CN208723068U - A kind of multiple resonant cavity based on multiple metal composite nano dielectric posts - Google Patents
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Abstract
The utility model discloses a kind of multiple resonant cavities based on multiple metal composite nano dielectric posts, belong to electromagnetic technology field.The multiple resonant cavity of the utility model is made of three layers of 18 metal composite nano dielectric posts altogether, and 6 metal composite nano dielectric posts of first layer press rectangular arranged, each 6 of second and third layer are evenly distributed in respectively on inside and outside two circles；The structure constitutes 9 cavitys of 4 kinds of difference in size.The multiple resonant cavity of the utility model passes through the gap between dielectric posts, by external excitation resonance, the resonance plasma wave of incidence wave excitation simultaneously forms six kinds of entirely different resonance mechanism by 9 cavitys of 4 kinds of different sizes in different frequency, the plasma wave for exciting resonance to the incidence wave of different frequency is realized by the size of the material and thickness and the relative dielectric constant of innermost layer dielectric core that change metal coating, realizes the diversified multiple cavity resonator structure of different frequency.
Description
Technical Field
The utility model belongs to the technical field of the electromagnetism, specifically speaking relates to an electromagnetic resonant cavity, and more specifically says, relates to a multiple resonant cavity based on a plurality of metal composite nanometer medium posts.
Background
The resonant cavity of the common electromagnetic wave can effectively resonate only through the feed source in the cavity, and under the condition that the size and the shape of the common electromagnetic resonant cavity are determined, the resonant mode can only be determined low-frequency and high-frequency resonant modes, and the geometric dimension of the common electromagnetic resonant cavity determines the resonant frequency.
With the rapid development of nanotechnology, nano metal materials are different from pure medium nanorod materials, not only have the excellent properties of nano materials, but also integrate the unique characteristics of metals, thereby exhibiting unique performance in the fields of physics and chemistry. The influence of the application of the nano-metal material in the basic research of various fields is remarkable. Particularly, noble metals such as gold and silver can be used for the coating layer, and the coating layer has good optical performance. In addition, some metal nano materials are sensitive to temperature, light, sound and gas, and the sensors meeting different performance requirements can be prepared by using the nano metal materials. In the field of nanophotonics, surface plasmon optics gradually highlights its advantages. Metal surface plasmons are a unique surface electromagnetic wave that is formed by the interaction of incident light with free electrons inside a metal in nature. Surface plasmons are generated at the interface surface of the metal and the medium, and are a photon-electron coupling state formed by the action of photons and free electrons on the surface of the metal, and the coupling state enables the local field of the surface plasmon to be enhanced.
Disclosure of Invention
To the above-mentioned shortcoming and the deficiency that traditional electromagnetic resonator exists, the utility model aims to provide a multiple resonator structure of constituteing by the compound nanometer medium post of three-layer metal, unique optical characteristic and resonant mode have.
In order to solve the above problem, the utility model discloses the technical scheme who adopts as follows:
a multiple resonant cavity based on a plurality of metal composite nano-medium columns comprises 18 metal composite nano-medium columns which are respectively arranged in an inner layer region, a middle layer region and an outer layer region, wherein the central points of the inner layer region, the middle layer region and the outer layer region are superposed; 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are arranged in a rectangular mode in an inner layer region, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a circular mode in a middle layer region, the rest 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a circular mode in an outer layer region, and the metal composite nano-medium columns in the middle layer region and the metal composite nano-medium columns in the outer layer region are arranged in a staggered mode one by one; the 18 metal composite nano-medium columns are not contacted with each other, and 9 cavities with different four shapes are formed among the 18 metal composite nano-medium columns.
Further, the 18 metal composite nano-media columns comprise an inner-layer media column I, an inner-layer media column II, a middle-layer media column and an outer-layer media column; the inner layer area is rectangular, 4 inner layer medium columns I are respectively arranged on four vertexes of the inner layer area, 2 inner layer medium columns II are respectively arranged on the middle points of two long sides of the inner layer area, and the outer diameter of each inner layer medium column I is larger than that of each inner layer medium column II; the middle layer area is circular, and 6 middle layer medium columns are uniformly distributed on the boundary of the middle layer area; the outer layer area is circular, and there are 6 outer layer medium columns which are uniformly distributed on the boundary of the outer layer area.
Furthermore, the radius of the middle layer area is 208.75nm, the radius of the outer layer area is 257nm, the radius of the inner layer medium column I is 60nm, the distance between the circle center of the inner layer medium column I and the center point of the inner layer area is 120.8nm, the radius of the inner layer medium column II is 43.9nm, the radius of the middle layer medium column is 60nm, and the radius of the outer layer medium column is 67.5 nm.
Furthermore, the thickness of the metal coating of the metal composite nano-medium column is 14-30 nm.
Furthermore, the metal coating of the metal composite nano-medium column is made of gold or silver.
Furthermore, the relative dielectric constant range of the innermost dielectric core of the metal composite nano-dielectric column is 3.9-11.5.
Furthermore, the material of the innermost dielectric core of the metal composite nano-dielectric column is silicon or silicon dioxide.
Further, the metal composite nano-medium column has a relative magnetic permeability of 1.
Further, the metal composite nano-medium column is placed in an air environment.
Compared with the prior art, the beneficial effects of the utility model are that:
(1) compare in ordinary electromagnetic resonator, the utility model discloses a plasma wave resonant cavity that metal composite nanometer medium post is constituteed can pass through the gap between the medium post, by the outside excitation resonance.
(2) Compare in the single resonant mode of traditional electromagnetic resonator, the utility model discloses a resonant cavity structure can realize the diversified resonance mechanism to multiple frequency incident electromagnetic wave, and the plasma wave that different frequencies arouse forms the resonance of different forms at the cavity of difference.
(3) The electromagnetic resonant cavity geometric dimensions of ordinary resonant cavity have just decided resonant frequency, and the utility model discloses a metal composite nano-medium post can effectual change plasma wave's resonant frequency through the thickness that changes the metal level, and plasma wave's resonance space is not only that the metal encloses into geometric space moreover, still includes interface portion space.
(4) The utility model discloses a resonant cavity structure can be through the change to innermost medium core and outer metallic coating's material, arouses the plasma wave of resonance to the incident wave of different frequencies.
Drawings
Fig. 1 is a schematic diagram of multiple regions and multiple metal composite nano-media pillars of a multiple resonant cavity according to the present invention;
in the figure: 1. an inner layer medium column I; 2. an inner layer medium column II; 3. a middle layer medium column; 4. and an outer dielectric column.
Fig. 2 is a schematic arrangement diagram of a three-layer metal composite nano-media column according to the present invention;
in the figure: 101. a first inner dielectric column I; 102. a second inner layer medium column I; 103. a third inner layer medium column I; 104. a fourth inner layer medium column I; 201. a first inner layer medium column II; 202. a second inner layer medium column II; 301. a first middle layer dielectric pillar; 302. a second middle layer dielectric column; 303. a third middle layer dielectric column; 304; a fourth middle layer dielectric column; 305. a fifth middle layer dielectric column; 306. a sixth middle layer dielectric column; 401. a first outer dielectric column; 402. a second outer dielectric column; 403. a third outer dielectric column; 404. a fourth outer dielectric column; 405. a fifth outer dielectric column; 406. and a sixth outer dielectric column.
Fig. 3 is a schematic diagram of the absorption cross section of the silver coating with the incident angle of the external plane wave of 0 degree and the thickness of all three layers of metal composite nano-media columns of 18 nm.
FIG. 4 is a near magnetic field distribution plot of six peaks of the absorption cross section of FIG. 3;
where a is the incident frequency f (a) 9.261 × 1013Hz, b is incident frequency f (b) 1.347 × 1014Hz, c is incident frequency f (c) 1.563 x 1014Hz, d is incident frequency f (d) 1.682 × 1014Hz, e is incident frequency f (e) 1.779 × 1014Hz, f is the incident frequency f (f) 2.152 × 1014Resonant mode of plasma wave at Hz.
FIG. 5 is a schematic diagram of the absorption cross section of a three-layer metal composite nano-medium column obtained by changing the thickness (14nm, 18nm and 30nm) of the metal coating silver.
FIG. 6 is a near field diagram corresponding to six peaks when the thickness of the metal layer is 30 nm;
whereinAnd a is an incident frequency f (a) corresponding to the first peak value of 0.9583 × 1014Magnetic field distribution in Hz, b is the incident frequency f (b) corresponding to the second peak value of 1.422 × 1014Magnetic field distribution in Hz, c is the third peak, and the incident frequency is f (c) 1.706 × 1014Hz magnetic field distribution diagram, d is the incident frequency f (d) corresponding to the fourth peak value of 1.851 × 1014Magnetic field distribution at Hz, e is the incident frequency f (e) corresponding to the fifth peak of 1.983 × 1014In the magnetic field distribution diagram in Hz, f is the incident frequency f (f) corresponding to the sixth peak of 2.381 × 1014Magnetic field profile in Hz.
Fig. 7 is an absorption cross-sectional view obtained when the innermost core dielectric material is silicon and silicon dioxide, respectively.
Fig. 8 is a cross-sectional view of absorption obtained when the metal coating material is gold or silver, respectively.
Detailed Description
The present invention will be further described with reference to the following specific embodiments.
The multiple resonant cavities based on multiple metal composite nano-medium columns as shown in FIGS. 1-8 comprise 18 metal composite nano-medium columns. Four kinds of medium columns including an inner layer medium column I1, an inner layer medium column II 2, a middle layer medium column 3 and an outer layer medium column 4 are respectively arranged on the boundaries of an inner layer area, a middle layer area and an outer layer area, the inner layer area is rectangular, the middle layer area and the outer layer area are circular, and the central points of the inner layer area, the middle layer area and the outer layer area are overlapped.
Wherein: the first inner-layer medium column I101, the second inner-layer medium column I102, the third inner-layer medium column I103 and the fourth inner-layer medium column I104 are positioned on four vertexes of an inner-layer area; the first inner layer medium column II 201 and the second inner layer medium column II 202 are respectively positioned on the middle points of the two long sides of the inner layer area. The first middle layer dielectric cylinder 301, the second middle layer dielectric cylinder 302, the third middle layer dielectric cylinder 303, the fourth middle layer dielectric cylinder 304, the fifth middle layer dielectric cylinder 305 and the sixth middle layer dielectric cylinder 306 are evenly distributed on the boundary of the middle layer area. The first outer layer dielectric column 401, the second outer layer dielectric column 402, the third outer layer dielectric column 403, the fourth outer layer dielectric column 404, the fifth outer layer dielectric column 405 and the sixth outer layer dielectric column 406 are uniformly distributed on the boundary of the outer layer region. The middle layer medium columns 3 and the outer layer medium columns 4 are arranged in a staggered mode one by one. The connecting line between the circle center of the inner layer medium column I1 and the center point of the inner layer area and the circle centers of the 2 inner layer medium columns II 2 form an angle of 60 degrees or 120 degrees, and the connecting line between the circle centers of the second middle layer medium column 302 and the fifth middle layer medium column 305 is perpendicular to the connecting line between the circle centers of the first inner layer medium column II 201 and the second inner layer medium column II 202; the third outer layer medium column 403 and the sixth outer layer medium column 406 are positioned on the same straight line with the first inner layer medium column II 201 and the second inner layer medium column II 202.
The 18 nano-medium columns are not contacted but have gaps, and 4 kinds of 9 cavities with different sizes are formed among the 18 nano-medium columns, and the cavities comprise: two large left and right cavities (between a first middle layer medium column 301, a sixth outer layer medium column 406, a sixth middle layer medium column 306, a fourth inner layer medium column I104, a first inner layer medium column II 201, a first inner layer medium column I101; between a second inner layer medium column I102, a second inner layer medium column II 202, a third inner layer medium column I103, a fourth middle layer medium column 304, a third outer layer medium column 403, a third middle layer medium column 303), a cavity in the central area (between the first inner layer medium column I101, the second inner layer medium column I102, the third inner layer medium column I103, the fourth inner layer medium column I104, the first inner layer medium column II 201, the second inner layer medium column II 202), two small upper and lower triangular cavities (between the first inner layer medium column I101, the second inner layer medium column I102, the second middle layer medium column 302; between the third inner layer medium column 103, the fourth inner layer medium column I104, Fifth middle-layer dielectric pillars 305) and four outermost small cavities (among the first inner-layer dielectric pillar i 101, the first middle-layer dielectric pillar 301, the first outer-layer dielectric pillar 401, and the second middle-layer dielectric pillar 302; the second middle medium column 302, the second outer medium column 402, the third middle medium column 303 and the second inner medium column I102; a third inner layer medium column I103, a fourth middle layer medium column 304, a fourth outer layer medium column 404 and a fifth middle layer medium column 305; between the fourth inner media column i 104, the fifth middle media column 305, the fifth outer media column 405, and the sixth middle media column 306).
The relative dielectric constant of the innermost dielectric core of the metal composite nano dielectric column is 3.9-11.5, silicon or silicon dioxide can be adopted, the thickness of the metal coating is 14-30 nm, gold or silver coating can be adopted, and the relative permeability mu of the dielectric column is 1. The relative dielectric constant of the metal coating can be calculated by using a Drude-Lorentz dispersion model, and the specific formula is as follows:
where ω is the angular frequency of the light, ε∞Is the relative dielectric constant when ω → ∞; omegapIs the plasma frequency; Δ is Lorentz term weight; gamma-shapedLThe vibration spectrum is wide; omegaLThe Lorentz harmonic oscillator strength; subscript L denotes Lorentz model; i is an imaginary unit.
Wherein, the related parameters of the silver are as follows: omega is the angular frequency of the incident light, epsilon∞＝2.4046，ωP＝2π×2214.6×1012Hz，Δ＝1.6604，ΓL＝2π×620.7×1012Hz，ΩL＝2π×1330.1×1012Hz, i is an imaginary unit, γ is 4.8 × 2 π × 1012Hz; relevant parameters for gold are as follows: omega is the angular frequency of light, epsilon∞＝4.0903，ωP＝2π×2170.7×1012Hz，Δ＝4.9603，ΓL＝2π×849.1×1012Hz，ΩL＝2π×1006.4×1012Hz, i is an imaginary unit, γ is 17.4 × 2 π × 1012Hz。
The resonant cavity has a selection frequency of 5.0 × 1013Hz～2.5×1014Hz electromagnetic waves are incident from the left boundary (including and not limited to plane waves), and the incident angle θ is 0 ° (the angle of incident waves can be arbitrarily set, but is not limited to 0 °, and for convenience in calculation, the incident angle of 0 ° is taken), specificallySee fig. 2 (arrows are incident plane waves). For the metal composite nano-medium column with the coating, the whole area is divided into three areas, wherein the area 1 is a free space area except for the three layers of metal composite nano-medium columns, the area 2 is a metal coating area, and the area 3 is a medium column core area. Using the xoy coordinate system as the global coordinate system, assuming a TE plane wave incident,assuming an angle of incidenceAccording to the characteristics of cylindrical surface scattering, incident wave HzWritten in the form of cylindrical wavesSuppose (ρ)j，φj) The local coordinate system of j-order metal composite nano-medium column is expressed, and (phi)0，ΦM，ΦD) And (Ψ)0And ΨM) Defined as the incident cylindrical wave and the scattered wave in respective regions, where Φ represents a bessel function and Ψ represents a hankel function. The outer layer free space rho can be deduced by Maxwell equation, Graf addition theorem and boundary conditionj＞r1Intermediate metal layer r2＜ρj＜r1Innermost dielectric core ρj＜r2The expression of the magnetic field component | Hz | is:
wherein,is an amplitude coefficient of an incident wave represented by a cylindrical Fourier series expansion, whereinIs the angle of incidence; the left and right parts of equations (3) to (4) represent incident waves and scattered waves, i.e., (Φ)0，ΦM，ΦD) Representing inwardly propagating waves, (Ψ)0And ΨM) Represents the outward scattered wave, and the specific expression is as follows:
wherein JmIs a bezier function of order m,is a m-th order first class hank function;
in formula (5) GjIndicating the interconversion of different coordinate systems, the subscript j indicating the transformation of the scattered field of the other cylinder to the j object, in a scattered field of order j, GiAnd DjThe same process is carried out; σ in formula (5)q,jAnd αqThe transformation factors are additive theorems, and the expression is as follows:
Ap＝-T(1)·kp(p＝2,3,...,N) (12)
Dj＝[ein(j-1)θδnn′](14)
wherein, Λp，Ap，kpAre all transformation factors obtained using the Graf addition theorem, I is an identity matrix, δmIs a function of kronecker, k0Is the wave number in free space and is,is the wave number of the metal layer,is the wave number of the core in the medium, b is the amplitude vector of the incident wave; based on the local coordinate system (ρ, φ), the following coordinate transformation between cylindrical coordinates and planar coordinates is performed:
ζp＝π/2-(p-1)θ/2 (15)
dp＝2Rsin[(p-1)θ/2](16)
in formulae (2) to (5), T(1)，T(2)，T(3)And T(4)Both are transformation matrices of fields in both regions, representing the additive theorem of the transformation matrices, and both are diagonal matrices, the expression is as follows:
T(1)＝Rfm+Ffm·Rmd·(I-Rmf·Rmd)-1·Fmf(18)
T(2)＝(I-Rmf·Rmd)-1·Fmf(19)
T(3)＝Rmd·(I-Rmf·Rmd)-1·Fmf(20)
T(4)＝Fdm·(I-Rmf·Rmd)-1·Fmf(21)
wherein R isijAnd Fij(i, j ═ f, m, d) is a diagonal matrix representing reflected and transmitted cylindrical waves traveling from region "j" to region "i", and the indices f, m, d represent free space, metal layers, and dielectric cores; rfmAnd FfmRepresenting the reflection and transmission matrices, R, from the metal layer interface to free spacemdRepresenting the reflection matrix, R, from the dielectric core to the metallic interfacemfAnd FmfRepresenting the reflection matrix and the transmission matrix from the outer free space to the interface of the intermediate metal layer.
In order to quantitatively research the optical characteristics of the nano-cylindrical structure with the metal coating layer more completely, the absorption section sigma is absorbedabsAnd scattering cross section σscaThe far field characteristics of the metal composite nano cylindrical structure are explored through numerical analysis.
In order to build a model of a plurality of metal composite nano-medium column structures, a local coordinate system is used(i 1,2 ….) the formula expressing the scattered field is converted into a global coordinate systemExpressing the scatterfield equation, two metal composite nanopillars are used as an example, the transformation matrix β01、β02Will be a local coordinate systemΨ of0,1AndΨ of0,2Conversion to Ψ0An expression formula of the external scattered field can be obtained:
wherein:
β01(m,n)＝(-1)m-nJm-n(k0d/2) (24)
β02(m,n)＝Jm-n(k0d/2) (25)
whereinRepresenting the scattering amplitude coefficients of two metal composite nanocylindrical structures.
The scattering and absorption cross sections of two metal composite nanocylinder structures can be deduced, and the specific expression is as follows:
in the formula,the (m, n) th element, P, of the scattering amplitude coefficient A in equation (27)nRepresents the amplitude coefficient of the incident plane wave.
Example 1
Referring to fig. 1 and 2, in the present embodiment, the radius of the middle layer region is 208.75nm, and the radius of the outer layer region is 257 nm; the radius of the inner-layer dielectric column I1 is 60nm, and the distance between the circle center of the inner-layer dielectric column I1 and the center point of the inner-layer area is 120.8 nm; the radius of the inner layer medium column II 2 is 43.9 nm; the radius of the middle layer medium column 3 is 60 nm; the radius of the outer dielectric column 4 is 67.5 nm.
The metal composite nano-medium column of the multiple resonant cavity of the embodiment adopts a silver coating, and the relative magnetic permeability of an inner layer medium core is 1 in a common silicon medium with the relative dielectric constant of 10.
The selection frequency is 5.0 × 10 according to the size of the nano-pillars13Hz～2.5×1014Hz electromagnetic wave is incident from the left boundary, the incident angle theta is 0 DEG, and the sigma of the three-layer metal composite nano-medium column is obtained by numerical solutionabs(absorption cross section), it can be clearly seen from the schematic diagram of the absorption cross section shown in fig. 3 that there are 6 peaks, which represent that the energy of the incident electromagnetic wave will cause the resonance of the plasma wave, and coupling absorption will occur, resulting in the energy of the reflected wave being reduced, and an absorption peak appears on the absorption cross section. According to the 6 peak values, a near magnetic field H corresponding to the 6 resonance peak values is madezThe distribution of (c) is shown in fig. 4, and it can be clearly seen that 6 resonance peaks correspond to 6 different resonance modes.
The first resonance mode is shown in FIG. 4(a), and the incident frequency is 9.261 × 1013Hz. At the frequency, the magnetic field is mainly distributed in the first inner dielectric column I101, the second inner dielectric column I102 and the third inner dielectric columnAnd a central area is surrounded by the layer medium column I103, the fourth inner layer medium column I104, the first inner layer medium column II 201 and the second inner layer medium column II 202, and stronger resonance is formed.
The second resonance mode is shown in FIG. 4(b), and the incident frequency is 1.347X 1014Hz. The excited plasma wave forms strong resonance in a left cavity and a right cavity which are respectively enclosed by the first middle layer medium column 301, the sixth outer layer medium column 406, the sixth middle layer medium column 306, the fourth inner layer medium column I104, the first inner layer medium column II 201, the first inner layer medium column I101, the second inner layer medium column I102, the second inner layer medium column II 202, the third inner layer medium column I103, the fourth middle layer medium column 304, the third outer layer medium column 403 and the third middle layer medium column 303, and the phases of the resonant plasma waves are opposite in the two resonant cavities.
The third resonant mode is shown in FIG. 4(c), and the incident frequency is 1.563 × 1014Hz. At this frequency, the plasma is concentrated in the upper and lower triangular regions respectively enclosed by the first inner layer dielectric column i 101, the second inner layer dielectric column i 102, the second middle layer dielectric column 302, the third inner layer dielectric column i 103, the fourth inner layer dielectric column i 104 and the fifth middle layer dielectric column 305 in addition to the regions same as those in fig. 4(b), and the phases of the resonant plasma waves are the same in the left and right two resonators, and the phases of the upper and lower cavities are the same and opposite to those of the plasma waves in the left and right cavities.
The fourth resonant mode is shown in FIG. 4(d), and the incident frequency is 1.682 × 1014Hz. The plasma is mainly concentrated in a central cavity (same as that in fig. 4 (a)), and outermost cavities surrounded by a first inner-layer dielectric column i 101, a first middle-layer dielectric column 301, a first outer-layer dielectric column 401, a second middle-layer dielectric column 302, a second outer-layer dielectric column 402, a third middle-layer dielectric column 303, a second inner-layer dielectric column i 102, a third inner-layer dielectric column i 103, a fourth middle-layer dielectric column 304, a fourth outer-layer dielectric column 404, a fifth middle-layer dielectric column 305, a fourth inner-layer dielectric column i 104, a fifth middle-layer dielectric column 305, a fifth outer-layer dielectric column 405, and a sixth middle-layer dielectric column 306 respectivelyIn the four small cavities, the phase of the resonant plasma wave in the central area is opposite to that of the plasma wave in the outer four small cavities.
The fifth resonance mode is shown in FIG. 4(e), and the incident frequency is 1.779X 1014Hz. In this case, the plasma wave forms resonance only in the four small cavities at the outermost layer, and the phases of the plasma waves in the left and right small cavities are opposite.
The sixth resonance mode is shown in FIG. 4(f), and the incident frequency is 2.152X 1014Hz. At the moment, the frequency of incident waves is high, so that stronger resonant plasma waves appear in four small cavities at the outermost layer, an upper triangular cavity, a lower triangular cavity and a central area, wherein two symmetrically distributed triangular areas and other strong resonant areas are opposite in phase.
Example 2
The three-layer metal composite nano-medium column arrangement and parameters of the present embodiment are substantially the same as those of embodiment 1, except for the thickness of the metal coating.
The thickness of the silver coating is respectively 14nm, 18nm and 30nm, and the selection frequency is 5 multiplied by 1013Hz to 2.5X 1014The Hz plane wave is incident from the left boundary at an incidence angle θ of 0 °, and absorption cross-sectional views corresponding to the three thicknesses shown in fig. 5 are obtained, in which the silver layer thickness of 14nm is shown by a solid line, the thickness of 18nm is shown by a broken line, and the thickness of 30nm is shown by a dotted line. It can be seen that as the thickness of the metal layer increases, the excitation frequency of the resonance peak of the Absorption Cross Section (ACS) becomes larger, and the peak value shown on the absorption cross section is shifted to the right, and the higher the frequency, the more obvious the corresponding peak value is shifted to the right. FIG. 6 is a near field diagram corresponding to six peaks when the thickness of the metal layer is 30nm, and it can be seen from FIG. 6 that although the thickness of the metal layer is changed, the geometric dimension of the cavity structure surrounded by the metal composite nanocylinder is not changed, so six plasmon resonance modes corresponding to the same six resonance peaks appear, which is consistent with FIG. 4, but the corresponding frequency is higher, and thus it can also be seen that the incident electromagnetic wave is incident on the multilayer composite mediumThe plasmon resonance excited in the column cavity is different from the general electromagnetic wave resonance, and there is no fixed resonance mode or frequency.
Example 3
The three-layer metal composite nano-medium column arrangement and parameters of the present embodiment are substantially the same as those of embodiment 1, except for the material of the innermost core medium.
The absorption cross section of the three-layer metal composite nano-dielectric column shown in fig. 7 is obtained by respectively selecting silicon with a relative dielectric constant of 11.5 and silicon dioxide with a relative dielectric constant of 3.9, wherein the silicon is represented by a solid line, and the silicon dioxide is represented by a dotted line. As can be seen from fig. 7, since the geometric structures of the plurality of metal nano-composite columns are the same, the number and the structure of the cavities of the formed nano-dielectric columns are also the same, and although the dielectric constants of the inner layer materials of the dielectric columns are different, six absorption peaks respectively appear, which indicates that the change of the dielectric constant of the dielectric column does not change the resonance rule of the plasma wave in the composite structure. However, it can be seen that when the relative dielectric constant is reduced, the resonance peak formed by the excited plasma wave is obviously shifted to the right, and the higher the frequency, the larger the right shift, which means that the smaller the relative dielectric constant of the dielectric column, the higher the incident frequency of the resonance peak generated by forming the plasma wave on the dielectric and the metal surface, and therefore, different plasma resonances can be obtained by changing the material of the innermost core dielectric.
Example 4
The three-layer metal composite nano-medium column arrangement and parameters of the present embodiment are substantially the same as those of embodiment 1, except for the material of the outer metal coating.
Two different coatings of 18nm thick silver and gold, respectively, were used, both described using the Drude-Lorentz dispersion model, and the specific calculations were determined by equation (1). Analysis of the absorption cross section of the obtained corresponding gold and silver coated composite nano-media column (see fig. 8) can find that the electromagnetic absorption cross section of silver is obviously larger than that of gold under the same thickness of 18 nm. Particularly, in the high-frequency component, the absorption cross section of gold is obviously reduced, and the resonance frequency of high-frequency plasma disappears, namely, the excitation intensity of the plasma of gold in the composite nano-pillar cavity is weakened under the high-frequency condition, and obvious resonance can not be formed, which shows that silver is more sensitive to high-frequency electromagnetic wave induction than gold. Meanwhile, it can be seen that, relative to silver, the plasmon wave resonance frequency formed by the gold nanocomposite columns is slightly lower than that of silver in the same mode.
Claims (9)
1. A multi-resonant cavity based on a plurality of metal composite nano-medium columns is characterized by comprising 18 metal composite nano-medium columns which are respectively arranged in an inner layer region, a middle layer region and an outer layer region, wherein the central points of the inner layer region, the middle layer region and the outer layer region are superposed; 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are arranged in a rectangular mode in an inner layer region, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a circular mode in a middle layer region, the rest 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a circular mode in an outer layer region, and the metal composite nano-medium columns in the middle layer region and the metal composite nano-medium columns in the outer layer region are arranged in a staggered mode one by one; the 18 metal composite nano-medium columns are not contacted with each other, and 9 cavities with different four shapes are formed among the 18 metal composite nano-medium columns.
2. The multi-resonant cavity according to claim 1, wherein the 18 metal composite nano-media pillars comprise an inner-layer dielectric pillar I (1), an inner-layer dielectric pillar II (2), a middle-layer dielectric pillar (3) and an outer-layer dielectric pillar (4); the inner layer area is rectangular, 4 inner layer medium columns I (1) are respectively arranged on four vertexes of the inner layer area, 2 inner layer medium columns II (2) are respectively arranged on the middle points of two long edges of the inner layer area, and the outer diameter of each inner layer medium column I (1) is larger than that of each inner layer medium column II (2); the middle layer area is circular, 6 middle layer medium columns (3) are uniformly distributed on the boundary of the middle layer area; the outer layer area is circular, and the number of the outer layer medium columns (4) is 6, and the outer layer medium columns are uniformly distributed on the boundary of the outer layer area.
3. The multiple resonant cavity according to claim 2, wherein the radius of the middle layer region is 208.75nm, the radius of the outer layer region is 257nm, the radius of the inner layer dielectric pillar I (1) is 60nm, the distance between the center of the inner layer dielectric pillar I (1) and the center point of the inner layer region is 120.8nm, the radius of the inner layer dielectric pillar II (2) is 43.9nm, the radius of the middle layer dielectric pillar (3) is 60nm, and the radius of the outer layer dielectric pillar (4) is 67.5 nm.
4. The multi-resonant cavity of claim 1 or 3, wherein the metal coating of the metal composite nano-dielectric pillar has a thickness of 14 to 30 nm.
5. The multi-resonant cavity according to claim 1 or 3, wherein the metal coating of the metal composite nano-dielectric pillar is made of gold or silver.
6. The multi-resonant cavity according to claim 1 or 3, wherein the relative dielectric constant of the innermost dielectric core of the metal composite nano-dielectric pillar is in a range of 3.9 to 11.5.
7. The multi-resonant cavity according to claim 1 or 3, wherein the innermost dielectric core of the metal composite nano-dielectric pillar is made of silicon or silicon dioxide.
8. The multi-resonant cavity of claim 1 or 3, wherein the metal composite nano-dielectric pillar has a relative magnetic permeability of 1.
9. The multi-resonant cavity of claim 1 or 3, wherein the metal composite nano-dielectric pillar is placed in an air environment.
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| CN109149046B (en) * | 2018-10-19 | 2023-10-24 | 南京林业大学 | Multiple resonant cavity based on multiple metal composite nano medium columns and application thereof |
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