49 research outputs found
Broadband reflectionless metasheets: Frequency-selective transmission and perfect absorption
Energy of propagating electromagnetic waves can be fully absorbed in a thin
lossy layer, but only in a narrow frequency band, as follows from the causality
principle. On the other hand, it appears that there are no fundamental
limitations on broadband matching of thin absorbing layers. However, known thin
absorbers produce significant reflections outside of the resonant absorption
band. In this paper we explore possibilities to realize a thin absorbing layer
which produces no reflected waves in a very wide frequency range, while the
transmission coefficient has a narrow peak of full absorption. Here we show,
both theoretically and experimentally, that a wide-band-matched thin resonant
absorber, invisible in reflection, can be realized if one and the same resonant
mode of the absorbing array unit cells is utilized to create both electric and
magnetic responses. We test this concept using chiral particles in each unit
cells, arranged in a periodic planar racemic array, utilizing chirality
coupling in each unit cell but compensating the field coupling at the
macroscopic level. We prove that the concept and the proposed realization
approach also can be used to create non-reflecting layers for full control of
transmitted fields. Our results can have a broad range of potential
applications over the entire electromagnetic spectrum including, for example,
perfect ultra-compact wave filters and selective multi-frequency sensors.Comment: 9 pages, 10 figure
Non-scattering Metasurface-bound Cavities for Field Localization, Enhancement, and Suppression
We propose and analyse metasurface-bound invisible (non-scattering) partially
open cavities where the inside field distribution can be engineered. It is
demonstrated both theoretically and experimentally that the cavities exhibit
unidirectional invisibility at the operating frequency with enhanced or
suppressed field at different positions inside the cavity volume. Several
examples of applications of the designed cavities are proposed and analyzed, in
particular, cloaking sensors and obstacles, enhancement of emission, and
"invisible waveguides". The non-scattering mode excited in the proposed cavity
is driven by the incident wave and resembles an ideal bound state in the
continuum of electromagnetic frequency spectrum. In contrast to known bound
states in the continuum, the mode can stay localized in the cavity infinitely
long, provided that the incident wave illuminates the cavity
Full light absorption in single arrays of spherical nanoparticles
In this paper we show that arrays of core-shell nanoparticles function as
effective thin absorbers of light. In contrast to known metamaterial absorbers,
the introduced absorbers are formed by single planar arrays of spherical
inclusions and enable full absorption of light incident on either or both sides
of the array. We demonstrate possibilities for realizing different kinds of
symmetric absorbers, including resonant, ultra-broadband, angularly selective,
and all-angle absorbers. The physical principle behind these designs is
explained considering balanced electric and magnetic responses of unit cells.
Photovoltaic devices and thermal emitters are the two most important potential
applications of the proposed designs.Comment: (e.g.: 18 pages, 5 figures
Unleashing infinite momentum bandgap using resonant material systems
The realization of photonic time crystals is a major opportunity but also comes with significant challenges. The most pressing one, potentially, is the requirement for a substantial modulation strength in the material properties to create a noticeable momentum bandgap. Reaching that noticeable bandgap in optics is highly demanding with current, and possibly also future, material platforms since their modulation strength is small by tendency. Here we demonstrate that by introducing temporal variations in a resonant material, the momentum bandgap can be drastically expanded, potentially approaching infinity with modulation strengths in reach with known low-loss materials and realistic laser pump powers. The resonance can emerge from an intrinsic material resonance or a suitably spatially structured material supporting a structural resonance. Our concept is validated for resonant bulk media and optical metasurfaces and paves the way toward the first experimental realizations of photonic time crystals
Optical Tellegen metamaterial with spontaneous magnetization
The nonreciprocal magnetoelectric effect, also known as the Tellegen effect,
promises a number of groundbreaking phenomena connected to fundamental (e.g.,
electrodynamics of axion and relativistic matter) and applied physics (e.g.,
magnetless isolators). We propose a three-dimensional metamaterial with an
isotropic and resonant Tellegen response in the visible frequency range. The
metamaterial is formed by randomly oriented bi-material nanocylinders in a host
medium. Each nanocylinder consists of a ferromagnet in a single-domain magnetic
state and a high-permittivity dielectric operating near the magnetic Mie-type
resonance. The proposed metamaterial requires no external magnetic bias and
operates on the spontaneous magnetization of the nanocylinders. By leveraging
the emerging magnetic Weyl semimetals, we further show how a giant bulk
effective magnetoelectric effect can be achieved in a proposed metamaterial,
exceeding that of natural materials by almost four orders of magnitude.Comment: 11 pages, 4 figure
Parametric Mie resonances and directional amplification in time-modulated scatterers
We provide a theoretical description of light scattering by a spherical
particle whose permittivity is modulated in time at twice the frequency of the
incident light. Such a particle acts as a finite-sized photonic time crystal
and, despite its sub-wavelength spatial extent, can host optical parametric
amplification. Conditions of parametric Mie resonances in the sphere are
derived. We show that time-modulated materials provide a route to tailor
directional light amplification, qualitatively different from that in
scatterers made from a gain media. We design two characteristic time-modulated
spheres that simultaneously exhibit light amplification and desired radiation
patterns, including those with zero backward and/or vanishing forward
scattering. The latter sphere provides an opportunity for creating shadow-free
detectors of incident light.Comment: 8 pages, 4 figure
ΠΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ ΠΆΠΈΠ΄ΠΊΠΈΡ ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° ΡΠ°ΡΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ Π±ΠΈΠΎΠΌΠ°ΡΡΡ Ρ ΡΡΠ΅ΡΠΎΠΌ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΈΡ ΠΎΡ Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ
The article presents the results of computational and experimental studies of thermochemical conversion of wood biomass to obtain liquid pyrolysis products taking into account their cooling rate. The method of calculating the optimal operating parameters (temperature and cooling rate) of the techno-logical process is presented. An expression is proposed to determine the consumption of wood raw materials depending on the temperature of the thermochemical conversion process. It is noted that the mass yield of liquid pyrolysis products from the reactor poorly depends on temperature and is approximately 0.45 in the range from 573 to 923 K. To assess the effect of the cooling rate of liquid pyrolysis products, a third-order differential equation was used for a model limited by the reaction rate. It has been shown that when liquid pyrolysis products are cooled, the degree of their conversion tends to a certain value other than 1 (depending on the cooling rate). Calculated data on the dependence of the degrees of conversion of liquid wood pyrolysis products on time at different cooling rates and temperatures of thermochemical conversion of biomass have been obtained. It has been established also that the ratio of the mass yield of cooled liquid pyrolysis products to the initial loading of the pyrolysis reactor makes it possible to find optimal cooling conditions for the primary products of biomass pyrolysis carried out at certain temperatures. Graphs of the dependence of this parameter on the temperature of the thermochemical conversion of wood biomass for different cooling rates of liquid pyrolysis products are presented. It is shown that the maximum possible yield of liquid products is provided at a reactor temperature of 923β973 K and a cooling rate of 700000β1200000 degrees/min. However, achieving such cooling rates is rather a difficult technical task. Therefore, more limited temperature 773β800 K is accepted, at which a practically realizable cooling rate of primary biomass de-composition products is achieved.Π ΡΡΠ°ΡΡΠ΅ ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠ°ΡΡΠ΅ΡΠ½ΡΡ
ΠΈ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΡΠ΅ΡΠΌΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ Π΄ΡΠ΅Π²Π΅ΡΠ½ΠΎΠΉ Π±ΠΈΠΎΠΌΠ°ΡΡΡ Ρ ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΠ΅ΠΌ ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° Ρ ΡΡΠ΅ΡΠΎΠΌ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΈΡ
ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ. ΠΡΠΈΠ²Π΅Π΄Π΅Π½Π° ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΡΠ°ΡΡΠ΅ΡΠ° ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΡ
ΡΠ΅ΠΆΠΈΠΌΠ½ΡΡ
ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² (ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΡ ΠΈ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ) ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΡΠΎΡΠ΅ΡΡΠ°. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ΠΎ Π²ΡΡΠ°ΠΆΠ΅Π½ΠΈΠ΅ Π΄Π»Ρ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ ΡΠ°ΡΡ
ΠΎΠ΄Π° Π΄ΡΠ΅Π²Π΅ΡΠ½ΠΎΠ³ΠΎ ΡΡΡΡΡ Π² Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΠΎΡ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΡ ΡΠ΅ΡΠΌΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ. ΠΡΠΌΠ΅ΡΠ΅Π½ΠΎ, ΡΡΠΎ ΠΌΠ°ΡΡΠΎΠ²ΡΠΉ Π²ΡΡ
ΠΎΠ΄ ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° ΠΈΠ· ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΡΠ»Π°Π±ΠΎ Π·Π°Π²ΠΈΡΠΈΡ ΠΎΡ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΡ ΠΈ ΡΠ°Π²Π΅Π½ ΠΏΡΠΈΠΌΠ΅ΡΠ½ΠΎ 0,45 Π² Π΄ΠΈΠ°ΠΏΠ°Π·ΠΎΠ½Π΅ ΠΎΡ 573 Π΄ΠΎ 923 Π. ΠΠ»Ρ ΠΎΡΠ΅Π½ΠΊΠΈ Π²Π»ΠΈΡΠ½ΠΈΡ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΈΡ
ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΎ Π΄ΠΈΡΡΠ΅ΡΠ΅Π½ΡΠΈΠ°Π»ΡΠ½ΠΎΠ΅ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅ ΡΡΠ΅ΡΡΠ΅Π³ΠΎ ΠΏΠΎΡΡΠ΄ΠΊΠ° Π΄Π»Ρ ΠΌΠΎΠ΄Π΅Π»ΠΈ, Π»ΠΈΠΌΠΈΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΡΠΊΠΎΡΠΎΡΡΡΡ ΡΠ΅Π°ΠΊΡΠΈΠΈ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΠΏΡΠΈ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΠΈ ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° ΡΡΠ΅ΠΏΠ΅Π½Ρ ΠΈΡ
ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ ΡΡΡΠ΅ΠΌΠΈΡΡΡ ΠΊ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Π½ΠΎΠΌΡ Π·Π½Π°ΡΠ΅Π½ΠΈΡ, ΠΎΡΠ»ΠΈΡΠ½ΠΎΠΌΡ ΠΎΡ 1. ΠΠΎΠ»ΡΡΠ΅Π½Ρ ΡΠ°ΡΡΠ΅ΡΠ½ΡΠ΅ Π΄Π°Π½Π½ΡΠ΅ ΠΏΠΎ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΡΡΠ΅ΠΏΠ΅Π½ΠΈ ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° Π΄ΡΠ΅Π²Π΅ΡΠΈΠ½Ρ ΠΎΡ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ ΠΏΡΠΈ ΡΠ°Π·Π»ΠΈΡΠ½ΠΎΠΉ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΈΡ
ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ ΠΈ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ΅ ΡΠ΅ΡΠΌΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ Π±ΠΈΠΎΠΌΠ°ΡΡΡ. Π£ΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ, ΡΡΠΎ ΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠ΅ ΠΌΠ°ΡΡΠΎΠ²ΠΎΠ³ΠΎ Π²ΡΡ
ΠΎΠ΄Π° ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½Π½ΡΡ
ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° ΠΊ Π½Π°ΡΠ°Π»ΡΠ½ΠΎΠΉ Π·Π°Π³ΡΡΠ·ΠΊΠ΅ ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π½ΠΎΠ³ΠΎ ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ Π½Π°ΠΉΡΠΈ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΠ΅ ΡΡΠ»ΠΎΠ²ΠΈΡ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ ΠΏΠ΅ΡΠ²ΠΈΡΠ½ΡΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° Π±ΠΈΠΎΠΌΠ°ΡΡΡ, ΠΎΡΡΡΠ΅ΡΡΠ²Π»ΡΠ΅ΠΌΠΎΠ³ΠΎ ΠΏΡΠΈ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Π½ΡΡ
ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ°Ρ
. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ Π³ΡΠ°ΡΠΈΠΊΠΈ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΡΠΊΠ°Π·Π°Π½Π½ΠΎΠ³ΠΎ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠ° ΠΎΡ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΡ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΡΠ΅ΡΠΌΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠΎΠ½Π²Π΅ΡΡΠΈΠΈ Π΄ΡΠ΅Π²Π΅ΡΠ½ΠΎΠΉ Π±ΠΈΠΎΠΌΠ°ΡΡΡ Π΄Π»Ρ ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΡΠΊΠΎΡΠΎΡΡΠ΅ΠΉ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΡΠΉ ΠΈΡ
Π²ΡΡ
ΠΎΠ΄ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠΈΠ²Π°Π΅ΡΡΡ ΠΏΡΠΈ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ΅ Π² ΡΠ΅Π°ΠΊΡΠΎΡΠ΅ 923β973 Π ΠΈ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ 700000β1200000 Π³ΡΠ°Π΄./ΠΌΠΈΠ½. ΠΠ΄Π½Π°ΠΊΠΎ ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΠ΅ ΡΠ°ΠΊΠΎΠΉ ΡΠΊΠΎΡΠΎΡΡΠΈ β Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ ΡΠ»ΠΎΠΆΠ½Π°Ρ ΡΠ΅Ρ
Π½ΠΈΡΠ΅ΡΠΊΠ°Ρ Π·Π°Π΄Π°ΡΠ°. ΠΠΎΡΡΠΎΠΌΡ ΠΏΡΠΈ ΠΎΡΡΡΠ΅ΡΡΠ²Π»Π΅Π½ΠΈΠΈ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ ΠΆΠΈΠ΄ΠΊΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΠΏΠΈΡΠΎΠ»ΠΈΠ·Π° ΠΎΠ³ΡΠ°Π½ΠΈΡΠΈΠ²Π°ΡΡΡΡ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ°ΠΌΠΈ 773β800 Π, ΠΏΡΠΈ ΠΊΠΎΡΠΎΡΡΡ
ΠΌΠΎΠΆΠ½ΠΎ Π΄ΠΎΡΡΠΈΡΡ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΈ ΡΠ΅Π°Π»ΠΈΠ·ΡΠ΅ΠΌΠΎΠΉ ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ ΠΏΠ΅ΡΠ²ΠΈΡΠ½ΡΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠΎΠ² ΡΠ°Π·Π»ΠΎΠΆΠ΅Π½ΠΈΡ Π±ΠΈΠΎΠΌΠ°ΡΡΡ
Modular approach to understanding and synthesis of metamaterials and metasurfaces
The vast majority of previously proposed metamaterials and metasurfaces are anisotropic or bianisotropic (exhibiting magnetoelectric coupling). Nevertheless, their anisotropy was not fully exploited as they were designed only for one or several specific illumination directions. In this talk, we propose a simple analytical approach to characterize properties of general bianisotropic meta-atoms for an arbitrary illumination. The approach is based on the qualitative decomposition of an arbitrary meta-atom into separate basic Β»modulesΒ» with elementary polarization properties. Such decomposition can be used for comprehensive characterization of previously designed structures as well as for synthesizing novel bianisotropic inclusions of arbitrary complexity and with desired response.Peer reviewe