Interaction of Electromagnetic Waves with Complex Structures and Media
Fundamental research aimed at creation and
studying of substances
and materials with unique properties that cannot be found in nature
( Principal investigator - V.N. Kissel )
Scientific research carried
out in ITAE (including the program of RAS) resulted in electrodynamic
simulation and investigation of resonance properties of separated medium
inclusions with complex structure. Methods to describe such a medium through
its effective properties based on the strict solution of boundary problems for
complex inclusions of resonance type are developed and studied.
Theoretical and experimental investigations have been performed to study unique focusing features of metamaterial plates and coatings, other properties of structures and substances with negative permeability and permittivity are studied as well.
Unique properties of media with simultaneously negative real parts of permeability and permittivity ε and µ (including the possibility to focus radiation of point-like sources by a plane-parallel plate) were forecast by Prof. V.G. Veselago in the late 60s. Several leading world scientific centers have lately elaborated different options for practical implementation of composites (metamaterials) with the mentioned effective parameters (ITAE was the first to produce the materials both with negative permeability and negative permittivity). A particular interest of the scientific community was attracted to a theoretical study by Prof J.B. Pendry, which pointed out that a plane-parallel plate under certain conditions (ε = µ = ‑1) can serve as a “superlense” with unique focusing properties, its resolution ability is not limited by a well known diffraction limit (a wave length order). The investigations performed in ITAE have revealed the reasons, which limit the possible attainable system resolution, calculations and specially conducted (for the first time) experiment have confirmed the possibility of obtaining in real conditions images of sources, the distance between which is considerably shorter than the wavelength. Many other unique properties of metamaterials have been studied, as well.
See the drawing
of the mentioned experiment
with a plate of metamaterial consisting of resonance elements
in shapes of
spirals and linear half-wave pieces of copper wire excited by magnetic and
electrical field component correspondingly. Microwave image of sources
(half-wave vibrators 1 and 2 separated by a distance considerably shorter than
the wave length) was recorded by receiving antenna 3 in the process of its
movement parallel to the plate surface, see the figure.
The results of field measurements in the absence of a plate between antennas, with a quartz plate and, finally, with a plate of metamaterial are given below. In the latter case the frequency range (here: 1,65 ÷ 1,8 GHz) with separate images of two close sources (spaced apart by the distance of 1/6 of wavelength) is clearly seen.
That was the first experimental result obtained in the world practice, the research results became widely known and recognized in the world. Study of specific properties of composites goes on.
At
present construction of more precise electrodynamic models of wire-based
composites is in the process of elaboration. A rigorous method of integral
equations
is applied for the purpose. The results
of numerical simulation of
the structure used in 
the
described
experiment
are
already
available. The calculations both reproduce the observed effects
of focusing
and “super-resolution”
in
presence of complex composite medium and establish correlations between
phenomena in real sample of meta-materials (periodical systems of resonance
elements) and in homogeneous media with negative electrodynamic parameters
that can exist only in theory.
The results were published in leading Russian and foreign scientific
journals (e.g. A.N. Lagarkov, V.N. Kissel. Near-Perfect Imaging in a Focusing
System Based on a Left-handed-material Plate//Physical Review Letters, vol.
92, 077401, 2004. Focusing Quality of
Electromagnetic radiation of plane-parallel plate of substance with negative
refraction factor// Reports of the Academy of Sciences, 2004, vol. 394, no.
1), the results were reviewed in such respected scientific as:
«Science»,
«The AIP Bulletin of Physics News», «The Industrial Physicist»:
Kim Krieger.
Lens once deemed impossible now rules the waves//
Science. vol. 303. Issue 5664, 1597, 12 March 2004;
Phil Schewe.
Sub-wavelength lensing // Physics News Update.
The AIP Bulletin of Physics News. no. 675#2. March 3, 2004.
– (http://www.aip.org/pnu/2004/split/675-2.html);
Eric J. Lerner.
Superlenses // The Industrial Physicist. no. 3 (June/July), 2004. p. 10.
– (http://www.aip.org/tip/INPHFA/vol-10/iss-3/p10.html);
They were included into «The Top Physics Story for 2004» of «The AIP Bulletin of Physics News»:
lensing of
microwaves using a flat panel of left-handed material,
–
http://www.aip.org/pnu/2004/split/711-1.html);
and discussed on many scientific Internet sites, E.g.:
ICPR (Information
Center for Physics Research).
–
http://icpr.snu.ac.kr/news/na_view.php?sn=391);
Wissenschaft: Stefan Maier. Mit flacher Linse ganz nah dran//
Wissenschaft de News. 09.03.2004 – Physik.
–
http://www.wissenschaft.de/wissen/news/238770.html;
Metamaterials : Near-Perfect Imaging in a Focusing System
Based on a Left-Handed-Material
Plate. Prof. Lagarkov and Dr. Kissel
interview. – Posted on Monday, March 22, 2004.
–
http://www.metamaterials.net/
Back to themes To the beginning
Investigation of three-dimensional plasma and plasma-dielectric structures
The idea to use plasma as a reflector or absorber of electromagnetic waves has been explored for a long time [1-4]. The screen should either scatter electromagnetic wave in a safe direction, or absorb them efficiently. In the first case plasma can be low-collisional, though with high density, the shape of plasma is convex. In the second case plasma is rarefied, with high collision frequency and considerable thickness.
At present the application of plasma as a screen in micro wave range is still at the design stage. It is mainly caused by difficulties in creating absorbing plasma without substances and devices that limit its sphere of application (electron beam, photoionisation) [2].
Here scattering plasma is considered.
For the screen operation in the wave range of 3 ÷ 10 cm plasma thickness should be 1 ÷ 5 cm at density of n0 ~ (3÷10)×1012 cm-3.
Gas discharge plasma in tubes of several cm in diameter possesses noticeable reflecting properties. The discharge tube production process has long been brought to a commercial level. To initiate the discharge only several kW of voltage is required, to maintain the discharge voltage not exceeding a hundred of volts and specific power of several kV/m2 are required.
Plane periodic grating
Scattering
of electromagnetic wave by periodic grating assembled of gas discharge tubes
filled with plasma
and
without it
have been studied.
Discharge tubes arranged in a flat layer
directly against each other, as shown in Fig.1. Glass and quartz tubes were
used. DC power supply was connected to the tubes. Transmission and reflection
factors were measured. The measurements were made in the frequency range of 3 ÷ 16
GHz with
the help of panoramic meters of microwave attenuation.
The
estimated pattern based on proper functions method was developed by V.A.
Permiakov [5]
to
calculate electromagnetic scattering factors of a periodical grating
consisting of an infinite number of infinitely long circular tubes filled with
plasma. Elementary theory was used to calculate plasma permittivity, radial
distribution of plasma density is described by the Bessel function of zero
order. In order to correlate the calculated and experimental results the
plasma density was estimated by the tube current with account to electron
mobility and electric field strength.
The
measurement results satisfy the calculations (Fig.2). A greater attenuation is
observed within the low frequency range for E-wave
(E vector is parallel to the tube axis),
for H-wave (E
vector is perpendicular to the tube axis) it is in the high frequency range.
E-wave absorption is conditioned by
electron collisions. An interesting feature of E-wave
scattering is a passage increase at certain frequencies that depend on the
diameter and permittivity of tubes (~15
GHz
at the diameter of 16 mm, Fig.2).
It
is caused by resonance properties of a periodical screen made of dielectric
cells. H-wave dissipation is conditioned
not only by electron collisions, rather by resonance absorption that is
connected with electromagnetic wave transformation into plasma wave due to
radial gradient of plasma density
ne
[5].
Besides screen protection properties the
investigation of grating transmission factor at switched-off tubes is of
interest too. The screen in that state should be maximum transparent. The
transmission factor calculation was performed following integral equations
method by the algorithm of A.I. Fedorenko, N.N. Kisel
[6].
The
measurement method is similar to that applied in the case of tubes filled with
plasma. The highest space modes that deteriorate the main mode transmission at
some frequency intervals or wave incidence, can occur in the scattered field
of those grating (Fig.3). To prevent highest modes excitation and to optimize
wave transmission we should use grating with period l that is less that the
wavelength and with the lowest permittivity of walls.
Fig. 3.
Frequency (a, b,
ψ=0) and angle (c, d,
f=9.4 GHz) dependencies of transmission factors.
a, b – H-wave;
c, d – E-wave.
Glass (2a=13 mm, 2b=14.8 mm, l=14.8 mm):
calculation (ε=5,
curve l -
following
Federenko;
2 -
following Permiakov)
and □ -
experiment;
Quartz (2a=13,7 mm; 2b=15,5 mm; l=15,5 mm):
calculation (ε=3,8; 3 - following Fedorenko; 4 - following Permiakov) and ∆ - experiment.
Radar cross section of plasma tube structures
Measurements and calculations of mono-static radar cross section (RCS) of flat, cylinder and spherical screens assembled of discharge tubes were performed. Flat screen was made of straight tubes 400 mm long with diameter of 16 mm. Cylinder screen was constructed of similar tubes placed by a semi-arch with diameter of 183 mm. Spherical screen was made of tubes bent by an arch with discretely changing radius. The measurements were taken at frequency radiation of 3 and 9.4 GHz at two linear polarizations. The calculations of reflection from flat and cylinder screens were made by the algorithm developed by Permiakov et al. [7,8]. The comparison of experimental values of RCS related to finite size objects (a rectangular plate, a cylinder of a finite length) with calculations for 2D objects (infinitely long band and cylinder) was made by means of the formula:
σ(φ) = σ2(φ)2h2/λ (1)
Here
σ(φ) is
the RCS of a 3D object; σ2(φ)
is the RCS
of a 2D object per unit length;
φ is
the angle of wave incidence in the plane perpendicular to the object’s axis;
h is the 3D object length.
That
kind of approach to approximation of RCS of a 3D object by the scattering
pattern of a 2D object was successfully applied in
[9].
Besides, screen RCS were estimated in approximation of physical optics.
σ=σМ|R|2 (2)
Here σМ is the RCS of an ideal reflector of the shape of the screen, |R|2 is reflection factor of Е- or Н- wave from a plane periodic grating assembled of tubes.
Measurements of the RCS of flat and cylinder screens correlate satisfactory with the RCS calculations by Permiakov’s algorithm and calculations in approximation of physical optics by formula (2). The application of formula (2) to evaluate the RCS of a tube spherical reflector gives the value 2-3 times lower than the experimental one.
1. Гуревич А.В. Ионизованный слой в
газе (в атмосфере)//
УФН, 1980,
т. 132,
вып. 4, с. 685-690.
2.
Vidmar R.J. On the use of
atmospheric pressure plasmas as electromagnetic
reflectors and absorbers//IEEE
Trans. Plasma Sci., 1990, v.
18, p. 733-741.
3.
Koretzky Е., Kuo S.P. Charactarization of an atmospheric pressure plasma
generated by a plasma torch
array//Phys. Plasmas, 1998, v. 5, p. 3774-3780.
4.
Manheimer W.M. Plasma reflectors for
electronic beam steering in radar
systems//IEEE Trans. Plasma Sci, 1991, v.
19, p. 1228-1234.
5.
Danilov A.V., Ilchenko S.A., Kunavin
A.T., Markov A.V., Permyakov V.A., Sapozhnikov D.V.,
Tsemko S.N., Volsky V.A.,
Yakovlev V.Y. Electromagnetic wave scattering by an array
of tubes filled with
plasma//J. Phys. D: Appl. Phys., 1997, v. 30, p.
2313-2319.
6.
Данилов А.В., Ильченко С.А., Кисель
Н.Н., Кунавин А.Т., Марков А.В., Сапожников
Д.В., Федоренко А,И., Яковлев В.Е.
Дифракция электромагнитной волны на решетке
из диэлектрических трубок//Препринт ОИВТ РАН,
№ 8-437, ‑М., 1999, 27 с.
7.
Дорофеев И.В., Пермяков В.А.
Дифракция плоской электромагнитной волны
на системе параллельных произвольно
расположенных плазменных цилиндров//
Тезисы докладов XIX Всероссийской научной
конференции "Распространение
радиоволн", Казань, 22-25 июня 1999,
с. 413.
8. Пермяков В.А., Лебедев А.К.,
Дорофеев И.В. Радиолокационные характеристики
искусственных плазменных
образований//Тезисы докладов. VIII международная
конференция по спиновой
электронике (секция по гиромагнитной электронике и
электродинамике). М., 14
ноября 1999, с. 307.
9. Федоренко А.И. Электродинамические
модели элементов конструкции объектов с
малой радиолокационной заметностью//Дисс. д.т.н., Москва, 1996, 475 с.