical problem. The article presents the results of the study of gunshot injuries caused by large-caliber weapons on the example of the wounds caused by armor-piercing B-32 bullets during shots from Vladimirov tank machine gun. This 14.5-mm large-caliber machine gun is a powerful and efficient automatic weapon designed to defeat light-armored ground targets at distances of up to 1000 m, unarmed targets at distances up to 2000 m, as well as air low-flying low-speed targets at altitudes up to 1500 m at distances up to 2000 m. As an example, there is a specific case of practice that occurred on the territory of Donetsk region in May 2014. Two people were deadly wounded when a vehicle was shot from a large-gauge machine gun at a distance of about 300 m. During the inspection of the event, numerous transverse spherical openings of the cockpit of the car were installed with damage to the engine compartment and parts of the cabin, as well as found fragments of bullets B-32 cartridges of caliber 14.5 mm. Article shows the morphological characteristics of damage to the human body occurring after shots from large-caliber weapons through an obstacle (truck cabin) from a non-short distance. The amount of body injuries found during the corpses examination indicates massive injuries (unusual for ballistic guns as a result of the use of medium-caliber small arms), and is characterized by the presence of numerous injuries from secondary shells, which is more characteristic of an explosive trauma. The described type of gunshot wounds requires further careful study due to the complexity of their differential diagnosis., В статье представлены результаты исследования огнестрельных повреждений, причиненных с крупнокалиберного оружия на примере поражений бронебойно-зажигательными пулями Б-32 при выстрелах с танкового пулемета Владимирова. Показано морфологические характеристики повреждений тела человека, возникающие при выстрелах из крупнокалиберного оружия через препятствие (кабина грузового автомобиля) с неблизкой дистанции. Приведенный объем телесных повреждений, установленный при экспертизе трупов, свидетельствует о массивности телесных повреждений, нетипичной для пулевых огнестрельных ранений в результате применения стрелкового оружия среднего калибра. Указанные ранения также отличаются наличием многочисленных повреждений от вторичных снарядов, что более характерно для взрывной травмы и требуют дальнейшего тщательного изучения, в связи со сложностью дифференциальной диагностики., У статті представлені результати дослідження вогнепальних ушкоджень, завданих із великокаліберної зброї на прикладі уражень бронебійно-запалювальними кулями Б-32 при пострілах із танкового кулемету Володимирова. Показано морфологічні характеристики ушкоджень тіла людини, що виникають при пострілах із великокаліберної зброї через перешкоду (кабіна вантажного автомобіля) з неблизької дистанції. Наведений обсяг тілесних ушкоджень, що був встановлений при експертизі трупів, свідчить про масивність тілесних ушкоджень, нетипову для кульових вогнепальних поранень внаслідок застосування стрілецької зброї середнього калібру. Наведені поранення також вирізняються наявністю численних ушкоджень від вторинних снарядів, що є більш характерним для вибухової травми та потребують подальшого ретельного вивчення, у зв’язку зі складністю диференційної діагностики.

Photonic spin Hall effect in transmission is a transverse beam shift of the out-coming beam depending on polarization of the in-coming beam. The effect can be significantly enhanced by materials with high anisotropy. We report the first experimental demonstration of the photonic spin Hall effect in a multilayer hyperbolic metamaterial at visible wavelengths (wavelengths of 520 nm and 633 nm). The metamaterial is composed of alternating layers of gold and alumina with deeply-subwavelength thicknesses, exhibiting extremely large anisotropy. The angle resolved polarimetric measurements showed the shift of 165 $\mu m$ for the metamaterial of 176 nm in thickness. Additionally the transverse beam shift is extremely sensitive to the variations of the incident angle changing theoretically by 270 $\mu m$ with one milli-radian ($0.057^\circ$). These features can lead to minituarized spin Hall switches and filters with high angular resolution., Comment: 4 pages, 4 figures

Nanoantennas for highly efficient excitation and manipulation of surface waves at nanoscale are key elements of compact photonic circuits. However, previously implemented designs employ plasmonic nanoantennas with high Ohmic losses, relatively low spectral resolution, and complicated lithographically made architectures. Here we propose an ultracompact and simple dielectric nanoantenna (silicon nanosphere) allowing for both directional launching of surface plasmon polaritons on a thin gold film and their demultiplexing with a high spectral resolution. We show experimentally that mutual interference of magnetic and electric dipole moments supported by the dielectric nanoantenna results in opposite propagation of the excited surface waves whose wavelengths differ by less than 50 nm in the optical range. Broadband reconfigurability of the nanoantennas operational range is achieved simply by varying the diameter of the silicon sphere. Moreover, despite subwavelength size ($, Comment: added relevant references; fixed typos in Supplementary eq. 8,9,11

Optical metasurfaces have great potential to form the platform for manipulation of surface waves. A plethora of advanced surface-wave phenomena utilizing negative refraction, self-collimation and channeling of 2D waves can be realized through on-demand engineering of dispersion properties of a periodic metasurface. In this letter, we report on the first-time direct experimental polarization-resolved measurement of dispersion of 2D optical plasmons supported by an anisotropic metasurface. We demonstrate that a subdiffractive array of strongly coupled resonant anisotropic plasmonic nanoparticles supports unusual optical surface waves with mixed TE- and TM-like polarizations. With the assistance of numerical simulations we identify dipole and quadrupole dispersion bands. The shape of isofrequency contours changes drastically with frequency exhibiting nontrivial transformations of their curvature and topology that is consistently confirmed by the experimental data. By revealing polarization degree of freedom for surface waves, our results open new routes for designing of planar on-chip devices for surface photonics.

Metasurfaces offer great potential to control near- and far-fields through engineering of optical properties of elementary cells or meta-atoms. Such perspective opens a route to efficient manipulation of the optical signals both at nanoscale and in photonics applications. In this paper we show that by using an effective surface conductivity tensor it is possible to unambigiously describe optical properties of an anisotropic metasurface in the far- and near-field regimes. We begin with retrieving the effective surface conductivity tensor from the comparative analysis of experimental and numerical reflectance spectra of a metasurface composed of elliptical gold nanoparticles. Afterwards restored conductivities are validated in the crosscheck versus semianalytic parameters obtained with the discrete dipole model with and without dipoles interaction contribution. The obtained effective parameters are further used for the dispersion analysis of surface plasmons localized at the metasurface. The effective medium model predicts existence of both TE- and TM-polarized plasmons in a wide range of optical frequencies and describes peculiarities of their dispersion, in particularly, topological transition from the elliptical to hyperbolic regime with eligible accuracy. The analysis in question offers a simple practical way to describe properties of metasurfaces including ones in the near-field zone by extracting effective parameters from the convenient far-field characterisation., Comment: 29 pages, 9 figures

We analyze surface electromagnetic waves with hyperbolic dispersion supported at the interface between a semi-infinite isotropic medium and an effective uniaxial material. Apart from known types plasmons with hyperbolic dispersion curve, sometimes referred to as Dyakonov plasmons [Z. Jacob and E. E. Narimanov, APL 93, 221109 (2008)], we classify two new types of surface waves with hyperbolic dispersion. One type of such waves, in contrary to Dyakonov plasmons, does not require hyperbolic metamaterials to be involved. These hybrid-polarized plasmon modes with both TE and TM electromagnetic components are directional. Their propagation direction can be controlled by changing material parameters., 11 pages, 3 figures

The article introduces a classical-method-based analysis procedure for transients in the control cascade of an electromagnetic valve for combustion engine exhaust sampling. Analytical expressions for currents and voltage on the cascade basic elements are obtained to allow specifying the optimal parameters of these elements in terms of speed and reliability., Предложена процедура анализа переходных процессов в каскаде управления электромагнитным клапаном для отбора проб выпускных газов двигателя внутреннего сгорания, базирующаяся на классическом методе, получены аналитические выражения для токов и напряжений на основных элементах каскада, позволяющие определить оптимальные по быстродействию и надежности значения параметров этих элементов., Запропонована процедура аналізу перехідних процесів в каскаді управління електромагнітним клапаном для відбору проб випускних газів двигуна внутрішнього згорання, що базується на класичному методі, отримані аналітичні вирази для струмів і напруг на основних елементах каскаду, що дозволяють визначити оптимальні по швидкодії та надійності значення параметрів цих елементів.

We propose several planar layouts of ultra-compact plasmonic waveguide modulators that utilize alternative CMOS-compatible materials. The modulation is efficiently achieved by tuning the carrier concentration in a transparent conducting oxide layer, thereby tuning the waveguide either in plasmonic resonance or off-resonance. Resonance significantly increases the absorption coefficient of the plasmonic waveguide, which enables larger modulation depth. We show that an extinction ratio of 86 dB/um can be achieved, allowing for a 3-dB modulation depth in less than one micron at the telecommunication wavelength. Our multilayer structures can potentially be integrated with existing plasmonic and photonic waveguides as well as novel semiconductor-based hybrid photonic/electronic circuits.

We study emission of photoelectrons from plasmonic nanoparticles into surrounding matrix. We consider two mechanisms of the photoelectric effect from nanoparticles - surface and volume ones, and use models of these two effects which allow us to obtain analytical results for the photoelectron emission rates from nanoparticle. Calculations have been done for the step potential at surface of spherical nanoparticle, and the simple model for the hot electron cooling have been used. We highlight the effect of the discontinuity of the dielectric permittivity at the nanoparticle boundary in the surface mechanism, which leads to substantial (by 5 times) increase of photoelectron emission rate from nanoparticle compared to the case when such discontinuity is absent. For plasmonic nanoparticle, a comparison of two mechanisms of the photoeffect was done for the first time and showed that surface photoeffect, at least, does not concede the volume one, which agrees with results for the flat metal surface first formulated by Tamm and Schubin in their pioneering development of quantum-mechanical theory of photoeffect in 1931. In accordance with our calculations, this predominance of the surface effect is a result of effective cooling of hot carriers, during their propagation from volume of the nanoparticle to its surface in the scenario of the volume mechanism. Taking into account both mechanisms is essential in development of devices based on the photoelectric effect and in usage of hot electrons from plasmonic nanoantenna., Comment: 13 pages, 10 figures, 61 references

Photoelectric properties of metamaterials containing non-centrosymmetric, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically studied. Due to the asymmetric shape of the nanoparticle boundary, photoelectron emission acquires a preferred direction, resulting in a photocurrent flow in that direction when nanoparticles are uniformly illuminated by a homogeneous plane wave. This effect is a direct analogy of the photogalvanic (or bulk photovoltaic) effect known to exist in media with non-centrosymmetric crystal structure, such as doped lithium niobate or bismuth ferrite, but is several orders of magnitude stronger. Termed the giant plasmonic photogalvanic effect, the reported phenomenon is valuable for characterizing photoemission and photoconductive properties of plasmonic nanostructures, and can find many uses for photodetection and photovoltaic applications., Comment: 8 pages, 4 figures

A planar Babinet-inverted dimer metamaterial possessing strong optical activity is proposed and characterized. An original fabrication method to produce large area (up to several cm2) freely suspended flexible metallic membranes is implemented to fabricate the metamaterial. Its optical properties are characterized by terahertz time-domain spectroscopy, revealing anisotropic transmission with high optical activity. A simple coupled resonator model is applied to explain the principal optical features of the dimers, with predictive power of positions and number of resonances through a parametrical model. The model is validated for correct polarization-dependent quantitative results on the optical activity in transmission spectra. The fabrication method presented in this work as well as the slit dimer design has great potential for exploitation in terahertz optics.

Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/pip.2278 We model the electron photoemission frommetal nanoparticles into a semiconductor in a Schottky diode with a conductive oxide electrode hosting the nanoparticles. We show that plasmonic effects in the nanoparticles lead to a substantial enhancement in photoemission compared with devices with continuous metal films. Optimally designed metal nanoparticles can provide an effectivemechanismfor the photon absorption in the infrared range below the semiconductor bandgap, resulting in the generation of a photocurrent in addition to the photocurrent from band-to-band absorption in a semiconductor. Such structure can form the dais of the development of plasmonic photoemission enhanced solar cells.

An alternative, field-based formulation of transformation optics is proposed. Field transformations are expressed in the language of boundary conditions for the electromagnetic fields facilitated through the introduction of generalized potential functions. It is shown that the field-based approach is equivalent to the conventional coordinate-transformation approach but is preferable when looking for specific field distribution. A set of example devices such as invisibility cloaks, concentrators, rotators, and transformation optics lenses capable of creating light beams with predetermined field distribution (e.g., Gaussian and sinusoidal) is studied to validate the effectiveness of the field-based formulation. As for the boundary conditions for the cloaked region the absence of the normal component of the Poynting vector is justified. In the frames of the field-based approach the physical reasons behind infinite components (singularities) of the material parameters of transformation optics devices are straightforwardly revealed.

An efficient and compact coupler—a device that matches a microwaveguide and a nanowaveguide—is an essential component for practical applications of nanophotonic systems. The number of coupling approaches has been rapidly increasing in the past ten years with the help of plasmonic structures and metamaterials. In this paper we overview recent as well as common solutions for nanocoupling. More specifically we consider the physical principles of operation of the devices based on a tapered waveguide section, a direct coupler, a lens, and a scatterer and support them with a number of examples.

We perform ultrabroadband THz spectroscopy of the dielectric function of arsenic trisulfide (As2S3). We observe the transition from universal scaling of the absorption at low frequencies to medium- and short-range-order at higher frequencies.

We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by re-seeding the cavity after a short cool-down period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented., Comment: Accepted for publication in Physical Review Letters. Published, somewhat shortened version

Udgivelsesdato: May

It is shown that total reflection for all incident angles does not require a two- or three-dimensional photonic crystal. We demonstrate that a one-dimensional photonic crystal can exhibit total omni-directional reflection for any incident wave within some frequency region. The formation of the omni-directional gap is discussed and a wide range of realistic fabrication parameters is proposed., 4 pages, 7 figures; submitted to Physical Review Letters on June 1, 1998, resubmitted on October 12, 1998