CN117148603A - Terahertz wave front regulating and controlling device based on vanadium dioxide-graphene - Google Patents
Terahertz wave front regulating and controlling device based on vanadium dioxide-graphene Download PDFInfo
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- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 129
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 43
- 229910052720 vanadium Inorganic materials 0.000 title claims abstract description 40
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 title claims abstract description 40
- 230000001276 controlling effect Effects 0.000 title claims description 25
- 229910052751 metal Inorganic materials 0.000 claims abstract description 102
- 239000002184 metal Substances 0.000 claims abstract description 102
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 89
- 229910021542 Vanadium(IV) oxide Inorganic materials 0.000 claims abstract description 69
- GRUMUEUJTSXQOI-UHFFFAOYSA-N vanadium dioxide Chemical compound O=[V]=O GRUMUEUJTSXQOI-UHFFFAOYSA-N 0.000 claims abstract description 69
- 239000000758 substrate Substances 0.000 claims abstract description 19
- 230000005540 biological transmission Effects 0.000 claims abstract description 18
- 230000002159 abnormal effect Effects 0.000 claims abstract description 17
- 238000005388 cross polarization Methods 0.000 claims abstract description 13
- 238000006243 chemical reaction Methods 0.000 claims abstract description 8
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- 239000000463 material Substances 0.000 claims description 17
- 239000004642 Polyimide Substances 0.000 claims description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 9
- 229920001721 polyimide Polymers 0.000 claims description 9
- 230000005284 excitation Effects 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 239000010410 layer Substances 0.000 description 63
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- 238000009826 distribution Methods 0.000 description 11
- 230000005684 electric field Effects 0.000 description 8
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/017—Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
- G02F1/0063—Optical properties, e.g. absorption, reflection or birefringence
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Abstract
The invention discloses a terahertz wave front regulating device based on vanadium dioxide-graphene, and belongs to the field of terahertz devices. The device is formed by continuously and periodically arranging and splicing device units on a plane in an array mode; the device units are of a multi-layer composite structure, and are a vanadium dioxide substrate, a metal bottom layer, a lower dielectric layer, an intermediate metal layer, an upper dielectric layer and a graphene top layer from bottom to top in sequence. When vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, the device forms a transmission type super surface, and cross polarization conversion, abnormal refraction, a focusing lens and orbital angular momentum functions can be realized by adjusting the geometric parameters of a unit structure. In addition, when vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV, the device forms a reflective super-surface, and the functions of terahertz beam splitting, diffuse scattering and abnormal reflection of single beam can be realized by adjusting the geometric parameters of the unit structure.
Description
Technical Field
The invention belongs to the field of terahertz devices, and particularly relates to a terahertz wave front regulating device based on vanadium dioxide-graphene.
Background
The super surface is an ultrathin artificial composite two-dimensional planar metamaterial, has characteristics which are not possessed by many natural materials, is simple in structure and easy to integrate in the design process, and can realize flexible regulation and control of 2 pi full phases of electromagnetic waves. The supersurface can manipulate incident light by changing the phases, amplitudes and polarization states of transmitted and reflected waves, and thus abrupt phase discontinuities can be introduced on the supersurface to achieve arbitrary wavefront manipulation, such as extraordinary refraction, extraordinary reflection, superlenses, orbital angular momentum generators, high resolution holograms, etc. The prior super surface is mainly limited to realizing relative fixed and single functions by using the super surface with a simple structure, and the super surface is generally difficult to adjust in time once the structural design is finished.
The appearance of the adjustable material ensures that the multifunctional switching of the super-surface structure has wider application space. Common tunable materials include photosensitive silicon, graphene, vanadium dioxide, and the like. The surface conductivity of graphene is determined by its fermi level, and the surface plasmon effect of single-layer graphene in the terahertz band can be tuned dynamically by applying an external bias voltage; the vanadium dioxide is simple to prepare, the conductivity changes along with the change of temperature, and the modulation depth can be improved. Therefore, if the characteristics that the structural characteristics of the metamaterial, the phase change characteristics of vanadium dioxide and the Fermi energy level of graphene change along with the chemical potential change can be combined, a plurality of different functions can be integrated into a single metamaterial device, and the method has important application prospects in the aspects of terahertz transmission, imaging, communication and the like.
Disclosure of Invention
The existing super-surface is mainly limited to a super-surface with a simple structure to realize a relatively fixed and single function, when the super-surface is designed, the function is difficult to adjust in time, and most of the super-surface is generally limited to one of a reflective type and a transmissive type, so that flexible switching between transmission and reflection cannot be realized. Therefore, there is an urgent need for a multifunctional metamaterial device capable of conveniently adjusting and switching functions.
The invention aims to overcome the technical problems and provide a terahertz wave front regulating device based on vanadium dioxide-graphene, so that when the vanadium dioxide is in an insulating state and the Fermi level of the graphene is 1eV, a transmission type super surface is formed, and the functions of cross polarization conversion, abnormal refraction, focusing lenses and orbital angular momentum are realized by adjusting the geometric parameters of a unit structure; when vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV, the device forms a reflective super-surface, and the functions of terahertz beam splitting, diffuse scattering and abnormal reflection of single beam are realized.
The specific technical scheme adopted by the invention is as follows:
a terahertz wave front regulating and controlling device based on vanadium dioxide-graphene is formed by continuously and periodically arranging and splicing device units on a plane in an array mode;
the device units are of a multi-layer composite structure and sequentially comprise a vanadium dioxide substrate, a metal bottom layer, a lower dielectric layer, an intermediate metal layer, an upper dielectric layer and a graphene top layer from bottom to top;
the cross sections of the vanadium dioxide substrate, the upper dielectric layer and the lower dielectric layer are all the same square; the cross section of the metal bottom layer is three rectangular metal strips which are parallel to each other and are arranged at intervals, the cross section of the graphene top layer is three rectangular graphene strips which are parallel to each other and are arranged at intervals, and the long side directions of the rectangular metal strips and the rectangular graphene strips are mutually orthogonal; the intermediate metal layer is composed of a metal split resonant ring and a metal circular patch which are concentrically arranged.
Preferably, the vanadium dioxide substrate is made of vanadium dioxide, the cross section length and width are 120-130 μm, and the thickness is 0.2-0.5 μm.
Preferably, the metal bottom layer is made of metal aluminum, wherein the three rectangular metal strips have the same shape; each rectangular metal strip has a length of 120-130 μm, a width of 5-10 μm, a thickness of 0.5-1.0 μm, and an interval between adjacent rectangular metal strips of 20-25 μm.
Preferably, the lower dielectric layer is polyimide, and has a cross section length and width of 120-130 μm and a thickness of 40-50 μm.
Preferably, the material of the intermediate metal layer is metallic aluminum; wherein the metal split resonant ring is a metal ring with an opening, the outer radius is 55-60 mu m, the inner radius is 45-50 mu m, the thickness is 0.5-1.0 mu m, the opening size is 0-120 mu m but not 0, the radius of the circular patch is 20-25 mu m, and the thickness is 0.5-1.0 mu m.
Preferably, the upper dielectric layer is polyimide, the length and width of the cross section are 120-130 μm, and the thickness is 40-50 μm.
Preferably, the material of the top layer of the graphene is graphene, wherein three rectangular graphene strips have the same shape; each rectangular graphene strip has a length of 5-10 mu m, a width of 120-130 mu m, a thickness of 1.0-1.2 nm, and an interval between adjacent rectangular graphene strips is 20-25 mu m.
Preferably, the device is formed by periodically and continuously arranging n×n device units on a plane, where N is an integer greater than 1.
Preferably, in the device unit, vanadium dioxide in a vanadium dioxide substrate is controlled to be in an insulating state through external excitation, the fermi level of graphene in the top layer of graphene is 1eV, so that the device is in a transmission type super-surface and is used for realizing cross polarization conversion, abnormal refraction, a focusing lens and orbital angular momentum functions.
Preferably, in the device unit, vanadium dioxide in a vanadium dioxide substrate is regulated and controlled to be in a metal state through external excitation, the fermi level of graphene in a graphene top layer is 0.01eV, so that the device is a reflective super-surface and is used for realizing the abnormal reflection functions of terahertz beam splitting, four-beam splitting, diffuse scattering and single beam.
Compared with the prior art, the invention has the following beneficial effects:
1) The terahertz wave front regulating and controlling super surface based on the vanadium dioxide-graphene provided by the invention has the advantages that under the environment condition that the vanadium dioxide is in an insulating state and the Fermi energy level of the graphene is 1eV, the cross polarization is realized in the range of 0.5-0.96THz when electromagnetic waves propagate along the +z directionTransmission coefficient t yx Greater than 0.7, cross-polarization transmission coefficient t when an electromagnetic wave propagates in the-z direction xy Greater than 0.7. PCR in the range of 0.282-1.199THz y Approximately 1, and PCR x The y-polarized wave propagating in the-z direction is almost completely converted into the x-polarized wave, while the incident x-polarized wave is not converted into the y-polarized wave, realizing the function of the cross-polarization converter.
2) According to the invention, under the environment condition that vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, abnormal refraction, one-dimensional cylindrical focusing lens, two-dimensional point focusing lens, first-order orbital angular momentum and second-order orbital angular momentum functions are realized at 0.63THz after electromagnetic waves are incident along the-z direction by changing the size and the direction of an intermediate layer split resonant ring.
3) According to the invention, under the environmental conditions that vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV, the size and the direction of the split resonant ring of the middle layer are changed, and after electromagnetic waves are incident along the-z direction, the abnormal refraction functions of two-beam splitting, four-beam splitting, diffuse scattering and single beam are realized at the position of 0.63 THz.
4) The terahertz wave front regulating and controlling device based on vanadium dioxide-graphene provided by the invention adopts the structural design of the circular patch and the open resonance ring, has good structural properties in unit structure, has the characteristic of perfect asymmetry, can effectively improve conversion efficiency, abnormal refraction/reflection effect, superlens focusing effect, orbital angular momentum vortex effect and beam splitting effect in the metamaterial application process, and can reduce experimental errors caused by electromagnetic wave polarization in a certain range. Based on the tunable material, the invention can realize the free switching of multiple functions in the metamaterial by changing the external temperature and the chemical potential of the graphene, achieves the purpose of active control, and has wide application scenes.
Drawings
Fig. 1 is a schematic geometric diagram of a terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene.
Fig. 2 is a schematic diagram of an intermediate layer of a terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene.
Fig. 3 is a schematic diagram of a metal bottom layer of a terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene.
Fig. 4 shows the transmittance of the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene, when the vanadium dioxide is in an insulating state and the fermi level of the graphene is 1eV, the electromagnetic wave is incident along the +z and-z directions.
Fig. 5 is an AT parameter diagram of the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene, when electromagnetic waves are incident along the-z direction when the vanadium dioxide is in an insulating state and the fermi level of the graphene is 1 eV.
Fig. 6 is a Polarization Conversion Rate (PCR) diagram of the terahertz wave front-regulating and controlling super surface based on vanadium dioxide-graphene, when electromagnetic waves are incident along the-z direction when the vanadium dioxide is in an insulating state and the fermi level of the graphene is 1 eV.
FIG. 7 is an abnormal refraction (a) electric field distribution diagram of a terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene, when electromagnetic waves are incident along the-z direction when the vanadium dioxide is in an insulating state and the Fermi level of the graphene is 1 eV; (b) normalizing the far field power density profile.
Fig. 8 is a schematic diagram of an intermediate layer structure of (a) a one-dimensional cylindrical focusing lens when electromagnetic waves are incident along the-z direction when vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV on the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene; (b) -cross-polarized electric field density profile in the xoy plane, (c) -xoz plane and (d) focal plane.
Fig. 9 is a schematic diagram of an intermediate layer structure of (a) a two-dimensional point focusing lens when electromagnetic waves are incident along the-z direction when vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV on the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene; (b) xoz plane, (c) xoy plane, and (d) focal plane.
Fig. 10 is a schematic diagram of the phase distribution of (a) and (d) when the first-order and second-order orbital angular momentum of electromagnetic waves is 0.63THz when the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene is realized when the vanadium dioxide is in an insulating state and the fermi level of the graphene is 1 eV; (b) (e) x-polarization phase distribution; (c) (f) x-polarization normalized electric field density distribution.
FIG. 11 shows the reflection amplitude of (a) when the intermediate layer opening resonance ring rotates or does not rotate when electromagnetic waves are incident along the-z direction when vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV on the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene; b) Reflection phase
Fig. 12 is a schematic coding diagram of the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene, wherein the coding diagram is (a) with '010101 … …' arrangement when electromagnetic waves are incident along the-z direction when vanadium dioxide is in a metal state and the fermi level of graphene is 0.01 eV; (b) a two-beam far-field scattering map; (c) a coding scheme having a checkerboard arrangement; (b) Four-beam far-field scattering diagram
FIG. 13 is a schematic diagram of coding of random arrangement of (a) electromagnetic waves when electromagnetic waves are incident along the-z direction when vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV on the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene; (b) a far field scatter plot; (c) Diffuse scattering contrast reduction map
Fig. 14 is a schematic diagram of coding of "12345678/1234 … …" when electromagnetic waves are incident along the-z direction when the terahertz wave front regulating and controlling super surface based on vanadium dioxide-graphene, which is realized by the present invention, is in a metallic state when vanadium dioxide is in a metal state and the fermi level of graphene is 0.01 eV; (b) 8 units of reflected amplitude and phase
FIG. 15 shows (a) a far-field scattering diagram of an electromagnetic wave with the Fermi level of 0.01eV of graphene when vanadium dioxide is in a metal state and the terahertz wave front regulating and controlling super surface based on the vanadium dioxide-graphene is incident along the-z direction; (b) normalizing the reflection amplitude.
Detailed Description
The invention is further illustrated and described below with reference to the drawings and detailed description. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.
In a preferred embodiment of the present invention, a terahertz wave front regulating device based on vanadium dioxide-graphene is provided, which is formed by continuously and periodically arranging and splicing a series of identical device units in an array form on a plane, and the specific shape formed by splicing is not limited and can be determined according to the actual device design requirement.
As shown in fig. 1, the device unit is a multilayer composite structure with a square top surface, and comprises a vanadium dioxide substrate 1, a metal bottom layer 2, a lower dielectric layer 3, an intermediate metal layer 4, an upper dielectric layer 5 and a graphene top layer 6 from bottom to top. The cross sections of the vanadium dioxide substrate 1, the upper dielectric layer 5 and the lower dielectric layer 3 are all the same square; the cross section of the metal bottom layer 2 is three rectangular metal strips which are parallel to each other and are arranged at intervals, the cross section of the graphene top layer 6 is three rectangular graphene strips which are parallel to each other and are arranged at intervals, and the long side directions of the rectangular metal strips and the rectangular graphene strips are mutually orthogonal; the intermediate metal layer 4 is composed of a concentrically arranged metal split ring resonator and a metal circular patch. In a device unit, a vanadium dioxide substrate 1, a metal bottom layer 2, a lower dielectric layer 3, an intermediate metal layer 4, an upper dielectric layer 5 and a graphene top layer 6 are mutually attached, and the geometric center is on a straight line.
The intermediate metal layer 4 and the metal underlayer 2 are both thin-layer structures of metal patterns. As shown in fig. 2, the center of the circular metal patch is the circular metal patch, and the outside of the circular metal patch surrounds a metal split resonant ring, wherein the split resonant ring coincides with the center of the circle of the circular patch and is positioned on the same straight line perpendicular to the surface of the device as the geometric center of the whole device. As shown in fig. 3, three rectangular metal strips in the metal bottom layer 2 are arranged vertically, while rectangular graphene strips in the graphene top layer 6 need to be arranged horizontally and are just perpendicular to the rectangular metal strips.
In the vanadium dioxide-graphene terahertz wave front regulating and controlling super-surface device, the materials and parameters of each component can be as follows:
the planar shape of the whole device unit is square with the side length p of 120-130 mu m. The vanadium dioxide substrate 1 is made of vanadium dioxide, the length and the width of the square cross section are p=120-130 mu m, and the thickness is 0.2-0.5 mu m. The metal bottom layer 2 is made of metal aluminum, wherein the three rectangular metal strips have the same shape; each rectangular metal strip has a length of p=120-130 μm, a width of 5-10 μm and a thickness of 0.5-1.0 μm, and the spacing between adjacent rectangular metal strips is 20-25 μm. The lower dielectric layer 3 is made of polyimide, and the length and width of the square cross section are p=120-130 mu m, and the thickness is 40-50 mu m. The material of the intermediate metal layer 4 is metal aluminum; wherein the metal split resonant ring is a metal ring with an opening, the outer radius is 55-60 mu m, the inner radius is 45-50 mu m, the thickness is 0.5-1.0 mu m, the opening size is 0-120 mu m but not 0, the radius of the circular patch is 20-25 mu m, and the thickness is 0.5-1.0 mu m. The upper dielectric layer 5 is made of polyimide, and the length and the width of the square cross section are p=120-130 mu m, and the thickness is 40-50 mu m. The material of the graphene top layer 6 is graphene, wherein the three rectangular graphene strips have the same shape; each rectangular graphene strip has a length of 5-10 mu m, a width of p=120-130 mu m, a thickness of 1.0-1.2 nm, and an interval between adjacent rectangular graphene strips is 20-25 mu m.
It should be noted that the split ring resonator in the present invention is a metal ring with an opening, and thus the opening size is defined as the distance between two ends of the opening in the metal ring. As can be seen from fig. 2, the opening in the metal ring is obtained by cutting the ring body through the long sides of a rectangle, so that the opening size is also equivalent to the width of the rectangle.
When the terahertz wave front regulating and controlling super-surface device based on vanadium dioxide-graphene is in actual use, the vanadium dioxide and the graphene can be subjected to reversible intersection between a semiconductor and metal in a short time by applying different electric fields, magnetic fields and the like to the device and changing corresponding external environment conditions, so that the conductivity of the vanadium dioxide is changed between 10S/m and 200000S/m, the fermi level of the graphene is changed between 0.01eV and 1eV, and the function switching between the transmission-type super-surface and the reflection-type super-surface is realized.
The device units are basic component structures forming the multifunctional terahertz wave front-regulating and controlling super-surface device, and the whole converter can be formed by periodically and continuously arranging N multiplied by N device units on a plane, wherein N is an integer greater than 1. The shape of the finally spliced device can be changed correspondingly according to the requirements of the device.
In the above device, n×n device units are continuously spliced to form a super surface, and device parameters among different device units are kept consistent, but the opening size and opening direction, that is, the phase of the metal split ring in the intermediate metal layer 4 may be different. In addition, the switching of the vanadium dioxide in the vanadium dioxide substrate 1 between an insulating state and a metal state can be regulated and controlled by external excitation, and the fermi level of the graphene in the graphene top layer 6 can be correspondingly regulated. The vanadium dioxide in the vanadium dioxide substrate 1 is in an insulating state through external excitation, the Fermi level of graphene in the graphene top layer 6 is 1eV, the device is made to be a transmission type super-surface, and cross polarization conversion, abnormal refraction, focusing lenses and orbital angular momentum functions are realized through changing the size and the direction of an interlayer split resonance ring. In addition, vanadium dioxide in the vanadium dioxide substrate 1 can be regulated and controlled to be in a metal state through external excitation, the Fermi level of graphene in the graphene top layer 6 is 0.01eV, so that the device is a reflective super-surface, and the abnormal reflection functions of terahertz beam splitting, four-beam splitting, diffuse scattering and single beam are realized through changing the size and the direction of an intermediate layer split resonant ring.
The specific technical effects of the terahertz wave-front regulating device based on vanadium dioxide-graphene are described below by way of example.
Examples
In this embodiment, the structure and the shape of each component of the terahertz wave-front adjusting device based on vanadium dioxide-graphene are as described above, and are specifically shown in fig. 1 to 3, and are not described here again. The specific parameters of each component are as follows:
the planar shape of the individual device cells was square with a side length p of 120 μm. In the embodiment, all metal parts of the terahertz wave front-regulating and controlling super-surface device based on vanadium dioxide-graphene are made of metal aluminum, and the conductivity is sigma (Al) =3.56×10 7 And the two dielectric layers are polyimide with a dielectric constant of 3.5 and a loss tangent of 0.0027. Specifically, the material of the vanadium dioxide substrate 1 is vanadium dioxide, and the square cross section length and width are p=120 μm and the thickness is 0.2 μm. The material of the metal bottom layer 2 is that the conductivity is 3.56 multiplied by 10 7 S/m of metal aluminum, wherein the three rectangular metal strips have the same shape; each rectangular metal strip has a length of p=120 μm, a width of 8 μm and a thickness of 0.5 μm, and the spacing between adjacent rectangular metal strips is 20 μm. The material of the lower dielectric layer 3 is polyimide with a dielectric constant of 3.5 and a loss tangent of 0.0027, and the square cross section has a length and width of p=120 μm and a thickness of 40 μm. The intermediate metal layer 4 is made of a material with conductivity of 3.56×10 7 S/m of metallic aluminum; wherein the metal split resonant ring is a metal ring with an opening, the outer radius is 55 μm, the inner radius is 45 μm, the thickness is 0.5 μm, the opening size is 35 μm, the radius of the circular patch is 20 μm, and the thickness is 0.5 μm. The upper dielectric layer 5 is made of polyimide with a dielectric constant of 3.5 and a loss tangent of 0.0027, and the square cross section has a length and width of p=120 μm and a thickness of 40 μm. The material of the graphene top layer 6 is graphene, wherein the three rectangular graphene strips have the same shape; each rectangular graphene strip has a length of 8 μm, a width of p=120 μm and a thickness of 1.0nm, and the intervals between adjacent rectangular graphene strips are20μm。
In the device, when vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, the device mainly presents a transmission type super surface to realize cross polarization conversion, abnormal refraction, a focusing lens and orbital angular momentum functions; when vanadium dioxide is in a metal state and the Fermi level of graphene is 0.01eV, the vanadium dioxide mainly presents a reflective super-surface, and the abnormal reflection functions of two-beam splitting, four-beam splitting, diffuse scattering and single-beam splitting are realized. When the device units are periodically arranged to construct devices, the opening size and the direction of the metal split resonant ring can be reasonably regulated and controlled according to the functions to be realized.
The specific performance results of the terahertz wave-front regulating device based on vanadium dioxide-graphene are shown below:
as can be seen from FIG. 4, under the environment that vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, FIG. 4 (a) shows the transmission curve of the ultra-surface device provided by the invention when electromagnetic waves are incident along the +z direction, and the cross polarization transmission coefficient t is in the range of 0.5-0.96THz yx Greater than 0.7, i.e. the incident x-polarized wave is substantially converted to y-polarized wave, and over this frequency band, the cross-polarized transmission coefficient t xy Co-polarized transmission coefficient t xx 、t yy Substantially below 0.4. FIG. 4 (b) shows the transmission coefficient of the proposed subsurface device in the electromagnetic wave propagation in the-z direction, where the cross-polarized transmission coefficient is opposite to that in FIG. 4 (a), i.e., the cross-polarized transmission coefficient t xy Greater than 0.7, i.e. the incident y-polarized wave is substantially converted to an x-polarized wave, co-polarized transmission coefficient t xx 、t yy Remain unchanged.
As can be seen from FIG. 5, under the environmental conditions that vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, the AT parameter of the super-surface device provided by the inventionGreater than 0.6 in the range of 0.632-0.891THz, and +.>The symmetry is reversed and the cell structure exhibits no alignment at all to the transmission characteristics.
As can be seen from FIG. 6, under the environmental conditions that vanadium dioxide is in an insulating state and the Fermi level of graphene is 1eV, the super-surface device provided by the invention is in a PCR (polymerase chain reaction) at 0.282-1.199THz y Approximately 1, and PCR x Then it is close to 0, which means that in this band, the y-polarized wave propagating in the-z direction is almost completely converted into an x-polarized wave, while the incident x-polarized wave is not converted into a y-polarized wave.
As can be seen from fig. 7, under the environment condition that vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV, the ultra-surface device provided by the invention has a significant deflection of the propagation direction after the electromagnetic wave enters along the-z direction and passes through the ultra-surface at 0.63 THz. Meanwhile, the maximum value of far-field power density is 28.2 DEG, and the formula is shown in the specificationThe theoretical value obtained is 29.7 degrees close.
As can be seen from fig. 8, under the environment condition that vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV, the super-surface device provided by the invention is at 0.63THz, fig. 8 (a) is a schematic diagram of a one-dimensional lens intermediate layer, the size and direction of an opening along the x-axis direction are different, so as to realize compensation phase, and fig. 8 (b) and (c) are respectively cross polarization electric field density distribution of the super-surface structure in the xoy plane and the xoz plane, so that it can be obviously seen that an incident electromagnetic wave forms a light column after passing through the super-surface, and the focal length is 770 μm and is similar to a preset value (800 μm). Fig. 8 (d) shows the electric field density distribution in the focal plane, with a maximum at x=0 and a Full Width Half Maximum (FWHM) of 292.6 μm.
As can be seen from fig. 9, in the environment condition that vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV, the super-surface device provided by the invention is at 0.63THz, fig. 9 (a) is a schematic diagram of an intermediate layer of a two-dimensional lens, and fig. 9 (b) and (c) are respectively cross polarization electric field density distributions of a super-surface structure in a xoz plane and an xoy plane, so that it can be obviously seen that an incident electromagnetic wave forms a focusing point after passing through the super-surface, and the focal length is 706 μm and is close to a preset value (800 μm). Fig. 9 (d) shows the electric field density distribution in the focal plane, with a maximum at x=0, and a Full Width Half Maximum (FWHM) of 301.7 μm.
As can be seen from fig. 10, in the environment where vanadium dioxide is in an insulating state and the fermi level of graphene is 1eV, the ultra-surface device proposed by the present invention has a phase distribution required when m= +1 and m= +2 are shown in fig. 10 (a) and (d), the phase difference between adjacent regions is pi/4, and when the topological charge m= +1 is shown in fig. 10 (b) and (c), the phase distribution of the x polarized wave shown by the xoy plane can be seen, the incident electromagnetic wave is converted into a vortex beam carrying one spin arm and having one central singular point. Fig. 7 (e) (f) shows that when the topological charge m= +2, the phase distribution of the x-polarized wave shown by the xoy plane can be seen, and the incident electromagnetic wave is converted into a vortex beam carrying two spin arms and having two central singular points.
As can be seen from fig. 11, under the environmental conditions that vanadium dioxide is in a metal state and the fermi level of graphene is 0.01eV, the co-polarized reflection coefficient and the cross-polarized reflection coefficient remain unchanged, but the phase is shifted by 180 degrees after the split resonant ring is clockwise rotated by 90 degrees at 0.63 THz. The intermediate layer opening resonance ring is respectively rotated to be used as '0' coding particles, and is not rotated to be used as '1' coding particles, so that the 1-bit coding super-surface beam function is realized.
As can be seen from fig. 12, in the environment condition that vanadium dioxide is in a metal state and the fermi level of graphene is 0.01eV, the super-surface device provided by the invention arranges the coding elements according to the periodic coding mode of '010101 … …' at 0.63THz, the far-field scattering under the coding sequence can clearly see that y polarized wave is incident on the super-surface and then reflected into two x polarized light beams, the coding elements are arranged according to the periodic coding mode of checkerboard, and the far-field scattering under the coding sequence can clearly see that y polarized wave is incident on the super-surface and then reflected into four x polarized light beams.
As can be seen from fig. 13, in the environment condition that vanadium dioxide is in a metal state and the fermi level of graphene is 0.01eV, the super-surface device provided by the invention arranges the coding elements at 0.63THz according to a disordered coding mode, and far-field scattering under the coding sequence can clearly show that y polarized waves are scattered to all directions after being incident on the super-surface, so that diffuse reflection is formed. And selecting a metal flat plate with the same size as the super surface for simulation, thereby comparing and verifying the Radar Cross Section (RCS) reduction effect of the super surface. The far field pattern simulation results for the coded super surface and the metal plate at 0.63THz are shown in fig. 12 (c). The strongest reflected beam of the metal plate is at θ=0°, while the strongest reflected beam of the encoded super surface is at θ= ±46°, with an intensity decrease of about 15dB (sw)
As can be seen from fig. 14, in the environment condition that vanadium dioxide is in a metal state and the fermi level of graphene is 0.01eV, four types of device units with opening sizes of 80 μm, 99 μm, 9 μm and 40 μm are selected at the 0.63THz position, each column (Unit) is a device Unit with the same opening size and direction, units 1-Unit2 and 7-Unit8 are the open resonance ring and rotate by 90 degrees, and units 3-Unit6 are the open resonance ring and do not rotate by 90 degrees. As can be seen from fig. 12 (b), at 0.63THz, the phase of Unit1-Unit8, which has a cross polarization reflection coefficient greater than 0.8,8 units, satisfies a phase gradient in the range of 360 °.
As can be seen from FIG. 15, under the environmental condition that vanadium dioxide is in a metal state, the ultra-surface device provided by the invention realizes scattering control of-29 degrees of deflection angle after y polarized wave is incident on the terahertz ultra-surface at 0.63THz, and the abnormal deflection angle can be represented by the formulaCalculated, theoretical result is-29.7 °.
The above embodiment is only a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the equivalent substitution or equivalent transformation are within the protection scope of the invention.
Claims (10)
1. The terahertz wave front regulating and controlling device based on vanadium dioxide-graphene is characterized by being formed by continuously and periodically arranging and splicing device units on a plane in an array mode;
the device units are of a multi-layer composite structure, and are a vanadium dioxide substrate (1), a metal bottom layer (2), a lower dielectric layer (3), an intermediate metal layer (4), an upper dielectric layer (5) and a graphene top layer (6) in sequence from bottom to top;
the cross sections of the vanadium dioxide substrate (1), the upper dielectric layer (5) and the lower dielectric layer (3) are all the same square; the cross section of the metal bottom layer (2) is three rectangular metal strips which are parallel to each other and are arranged at intervals, the cross section of the graphene top layer (6) is three rectangular graphene strips which are parallel to each other and are arranged at intervals, and the long side directions of the rectangular metal strips and the rectangular graphene strips are mutually orthogonal; the intermediate metal layer (4) is composed of a metal split resonant ring and a metal circular patch which are concentrically arranged.
2. The terahertz wave front regulating device based on vanadium dioxide-graphene as set forth in claim 1, wherein the vanadium dioxide substrate (1) is made of vanadium dioxide, and has a cross section length and width of 120-130 μm and a thickness of 0.2-0.5 μm.
3. The terahertz wave front regulating device based on vanadium dioxide-graphene as set forth in claim 1, wherein the material of the metal bottom layer (2) is metal aluminum, and three rectangular metal strips have the same shape; each rectangular metal strip has a length of 120-130 μm, a width of 5-10 μm, a thickness of 0.5-1.0 μm, and an interval between adjacent rectangular metal strips of 20-25 μm.
4. The terahertz wave front regulating device based on vanadium dioxide-graphene as set forth in claim 1, wherein the lower dielectric layer (3) is made of polyimide, and has a cross section length and width of 120-130 μm and a thickness of 40-50 μm.
5. The terahertz wave front regulating device based on vanadium dioxide-graphene as set forth in claim 1, wherein the material of the intermediate metal layer (4) is metallic aluminum; wherein the metal split resonant ring is a metal ring with an opening, the outer radius is 55-60 mu m, the inner radius is 45-50 mu m, the thickness is 0.5-1.0 mu m, the opening size is 0-120 mu m but not 0, the radius of the circular patch is 20-25 mu m, and the thickness is 0.5-1.0 mu m.
6. The terahertz wave front regulating device based on vanadium dioxide-graphene as set forth in claim 1, wherein the upper dielectric layer (5) is polyimide, and the cross section length and width are 120-130 μm and the thickness is 40-50 μm.
7. The terahertz wave front regulating device based on vanadium dioxide-graphene according to claim 1, wherein the material of the graphene top layer (6) is graphene, and three rectangular graphene strips have the same shape; each rectangular graphene strip has a length of 5-10 mu m, a width of 120-130 mu m, a thickness of 1.0-1.2 nm, and an interval between adjacent rectangular graphene strips is 20-25 mu m.
8. The vanadium dioxide-graphene-based terahertz wave-front modulating device according to claim 1, wherein the device is formed by periodically and continuously arranging n×n device units on a plane, wherein N is an integer greater than 1.
9. The terahertz wave front regulating device based on vanadium dioxide-graphene according to any one of claims 1-8, characterized in that in the device unit, vanadium dioxide in a vanadium dioxide substrate (1) is regulated and controlled to be in an insulating state through external excitation, the fermi level of graphene in a graphene top layer (6) is 1eV, so that the device is a transmission type super surface and is used for realizing cross polarization conversion, abnormal refraction, a focusing lens and orbital angular momentum functions.
10. The terahertz wave front regulating device based on vanadium dioxide-graphene according to any one of claims 1-8, characterized in that in the device unit, vanadium dioxide in a vanadium dioxide substrate (1) is regulated and controlled to be in a metal state by external excitation, the fermi level of graphene in a graphene top layer (6) is 0.01eV, so that the device is a reflective super-surface and is used for realizing the functions of terahertz beam splitting, four-beam splitting, diffuse scattering and abnormal reflection of a single beam.
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