CN109149046B - Multiple resonant cavity based on multiple metal composite nano medium columns and application thereof - Google Patents
Multiple resonant cavity based on multiple metal composite nano medium columns and application thereof Download PDFInfo
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- 239000002905 metal composite material Substances 0.000 title claims abstract description 71
- 229910052751 metal Inorganic materials 0.000 claims abstract description 35
- 239000002184 metal Substances 0.000 claims abstract description 35
- 238000000576 coating method Methods 0.000 claims abstract description 22
- 239000011248 coating agent Substances 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 9
- 229910052709 silver Inorganic materials 0.000 claims description 17
- 239000004332 silver Substances 0.000 claims description 17
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 13
- 229910052737 gold Inorganic materials 0.000 claims description 13
- 239000010931 gold Substances 0.000 claims description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 12
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000010703 silicon Substances 0.000 claims description 7
- 235000012239 silicon dioxide Nutrition 0.000 claims description 6
- 239000000377 silicon dioxide Substances 0.000 claims description 6
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 4
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- 230000007246 mechanism Effects 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 178
- 238000010521 absorption reaction Methods 0.000 description 20
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 16
- 239000011159 matrix material Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- 239000002131 composite material Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 239000002061 nanopillar Substances 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
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- 230000005284 excitation Effects 0.000 description 2
- 239000003574 free electron Substances 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- 239000002114 nanocomposite Substances 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 1
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- 239000011247 coating layer Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/06—Cavity resonators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/10—Dielectric resonators
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Abstract
The invention discloses a multiple resonant cavity based on multiple metal composite nano-medium columns and application thereof, and belongs to the technical field of electromagnetism. The multiple resonant cavity of the invention is composed of three layers of 18 metal composite nano medium columns, wherein the first layer of 6 metal composite nano medium columns are arranged in a rectangular shape, and the second layer and the third layer of 6 metal composite nano medium columns are respectively and uniformly distributed on an inner circle and an outer circle; this structure constitutes 9 cavities of 4 size differences. The multiple resonant cavities of the invention are excited to resonate from outside through gaps among dielectric columns, meanwhile, the resonant plasma wave excited by the incident wave forms six completely different resonant mechanisms by 4 cavities with different sizes at different frequencies, and the plasma wave excited to resonate by the incident wave with different frequencies is realized by changing the material and thickness of the metal coating and the relative dielectric constant of the innermost dielectric core, thus realizing multiple resonant cavity structures with different frequency diversification.
Description
Technical Field
The invention belongs to the technical field of electromagnetism, in particular to an electromagnetic resonant cavity, and more particularly relates to a multiple resonant cavity based on a plurality of metal composite nano-medium columns and application thereof.
Background
The resonant cavity of the common electromagnetic wave can effectively resonate through a 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 a determined low-frequency resonant mode and a determined high-frequency resonant mode, and the geometric size of the common electromagnetic resonant cavity determines the resonant frequency.
With the rapid development of nano technology, the nano metal material is different from the pure medium nano column material, has the excellent property of the nano material, integrates the unique characteristics of metal, and therefore, has unique performance in the fields of physics and chemistry. The influence of the application of nano-metallic materials in basic research in various fields is remarkable. In particular, noble metals such as gold, silver and the like can be used for the coating layer, and have good optical properties. In addition, some metal nanomaterials are sensitive to temperature, light, sound and gas, and nanomaterials can be used to make sensors that meet different performance requirements. In the field of nanophotonics, surface plasmon optics gradually highlights its advantages. Metal surface plasmons are unique surface electromagnetic waves, essentially formed by the interaction of incident light with free electrons within the metal. Surface plasmons are generated at the interface surface of the metal and the medium, and are photon-electron coupled states formed by the free electron action of photons and the metal surface, and the coupled states enable the local field of the surface plasmons to be enhanced.
Disclosure of Invention
In order to overcome the above-mentioned disadvantages and shortcomings of the conventional electromagnetic resonant cavity, the present invention aims to provide a multiple resonant cavity structure composed of three layers of metal composite nano-medium pillars, which has unique optical characteristics and resonance modes, and another purpose of the present invention is to provide an application method of the resonant cavity.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the multiple resonant cavity based on the multiple metal composite nano medium columns comprises 18 metal composite nano medium columns respectively arranged in an inner layer region, a middle layer region and an outer layer region, wherein center points of the inner layer region, the middle layer region and the outer layer region are overlapped; 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are arranged in a rectangular manner in an inner layer area, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a round manner in a middle layer area, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a round manner in an outer layer area, and the metal composite nano-medium columns in the middle layer area and the metal composite nano-medium columns in the outer layer area are staggered one by one; the 18 metal composite nano medium columns are not contacted with each other, and four cavities with different shapes are formed among the 18 metal composite nano medium columns.
Further, the 18 metal composite nano-medium columns comprise an inner-layer medium column I, an inner-layer medium column II, a middle-layer medium column and an outer-layer medium column; the inner layer area is rectangular, 4 inner layer dielectric columns I are respectively arranged on four vertexes of the inner layer area, 2 inner layer dielectric columns II are respectively arranged on the midpoints of two long sides of the inner layer area, and the outer diameter of each inner layer dielectric column I is larger than that of each inner layer dielectric column II; the middle layer area is round, and the number of the middle layer medium columns is 6 and is 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 is 6 and is uniformly distributed on the boundary of the outer layer area.
Further, 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 is 60nm, the distance between the center of the inner layer dielectric pillar I and the center point of the inner layer region is 120.8nm, the radius of the inner layer dielectric pillar II is 43.9nm, the radius of the middle layer dielectric pillar is 60nm, and the radius of the outer layer dielectric pillar is 67.5nm.
Further, the thickness of the metal coating of the metal composite nano medium column is 14-30 nm.
Further, the metal coating of the metal composite nano-medium column is made of gold or silver.
Further, the relative dielectric constant of the innermost dielectric core of the metal composite nano dielectric column ranges from 3.9 to 11.5.
Further, the innermost dielectric core of the metal composite nano dielectric column is made of silicon or silicon dioxide.
Still further, the relative permeability of the metal composite nanomedia column is 1.
Still further, the metal composite nanomedia column is placed in an air environment.
The application of the multiple resonant cavities can make the incident electromagnetic wave have frequency of 5.0×10 13 Hz～2.5×10 14 Hz。
Compared with the prior art, the invention has the beneficial effects that:
(1) Compared with the common electromagnetic resonant cavity, the plasma wave resonant cavity formed by the metal composite nano-medium columns can be excited to resonate from outside through gaps among the medium columns.
(2) Compared with the single resonant mode of the traditional electromagnetic resonant cavity, the resonant cavity structure can realize a resonant mechanism for diversifying the incident electromagnetic waves with various frequencies, and plasma waves excited by different frequencies form different types of resonance in different cavities.
(3) The electromagnetic resonant cavity geometric dimension of the common resonant cavity determines the resonant frequency, and the metal composite nano medium column can effectively change the resonant frequency of the plasma wave by changing the thickness of the metal layer, and the resonant space of the plasma wave is not only the geometric space surrounded by metal, but also the interface part space.
(4) The resonant cavity structure can excite resonant plasma waves for incident waves with different frequencies through changing the materials of the innermost dielectric core and the outer metal coating.
Drawings
FIG. 1 is a schematic diagram of multiple regions of multiple resonators and multiple metal composite nanomedia pillars according to the present invention;
in the figure: 1. an inner medium column I; 2. an inner layer dielectric column II; 3. a middle layer dielectric column; 4. and an outer layer medium column.
FIG. 2 is a schematic illustration of an arrangement of three-layer metal composite nanomedia pillars according to the present invention;
in the figure: 101. a first inner layer medium column I; 102. a second inner medium column I; 103. a third inner layer medium column I; 104. a fourth inner 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 pillar; 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 layer dielectric column; 402. a second outer layer dielectric pillar; 403. a third outer layer dielectric column; 404. a fourth outer layer dielectric column; 405. a fifth outer layer dielectric column; 406. and a sixth outer layer medium column.
Fig. 3 is a schematic drawing of an absorption cross section of an 18nm thick silver coating for all three-layer metal composite nanomedia pillars with an external plane wave incident angle of 0 °.
FIG. 4 is a plot of the near field profile for six peaks of the absorption cross-section of FIG. 3;
wherein a is the incident frequency f (a) = 9.261 ×10 13 Hz, b is the incident frequency f (b) = 1.347 ×10 14 Hz, c is the incident frequency f (c) =1.563×10 14 Hz, d is the incident frequency f (d) =1.682×10 14 Hz, e is the incident frequency f (e) = 1.779 ×10 14 Hz, f is the incident frequency f (f) = 2.152 ×10 14 Plasma wave resonant mode at Hz.
FIG. 5 is a schematic drawing showing the absorption cross section of a three-layer metal composite nanomedia column obtained by changing the thickness of the metal coating silver (14 nm,18nm,30 nm).
FIG. 6 is a near field plot corresponding to six peaks at a metal layer thickness of 30 nm;
wherein a is the incident frequency f (a) = 0.9583 ×10 corresponding to the first peak 14 A magnetic field distribution diagram of Hz, b is the incident frequency f (b) =1.422×10 corresponding to the second peak 14 A magnetic field distribution diagram at Hz, c is the incidence frequency corresponding to the third peak value f (c) = 1.706 ×10 14 The Hz magnetic field profile, d, is the incident frequency f (d) =1.851×10 corresponding to the fourth peak 14 The magnetic field distribution diagram at Hz, e is the incident frequency f (e) =1.983×10 corresponding to the fifth peak 14 Magnetic field distribution diagram at Hz, f is the incident frequency f (f) =2.381×10 corresponding to the sixth peak 14 Hz magnetic field profile.
Fig. 7 is an absorption cross-sectional view obtained when the innermost core dielectric material is silicon or silicon dioxide, respectively.
Fig. 8 is an absorption cross-sectional view obtained when the metal coating materials are gold and silver, respectively.
Detailed Description
The invention is further described below in connection with specific embodiments.
The multiple resonant cavity based on a plurality of metal composite nano-media pillars as shown in fig. 1-8 comprises 18 metal composite nano-media pillars. The inner layer medium column I1, the inner layer medium column II 2, the middle layer medium column 3 and the outer layer medium column 4 are respectively arranged on the boundaries of the inner layer region, the middle layer region and the outer layer region, the inner layer region is rectangular, the middle layer region and the outer layer region are circular, and the central points of the inner layer region, the middle layer region and the outer layer region are coincident.
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 the inner layer area; the first inner dielectric pillar ii 201 and the second inner dielectric pillar ii 202 are located at midpoints of two long sides of the inner layer region, respectively. The first middle-layer dielectric pillar 301, the second middle-layer dielectric pillar 302, the third middle-layer dielectric pillar 303, the fourth middle-layer dielectric pillar 304, the fifth middle-layer dielectric pillar 305 and the sixth middle-layer dielectric pillar 306 are uniformly distributed on the boundary of the middle-layer region. The first outer dielectric pillar 401, the second outer dielectric pillar 402, the third outer dielectric pillar 403, the fourth outer dielectric pillar 404, the fifth outer dielectric pillar 405, and the sixth outer dielectric pillar 406 are uniformly distributed on the boundary of the outer region. The middle layer medium columns 3 and the outer layer medium columns 4 are arranged in a one-to-one staggered mode. The connecting line between the circle center of the inner layer dielectric column I1 and the center point of the inner layer region and the circle center of the 2 inner layer dielectric columns II 2 are 60 degrees or 120 degrees, and the connecting line between the circle centers of the second middle layer dielectric column 302 and the fifth middle layer dielectric column 305 is perpendicular to the connecting line between the circle centers of the first inner layer dielectric column II 201 and the second inner layer dielectric column II 202; the third outer dielectric pillar 403 and the sixth outer dielectric pillar 406 are positioned on the same line with the first inner dielectric pillar ii 201 and the second inner dielectric pillar ii 202.
The 18 nano-medium columns are not contacted but are provided with gaps, 4 cavities with different sizes are formed between the 18 nano-medium columns, and the 18 nano-medium columns comprise: left and right large cavities (between the first middle layer dielectric column 301, the sixth outer layer dielectric column 406, the sixth middle layer dielectric column 306, the fourth inner layer dielectric column I104, the first inner layer dielectric column II 201 and the first inner layer dielectric 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 are arranged in the middle area, a cavity is formed in the center area (between 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, between the first inner layer medium column II 201 and the second inner layer medium column II 202), an upper small triangle cavity and a lower small triangle cavity are formed in the center area (between the first inner layer medium column I101, the second inner layer medium column I102 and the second inner layer medium column 302, between the third inner layer medium column I103, the fourth inner layer medium column I104 and the fifth middle layer medium column 305, between the fourth inner layer medium column I101, the first middle layer medium column 301, the first outer layer medium column 401 and the second inner layer medium column 302, between the second middle layer medium column 302, between the second outer layer medium column I402, the third inner layer medium column 303, the third inner layer medium column I103, the fourth inner layer medium column 102, the fifth inner layer medium column 305, the fifth inner layer medium column 102 and the fifth inner layer medium column 305).
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 magnetic conductivity mu=1 of the dielectric column. The relative dielectric constant of the metal coating can be calculated using a Drude-Lorentz dispersion model, and the specific formula is:
wherein ω is the angular frequency of the light, ε ∞ Is the relative dielectric constant at ω→infinity; omega p Is the plasma frequency; delta is Lorentz term weight; Γ -shaped structure L The vibration spectrum is wide; omega shape L The intensity of Lorentz harmonic oscillator; subscript L represents the Lorentz model; i is an imaginary unit.
Wherein, the relevant parameters of silver are as follows: omega is the angular frequency of the incident light, ε ∞ ＝2.4046，ω P ＝2π×2214.6×10 12 Hz，Δ＝1.6604，Γ L ＝2π×620.7×10 12 Hz，Ω L ＝2π×1330.1×10 12 Hz, i is imaginary orderBits, γ=4.8×2pi×10 12 Hz; the relevant parameters for gold are as follows: omega is the angular frequency of light, epsilon ∞ ＝4.0903，ω P ＝2π×2170.7×10 12 Hz，Δ＝4.9603，Γ L ＝2π×849.1×10 12 Hz，Ω L ＝2π×1006.4×10 12 Hz, i is an imaginary unit, γ=17.4×2pi×10 12 Hz。
The resonant cavity has a selection frequency of 5.0X10 13 Hz～2.5×10 14 Hz electromagnetic waves are incident from the left boundary (including but not limited to plane waves), the incident angle θ=0° (the angle of the incident wave may be arbitrarily set to be not limited to 0 °, and an incident angle of 0 ° is taken for convenience in calculation), and specifically, see fig. 2 (the arrow is the incident plane wave). For the metal composite nano medium column provided with the coating, the whole area is divided into three areas, the area 1 is a free space area outside the three-layer metal composite nano medium column, the area 2 is a metal coating area, and the area 3 is a medium column inner core area. Taking the xoy coordinate system as the global coordinate system, assuming a TE plane wave is incident,let the incident angle +.>According to the cylindrical scattering characteristics, incident wave H z Write in the form of a cylindrical wave->Hypothesis (ρ) j ，φ j ) Representing the local coordinate system of the j-order metal composite nano-medium column, the (phi) 0 ，Φ M ，Φ D ) Sum (ψ) 0 And psi is M ) Is defined as an incident cylindrical wave and a scattered wave in the respective regions, where Φ represents a Bessel function and ψ represents a Hanker function. From Maxwell's equations, graf's addition theorem and boundary conditions, the outer free space ρ can be deduced j ＞r 1 Intermediate metal layer r 2 ＜ρ j ＜r 1 Innermost dielectric core ρ j ＜r 2 Magnetic field component |H at z Expression of IThe formula is:
wherein, the liquid crystal display device comprises a liquid crystal display device,is the amplitude coefficient of the incident wave represented by the cylindrical Fourier series expansion, wherein +.>Is the angle of incidence; the left and right parts of formulas (3) to (4) represent the incident wave and the scattered wave, respectively, i.e. (Φ) 0 ，Φ M ，Φ D ) Represents an inwardly propagating wave, (ψ) 0 And psi is M ) Represents outward scattered waves, and the specific expression is as follows:
wherein J m Is m orderThe function of the bessel (r) is that,is m-order first-class hanker function;
g in formula (5) j Representing the mutual conversion of different coordinate systems, the subscript j represents the transformation of the scattered field of other cylinders to the j object, in the scattered field of order j, G i And D j And the same is done; sigma in formula (5) q,j And alpha q The conversion factors of the addition theorem are expressed as follows:
α q ＝[(-1) m-n J m-n (k 0 R)e in(q-1)θ ] (10)
A p ＝-T (1) ·k p (p＝2,3,...,N) (12)
D j ＝[e in(j-1)θ δ nn′ ] (14)
wherein, lambda p ，A p ，k p Are all transformation factors obtained using Graf addition theorem, I is a unitary matrix, delta m Is a Croneck function, k 0 Is the wave number of the free space,wavenumber of metal layer, < >>Wavenumber of the medium core, b is incident waveAmplitude vectors of (a); based on the local coordinate system (ρ, φ), coordinate transformation between the following cylindrical coordinates and planar coordinates is performed:
ζ p ＝π/2-(p-1)θ/2 (15)
d p ＝2Rsin[(p-1)θ/2] (16)
in the formulas (2) to (5), T (1) ，T (2) ，T (3) And T (4) The transformation matrices of the fields in both regions represent the addition theorem of the transformation matrices, and are diagonal matrices, expressed as follows:
T (1) ＝R fm +F fm ·R md ·(I-R mf ·R md ) -1 ·F mf (18)
T (2) ＝(I-R mf ·R md ) -1 ·F mf (19)
T (3) ＝R md ·(I-R mf ·R md ) -1 ·F mf (20)
T (4) ＝F dm ·(I-R mf ·R md ) -1 ·F mf (21)
wherein R is ij And F ij (i, j=f, m, d) is a diagonal matrix representing reflected and transmitted pillars directed from the "j" region to the "i" region, and the indices f, m, d represent free space, metal layer, and dielectric kernel; r is R fm And F fm Representing the reflection matrix and transmission matrix from the interface of the metal layer to free space, R md Representing the reflection matrix, R, from the medium core to the metal interface mf And F mf Representing the reflection matrix and transmission matrix from the outer free space to the interface of the intermediate metal layer.
For more comprehensive quantitative investigation of the optical properties of metallic coated nano-cylindrical structures by absorption cross section sigma abs And a scattering cross section sigma sca The far field characteristics of the metal composite nano cylindrical structure are explored.
In order to construct a model of a plurality of metal composite nano-medium column structures, a local coordinate system is required to be used(i=1, 2 …) to a global coordinate system +.>Expressing a fringe field formula. Taking two metal composite nano-pillars as an example, a transformation matrix beta is used 01 、β 02 Local coordinate System +.>T of (3) 0,1 And->T of (3) 0,2 Conversion to ψ 0 The expression formula of the external scattering field can be obtained:
wherein:
β 01 (m,n)＝(-1) m-n J m-n (k 0 d/2) (24)
β 02 (m,n)＝J m-n (k 0 d/2) (25)
wherein the method comprises the steps ofRepresenting the scattering amplitude coefficient of two metal composite nano-cylindrical structures.
The scattering and absorption cross sections of two metal composite nano cylindrical structures can be deduced, and the specific expression is as follows:
in the method, in the process of the invention,the (m, n) th element of the scattering amplitude coefficient A, P in equation (27) n Representing 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 257nm; the radius of the inner medium column I1 is 60nm, and the distance between the center of the inner medium column I and the center point of the inner medium column I is 120.8nm; the radius of the inner layer dielectric column II 2 is 43.9nm; the radius of the middle layer dielectric column 3 is 60nm; the radius of the outer dielectric column 4 was 67.5nm.
The metal composite nano-medium column of the multiple resonant cavities adopts a silver coating, and the relative magnetic conductivity of the inner medium core is 1, which is a common silicon medium with the relative dielectric constant of 10.
According to the size of the nano-pillars, the frequency is selected to be 5.0X10 13 Hz～2.5×10 14 Electromagnetic waves of Hz are incident from the left boundary, the incident angle theta=0°, and sigma of the three-layer metal composite nano-medium column is obtained by numerical solution abs (absorption section) it is clear from the absorption section schematic diagram shown in fig. 3 that 6 peaks exist, the peaks representing that the energy of the incident electromagnetic wave will cause resonance of the plasma wave, coupling absorption occurs, resulting in reduction of reflected wave energy, and absorption peaks appear on the absorption section. Based on the 6 peaks, a near magnetic field H corresponding to 6 resonance peaks is generated z As shown in fig. 4, it is clearly seen that 6 formants correspond to 6 kinds of non-formantsThe same resonant mode.
The first resonant mode is shown in FIG. 4 (a) and has an incident frequency of 9.261 ×10 13 Hz. The magnetic field is mainly distributed in a central area surrounded by a first inner layer dielectric column I101, a second inner layer dielectric column I102, a third inner layer dielectric column I103, a fourth inner layer dielectric column I104, a first inner layer dielectric column II 201 and a second inner layer dielectric column II 202 during the frequency, and stronger resonance is formed.
The second resonance mode is shown in FIG. 4 (b), the incident frequency is 1.347 ×10 14 Hz. The excited plasma wave forms strong resonance in the left and right larger cavities surrounded by the first middle layer dielectric column 301, the sixth outer layer dielectric column 406, the sixth middle layer dielectric column 306, the fourth inner layer dielectric column I104, the first inner layer dielectric column II 201, the first inner layer dielectric column I101, the second inner layer dielectric column I102, the second inner layer dielectric column II 202, the third inner layer dielectric column I103, the fourth middle layer dielectric column 304, the third outer layer dielectric column 403 and the third middle layer dielectric column 303 respectively, 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 has an incident frequency of 1.563×10 14 Hz. At this frequency, the plasma is concentrated in two small triangle areas, namely, an upper small triangle area and a lower small triangle area, which are respectively surrounded by the first inner dielectric pillar I101, the second inner dielectric pillar I102, the second middle dielectric pillar 302, the third inner dielectric pillar I103, the fourth inner dielectric pillar I104 and the fifth middle dielectric pillar 305, are arranged in the same area as in fig. 4 (b), and the resonant plasma wave has the same phase in the left resonant cavity and the right resonant cavity, has the same phase in the upper cavity and the lower cavity, and has opposite phase with the plasma wave in the left cavity and the right cavity.
The fourth resonant mode is shown in FIG. 4 (d) and has an incident frequency of 1.682×10 14 Hz. The plasma is mainly concentrated in the central cavity (same as in fig. 4 (a)) and in the first inner dielectric column i 101, the first middle dielectric column 301, the first outer dielectric column 401 and the second middle dielectric column 302, the second outer dielectric column 402, the third middle dielectric column 303 and the second inner dielectric column i 102, the third inner dielectric column i 103, the fourth middleThe phase of the resonance plasma wave in the central area is opposite to the phase of the plasma wave in the outer four small cavity areas, wherein the four small cavities are respectively surrounded by the layer dielectric column 304, the fourth outer layer dielectric column 404 and the fifth middle layer dielectric column 305, the fourth inner layer dielectric column I104, the fifth middle layer dielectric column 305, the fifth outer layer dielectric column 405 and the sixth middle layer dielectric column 306.
The fifth resonance mode is shown in FIG. 4 (e), and the incident frequency is 1.779 ×10 14 Hz. At this time, the plasma wave only forms resonance in the four outermost small cavities, and the phases of the plasma waves in the left and right small cavities are opposite.
The sixth resonant mode is shown in FIG. 4 (f) and has an incident frequency of 2.152 ×10 14 Hz. At this time, the frequency of the incident wave is higher, so that the four small cavities at the outermost layer, the upper triangular cavity, the lower triangular cavity and the central area all generate strong resonant plasma waves, and the two triangular areas and other strong resonant areas which are symmetrically distributed are opposite in phase.
Example 2
The three-layer metal composite nanomedia column arrangement and various parameters of this example were substantially the same as those of example 1, except for the thickness of the metal coating.
The thickness of the silver coating is 14nm,18nm and 30nm, and the selection frequency is 5×10 13 Hz to 2.5X10 14 The Hz plane wave is incident from the left boundary, the incident angle θ=0°, and an absorption cross-sectional view corresponding to three thicknesses shown in fig. 5 is obtained, the silver layer thickness 14nm is represented by a solid line, the thickness 18nm is represented by a broken line, and the thickness 30nm is represented by a dotted line. It can be seen that as the thickness of the metal layer increases, the excitation frequency of the Absorption Cross Section (ACS) resonance peak becomes greater, the peak shown on the absorption cross section shifts to the right, and the higher the frequency, the more pronounced the corresponding peak shifts to the right. FIG. 6 is a near field plot corresponding to six peaks at a metal layer thickness of 30nm. As can be seen from FIG. 6, although the metal layer thickness is changed, the geometry of the cavity structure surrounded by the metal composite nano-cylinder is not changed, so that six resonant peaks appear corresponding to the same six plasmon resonance modes, which are consistent with FIG. 4, but the corresponding frequencies are higher, and thus the incident electricity can also be seenThe resonance of plasma wave excited by magnetic wave in the cavity of the multilayer composite dielectric column is different from the resonance of common electromagnetic wave, and no fixed resonance mode or frequency exists.
Example 3
The three-layer metal composite nanomedia column arrangement and various parameters of this embodiment are substantially the same as those of embodiment 1, except for the material of the innermost core medium.
Silicon with a relative dielectric constant of 11.5 and silicon dioxide with a relative dielectric constant of 3.9 are respectively selected to obtain an absorption section view of the three-layer metal composite nano-medium column shown in fig. 7, wherein silicon is represented by a solid line, and 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 structure of the formed nano dielectric column cavities are the same, and although the dielectric constants of the inner layer materials of the dielectric columns are different, six corresponding absorption peaks still appear respectively, which indicates that the change of the dielectric constants of the dielectric columns does not change the resonance rule of the plasma wave in the composite structure. But at the same time, when the relative dielectric constant is reduced, the resonance peak formed by the excited plasma wave is obviously shifted to the right, the higher the frequency is, the larger the right shift is, which means that the smaller the relative dielectric constant of the dielectric column is, the higher the incidence frequency of the resonance peak generated by forming the plasma wave on the dielectric and metal surfaces is, and therefore, different plasma resonances can be obtained by changing the material of the innermost core dielectric.
Example 4
The three-layer metal composite nanomedia column arrangement and various parameters of this example are substantially the same as those of example 1, except for the material of the outer metal coating.
Two different coatings, 18nm thick silver and gold, were used, both described using the Drude-Lorentz dispersion model, the specific calculation being determined by equation (1). Analysis of the absorption cross section (see fig. 8) of the obtained composite nano-media column with the corresponding gold and silver coatings shows that the electromagnetic absorption cross section of silver is obviously larger than that of gold at the same thickness of 18 nm. Particularly, in the high-frequency component, the absorption section of gold is obviously reduced, and meanwhile, the resonance frequency of high-frequency plasma disappears, namely, the excitation intensity of the gold in the plasma of the composite nano-pillar cavity is weakened under the high-frequency condition, obvious resonance cannot be formed, and the silver is more sensitive to high-frequency electromagnetic wave induction than gold. It can also be seen that the plasmon resonance frequency formed by the gold nanocomposite column is slightly lower than the frequency of silver in the same mode relative to silver.
Claims (8)
1. The multi-resonant cavity based on the metal composite nano-medium columns is characterized by comprising 18 metal composite nano-medium columns 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 overlapped; 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are arranged in a rectangular manner in an inner layer area, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a round manner in a middle layer area, the other 6 metal composite nano-medium columns in the 18 metal composite nano-medium columns are uniformly arranged in a round manner in an outer layer area, and the metal composite nano-medium columns in the middle layer area and the metal composite nano-medium columns in the outer layer area are staggered one by one; the 18 metal composite nano medium columns are not contacted with each other, and four cavities with different shapes are formed among the 18 metal composite nano medium columns;
the 18 metal composite nano medium columns comprise an inner medium column I (1), an inner medium column II (2), a middle medium column (3) and an outer medium column (4); the inner layer area is rectangular, 4 inner layer dielectric columns I (1) are respectively arranged on four vertexes of the inner layer area, 2 inner layer dielectric columns II (2) are respectively arranged on the midpoints of two long sides of the inner layer area, and the outer diameter of the inner layer dielectric column I (1) is larger than that of the inner layer dielectric column II (2); the middle layer area is round, and 6 middle layer dielectric columns (3) are uniformly distributed on the boundary of the middle layer area; the outer layer area is circular, and 6 outer layer medium columns (4) are uniformly distributed on the boundary of the outer layer area;
the metal composite nano medium column comprises an innermost medium core and a metal coating coated outside the innermost medium core, and the innermost medium core of the metal composite nano medium column is made of silicon or silicon dioxide;
the multiple resonant cavities excite resonant plasma waves to incident waves with different frequencies through changing the materials of the innermost dielectric core and the outer metal coating.
2. The multiple resonant cavity of claim 1, 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 67.5nm.
3. The multiple resonant cavity according to claim 1 or 2, wherein the thickness of the metal coating of the metal composite nano-dielectric pillar is 14-30 nm.
4. The multiple resonant cavity of claim 1 or 2, wherein the metal coating of the metal composite nano-dielectric pillar is made of gold or silver.
5. The multiple resonant cavity according to claim 1 or 2, wherein the relative dielectric constant of the innermost dielectric core of the metal composite nano-dielectric pillar is in the range of 3.9-11.5.
6. The multiple resonant cavity of claim 1 or 2, wherein the metal composite nanomedia pillar has a relative permeability of 1.
7. The multiple resonant cavity of claim 1 or 2, wherein the metal composite nanomedia pillar is placed in an air environment.
8. The use of multiple resonant cavities according to any one of claims 1-7, wherein the frequency of the incident electromagnetic wave is 5.0 x 10 13 Hz~2.5×10 14 Hz。
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