JPWO2007000989A1 - Electromagnetic wave control element, electromagnetic wave control device, electromagnetic wave control plasma and electromagnetic wave control method - Google Patents

Abstract

An electromagnetic wave control element and an electromagnetic wave control device capable of easily changing the control state of an electromagnetic wave. The electromagnetic wave control element 2 includes electrodes (22a and 22b) for supplying electric power for generating plasma (P) and plasma (P) in order to generate plasma (P) that is two-dimensionally or three-dimensionally periodically distributed. A housing (21) that holds a gas to be ionized and that transmits an electromagnetic wave (R) to be controlled to generate plasma), and allows the plasma (P) to pass the electromagnetic wave (R). This controls the propagation state of the electromagnetic wave (R).

Description

  The present invention relates to an electromagnetic wave control element for controlling an electromagnetic wave, an electromagnetic wave control device including the electromagnetic wave control element, an electromagnetic wave control plasma and an electromagnetic wave control method for controlling an electromagnetic wave.

  Electromagnetic waves are innumerable in their roles as information transmission media in the field of information and communications and as means for creating and modifying various substances. Therefore, elements that control electromagnetic waves are constantly being improved in various ways depending on the needs in their fields of application.

  In particular, electromagnetic waves from the microwave to the terahertz band are frequency bands that have not been industrially sufficiently used, and are expected to have technical and market progress in the future, and research and development of control devices suitable for them are desired. It is rare.

  As an electromagnetic wave control element, a branch element, an attenuator, a resonator, a frequency filter, a lens, etc. are realized by various structures of various substances.

  In recent years, a structure having a periodic structure of a refractive index change called a photonic crystal has been called radio wave to a light wave (a terahertz band (wavelength of about 0.1 mm) and an electromagnetic wave having a longer wavelength than this, which is called "radio wave". Also, an electromagnetic wave having a short wavelength is called as a “light wave”. It is in the limelight as a control element in the region of “light wave”, and research and development with a view to various applications are active (for example, see Non-Patent Document 1). That is, a function that cannot be realized by a conventional single substance has been realized by adopting a two-dimensional or three-dimensional periodic structure.

  The photonic crystal has realized its function by a dielectric or a periodic structure of metal. When a dielectric is used, the dielectric constant and refractive index of the dielectric are important control parameters in addition to the shape of the periodic structure, the periodic length of the periodic structure, and the dimension of the intraperiodic structure. When a metal is used, the metal has a negative dielectric constant when regarded as a dielectric, and can be said to be a medium in which electromagnetic waves cannot propagate inside.

  Various functions have been realized so far in the photonic crystal formed by using the above substances. Examples of realized functions include a frequency filter, an optical path controller (waveguide), a resonator, a lens, and a surface emitting laser.

  Generally, plasma is known as a medium having conductivity as well as dielectric. Then, in Non-Patent Document 2, by using the above-described characteristics of plasma, a configuration for controlling electromagnetic waves in the millimeter wave band to the submillimeter wave band and having a function like a photonic crystal (so-called "plasma photonic crystal" )) is pointed out.

On the other hand, in Non-Patent Document 3, by arranging a periodic structure of a dielectric material two-dimensionally to periodically form a plasma-free portion in a uniform plasma, the electromagnetic wave in the millimeter wave band is generated. Studies have been disclosed to control the direction of propagation. The term “plasma photonic crystal” is also used in Non-Patent Document 3.
Susumu Noda, "Present and future prospects of two-dimensional and three-dimensional photonic crystals" Applied Physics Vol. 74 No. 2 (2005) pp.147-159 K. Tachibana, et. al. "Diagnostics of microdischarge-integrated plasma sources for display and materials processing", Plasma Phys. Control. Fusion, Vol. 47, No. 5A (2005) pp. A167-A177. Naoto Uchida et al., "Simulation of Electromagnetic Wave Propagation in Two-Dimensional Plasma Photonic Crystals" Proceedings of the Physical Society of Japan Volume 60 Volume 1 Volume 2 (2005) Page 263

  However, the photonic crystal that has been conventionally researched and developed has the following problems.

  Since the conventional photonic crystal uses a solid material such as a dielectric or a metal, except for the plasma photonic crystal of Non-Patent Document 3 described above, once the structure is manufactured, its refractive index and dielectric constant can be changed. Is not easy. That is, it is difficult to change the response characteristic of the photonic crystal with respect to the frequency of the electromagnetic wave unless the photonic crystal itself is replaced.

  That is, although the photonic crystal can realize various functions that cannot be realized by the existing electromagnetic wave control elements, the function of the photonic crystal once manufactured is limited to almost one.

  On the other hand, in the case of the plasma photonic crystal of Non-Patent Document 3, since the gap of the periodic structure of the dielectric is filled with plasma, the dielectric constant of the gap can be changed by changing the characteristics of the plasma. Is possible.

  However, in the above plasma photonic crystal, the dielectric is periodically provided and the other part is filled with the plasma, so that the attenuation of energy in the plasma becomes remarkable (especially, the relative permittivity of the plasma is negative. When it is set to a value of 1), it becomes difficult for the electromagnetic wave to propagate in the plasma photonic crystal, and therefore it is actually difficult to widely change the response characteristics of the plasma photonic crystal.

  Further, in the above plasma photonic crystal, since it is premised that uniform plasma is used, it is difficult to control a partial portion of plasma, and it is difficult to widely control the response characteristics of the plasma photonic crystal.

  Furthermore, Non-Patent Document 2 does not disclose any specific configuration of a so-called "plasma photonic crystal" or specific content for producing the same.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electromagnetic wave control element and an electromagnetic wave control device that can easily change the control state of an electromagnetic wave.

  An electromagnetic wave control element according to the present invention includes a plasma generation unit that generates plasma that is periodically distributed in a two-dimensional or three-dimensional manner, and controls the propagation state of the electromagnetic wave by passing the electromagnetic wave through the plasma. Is characterized by.

  In the above configuration, the plasma generating means generates the plasma that is periodically distributed in two dimensions or three dimensions. The refractive index of the portion where plasma is generated is different from that of the surrounding. Therefore, by generating a two-dimensionally or three-dimensionally periodically distributed plasma, it is possible to form a periodic change in the refractive index as in the case of the conventional photonic crystal. Can be controlled.

  In the conventional photonic crystal, when the material and shape of the photonic crystal are determined, the periodic change of the refractive index is determined, and thus the control state of electromagnetic waves is also determined. Therefore, in order to change the control state of the electromagnetic wave, it is necessary to change the material and shape of the photonic crystal, which means that the photonic crystal itself is replaced.

  On the other hand, the plasma can change the refractive index of the plasma by changing the electron density in the plasma or the pressure of the gas to be ionized in order to generate the plasma. Therefore, in the above configuration, the refractive index, which is a control parameter, can be easily changed by changing the electron density in plasma or the pressure of the gas to be ionized, and the control state of electromagnetic waves can also be changed.

  As described above, with the above configuration, it is possible to realize an electromagnetic wave control element capable of changing the control state of electromagnetic waves.

  Further, the electromagnetic wave control plasma according to the present invention is characterized in that the propagation state of the electromagnetic wave passing therethrough is controlled by being periodically distributed two-dimensionally or three-dimensionally. Further, the electromagnetic wave control method according to the present invention is characterized in that a plasma that is periodically distributed two-dimensionally or three-dimensionally is generated and the propagation state of the electromagnetic wave is controlled by passing the electromagnetic wave through the plasma. There is. Also by these, the control state of the electromagnetic wave can be easily changed like the electromagnetic wave control element.

  The plasma generating means includes an electrode for supplying electric power for generating the plasma, and a gas holding means for internally holding a gas to be ionized to generate the plasma and transmitting an electromagnetic wave to be controlled. It can be configured by

  Further, the electrodes may be periodically arranged, and the plasma may have a periodic distribution according to the periodical arrangement of the electrodes.

  Further, the gas holding means may have a plurality of holes that are periodically formed, and a periodic distribution of the plasma may be formed by generating plasma in the holes. it can.

  In the above configuration, since plasma is generated in the holes of the gas holding means, the plasma can be confined inside the gas holding means, and the boundary surface of the plasma can be clearly defined. Then, the difference in electron density at this boundary surface can be made large, and the influence of the periodic distribution of plasma can be made more apparent.

  Further, the gas holding means may be made of a dielectric having the plurality of holes.

  In the above structure, the portion other than the holes is filled with the dielectric. This makes it possible to make a large difference in the electron density at the boundary surface and also make a large difference in the relative permittivity at the boundary surface. As a result, the influence of the periodical distribution of plasma can be further manifested.

  Further, the plasma generating means further includes an electron emitting means exposed to the inside of the gas holding means and made of a material having a secondary electron emission coefficient higher than that of the surroundings, and the electron emitting means are arranged periodically. Alternatively, the periodic distribution of the plasma may be formed according to the periodic arrangement of the electron emitting means.

  The plasma generating means may be configured to surround the periodic plasma and further generate plasma having an electron density different from that of the plasma.

  In the above configuration, since it is possible to change the refractive index of both the periodic plasma portion and the portion surrounding the periodic plasma portion, that is, the plasma portion having a different electron density from the periodic plasma, it is possible to more flexibly control electromagnetic waves. You can change the state.

  Further, the plasma generation means may be configured to include an extraction electrode that applies a voltage for extracting the plasma generated by the electrode.

  In the above structure, the length of the plasma can be adjusted by extracting the plasma generated by the preliminary discharge.

  An electromagnetic wave control device according to the present invention is characterized by including any one of the electromagnetic wave control elements described above and power control means for controlling electric power for generating plasma by the plasma generation means.

  In the above configuration, the electron density in the plasma can be controlled by controlling the power for generating the plasma by the power control means. As a result, the refractive index, which is a control parameter, can be controlled, and the control state of electromagnetic waves can also be changed.

  An electromagnetic wave control device according to the present invention is characterized by including any one of the electromagnetic wave control elements described above and a plasma distribution control means for controlling a distribution state of plasma generated by the plasma generation means.

  In the above configuration, since the plasma distribution state can be controlled by the plasma distribution control means, the periodic structure of the refractive index change can be changed. Thereby, the control state of the electromagnetic wave can be changed more flexibly.

  An electromagnetic wave control device according to the present invention is characterized by including any one of the electromagnetic wave control elements described above and a gas pressure control means for controlling the pressure of a gas to be ionized in order to generate the plasma.

  In the above configuration, the electron density in the plasma can be controlled by controlling the pressure of the gas to be ionized. As a result, the refractive index, which is a control parameter, can be controlled, and the control state of electromagnetic waves can also be controlled.

  As described above, the electromagnetic wave control element according to the present invention is provided with the plasma generation means for generating the plasma that is periodically distributed in the two-dimensional or three-dimensional manner, and the electromagnetic wave is propagated by passing the electromagnetic wave through the plasma. This is a configuration for controlling the state.

  In the above structure, the refractive index, which is a control parameter, can be easily changed by changing the electron density in plasma or the pressure of the gas to be ionized, and the control state of electromagnetic waves can also be changed.

  As described above, the above-described configuration has the effect of realizing an electromagnetic wave control element capable of changing the control state of electromagnetic waves.

It is sectional drawing which shows the electromagnetic wave control apparatus of 1st Embodiment of this invention. FIG. 2 is a cross-sectional view taken along the line AA of the electromagnetic wave control device of FIG. 1. FIG. 2 is a sectional view taken along the line AA of the electromagnetic wave control device of FIG. 1, showing a plasma distribution state. FIG. 2 is a cross-sectional view taken along the line AA of the electromagnetic wave control device of FIG. 1, showing another distribution state of plasma. FIG. 6 is a cross-sectional view taken along the line AA of the electromagnetic wave control device of FIG. 1, showing another distribution state of plasma. It is sectional drawing which shows the modification of the electromagnetic wave control element in the electromagnetic wave control apparatus of FIG. It is sectional drawing which shows the other modification of the electromagnetic wave control element in the electromagnetic wave control apparatus of FIG. It is sectional drawing which shows the further another modified example of the electromagnetic wave control element in the electromagnetic wave control apparatus of FIG. It is sectional drawing which shows the electromagnetic wave control apparatus of 2nd Embodiment of this invention. It is sectional drawing which shows the electromagnetic wave control apparatus of 3rd Embodiment of this invention. It is sectional drawing which shows the electromagnetic wave control apparatus of 4th Embodiment of this invention. FIG. 12 is a cross-sectional view taken along the line BB of the electromagnetic wave control device of FIG. 11. It is sectional drawing which shows the electromagnetic wave control apparatus of 5th Embodiment of this invention. It is a figure which shows the dispersion relation of the electromagnetic wave which propagates in a two-dimensional plasma array. It is a figure which shows distribution of the equal frequency line on the two-dimensional wavenumber plane of the electromagnetic wave which propagates in a two-dimensional plasma array.

Explanation of symbols

1 Electromagnetic Wave Control Device 2 Electromagnetic Wave Control Element 3 Power Control System (Power Control Means, Plasma Distribution Control Means)
4 Gas control system (gas pressure control means)
21 housing (plasma generating means, gas holding means)
22a electrode (plasma generating means)
22b electrode (plasma generating means)
23 Cylindrical member (plasma generating means, gas holding means)
24 Dielectric member (plasma generating means, gas holding means)
101 electromagnetic wave control device 102 electromagnetic wave control element 103 power control system (power control means)
122a electrode (plasma generating means)
122b electrode (plasma generating means)
123a Electron emitting member (plasma generating means, electron emitting means)
123b Electron emitting member (plasma generating means, electron emitting means)
201 electromagnetic wave control device 202 electromagnetic wave control element 203 power control system (power control means, plasma distribution control means)
223a electrode (plasma generating means)
223b electrode (plasma generating means)
301 Electromagnetic wave control device 302 Electromagnetic wave control element 303 Power control system (power control means)
322a electrode (plasma generating means)
322b electrode (plasma generating means)
323 electrode (plasma generating means)
401 Electromagnetic wave control device 402 Electromagnetic wave control element 403 Power control system (power control means, plasma distribution control means)
P Plasma R Electromagnetic wave

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

  In the electromagnetic wave control element of this embodiment, plasma is used for controlling the electromagnetic wave. Therefore, first, the properties of plasma will be described.

In general, when plasma is generated, it is known that the relative permittivity ε _r for an electromagnetic wave passing through the part is expressed by the following equation (1).

Here, ω _pe /2π is an electron plasma frequency (also referred to as “electron plasma frequency”; hereinafter simply referred to as “plasma frequency”), ω/2π is a frequency of an electromagnetic wave passing through plasma, and a relative permittivity ε. The relationship between _r and the refractive index n is n=ε _r ^1/2 .

From the equation (1), the relative permittivity ε _r has a value smaller than 1 and takes a positive value when ω is larger than ω _pe . Thus, if ω is greater than ω _pe , the plasma can be considered a dielectric.

Further, according to the equation (1), when ω is smaller than ω _pe , the relative permittivity ε _r has a negative value, and the electromagnetic wave can enter only a very thin region called the skin depth in the plasma. Electromagnetic waves can be regarded as almost impossible to propagate in plasma. Therefore, when ω is smaller than ω _pe , the plasma behaves like a metal.

Therefore, when plasma is generated or extinguished, the relative permittivity ε _r at that location changes greatly. Further, even in the presence of plasma, by changing ω _pe , it is possible to switch between a state in which electromagnetic waves can propagate in plasma and a state in which electromagnetic waves can hardly propagate.

Note that ω _pe is a function of the electron density (plasma intensity) in the plasma, and is proportional to the electron density to the 1/2 power. More specifically, the relationship between electron density and plasma frequency is expressed by the following equation (2).

Here, n _e is the electron density, e is the elementary charge amount, _me is the electron mass, and ε ₀ is the dielectric constant in vacuum. Further, the relationship between the electron density and the plasma frequency is shown in Table 1 below by a specific numerical example.

  Therefore, by changing the electron density of the plasma, it is possible to switch between a state in which the electromagnetic wave can propagate in the plasma and a state in which the electromagnetic wave can hardly propagate.

  Compared with conventional photonic crystals, this means that by changing the electron density, various refractive indices can be set for electromagnetic waves, from those equivalent to dielectrics to those equivalent to metals. I can say.

  Such control of the refractive index of plasma can be performed as follows. The electron density in plasma can be adjusted by controlling the power for plasma generation. Therefore, by controlling the power for plasma generation, the electron density in the plasma can be controlled, and as a result, the refractive index of the plasma can be controlled.

To be more precise, the relative permittivity ε _r should consider the collision frequency ν _m between neutral particles existing in the plasma part and the electrons in the plasma (hereinafter, simply referred to as “collision frequency”). Is expressed by the following equation (3) as a complex number.

When collisions between neutral particles and electrons become more frequent to a certain extent and become a region of colliding plasma, even when ω is smaller than ω _{pe, the} skin thickness becomes thick and electromagnetic waves are absorbed in the plasma to some extent. It will come in.

Here, the inventors of the present invention have found that when ω is smaller than ω _pe in collisional plasma, a state called so-called anomalous dispersion in which dn/dω becomes negative is obtained. In the plasma exhibiting this anomalous dispersion, the phase velocity and the group velocity of the electromagnetic wave passing through it are opposite to each other, and when the electromagnetic wave is obliquely incident on the plasma surface, there is a phenomenon that the electromagnetic wave is turned back (refracted) in the opposite direction. It has been found that it is possible to cause a larger optical path change than the incidence on a normal dielectric surface.

  Therefore, the refractive index of the plasma can be controlled also by changing the neutral particle density in the plasma and changing the collision frequency. Neutral particle density in plasma can be controlled by the pressure of gas to be ionized to generate plasma, and this gas pressure can be easily controlled by adjusting the amount of gas filling the closed space. Is.

  The electromagnetic wave control element of the present embodiment realizes a structure corresponding to the periodic structure of the refractive index change in the photonic crystal by utilizing the above-mentioned characteristics of plasma. This makes it possible to greatly change the physical properties such as the refractive index of the plasma by adjusting the electron density in the plasma and the collision frequency, that is, adjusting the supply power and the gas pressure. It becomes controllable.

  Here, it will be described that the propagation state of the electromagnetic waves can be variously controlled by transmitting the electromagnetic waves through a two-dimensional plasma array configured by arranging plasmas two-dimensionally and periodically.

As an example of a two-dimensional plasma array, a configuration in which plasmas are arranged in a square lattice, more specifically, at each lattice point with a lattice spacing distance (lattice constant) of 2.5 mm, a column with a diameter of 1.0 mm (that It is assumed that plasma is generated in the axial direction (perpendicular to the lattice plane). The electron density of each plasma is 1×10 ¹³ cm ⁻³ (plasma frequency ω _pe /2π=28 GHz), the gas pressure of the ionization target for generating plasma is 30 kPa, and the gas species is helium. The electromagnetic wave to be controlled has an electromagnetic wave mode of TE mode (electric field direction is parallel to the lattice plane) and a propagation direction is parallel to the lattice plane.

  When the dispersion relation of electromagnetic waves at this time is theoretically derived, the theoretical curve is as shown in FIG. Although this dispersion relationship changes greatly depending on the parameters to be set, the characteristics described below are qualitatively common contents that do not depend on the parameters.

  First, on the lower frequency side of the plasma frequency (28 GHz), a propagation mode having a substantially constant frequency with respect to the wave number appears in a very narrow frequency band called a "flat band region". The region in which this propagation mode exists substantially corresponds to the region where the metallic behavior of plasma and the anomalous dispersion described above occur. Therefore, the above-mentioned propagation modes occur due to these phenomena in the plasma and the fact that the plasma itself has a two-dimensional periodic structure. As described above, the propagation mode is generated due to the large change in the refractive index in the two-dimensional plasma array, so that the amount of electromagnetic waves transmitted through the two-dimensional plasma array can be greatly increased or decreased. Conceivable. Such control of the amount of transmission of electromagnetic waves is a characteristic peculiar to a two-dimensional plasma array that cannot be realized by a dielectric photonic crystal.

  Next, a forbidden band in which no propagation mode exists is generated between the flat band region and the frequency corresponding to the plasma frequency (28 GHz). In this forbidden band, when an infinitely large two-dimensional plasma array is considered, electromagnetic waves cannot propagate in this two-dimensional plasma array and are blocked by this two-dimensional plasma array. In the case of a two-dimensional plasma array having a finite size, the attenuation amount of the transmitted electromagnetic wave is determined according to the plasma density (that is, the refractive index of the transmitted electromagnetic wave with respect to the frequency) and the size of the two-dimensional plasma array. Such control of the amount of transmission of electromagnetic waves is a characteristic peculiar to the two-dimensional plasma array that cannot be realized by the photonic crystal of the dielectric.

  Furthermore, the forbidden band is on the frequency side slightly higher than the condition that (plasma frequency × lattice constant/light velocity) = 0.5, that is, the condition that the lattice constant is 1/2 of the wavelength of electromagnetic waves, as the plasma frequency increases. Occurs. Even in this forbidden band, when considering an infinitely large two-dimensional plasma array, electromagnetic waves cannot be propagated in this two-dimensional plasma array and are blocked by this two-dimensional plasma array. In the case of a two-dimensional plasma array having a finite size, the attenuation amount of the transmitted electromagnetic wave is determined according to the plasma density (that is, the refractive index of the transmitted electromagnetic wave with respect to the frequency) and the size of the two-dimensional plasma array. This phenomenon is a phenomenon of a forbidden band similar to that of a dielectric photonic crystal. However, in the case of a two-dimensional plasma array, as described above, the plasma density can be temporally and spatially controlled, so that the time and frequency at which the forbidden band occurs can be easily controlled.

  Moreover, when the propagation of electromagnetic waves in the two-dimensional plasma array was analyzed, the following contents became clear. Regarding the electromagnetic waves and plasma parameters of the two-dimensional plasma array assumed above, the propagation of electromagnetic waves on the slightly higher frequency side than the plasma frequency (28 GHz) is illustrated as a distribution of equifrequency lines on the two-dimensional wave number plane, as shown in FIG. Became. In FIG. 15, “X direction” and “Y direction” of “X direction wave number” and “Y direction wave number” mean the array direction (row direction and column direction) of the lattice of the two-dimensional plasma array.

  In normal electromagnetic wave propagation, the frequency changes concentrically on the two-dimensional wave number plane, but as the frequency of the electromagnetic wave approaches the plasma frequency, the equi-frequency lines are distorted, and the anisotropy of the group velocity (dω/dt) changes. Occurs (note that the direction of the group velocity coincides with the normal direction at any point on the isofrequency line). That is, as shown in FIG. 15, the group velocity has directivity in the X direction and the Y direction.

  Since the energy of the electromagnetic wave generally flows in the direction of the group velocity, the electromagnetic wave having the distorted equal frequency lines as described above is given directivity in the X and Y directions. Therefore, when an electromagnetic wave is made incident on the two-dimensional plasma array so that the traveling direction is almost in the X direction, the electromagnetic wave propagates while diverging somewhat when the two-dimensional plasma array does not exist. When the two-dimensional plasma array is present, the directivity is given so that the energy flow is directed more in the X direction, and as a result, the amount of electromagnetic waves passing through the two-dimensional plasma array is considered to increase. Such control of the amount of transmission of electromagnetic waves is a characteristic peculiar to the two-dimensional plasma array that cannot be realized by the photonic crystal of the dielectric.

  Next, the configurations of the electromagnetic wave control element of the present embodiment and an electromagnetic wave control device using the same will be described. The overall configuration of the electromagnetic wave control device 1 of the present embodiment is shown in FIG. 1, and a sectional view taken along the line AA in FIG. 1 is shown in FIG.

  The electromagnetic wave control device 1 includes an electromagnetic wave control element 2, a power control system 3 that controls the power supplied to the electromagnetic wave control element 2, and a gas control system 4 that controls the gas in the electromagnetic wave control element 2.

  The electromagnetic wave control element 2 includes a housing 21 and a large number of electrodes 22a and 22b arranged inside the housing 21.

  The housing 21 is a box-shaped container having a rectangular parallelepiped outer shape, and has a structure that is sealed except for the gas supply port 21a and the gas discharge port 21b so that a predetermined gas can be held inside.

  A large number of electrodes 22a are arranged in a square lattice (matrix) on the inner upper surface of the casing 21, and a large number of electrodes 22b are also arranged on the inner lower surface of the casing 21 so as to face the electrodes 22a. They are arranged in a square lattice.

  The power control system 3 includes a power source 31 that generates power, a power controller 32 that controls the supply of power from the power source 31, and an electrical wiring that connects the power source 31, the power controller 32, and the electromagnetic wave control element 2. It has and.

  The power supply 31 generates AC power having a sine wave or a rectangular wave. The power generated by the power supply 31 is supplied to the power controller 32.

  The power controller 32 regulates the power supplied from the power supply 31 and selectively supplies the power to the electrode 22a. That is, the power controller 32 adjusts the power to be supplied by adjusting the voltage applied to the electrode 22a (the electrode 22b is grounded), and the power controller 32 selects one selected from a large number of electrodes 22a. It supplies regulated electric power. The electrode 22a to be supplied with electric power is preset, and the setting can be changed.

  The gas control system 4 includes a vacuum pump 41, a gas cylinder 42, an exhaust valve 43a, an intake valve 43b, an intake/exhaust controller 44, and the gas supply port 21a and the gas exhaust port 21b of the electromagnetic wave control element 2. It is equipped with connecting piping.

  The gas control system 4 can exhaust gas inside the electromagnetic wave control element 2, fill a predetermined gas, and adjust gas pressure.

  An electromagnetic wave control operation by the electromagnetic wave control device 1 having the above configuration will be described.

  In the initial state, the electromagnetic wave control element 2 is filled with air, and this air is exhausted by the vacuum pump 41. As a result, a predetermined gas (for example, helium) is fed from the gas cylinder 42 into the electromagnetic wave control element 2 that is in a vacuum state, so that the electromagnetic wave control element 2 is filled with this gas. The gas pressure inside the electromagnetic wave control element 2 is adjusted by controlling the opening/closing of the exhaust valve 43a and the intake valve 43b by the intake/exhaust controller 44.

  Then, the power supply from the power source 31 is started, and the power controller 32 applies a predetermined voltage to the predetermined electrode 22a. As a result, plasma P is generated between the electrode 22a to which the voltage is applied and the electrode 22b facing the electrode 22a.

  1 and 2 show a state in which plasma P is generated between all electrodes 22a and 22b by applying a voltage to all electrodes 22a. At this time, the plasma P is two-dimensionally and periodically distributed inside the electromagnetic wave control element 2.

  Then, the electromagnetic wave R to be controlled is incident on the electromagnetic wave control element 2 from the outside in the direction along the arrangement of the plasma P. The incident electromagnetic wave R is affected by the periodic structure of the refractive index change realized by the plasma P inside the electromagnetic wave control element 2, and its propagation state is controlled.

  The incident portion 21c of the casing 21 of the electromagnetic wave control element 2 that receives the electromagnetic wave R and the emitting portion 21d that emits the electromagnetic wave R are made of a material that transmits the electromagnetic wave R.

  The control of the propagation state of the electromagnetic wave R includes control of the focused or divergent state of the electromagnetic wave R, control of the traveling direction, control of attenuation (transmission), and control of resonance. At this time, the electromagnetic wave control element 2 functions as a lens, an optical path controller (waveguide), a frequency filter, and a resonator, respectively.

  These controls can be realized by adjusting the arrangement of the plasma P (controlling the distribution state of the plasma) in addition to adjusting the electron density and the collision frequency in the plasma described above.

  An example of adjusting the arrangement of the plasma P will be described based on FIGS. 3 to 5. As shown in FIG. 3, by generating the plasma P every other row and every other column of the electrode 22b, the period in which the plasma P is distributed can be lengthened. Further, as shown in FIG. 4, the plasma P can be distributed in a triangular lattice shape by alternately generating the plasma P in the row direction and the column direction of the electrodes 22b. Furthermore, as shown in FIG. 5, a line defect LD or a point defect PD can be formed in the periodic structure of the plasma P.

  Such adjustment of the arrangement of the plasma P can be realized by selecting the electrode 22a that supplies power by the power controller 32, as described above. Even in the case of the conventional photonic crystal, it is possible to set the periodic structure of the refractive index change by setting the shape of the member that constitutes the photonic crystal. Once determined, it is difficult to change its shape. On the other hand, in the electromagnetic wave control device 1, the periodic structure of the refractive index change can be easily changed by changing the arrangement of the plasma P by the power controller 32.

(Example 1)
A specific example of electromagnetic wave control using the electromagnetic wave control device 1 having the above configuration is shown below. Specific values of each control parameter in the electromagnetic wave control device 1 are as follows.

The electromagnetic wave R incident on the electromagnetic wave control element 2, that is, the electromagnetic wave R to be controlled has a frequency band of 10 to 100 GHz and an electromagnetic wave mode of TE mode (the direction of the electric field is parallel to the periodic array surface of the plasma P). .. The electron density of the plasma P is 2 to 3×10 ¹³ cm ⁻³ (ω _pe /2π=40 to 49 GHz), the gas pressure in the housing 21 is 30 to 100 kPa, and the gas species in the housing 21 is helium. The housing 21 is 8 mm (longitudinal direction in FIG. 1)×50 mm (depth direction in FIG. 1)×70 mm (horizontal direction in FIG. 1), and the incident portion 21c and the emitting portion 21d are 8 mm×50 mm. The inter-lattice distance of the electrodes 22a and 22b in the square lattice arrangement is 2.1 mm (longitudinal and lateral directions in FIG. 2), and the electrodes 22a and 22b each have a diameter of 1.4 mm (20 electromagnetic waves R traveling). Direction)×20 pieces (width direction of the electromagnetic wave R) are arranged. The diameter of each plasma P was about 1.4 mm.

  Next, the electromagnetic wave control characteristics of the electromagnetic wave control device 1 in which the control parameters are set as described above will be described.

  When the frequency of the electromagnetic wave R incident on the electromagnetic wave control element 2 was changed, the energy density of the electromagnetic wave R emitted from the electromagnetic wave control element 2 at the center of the emission portion 21d was reduced by about 30% when the frequency was 35 GHz or higher. On the other hand, when the frequency is 35 GHz or less, the energy density increased to about 400%. That is, it was confirmed that the electromagnetic wave control element 2 in this case functions as a lens for condensing the incident electromagnetic wave R.

This condensing phenomenon can be explained by anomalous dispersion and other effects when ω<ω _pe in the skin depth portion of the colliding plasma.

  Normally, the electromagnetic wave passes through the electromagnetic wave control element 2 while slightly expanding its propagation cross section. Then, a part of the energy is consumed by the collisional plasma and is emitted. This is considered to correspond to the case where the frequency is 35 GHz or higher.

On the other hand, when ω<ω _pe , the electromagnetic wave is affected by the anomalous dispersion of the plasma P and propagates while narrowing its propagation cross section. Then, although the energy is consumed by the collisional plasma, there is no such energy consumption in the gap of the plasma P, and as a result, the energy density is increased in the center of the emitting portion 21d. This is considered to correspond to the case where the frequency is 35 GHz or less.

  The above description is centered on the effect of the anomalous dispersion of plasma, but the light-collecting effect caused by the two-dimensional periodic change in the refractive index (for example, P.V.Parimi, WT.Lu, P.Vodo, and S Sridhar, Nature, vol. 426 (2003), p.404) is also considered to contribute to this result.

Alternatively, it is considered that the abnormal propagation phenomenon unique to the two-dimensional plasma array as described below also contributes to this result. That is, in the frequency band 10 to 100 GHz of the electromagnetic wave R, the propagating frequency band is a frequency band slightly lower than the plasma frequency (ω _pe /2π=40 to 49 GHz), which is shown in FIG. It corresponds to the described flat band region. That is, the increase of the observed electromagnetic wave signal is also one of the causes of the increase of the transmission amount due to the change of the refractive index due to the flat band region. As described above, this phenomenon of increasing the electromagnetic wave signal is considered to be a combination of these effects, and is the first phenomenon to be realized by the two-dimensional plasma array.

This phenomenon is characteristic of the TE mode. This is because the TE mode does not have an electric field component along the longitudinal direction (vertical direction in FIG. 1) of the plasma P even when ω<ω _pe , and it is difficult to be blocked.

  This condensing phenomenon disappeared by weakening the power for generating the plasma P. This indicates that by adjusting the electron density of the plasma P, it is possible to control whether or not the above phenomenon is exhibited.

In addition, an increase phenomenon of the electromagnetic wave signal was also observed in another frequency band. The electromagnetic wave signal increased to 110 to 150% over the frequency range of 43 GHz to 45 GHz. The reason for this phenomenon is considered to be that the following abnormal propagation phenomenon unique to the two-dimensional plasma array contributes. That is, the propagating electromagnetic wave is in the region of a frequency that is the same as or slightly higher than the plasma frequency (ω _pe /2π=40 to 49 GHz), and in this region, the anisotropy of the group velocity is as shown in FIG. Occurs. Along with this, it is considered that the energy of the electromagnetic wave is provided with directivity so as to flow toward the traveling direction of the electromagnetic wave, and the amount of the electromagnetic wave observed at the emitting portion 21d is increased.

On the contrary, the frequency band of the electromagnetic wave to be controlled can be changed by generating the plasma P by arc discharge and increasing the electron density. For example, by using arc discharge, plasma with an electron density of about 3×10 ¹⁶ cm ⁻³ can be obtained. At that time, the condition of ω=ω _pe is about 1 THz, and the frequency band is a control target. In this way, by changing the electron density, it effectively acts on the control of electromagnetic waves in various frequency bands.

  When the distance between the plasmas P is changed, the frequency of the controlled object changes in inverse proportion to the change. Further, when the diameter of the plasma P is changed, the frequency band to be controlled expands due to the expansion of the diameter.

  In addition, in the present embodiment, in addition to the various effects of using the plasma P as a constituent element of the periodic structure, the outer shape of the electromagnetic wave control element 2 is a simple flat plate structure, which facilitates manufacturing and arrangement. Have an effect. A conventional lens having a convex structure formed of a dielectric material is difficult to manufacture because it requires polishing of a curved surface of the lens, and its outer shape is a convex structure, and therefore the layout is likely to be restricted.

  The lens function as in this embodiment can be used for the output section of the radar. In the output part of the radar, a dielectric lens is usually used in order to provide the output electromagnetic wave with a focusing property, and the electromagnetic wave control device 1 can be provided in place of the dielectric lens. This makes it possible to change the corresponding frequency and directivity, and to realize a lens having a simple structure that is easy to manufacture because it has a flat plate structure instead of a convex structure.

  In addition, the lens function as in the present embodiment can be utilized even for electromagnetic waves having a frequency in the terahertz band by using the plasma P having a high electron density due to the above-mentioned arc discharge or the like. That is, when observing the transmitted light of the sample in the terahertz spectral imaging method, it is necessary to collect the incident light to the sample and the transmitted light from the sample. At that time, the variable lens function as in this embodiment is effective. Is.

(Example 2)
Next, another specific example of electromagnetic wave control using the electromagnetic wave control device 1 having the above configuration will be described below. Specific values of each control parameter in the electromagnetic wave control device 1 are as follows.

The electromagnetic wave R incident on the electromagnetic wave control element 2, that is, the electromagnetic wave R to be controlled has a frequency band of 10 to 100 GHz and an electromagnetic wave mode of TM mode (the direction of the electric field is perpendicular to the periodic array surface of the plasma P). .. The electron density of the plasma P is 2 to 3×10 ¹³ cm ⁻³ (ω _pe /2π=40 to 49 GHz), the gas pressure in the housing 21 is 30 to 100 kPa, and the gas species in the housing 21 is helium. The housing 21 is 8 mm (longitudinal direction in FIG. 1)×50 mm (depth direction in FIG. 1)×70 mm (horizontal direction in FIG. 1), and the incident portion 21c and the emitting portion 21d are 8 mm×50 mm. The inter-lattice distance in the arrangement of the electrodes 22a and 22b in a square lattice is 5.0 mm (longitudinal and lateral directions in FIG. 2), and the electrodes 22a and 22b each have a diameter of 2.0 mm and 20 electrodes each (the electromagnetic wave R travels). Direction)×20 pieces (width direction of the electromagnetic wave R) are arranged. The diameter of each plasma P was about 2.0 mm.

  Next, the electromagnetic wave control characteristics of the electromagnetic wave control device 1 in which the control parameters are set as described above will be described.

  When the frequency of the electromagnetic wave R incident on the electromagnetic wave control element 2 is changed, the energy density of the electromagnetic wave R emitted from the electromagnetic wave control element 2 at the center of the emission portion 21d is reduced by about 30% when the frequency is 45 GHz or higher. On the other hand, when the frequency is 40 to 45 GHz, the energy density is reduced by about 90%. That is, it was confirmed that the electromagnetic wave control element 2 in this case functions as a filter that blocks the incident electromagnetic wave R in a predetermined frequency band.

This interruption phenomenon can be explained by the fact that the electromagnetic wave is in the TM mode and the frequency is ω<ω _pe . In other words, it is considered that the TM-mode electromagnetic wave has only an electric field component along the longitudinal direction of the plasma P, so that the electric field cannot exist due to the generation of the plasma P and many electromagnetic waves are blocked. ..

More specifically, it can be explained by the effect that a large number of plasmas P have a two-dimensional periodic structure. That is, inside the plasma P, the relative permittivity ε _r represented by the equation (1) or the equation (3) is different from the surrounding portion of the plasma P, so that a so-called forbidden band structure is generated by the same principle as the photonic crystal. Is considered to be.

  This interruption phenomenon disappeared by weakening the power for generating the plasma P. This indicates that it is possible to control whether or not the above phenomenon is caused by adjusting the electron density of the plasma P.

  When the distance between the plasmas P is changed, the frequency of the controlled object changes in inverse proportion to the change. Further, when the diameter of the plasma P is changed, the frequency band to be controlled expands due to the expansion of the diameter.

  The filter function as in this embodiment should be used in place of the filter in a general electromagnetic wave transmitter (source, filter, amplifier and antenna) or receiver (antenna, amplifier, filter, self-heterodyne mixer and output terminal). You can In this case, since the corresponding frequency can be changed, it is most suitable as a filter in a UWB (Ultra Wide Band) compatible device that is expected to develop in the future.

  In addition, the lens function as in the present embodiment can be utilized even for electromagnetic waves having a frequency in the terahertz band by using the plasma P having a high electron density due to the above-mentioned arc discharge or the like. That is, it may be necessary to extract a specific wavelength in a terahertz wave in which electromagnetic waves of various frequencies are mixed, and at that time, the variable filter function as in this embodiment is effective.

(Example 3)
Next, another specific example of electromagnetic wave control using the electromagnetic wave control device 1 having the above configuration will be described below. Specific values of each control parameter in the electromagnetic wave control device 1 are as follows.

The electromagnetic wave R incident on the electromagnetic wave control element 2, that is, the electromagnetic wave R to be controlled has a frequency band of 10 to 100 GHz and an electromagnetic wave mode of TE mode (the direction of the electric field is parallel to the periodic array surface of the plasma P). .. The electron density of the plasma P is 1×10 ¹³ cm ⁻³ (ω _pe /2π=28 GHz), the gas pressure inside the housing 21 is 30 kPa, and the gas species inside the housing 21 is helium. The housing 21 is 8 mm (vertical direction in FIG. 1)×50 mm (depth direction in FIG. 1)×70 mm (horizontal direction in FIG. 1 ), and the incident portion 21 c and the emitting portion 21 d are 8 mm×50 mm. The inter-lattice distance in the square lattice arrangement of the electrodes 22a and 22b is 2.5 mm (vertical and horizontal directions in FIG. 2), and the number of the electrodes 22a and 22b is 30 (the traveling direction of the electromagnetic wave R)×20 (the electromagnetic wave). R width direction). The diameter of each plasma P was about 1.0 mm.

  Next, the electromagnetic wave control characteristics of the electromagnetic wave control device 1 in which the control parameters are set as described above will be described.

  When the frequency of the electromagnetic wave R incident on the electromagnetic wave control element 2 was changed, the amount of transmitted electromagnetic waves decreased to about 15% in the frequency range of 61 to 63 GHz. The reason for this is that the relationship between the frequency of the electromagnetic wave R and the inter-lattice distance of the two-dimensional plasma array is approximately frequency×lattice constant/light velocity=0.5, so that the frequency band of 61 to 63 GHz is two-dimensional plasma. This is probably because it corresponds to the forbidden band created by the array.

  Then, when the interstitial distance was changed to 2.1 mm, a similar decrease in the amount of transmitted electromagnetic waves occurred at 74 to 76 GHz. Further, when the interstitial distance was changed to 1.5 mm, a similar decrease in the amount of transmitted electromagnetic waves occurred at 103 to 105 GHz. All of these results almost occur under the condition of frequency×lattice constant/light velocity=0.5, and it is possible to realize a variable frequency filter by changing the spatial arrangement of the two-dimensional plasma array. all right.

(Modification)
The electromagnetic wave control device 1 can be variously modified as described below.

  The electromagnetic wave control device 1 has a configuration in which the gas pressure inside the electromagnetic wave control element 2 can be adjusted by the gas control system 4. However, when the gas pressure is not adjusted, a predetermined gas is previously stored inside the electromagnetic wave control element 2. The gas control system 4 can be omitted by encapsulating at a predetermined pressure.

  In addition, the electromagnetic wave control device 1 has a configuration in which the power controller 32 can adjust the supply power and the arrangement of the plasma P. However, when the supply power and/or the arrangement of the plasma P are not adjusted, the power control is performed. These may be fixedly set in the container 32. Further, the power controller 32 may change the supplied power or the arrangement of the plasma P with time.

  Further, although the 6 rows and 7 columns arrangement is shown as the arrangement of the electrodes 22a and 22b, various changes (for example, the number of rows and/or the number of columns, the row spacing and/or the column spacing, the triangle, It is possible to make a change to another arrangement pattern such as a grid pattern).

  Further, although the electrodes 22a and 22b are illustrated as being disc-shaped, the shapes may be variously modified. For example, it may be changed to a rectangular plate shape, or may be changed to needle electrodes 22a' and 22b' as shown in FIG. Furthermore, by changing the areas of these electrodes, the cross-sectional area of the plasma P (the cross-sectional area when cut by a plane orthogonal to the longitudinal direction) can be changed.

  Further, as shown in FIG. 7, between the electrodes 22a and 22b facing each other, a tube made of a material that has an inner surface shape that is substantially the same as the planar shape of the electrodes 22a and 22b and that transmits the electromagnetic wave R. The member 23 (for example, a cylindrical member) may be provided.

  In general, in the plasma, charged particles diffuse toward the outside at the outer periphery thereof, so that the boundary surface of the plasma becomes ambiguous. Therefore, in the configuration as shown in FIG. 1, adjacent plasmas P may be continuous with each other. Even in such a case, in each plasma P, an electron density gradient is generated from the center to the outer circumference, so that the periodic distribution of plasma is maintained, but the difference in electron density is reduced. The effect of the periodic structure will also be reduced.

  On the other hand, in the configuration in which the cylindrical member 23 is provided, the plasma P can be confined inside the cylindrical member 23, so that the boundary surface of the plasma P can be clearly defined, and the difference in electron density at this boundary surface can be determined. Can be big. As a result, the influence of the periodic distribution of plasma can be made more apparent.

  Further, as shown in FIG. 8, inside the electromagnetic wave control element 2, an inner surface made of a dielectric material that transmits the electromagnetic wave R and having substantially the same planar shape as that of the electrodes 22a and 22b between the electrodes 22a and 22b facing each other. You may provide the dielectric member 24 in which the void|hole which has a shape was formed. In this configuration, the inside of the electromagnetic wave control element 2 is filled with the dielectric member 24 except for the holes.

In this configuration, similar to the configuration in which the tubular member 23 is provided, in addition to the large difference in electron density at the boundary surface, the difference in relative permittivity at the boundary surface can be made larger. This is because the relative permittivity ε _r of the plasma P has a value smaller than 1 as described above, while the dielectric member 24 is a dielectric substance and thus has a relative permittivity larger than 1 (usually, the relative permittivity of the dielectric substance is greater than 2). This is because the difference in relative permittivity at the boundary surface is larger than that in the case where a gas (relative permittivity of gas is approximately 1) is present instead of the dielectric member 24. As a result, the influence of the periodical distribution of plasma can be further manifested.

  In the configuration of FIG. 8, it is conceivable that the plasma P and the dielectric member 24 are reversed, that is, the cylindrical dielectrics are periodically arranged and the periphery thereof is filled with plasma. Moreover, a periodic structure having a relatively high relative dielectric constant is formed against a background having a low relative dielectric constant. Therefore, the electromagnetic waves to be controlled have shorter wavelengths (higher frequencies) than those in the configuration of FIG. 8, and to control radio waves (terahertz band (wavelength of about 0.1 mm) and longer wavelengths). It becomes unsuitable.

  Furthermore, in the configuration in which cylindrical dielectrics are periodically arranged and the surroundings are filled with plasma, when the relative permittivity of plasma is set to a negative value in order to increase the difference in relative permittivity, the electromagnetic wave control element 2 Inside the electromagnetic wave, the energy of the electromagnetic wave is remarkably attenuated and almost cannot propagate. On the other hand, in the configuration of FIG. 8, the propagation state can be effectively controlled while suppressing the attenuation of the electromagnetic wave energy.

  In the electromagnetic wave control element 2, the electrodes 22a and 22b and the electrodes 22a′ and 22b′, the housing 21, the tubular member 23, and the dielectric member 24 serve as a plasma generation unit that generates plasma that is two-dimensionally periodically distributed. Function. Further, the housing 21, the tubular member 23, and the dielectric member 24 function as gas holding means for holding the gas to be ionized in order to generate plasma and transmitting the electromagnetic wave to be controlled. In particular, the tubular member 23 and the dielectric member 24 have a plurality of holes that are periodically formed, and the plasma is generated in the holes to realize the periodic distribution of the plasma. Further, the dielectric member 24 is made of a dielectric material in which the plurality of holes are formed.

  Further, the power control system 3 functions as a power control unit that controls power for generating plasma, and also functions as a plasma distribution control unit that controls a plasma distribution state. Then, the gas control system 4 functions as a gas pressure control unit that controls the pressure of the gas to be ionized.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIG.

  The configurations of the electromagnetic wave control element of the present embodiment and an electromagnetic wave control device using the same will be described. FIG. 9 shows the overall configuration of the electromagnetic wave control device 101 of this embodiment. In addition, the same reference numerals are used for the components having the same functions as the components described in the first embodiment, and the description thereof will be omitted.

  The electromagnetic wave control element 102 included in the electromagnetic wave control device 101 includes parallel plate-shaped electrodes 122a and 122b outside the housing 21, and the inside of the housing 21 includes the electrodes 22a and 122a in the electromagnetic wave control device 1 of the first embodiment. The electromagnetic wave control element of the electromagnetic wave control device 1 according to the first embodiment is provided with electron emission members 123a and 123b made of a material having a higher secondary electron emission coefficient than the inner surface of the housing 21 in the portion where the 22b was formed. Different from 2.

  Further, in the power control system 103 constituting the electromagnetic wave control device 101, the power controller 132 does not individually supply power to each plasma P, but supplies power to the electrodes 122a and 122b. The point that the electric power is comprehensively supplied to the plasma P is different from the electric power control system 3 of the electromagnetic wave control device 1 in the first exemplary embodiment.

  In this configuration, since the electrodes 122a and 122b are formed by parallel flat plates, power supply from the power control system 3 becomes easy. Then, by forming the electron emitting members 123a and 123b in a predetermined pattern, it is possible to form a periodic distribution of the plasma P according to the pattern. Further, since the electron emitting members 123a and 123b are made of a material having a higher secondary electron emission coefficient than the inner surface of the housing 21, the plasma P is easily generated.

  As a specific material for the electron emitting members 123a and 123b, metal, magnesium oxide, or the like is suitable. Even if one of the electron emitting members 123a and 123b is omitted, the plasma P having a desired pattern can be generated.

  In the electromagnetic wave control element 102, the electrodes 122a and 122b, the electron emitting members 123a and 123b, and the housing 21 function as a plasma generation unit that generates plasma that is two-dimensionally and periodically distributed. In particular, the electron emitting members 123a and 123b are exposed inside the housing 21 and function as electron emitting means made of a material having a higher secondary electron emission coefficient than the surroundings. Further, the housing 21 functions as a gas holding unit that holds a gas to be ionized in order to generate plasma and transmits an electromagnetic wave to be controlled.

  The power control system 103 also functions as a power control unit that controls the power for generating plasma.

[Embodiment 3]
Another embodiment of the present invention will be described below with reference to FIG.

  The configurations of the electromagnetic wave control element of the present embodiment and an electromagnetic wave control device using the same will be described. The overall configuration of the electromagnetic wave control device 201 of this embodiment is shown in FIG. In addition, about the component which has a function equivalent to the component demonstrated in Embodiment 1 and 2, the same code|symbol is used and the description is abbreviate|omitted.

  The electromagnetic wave control element 202 that constitutes the electromagnetic wave control device 201 includes, in addition to the electrodes 22a and 22b provided inside the housing 21, electrodes 223a and 223b forming a parallel plate outside the housing 21. This is different from the electromagnetic wave control element 2 of the electromagnetic wave control device 1 according to the first exemplary embodiment.

  In addition, in the power control system 203 that constitutes the electromagnetic wave control device 201, in the power controller 232, in addition to individually supplying power to the electrodes 22a and 22b, power is also supplied to the electrodes 223a and 223b. This is different from the power control system 3 of the electromagnetic wave control device 1 according to the first exemplary embodiment.

  In this configuration, similarly to the electromagnetic wave control element 2 of the first exemplary embodiment, the plasma P that is periodically distributed is generated by the electrodes 22a and 22b, and the periphery of the plasma P is covered by the electrodes 223aa and 223b. A plasma P′ having an electron density different from that of the plasma P is generated.

  Therefore, it is possible to change the refractive index of both the plasma P that is periodically distributed and the plasma P′ that surrounds the plasma P, and thus it is possible to more flexibly change the control state for electromagnetic waves.

  In the electromagnetic wave control element 202, the electrodes 22a and 22b and the housing 21 function as a plasma generation unit that generates plasma that is two-dimensionally periodically distributed. In particular, the electrodes 223aa and 223b surround the periodic plasma and further generate plasma having an electron density different from that of the plasma. Further, the housing 21 functions as a gas holding unit that holds a gas to be ionized in order to generate plasma and transmits an electromagnetic wave to be controlled.

  Further, the power control system 203 functions as a power control unit that controls the power for generating plasma, and also functions as a plasma distribution control unit that controls the distribution state of the plasma.

[Embodiment 4]
Another embodiment of the present invention will be described below with reference to FIGS. 11 and 12.

  The configurations of the electromagnetic wave control element of the present embodiment and an electromagnetic wave control device using the same will be described. FIG. 11 shows the overall configuration of the electromagnetic wave control device 301 of the present embodiment, and FIG. 12 shows a sectional view taken along the line BB in FIG. In addition, about the component which has a function equivalent to the component demonstrated in Embodiment 1, 2 and 3, the same code|symbol is used and the description is abbreviate|omitted.

  The electromagnetic wave control element 302 that constitutes the electromagnetic wave control device 301 includes electrodes 322a and 322b that are provided inside the housing 21 in close proximity to each other. The electrodes 322a and 322b are mesh-shaped electrodes having the same shape, and openings (slits) S are formed in each of the electrodes 322a and 322b so as to be arranged in a square lattice shape (matrix shape). The electrodes 322a and 322b are arranged with a predetermined gap so that their openings S overlap. In addition, the electromagnetic wave control element 302 is provided with a plate-shaped electrode 323 outside the housing 21. Note that the electrode 322b, the electrode 322a, and the electrode 323 are arranged in this order.

  Further, the power control system 303 constituting the electromagnetic wave control device 301 supplies power to the electrode 322b in the power controller 332 and grounds the electrodes 322a and 323.

  In this configuration, plasma is generated between the electrode 322b that is grounded and the electrode 322a that is supplied with power, and this plasma passes through the opening S of the electrode 322a by the potential of the electrode 323 that is grounded. It will be drawn out to the electrode 323 side. The drawn plasma P is distributed in a square lattice shape corresponding to the openings S.

  As described above, since the electric field strength between the electrodes 322a and 322b can be increased by generating plasma by the electrodes 322a and 322b arranged relatively close to each other, it is possible to easily generate plasma.

  In the electromagnetic wave control element 302, the electrodes 322a and 322b, the electrode 323, and the housing 21 function as a plasma generation unit that generates plasma that is two-dimensionally and periodically distributed. Further, the housing 21 functions as a gas holding unit that holds a gas to be ionized in order to generate plasma and transmits an electromagnetic wave to be controlled. The power control system 303 also functions as a power control unit that controls the power for generating plasma.

[Embodiment 5]
Another embodiment of the present invention will be described below with reference to FIG.

  The configurations of the electromagnetic wave control element of the present embodiment and an electromagnetic wave control device using the same will be described. FIG. 13 shows the overall configuration of the electromagnetic wave control device 401 of this embodiment. The constituents having the same functions as the constituents described in the first, second, third, and fourth embodiments are designated by the same reference numerals, and the description thereof will be omitted.

  The electromagnetic wave control element 402 that constitutes the electromagnetic wave control device 401 has a configuration in which the electromagnetic wave control elements 2 according to the first embodiment are stacked. As a result, the pair of electrodes 22a and 22b facing each other is three-dimensionally arranged, and the plasma P generated therebetween is also three-dimensionally distributed.

  In the power control system 403 that constitutes the electromagnetic wave control device 401, although not shown in FIG. 13, each electrode 22a is connected to the power controller 432 and each electrode 22b is grounded. . Then, the power controller 432 supplies regulated power to one selected from the electrodes 22a arranged three-dimensionally.

  With this configuration, the plasma P can be three-dimensionally periodically distributed, so that a so-called complete band gap can be realized, and the electromagnetic wave incident on the electromagnetic wave control element 402 from any direction from above, below, left, and right can be achieved. The filter effect can be exhibited.

  Further, in the conventional photonic crystal made of a solid material, there are many restrictions for realizing a three-dimensional structure due to manufacturing problems, but in the electromagnetic wave control element 402, the three-dimensional period is relatively easy. The structure can be realized.

  In the electromagnetic wave control element 402, the electrodes 22a and 22b and the housing 21 function as a plasma generation unit that generates plasma that is periodically distributed in three dimensions. Further, the housing 21 functions as a gas holding unit that holds a gas to be ionized in order to generate plasma and transmits an electromagnetic wave to be controlled. Further, the power control system 403 functions as a power control unit that controls power for generating plasma, and also functions as a plasma distribution control unit that controls a plasma distribution state.

  In this embodiment, the electromagnetic wave control element 402 of the first embodiment is stacked to form the electromagnetic wave control element 402. However, by stacking the electromagnetic wave control elements 102, 202, and 302 described in Embodiments 2 to 4, the electromagnetic wave control element 402 is stacked. 402 may be configured.

  As described above, according to the present invention, it is possible to realize an electromagnetic wave control element capable of dynamically and widely controlling a function by applying a signal from the outside, and an electromagnetic wave control device using the electromagnetic wave control element. The electromagnetic wave control device according to the present invention can be suitably used for controlling various electromagnetic waves, and particularly can be suitably used for controlling electromagnetic waves in the 10 GHz to terahertz band.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in the different embodiments can be appropriately combined and obtained. Embodiments are also included in the technical scope of the present invention.

  The electromagnetic wave control element of the present invention generates a large number of plasmas P (the individual plasmas P are also referred to as “plasma bodies”) so as to form a two-dimensional or three-dimensional periodic structure. It may have a function of adjusting the gas pressure in the space where a large number of plasma bodies are arranged. The large number of plasma bodies may be arranged in a dielectric body. The large number of plasma bodies may be arranged in a hollow cylindrical tube having the same periodic structure. The large number of plasma bodies may be arranged in a plasma having a different electron density. The large number of plasma bodies may be generated by arc discharge. It may have a function of controlling the arrangement positions of the large number of plasma bodies. The control function of the arrangement positions of the large number of plasma bodies may be realized by controlling generation of preliminary discharge in a part of the plasma bodies. The function of controlling the arrangement positions of the large number of plasma bodies may be realized by setting the material of the plasma body end contact portion. The plasma body may be provided with a power supply unit for generating power, and the generating power may be variable with time.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for controlling electromagnetic waves in the fields of communication and measurement, for example.

Claims (13)

A plasma generating means for generating a two-dimensionally or three-dimensionally periodically distributed plasma,
An electromagnetic wave control element, wherein the propagation state of the electromagnetic wave is controlled by passing the electromagnetic wave through the plasma.   The plasma generating means includes an electrode for supplying electric power for generating the plasma, and a gas holding means for internally holding a gas to be ionized to generate the plasma and transmitting an electromagnetic wave to be controlled. The electromagnetic wave control element according to claim 1, wherein:   The electromagnetic wave control element according to claim 2, wherein the electrodes are arranged periodically, and the periodic distribution of the plasma is formed according to the periodic arrangement of the electrodes.   The gas holding unit has a plurality of holes that are periodically formed, and a periodic distribution of the plasma is formed by generating plasma in the holes. 2. The electromagnetic wave control element according to 2.   The electromagnetic wave control element according to claim 4, wherein the gas holding means is made of a dielectric material in which the plurality of holes are formed. The plasma generating means further comprises an electron emitting means exposed to the inside of the gas holding means and made of a material having a secondary electron emission coefficient higher than that of the surroundings.
The electromagnetic wave control element according to claim 2, wherein the electron emission means are arranged periodically, and the periodic distribution of the plasma is formed according to the periodic arrangement of the electron emission means.   The electromagnetic wave control element according to claim 1, wherein the plasma generation means further generates a plasma that surrounds the periodic plasma and has a different electron density from the plasma.   The electromagnetic wave control element according to claim 2, wherein the plasma generation means includes an extraction electrode that applies a voltage for extracting the plasma generated by the electrode. An electromagnetic wave control element according to any one of claims 1 to 8,
An electromagnetic wave control device comprising: an electric power control unit that controls electric power for generating plasma by the plasma generation unit. An electromagnetic wave control element according to any one of claims 1 to 8,
An electromagnetic wave control device comprising: a plasma distribution control means for controlling a distribution state of plasma generated by the plasma generation means. An electromagnetic wave control element according to any one of claims 1 to 8,
An electromagnetic wave control device, comprising: a gas pressure control unit that controls the pressure of a gas to be ionized in order to generate the plasma.   An electromagnetic wave control plasma characterized by controlling a propagation state of an electromagnetic wave passing through by being distributed two-dimensionally or three-dimensionally periodically.   An electromagnetic wave control method, wherein a plasma that is two-dimensionally or three-dimensionally periodically distributed is generated, and an electromagnetic wave is passed through the plasma to control a propagation state of the electromagnetic wave.

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