阅读说明：本技术 一种可切换的宽带多功能超材料吸收器/极化转换器 (Switchable broadband multifunctional metamaterial absorber/polarization converter ) 是由 杨荣草 李照华 王佳云 张文梅 于 2020-12-31 设计创作，主要内容包括：本发明属于超材料吸收器和极化转换器领域,具体涉及一种可切换的宽带多功能超材料吸收器/极化转换器,包括从上至下依次设置的谐振图案层、第一介质层、石墨烯图案层、第二介质层、连续石墨烯层、第三介质层,底部金属板；所述谐振图案层由若干金属块和光敏硅块相间排列组成的条形谐振器周期排列而成；所述石墨烯图案层由单层碳原子石墨烯板和在单层碳原子石墨烯板上刻蚀的若干个周期排列的结构单元组成,每个结构单元都是由十字形凹槽连接的四个开口半圆环形凹槽组成。本发明可以工作在对电磁波的宽频完美吸收、宽频线极化波转换和宽频圆极化波转换三种模式,且能够自由调控。(The invention belongs to the field of metamaterial absorbers and polarization converters, and particularly relates to a switchable broadband multifunctional metamaterial absorber/polarization converter, which comprises a resonance pattern layer, a first dielectric layer, a graphene pattern layer, a second dielectric layer, a continuous graphene layer, a third dielectric layer and a bottom metal plate, wherein the resonance pattern layer, the first dielectric layer, the graphene pattern layer, the second dielectric layer, the continuous graphene layer, the third dielectric layer and the bottom metal plate are sequentially arranged from top to bottom; the resonance pattern layer is formed by periodically arranging strip-shaped resonators formed by alternately arranging a plurality of metal blocks and photosensitive silicon blocks; the graphene pattern layer is composed of a single-layer carbon atom graphene plate and a plurality of structural units which are etched on the single-layer carbon atom graphene plate and are arranged periodically, and each structural unit is composed of four opening semicircular annular grooves connected by cross-shaped grooves. The invention can work in three modes of perfect broadband absorption of electromagnetic waves, broadband linear polarized wave conversion and broadband circular polarized wave conversion, and can be freely regulated and controlled.)

1. The switchable broadband multifunctional metamaterial absorber/polarization converter is characterized by comprising a resonance pattern layer (1), a first dielectric layer (2), a graphene pattern layer (3), a second dielectric layer (4), a continuous graphene layer (5), a third dielectric layer (6) and a bottom metal plate (7), wherein the resonance pattern layer, the first dielectric layer, the graphene pattern layer, the second dielectric layer, the continuous graphene layer and the third dielectric layer are sequentially arranged from top to bottom; the resonance pattern layer (1) is formed by periodically arranging strip-shaped resonators formed by alternately arranging a plurality of metal blocks (9) and photosensitive silicon blocks (8); the graphene pattern layer (3) is composed of a single-layer carbon atom graphene plate and a plurality of structural units which are etched on the single-layer carbon atom graphene plate and are arranged periodically, and each structural unit is composed of four opening semicircular annular grooves (11) connected by cross-shaped grooves (10).

2. A switchable broadband multifunctional metamaterial absorber/polarization converter as claimed in claim 1, wherein the photosensitive silicon block (8) is a square photosensitive silicon block and the metal block (9) is a rectangular metal block.

3. A switchable broadband multifunctional metamaterial absorber/polarization converter as claimed in claim 1, wherein the stripe resonators are oriented in the same direction and along a diagonal of the unit cell.

4. A switchable broadband multifunctional metamaterial absorber/polarization converter as claimed in claim 1, characterized in that the photosensitive silicon block (8) and the metal block (9) are the same thickness of light.

5. A switchable broadband multifunctional metamaterial absorber/polarization converter as claimed in claim 1, wherein the cross-shaped groove (10) is connected at a middle position of a semicircular arc portion of the open semicircular annular groove (11).

6. A switchable broadband multifunctional metamaterial absorber/polarization converter according to claim 1, wherein a gap is left between the open semi-circular grooves (11) of adjacent structural units.

7. A switchable broadband multifunctional metamaterial absorber/polarization converter according to claim 1, characterized in that the open semi-circular annular grooves (11) in the structural units are not in contact with each other.

8. A switchable broadband multifunctional metamaterial absorber/polarization transformer as claimed in claim 1, wherein the openings of the open semi-circular groove (11) are located at the middle of the semi-circular diameter and the opening widths are all the same.

9. A switchable broadband multifunctional metamaterial absorber/polarization converter in accordance with claim 1, wherein the four open semi-circular annular grooves (11) are the same size.

10. A switchable broadband multifunctional metamaterial absorber/polarization converter as claimed in claim 1, wherein the cross-shaped groove (10) and the open semi-circular annular groove (11) have the same line width.

Technical Field

The invention belongs to the field of metamaterial absorbers and polarization converters, and particularly relates to a switchable broadband multifunctional metamaterial absorber/polarization converter.

Background

The metamaterial is an artificial composite electromagnetic material with a periodic structure, and due to the unique electromagnetic response, the metamaterial has attracted extensive research interest and has rapidly developed in recent years. The metamaterial has very wide application, and the superlens imaging, the graphene biosensing, the electromagnetic detection, the stealth technology and the like are reported at present.

Landy et al designed the first metamaterial perfect absorber based on an open resonant ring-metal wire structure in 2008, and realized a single-band perfect absorption effect. After that, many absorbers of different structures and different materials have been proposed in succession, the absorption operating band extending to dual, multiband and broadband bands. On the other hand, some metamaterials capable of changing incident linear polarization or circular polarization of electromagnetic waves are reported, for example: chen et al put forward a reflective metamaterial polarization converter based on a short metal wire array for the first time in 2013, and conversion of polarization directions of incident linearly polarized waves to reflected linearly polarized waves is achieved; von-monk et al proposed a multifunctional tunable metamaterial based on graphene, which can realize the conversion from coplanar polarization to cross polarization and from linear polarization to circular polarization.

Multifunctional metamaterials that integrate absorbers and polarization converters have recently attracted interest to researchers. This has certain limitations since conventional meta-material absorbers or polarization transformers have only a single function. Researchers have therefore begun to develop multifunctional metamaterials that can integrate absorbers and polarization converters, which can achieve arbitrary switching between multiple functions by embedding some tunable media, such as vanadium dioxide, gallium arsenide, photosensitive materials, graphene, PIN diodes, etc., in the metamaterial structure. However, the current multifunctional absorber/polarization converter can only switch between the absorption function and the linear polarization conversion function, or switch between the linear polarization conversion function and the circular polarization conversion function, and the working bandwidth is narrow or the working efficiency is not high. The invention designs a multifunctional metamaterial absorber/polarization converter based on graphene and photosensitive silicon, and the structure can realize the switching among three functions of broadband absorption, broadband linear polarization conversion and broadband circular polarization conversion. Compared with the prior structure, the multifunctional metamaterial provided by the invention has the advantages that all working modes are broadband, the working efficiency is high, and the working modes can be freely controlled.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: how to integrate three functions of efficient broadband perfect absorption, broadband linear polarization conversion and broadband circular polarization conversion in a metamaterial structure, and the integration can be freely regulated and controlled.

In order to achieve the purpose, the invention adopts the following technical scheme:

a switchable broadband multifunctional metamaterial absorber/polarization converter comprises a resonance pattern layer, a first dielectric layer, a graphene pattern layer, a second dielectric layer, a continuous graphene layer, a third dielectric layer and a bottom metal plate, wherein the resonance pattern layer, the first dielectric layer, the graphene pattern layer, the second dielectric layer, the continuous graphene layer and the third dielectric layer are sequentially arranged from top to bottom; the resonance pattern layer is formed by periodically arranging strip-shaped resonators formed by alternately arranging a plurality of metal blocks and photosensitive silicon blocks; the graphene pattern layer is composed of a single-layer carbon atom graphene plate and a plurality of structural units which are etched on the single-layer carbon atom graphene plate and are arranged periodically, and each structural unit is composed of four opening semicircular annular grooves connected by cross-shaped grooves.

Further, the photosensitive silicon block is a square photosensitive silicon block, and the metal block is a rectangular metal block.

Further, the directions of the stripe resonators are the same and are along the diagonal direction of the unit cell.

Furthermore, the thickness of the square photosensitive silicon block is the same as that of the rectangular metal block.

Further, the cross-shaped groove is connected to the middle position of the semicircular arc part of the semicircular annular groove.

Further, gaps are reserved between the semicircular annular grooves of the openings of the adjacent structural units.

Further, the open semicircular annular recesses in the structural units are not in contact with each other.

Furthermore, the opening of the opening semicircular annular groove is positioned in the middle of the diameter of the semicircular ring, and the width of the opening is the same.

Further, the four open semicircular annular grooves have the same size.

Further, the line width of the cross-shaped groove is the same as that of the opening semicircular annular groove.

The graphene pattern layer and the continuous graphene layer have the same electrical properties. When direct current bias voltage is applied to the graphene layer and the structure is placed under the condition of no pumping light excitation, the Fermi level of the graphene reaches mu_cThe photosensitive silicon is in an insulating state when the thickness is 0.85eV, and the multifunctional metamaterial works in a broadband absorption working mode, so that a perfect broadband absorption effect on incident electromagnetic waves can be realized; when the graphene layer is set to be applied with a direct current bias voltage of 0 and the structure is placed under the pumping illumination excitation condition, the Fermi level of the graphene is mu_cThe photosensitive silicon is in a metal state at 0eV, and the multifunctional metamaterial is in a polarization conversion working mode, so that the effect of converting incident linear polarized waves or circular polarized waves into corresponding cross polarized waves is realized.

Compared with the prior art, the invention has the following advantages:

the invention integrates three functions of high-efficiency broadband absorption, broadband linear polarization conversion and broadband circular polarization conversion in a metamaterial structure, and can freely control the working mode of the metamaterial structure.

Drawings

Fig. 1 is a schematic diagram of an array structure of a switchable broadband multifunctional metamaterial absorber/polarization transformer according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a cell structure of a switchable broadband multifunctional metamaterial absorber/polarization converter provided in an embodiment of the present invention;

fig. 3 is a front view of a resonant pattern layer of a switchable broadband multifunctional metamaterial absorber/polarization transformer provided by an embodiment of the present invention;

fig. 4 is a front view of a graphene pattern layer of a switchable broadband multifunctional metamaterial absorber/polarization transformer provided by an embodiment of the present invention;

fig. 5 is a side view of a cell structure of a switchable broadband multifunctional metamaterial absorber/polarization transformer provided by an embodiment of the present invention;

fig. 6 is a graph of reflection coefficient and absorption rate when a switchable broadband multifunctional metamaterial absorber/polarization converter provided by an embodiment of the present invention operates in an absorption mode;

fig. 7 is a linear polarization reflection coefficient, linear polarization conversion rate and phase difference graph of a switchable broadband multifunctional metamaterial absorber/polarization converter provided by an embodiment of the present invention when the switchable broadband multifunctional metamaterial absorber/polarization converter operates in a polarization conversion mode;

fig. 8 is a graph illustrating a circular polarization reflection coefficient, a circular polarization conversion rate and a phase difference of a switchable broadband multifunctional metamaterial absorber/polarization converter in a polarization conversion state according to an embodiment of the present invention;

in the figure, 1-resonance pattern layer, 2-first dielectric layer, 3-graphene pattern layer, 4-second dielectric layer, 5-continuous graphene layer, 6-third dielectric layer, 7-bottom metal plate, 8-photosensitive silicon block, 9-metal block, 10-cross groove, and 11-open semicircular groove.

Detailed Description

In order to make the objects, technical solutions and effects of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1 to 5, the switchable broadband multifunctional metamaterial absorber/polarization converter of the present invention includes a resonant pattern layer 1, a first dielectric layer 2, a graphene pattern layer 3, a second dielectric layer 4, a continuous graphene layer 5, a third dielectric layer 6, and a bottom metal plate 7, which are sequentially disposed from top to bottom;

the resonance pattern layer 1 is formed by periodically arranging strip-shaped resonators formed by alternately arranging a plurality of metal blocks 9 and photosensitive silicon blocks 8, wherein the photosensitive silicon blocks 8 are square photosensitive silicon blocks, the metal blocks 9 are rectangular metal blocks, the thicknesses of the photosensitive silicon blocks 8 and the metal blocks 9 are the same, the directions of the strip-shaped resonators are the same, and the strip-shaped resonators are arranged along the diagonal direction of a unit cell unit;

graphene pattern layer 3 comprises individual layer carbon atom graphite alkene board and the constitutional unit of a plurality of periodic arrangement of sculpture on individual layer carbon atom graphite alkene board, and every constitutional unit all comprises four opening semicircle annular grooves 11 that cross recess 10 is connected, cross recess 10 is connected at the intermediate position of 11 semicircle parts of opening semicircle annular groove, leave the gap between the opening semicircle annular groove 11 of adjacent constitutional unit, 11 mutual contactless of opening semicircle annular groove among the constitutional unit, opening semicircle annular groove 11's opening is located semicircle diameter intermediate position, and the opening width is the same, four opening semicircle annular grooves 11's size is the same, cross recess 10 is the same with opening semicircle annular groove 11's line width.

FIG. 2 is a schematic diagram of a cell structure in which the cell side is 100 μm; the rectangular metal block material of the strip resonator of the resonance pattern layer is gold, and the conductivity is 5.8 multiplied by 10⁷S/m, thickness 0.2 μm; the side length of the square photosensitive silicon block of the resonant pattern layer is 21 μm, the thickness is 0.2 μm, and the conductivity is sigma in the absence of pump light irradiation_Si1S/m, exhibits an insulating state, and when irradiated with pump light, the conductivity of the photosensitive silicon increases to σ_Si＝5×10⁵S/m, which is in a metallic state. The graphene pattern layer is formed by etching four open semicircular grooves connected by a cross-shaped groove on a single-layer graphene plate, the outer radius of each semicircular groove is 33 micrometers, the length of each central cross-shaped groove is 33.5 micrometers, the line width of each groove is 8 micrometers, and the conductivity of the graphene pattern layer is regulated and controlled by an external direct current bias voltage. The continuous graphene layer is a single-layer carbon atom graphene layer, and the electrical property of the continuous graphene layer is the same as that of the graphene pattern layer. The bottom metal plate is made of gold and has the conductivity of 5.8 multiplied by 10⁷S/m, thickness 0.2 μm. The materials of the first dielectric layer, the second dielectric layer and the third dielectric layer are all cycloolefin copolymer, the thicknesses of the cycloolefin copolymer are respectively 1 mu m, 12 mu m and 17 mu m, the dielectric constant is 2.1, and the loss tangent angle is 0.0006.

The structural unit in the embodiment is subjected to a simulation experiment through electromagnetic simulation software based on a finite integration method. Respectively applying unit cell boundary conditions in the X-axis direction and the Y-axis direction, and setting the unit cell boundary conditions as addspace boundary conditions in the Z-axis directionThe THz wave in the Y polarization direction is incident on the material surface along the Z axis direction, and the conversion rate for linear Polarization (PCR)_y) And circular polarized wave Polarization Conversion Ratio (PCR)_L) May be defined by the following formulas, respectively:

PCR_y＝|r_xy|²/(|r_xy|²+|r_yy|²) (1)

PCR_L＝|r_RL|²/(|r_RL|²+|r_LL|²) (2)

wherein r is_xyAnd r_yyRespectively, cross polarization and coplanar polarization reflection coefficients, r, corresponding to the incident Y-direction polarized wave_RLAnd r_LLRespectively corresponding cross polarization and coplanar polarization reflection coefficients of the incident left-handed circularly polarized wave; the absorbance can be calculated by the following formula:

A(ω)＝1-R(ω)-T(ω) (3)

where T (ω) is a transmittance, since the metal base plate can block transmission of electromagnetic waves, the transmittance is zero, i.e., T (ω) is 0; r (ω) is a reflectance, and R (ω) ═ R for an incident Y polarized wave_xy|²+|r_yy|².

When direct current bias voltage is applied to the graphene layer and the structure is placed under the condition of no pumping light excitation, the Fermi level of the graphene reaches mu_cThe photosensitive silicon is in an insulating state when the thickness is 0.85eV, the multifunctional metamaterial is in a broadband absorption working mode, can realize a perfect broadband absorption effect on incident electromagnetic waves, has the absorption rate of over 90 percent in a frequency band range of 1.748THz to 3.523THz, has the absorption bandwidth of 1.775THz, and has the relative bandwidth of 67.35 percent as shown in FIG. 6; when the graphene layer is set to be applied with a direct current bias voltage of 0 and the structure is placed under the pumping illumination excitation condition, the Fermi level of the graphene is mu_cAnd when the thickness is 0eV, the photosensitive silicon is in a metal state, and the multifunctional metamaterial is in a polarization conversion working mode. When linearly polarized waves are incident, the conversion effect from reflective broadband coplanar polarization to cross-polarized electromagnetic waves can be realized; when the left-hand/right-hand circularly polarized wave is incident, it can be converted into right-hand/left-hand circularly polarized reflected wave, for linear polarization and circular polarizationIn the conversion mode, the polarization conversion rate reaches more than 90% in the frequency band range of 1.541THz to 2.551THz, the conversion bandwidth is 1.01THz, and the relative bandwidth is 49.36%, as shown in FIGS. 7 and 8.

Therefore, the invention integrates three functions of high-efficiency broadband absorption, broadband linear polarization conversion and broadband circular polarization conversion in a metamaterial structure, and can freely control the working mode of the metamaterial through external excitation conditions.