Double-layer transmission type terahertz Huygens metasurface regulation and control method and metasurface

Abstract

The invention discloses a double-layer transmission-type terahertz Huygens metasurface regulation and control method and a metasurface, and relates to the field of electromagnetic waves and novel artificial electromagnetic materials, and the method comprises the steps: obtaining the arm length parameters of a cross structure and a Jerusalem cross structure of the metasurface, and carrying out the phase result simulation operation based on the arm length parameters, determining metasurface phase permissions according to simulation results; and analyzing the distribution condition of the discrete phase set value on the metasurface by using a metasurface phase permissible and data analysis modeling technology, and performing metasurface terahertz beam focusing regulation and control processing based on a distribution result. According to the double-layer transmission-type terahertz Huygens metasurface regulation and control method and the metasurface, the phase-change material is innovatively combined, the metasurface unit with the original single function can show different characteristics in different states, and compared with a single metasurface unit structure, the metasurface unit structure has the advantages that the metasurface unit structure is simple in structure and easy to implement. The dynamic terahertz wave beam regulation and control mode is explored very meaningfully, and the regulation and control efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic waves and novel artificial electromagnetic materials, and in particular to a double-layer transmission-type terahertz Huygens metasurface control method and a metasurface. Background Art

[0002] Terahertz waves are widely used in natural sciences due to their many excellent properties, such as high-speed wireless communications, imaging sensors, biomedicine, astronomy and the universe. As the demand for practical applications increases, single-function terahertz metasurfaces are no longer sufficient. In order to enable the metasurface to dynamically modulate the terahertz beam, the metasurface can be combined with materials with adjustable properties, such as liquid crystal, vanadium dioxide, and semiconductor materials, to form a tunable metasurface. By applying voltage, temperature, light and other stimuli to change the properties of the material, dynamic modulation of the metasurface can be achieved.

[0003] Vanadium dioxide has both metal and insulator properties, and its properties change with temperature. It also responds well in the terahertz frequency band and is also a commonly used phase change material for designing dynamically tunable terahertz metasurfaces. The existing technology is based on a three-state conversion metasurface of vanadium dioxide, and its unit structure is a double open circular ring. At frequencies of 1.89 terahertz and 2.67 terahertz, it achieves two perfect absorption switches to one reflection and one transmission, and is insensitive to the incident angle. There is also a "Janus" metasurface based on vanadium dioxide, which can adjust the temperature of the metasurface at 1 terahertz to incident terahertz waves in the front and rear directions, thereby achieving different focusing and imaging functions of the terahertz beam.

[0004] In addition, coupled mode theory is a theory that studies the general laws of coupling between two or more electromagnetic wave modes from a dynamic perspective. The transmission matrix of the resonant system can be obtained from the dynamic equations of the resonant mode and the dynamic conditions that satisfy the equations, thereby analyzing the response state of the resonant system to electromagnetic waves. It is widely used in mode analysis of metasurfaces. At the same time, the Huygens phenomenon manifests itself as a high transmission and large phase shift phenomenon when the magnetic resonance and electric resonance of the metasurface are orthogonal and the equivalent magnetic impedance and electrical admittance on the metasurface are the same.

[0005] For the Huygens metasurface, it can be understood that when the near-field coupling and far-field coupling of the two resonant modes meet a certain degree of strong coupling or weak coupling, the two resonant modes are degenerate and high transmission and large phase shift phenomena appear. However, the Huygens metasurface unit with high transmission characteristics in the prior art has a single structure and function, which makes it impossible for the metasurface unit to exhibit different characteristics in different states.

[0006] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0007] In view of the problems in the related art, the present invention proposes a double-layer transmission terahertz Huygens metasurface control method and metasurface to overcome the above-mentioned technical problems existing in the existing related technology.

[0008] To this end, the specific technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a double-layer transmission terahertz Huygens metasurface control method, the control method comprising:

[0010] Obtain arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, perform phase result simulation operation based on the arm length parameters, and determine the phase resolution of the metasurface according to the simulation results;

[0011] The metasurface phase analysis and data analysis modeling technology is used to analyze the distribution of discrete phase setting values ​​on the metasurface, and the metasurface terahertz beam focusing control is performed based on the distribution results.

[0012] Preferably, obtaining arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, and performing a phase result simulation operation based on the arm length parameters, and determining the phase resolution of the metasurface according to the simulation results includes:

[0013] Obtain arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, and collect the terminal length of the Jerusalem cross structure;

[0014] According to the simulation operation requirements, the terminal length is kept unchanged, the arm length parameters are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is determined according to the phase change;

[0015] According to the simulation operation requirements, the arm length parameters of the Jerusalem cross structure are kept unchanged, the arm length parameters of the cross structure and the terminal length are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is determined according to the phase change;

[0016] The optical path of electromagnetic waves from various positions on the metasurface to any position is analyzed according to the phase change and the superlens. The focusing state is analyzed using the optical path results to obtain the focal length. The phase resolution requirement relationship of the metasurface is set based on the focal length and the Fermat principle.

[0017] Preferably, the phase separation requirement is:

[0018]

[0019] In the formula, represents the phase difference, x and y represent the lateral center distance and longitudinal center distance from any point on the metasurface to the metasurface, λ represents the wavelength of the incident electromagnetic wave in free space, f represents the focal length, Indicates the correction phase.

[0020] Preferably, using metasurface phase analysis and data analysis modeling technology to analyze the distribution of discrete phase setting values ​​on the metasurface, and performing metasurface terahertz beam focusing control processing based on the distribution results includes:

[0021] Set the focal length and wavelength of the incident electromagnetic wave in free space, as well as the metasurface period and array size, and write the code using data analysis modeling techniques and metasurface phase resolution requirements;

[0022] The distribution of discrete phase thresholds on the metasurface is analyzed using codes and set numerical values, and the theoretical distribution of discrete phases is obtained based on the distribution.

[0023] Constructing a simulated metasurface structure at the same position of the electromagnetic field simulation software, and using data analysis modeling technology and electromagnetic field simulation software to translate the simulated metasurface structure to a position corresponding to the discrete phase theory distribution, to obtain a constructed superlens array;

[0024] The beam focusing situation is analyzed according to the superlens array and electromagnetic field simulation software, and the phase range is adjusted based on the analysis results to perform metasurface terahertz beam focusing control processing.

[0025] Preferably, analyzing the beam focusing condition according to the superlens array and the electromagnetic field simulation software, and adjusting the phase range based on the analysis result to perform the metasurface terahertz beam focusing control process includes:

[0026] Based on the superlens array, dual electric and dual magnetic boundary conditions are set in the electromagnetic field simulation software, and the waveguide port is set with a linearly polarized plane wave for simulation operation, and the beam focusing of the beam transmission superlens array is observed;

[0027] According to beam focusing, the arm lengths of the cross structure and the Jerusalem cross structure of the metasurface are regulated, the phase range is expanded using the regulated arm lengths, and the discrete phase is changed based on the phase range expansion result to increase the number of simulated metasurface structures;

[0028] The added results are used to regenerate the superlens array, which is combined with electromagnetic field simulation software to analyze the beam focusing situation and complete the control processing of the metasurface terahertz beam focusing.

[0029] In a second aspect, the present invention provides a double-layer transmission terahertz Huygens metasurface control method, the control method comprising:

[0030] Obtain the ambient temperature of the metasurface, change the properties of vanadium dioxide based on the ambient temperature results, connect the Jerusalem cross structure to form Huygens conditions according to the state results, and regulate the transmission state of the metasurface;

[0031] Initialize the conductivity of vanadium dioxide, analyze the action state of vanadium dioxide based on the conductivity, and combine the action state with numerical simulation technology to determine the switching trend of the projection and reflection states of the metasurface to perform metasurface control operations.

[0032] Preferably, initializing the conductivity of vanadium dioxide, analyzing the action state of vanadium dioxide based on the conductivity, and combining the action state with numerical simulation technology to determine the switching trend of the projection and reflection states of the metasurface to perform the metasurface control operation includes:

[0033] Initializing the conductivity of vanadium dioxide, determining the transmission state of the metasurface, and recording the transmission coefficient amplitude and absorption amplitude of the metasurface based on the transmission state as the action state of vanadium dioxide;

[0034] The conductivity of vanadium dioxide is gradually increased based on numerical simulation technology, and the transmission change trend of the metasurface is determined during the increase process. The transmission coefficient amplitude and absorption amplitude are analyzed using the transmission change trend.

[0035] Based on the analysis results and the transmission change trend, the switching trend of the metasurface projection and reflection states is determined, and the switching trend is used to change the conductivity of vanadium dioxide to perform metasurface regulation operations.

[0036] Preferably, when the conductivity of vanadium dioxide is 0 Siemens, the reflection and absorption amplitudes of the metasurface are both 0.2, and the projection coefficient amplitude is 0.9;

[0037] The electrical conductivity of vanadium dioxide is 1.1×10 5 When Siemens, the reflection and absorption amplitudes of the metasurface are both less than 0.2, and the projection coefficient amplitude is greater than 0.9;

[0038] The electrical conductivity of vanadium dioxide is 2×10 4 Siemens, the reflection and absorption amplitudes of the metasurface are both 0.25, and the projection coefficient amplitude is 0.8.

[0039] In a third aspect, the present invention provides a double-layer transmission terahertz Huygens metasurface, which is composed of a cross structure, an ultraviolet quartz substrate, a Jerusalem cross structure and vanadium dioxide.

[0040] Preferably, the thickness of the ultraviolet quartz substrate is 150 micrometers, and the thickness of the vanadium dioxide is 200 nanometers.

[0041] The beneficial effects of the present invention are:

[0042] 1. The double-layer transmission terahertz Huygens metasurface control method and metasurface proposed in the present invention innovatively combine phase change materials, so that the metasurface unit with a single function can show different characteristics under different states. Compared with the single metasurface unit structure, it conducts very meaningful exploration in the dynamic terahertz beam control method, thereby increasing the control efficiency.

[0043] 2. The present invention adds vanadium dioxide at the bottom terminal of the metasurface unit, which can achieve high modulation depth conversion of beam transmission and reflection through temperature control. By designing different geometric dimensions and relative positions of the structure, the terahertz beam focusing effect with a focal length of 2 cm for 2-bit and 3-bit pixels can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 is a flow chart of Example 1 according to an embodiment of the present invention;

[0046] Figure 2 According to the embodiment 1 of the present invention, c The phase change diagram is obtained unchanged;

[0047] Figure 3 The phase change diagram is obtained by keeping I0 unchanged in the first embodiment of the embodiment of the present invention;

[0048] Figure 4 is an ideal discrete phase distribution diagram of a 2-bit superlens in Example 1 according to an embodiment of the present invention;

[0049] Figure 5 This is a front structural diagram of a 2-bit superlens in Example 1 according to an embodiment of the present invention;

[0050] Figure 6 It is the reverse structure of the 2-bit super lens in the first embodiment of the present invention;

[0051] Figure 7 is a simulated beam distribution diagram after the beam is projected through the super lens array in the 2-bit case in embodiment 1 of the embodiment of the present invention;

[0052] Figure 8 is a simulated beam distribution diagram after the beam is projected through the superlens array in the case of 3 bits in embodiment 1 of the present invention;

[0053] Fig. 9 is a measured beam distribution diagram after the beam is projected through the super lens array in the 2-bit case in embodiment 1 of the embodiment of the present invention;

[0054] Fig.10 is a measured beam distribution diagram after the beam is projected through the superlens array in the case of 3 bits in embodiment 1 of the embodiment of the present invention;

[0055] Fig.11 is a flow chart of Example 2 according to an embodiment of the present invention;

[0056] Fig.12 is a simulation spectrum diagram when the conductivity is 0 Siemens in Example 2 of the embodiment of the present invention;

[0057] Fig.13 The conductivity is 1.1×10 5 Simulation spectrum diagram of Siemens time;

[0058] Fig.14 The conductivity is 2×10 4 Simulation spectrum diagram of Siemens time;

[0059] Fig.15 is a schematic structural diagram of a double-layer transmissive terahertz Huygens metasurface according to an embodiment of the present invention;

[0060] Fig.16 is a front view of a double-layer transmissive terahertz Huygens metasurface according to an embodiment of the present invention;

[0061] Fig.17 is a back view of a double-layer transmissive terahertz Huygens metasurface according to an embodiment of the present invention.

[0062] In the figure:

[0063] 1. Cross structure; 2. UV quartz substrate; 3. Jerusalem cross structure; 4. Vanadium dioxide. DETAILED DESCRIPTION

[0064] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments. They can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention.

[0065] According to an embodiment of the present invention, a double-layer transmission-type terahertz Huygens metasurface control method and a metasurface are provided.

[0066] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0067] Embodiment 1

[0068] See also Figure 1 According to a double-layer transmission terahertz Huygens metasurface control method according to an embodiment of the present invention, the control method comprises:

[0069] Step S101, obtaining arm length parameters of the cross structure 1 and the Jerusalem cross structure 3 of the metasurface, and performing a phase result simulation operation based on the arm length parameters, and determining the metasurface phase separation according to the simulation results;

[0070] Step S102: Analyze the distribution of discrete phase setting values ​​on the metasurface using metasurface phase analysis and data analysis modeling technology, and perform metasurface terahertz beam focusing control processing based on the distribution results.

[0071] In this embodiment, when the arm length parameters of the cross structure 1 and the Jerusalem cross structure 3 of the metasurface are obtained, and a phase result simulation operation is performed based on the arm length parameters, and the phase separation of the metasurface is determined according to the simulation results, the arm length parameters of the cross structure 1 and the Jerusalem cross structure 3 of the metasurface can be obtained, and the terminal length of the Jerusalem cross structure 3 can be collected; the terminal length is kept unchanged according to the simulation operation requirements, the arm length parameters are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is judged according to the phase change; the arm length parameters of the Jerusalem cross structure 3 are kept unchanged according to the simulation operation requirements, the arm length parameters of the cross structure 1 and the terminal length are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is judged according to the phase change; the optical path of the electromagnetic wave from each position of the metasurface to any position is analyzed according to the phase change and the superlens, the focal length is obtained by analyzing the focusing state using the optical path result, and the phase separation requirement relationship of the metasurface is set based on the focal length and the Fermat principle.

[0072] In this embodiment, when the distribution of discrete phase setting values ​​on the metasurface is analyzed by using metasurface phase analysis and data analysis modeling technology, and the metasurface terahertz beam focusing control processing is performed based on the distribution results, the focal length and the wavelength of the incident electromagnetic wave in the free space, as well as the metasurface period and the array scale can be set, and the code can be written using the data analysis modeling technology and the metasurface phase analysis requirements; the distribution of discrete phase thresholds on the metasurface is analyzed using the code and set numerical values, and the discrete phase theoretical distribution is obtained based on the distribution; a simulated metasurface structure is constructed at the same position of the electromagnetic field simulation software, and the simulated metasurface structure is translated to the position corresponding to the discrete phase theoretical distribution using the data analysis modeling technology and the electromagnetic field simulation software to obtain a constructed superlens array; the beam focusing situation is analyzed according to the superlens array and the electromagnetic field simulation software, and the phase range is adjusted based on the analysis results to perform metasurface terahertz beam focusing control processing.

[0073] In this embodiment, when analyzing the beam focusing situation according to the superlens array and the electromagnetic field simulation software, and adjusting the phase range based on the analysis results to perform the supersurface terahertz beam focusing control processing, the dual electric and dual magnetic boundary conditions can be set in the electromagnetic field simulation software based on the superlens array, and the linearly polarized plane wave is set at the waveguide port for simulation operation, and the beam focusing situation of the beam transmission superlens array is observed; according to the beam focusing, the arm lengths of the cross structure 1 and the Jerusalem cross structure 3 of the supersurface are controlled, and the phase range is expanded using the controlled arm lengths, and the discrete phase is changed based on the phase range expansion result to increase the number of simulated supersurface structures; the superlens array is regenerated using the increase result, and the beam focusing situation is analyzed in combination with the electromagnetic field simulation software to complete the control processing of the supersurface terahertz beam focusing.

[0074] From the transmission coefficient of the metasurface unit, it can be seen that the Huygens phenomenon not only has two high transmission amplitudes generated by resonant coupling, but also the phase change at the high transmission point reaches 360 degrees. Therefore, by changing the size parameters and relative position of the unit structure, a lens with a focal length of 2 cm for 2-bit and 3-bit pixels can be realized.

[0075] like Figure 2 and Figure 3 As shown, it needs to be explained that, in this embodiment, by changing the size parameters of the metasurface unit structure, a continuous phase change can be obtained, and the structural parameters that determine the phase change are mainly the arm length I of the cross structure 1 a ( Figure 2 ), Jerusalem cross structure 3 arms length I0( Figure 3 ), terminal length I c ( Figure 3 ), keep I c= 236 microns, and the other two parameters are changed. The phase change is -292 degrees to -562 degrees, and the amplitude of the transmission coefficient is kept above 0.75. Figure 2 As shown, keeping I0 = 543 microns unchanged and changing the other two parameters, the phase change range is -360 degrees to -605 degrees, and the transmission coefficient amplitude is kept above 0.6, as shown in Figure 3 As shown, combined with the above two results, by changing the unit size structure, a phase change of about 320 degrees can be obtained while maintaining a high transmission coefficient amplitude, as shown in Table 1 for the structural parameters in the 2-bit case, and four structural parameters with adjacent phase differences of 90 degrees.

[0076] Table 1 Phase structure parameters

[0077] I0(μm) Ia(micrometer) Amplitude Phase (degrees) 423 233 0.78 -292 525 378 0.79 -382 540 404 0.86 -472 557 440 0.96 -562

[0078] The basic principle of the metalens is that the phase of the metasurface can be continuously changed, so that the optical path of the electromagnetic waves passing through various positions of the metasurface to a certain position after the metasurface is the same, thereby achieving the purpose of focusing. According to the Fermat principle, the phase of the metasurface needs to satisfy the following relationship:

[0079]

[0080] In the formula, represents the phase difference, x and y represent the horizontal and vertical center distances from any point on the metasurface to the metasurface, respectively. Assuming that the center of the metasurface is located in the plane of z = 0, it is simplified to three-dimensional space distance, λ represents the wavelength of the incident electromagnetic wave in free space, f represents the focal length, Indicates the correction phase.

[0081] like Figures 4 to 6 , when the focal length f = 20mm, the wavelength λ = 1360um, the metasurface unit period p = 566um, and the metasurface array scale is 40×40, the distribution of the 2-bit discrete phase on the metasurface can be obtained by writing the code in Matlab according to the above formula, as shown in Figure 4 As shown in the figure, the four-phase metasurface unit structures are first established at the same position in CST, and then these four structures are translated to the positions corresponding to the discrete phase theoretical distribution through Matlab-CST joint simulation to complete the construction of the superlens array, as shown in the figure. Figure 5 and Figure 6 As shown in the figure, after obtaining the superlens array, in CST, set the double electric and double magnetic boundary conditions, set the linear polarized plane wave at the waveguide port, and simulate and observe the situation after the beam passes through the superlens array after the power flow field monitor, as shown in the figure. Figure 7As shown, it can be found that at the set focus z=20mm, the beam is obviously focused, and there is no focusing phenomenon at z=15 and 25mm. However, there is a slight focusing of the beam in the range of z=0-15mm. The reason for this phenomenon is that the discrete phase is set too little, resulting in insufficient continuity of the phase distribution, which leads to a little focusing of the beam at nearby locations.

[0082] In order to improve this phenomenon and improve the focusing quality, it is necessary to increase the number of discrete phases and the corresponding phase range. c The maximum phase range obtained by changing the size of the other two structures is 270°. Since the relative position of the two structures can also affect the coupling state, the phase of high transmission can be changed. Through the simulation of the relative position change of the two structures (translation and rotation), it is found that when the centers of the two structures are offset by 15μm in the x and y directions, the phase range can be expanded to 315°, and then 4 more structures can be found on the basis of the original 2-bit structure to form a 3-bit structure. The added 4 structural parameters are shown in Table 2, and then the additional 4 structural parameters of the 3-bit lens are formed in the original 2-bit case. Because the relative position change of the two structures will also affect the coupling state, according to the simulation of the relative position change (translation), it is found that when the centers of the two mechanisms are offset by 15 microns in the x and y directions, the phase range can be expanded.

[0083] Table 2 Structure table after modification

[0084] <![CDATA[I0 (microns)]]> <![CDATA[I a (micrometer)]]> <![CDATA[d x (micrometer)]]> <![CDATA[d y (micrometer)]]> Amplitude Phase (degrees) 558 420 15 -15 0.90 -247 519 330 0 0 0.54 -337 534 389.5 0 0 0.77 -427 546 420 0 0 0.92 -517

[0085] like Figure 7 and Figure 8 As shown, based on the above embodiments, 2-bit and 3-bit pixel superlenses are designed. It can be found that the beams of the two designs are obviously focused at the set focal point z=20 mm, and there is no focusing phenomenon at z=15 and 25 mm. Compared with the 2-bit lens, the focusing phenomenon of the 3-bit lens is significantly improved in the area z=0-15 mm closer to the metasurface. Relative to the energy density at the focal point, it can even be said that the focusing phenomenon in this area disappears. The 3-bit superlens can complete the terahertz beam focusing function with higher quality.

[0086] like Fig. 9 and Fig.10 The figures show the actual measured focusing conditions of 2-bit and 3-bit lenses at different positions. At the designed focus z=20 mm, both lenses have good focusing effects. At z=25 mm, both lenses are not focused. At z=15 mm, the 2-bit lens has a slight focusing condition, while the 3-bit lens has no focusing function, which is consistent with the simulation. This shows that the 3-bit lens can complete the focusing function of the set focus with higher quality.

[0087] Embodiment 2

[0088] See also Fig.11 According to another embodiment of the present invention, a double-layer transmission terahertz Huygens metasurface control method is provided, and the control method includes:

[0089] Step S201, obtaining the ambient temperature of the metasurface, changing the properties of the vanadium dioxide 4 based on the ambient temperature result, connecting the Jerusalem cross structure 3 to form a Huygens condition according to the state result, and regulating the transmission state of the metasurface;

[0090] Step S202, initialize the conductivity of vanadium dioxide 4, analyze the action state of vanadium dioxide 4 based on the conductivity, and combine the action state with numerical simulation technology to determine the switching trend of the supersurface projection and reflection states to perform supersurface control operations.

[0091] In this embodiment, when initializing the conductivity of vanadium dioxide 4, analyzing the action state of vanadium dioxide 4 based on the conductivity, and combining the action state with numerical simulation technology to determine the switching trend of the projection and reflection states of the supersurface to perform the supersurface regulation operation, the conductivity of vanadium dioxide 4 can be initialized, the transmission state of the supersurface is judged, and the transmission coefficient amplitude and absorption amplitude of the supersurface are recorded based on the transmission state as the action state of vanadium dioxide 4; the conductivity of vanadium dioxide 4 is gradually increased based on numerical simulation technology, and the transmission change trend of the supersurface is judged during the increase process, and the transmission coefficient amplitude and absorption amplitude are analyzed using the transmission change trend; the switching trend of the projection and reflection states of the supersurface is determined according to the analysis results and the transmission change trend, and the conductivity of vanadium dioxide 4 is changed using the switching trend to perform the supersurface regulation operation.

[0092] It should be explained that the properties of vanadium dioxide 4 are changed by temperature, thereby destroying the Huygens condition formed by the coupling between the two structures. At the same frequency point, vanadium dioxide 4 behaves in an insulating state at low temperature, which has no effect on the unit structure, and the metasurface still maintains the Huygens phenomenon of high transmission for the incident terahertz wave. When the temperature is high, vanadium dioxide 4 behaves in a metallic state, connecting the adjacent Jerusalem cross structure 3, changing the resonant properties of the structure, thereby destroying the conditions for the Huygens phenomenon with the other cross structure 1, and the high transmission disappears. The metasurface shows a high reflection phenomenon for the incident terahertz wave, which is the opposite of high transmission.

[0093] like Figure 12 to Figure 14As shown, (Magnitude represents amplitude, Transmission represents transmission, Reflection represents reflection, Absorption represents absorption, Frequency represents frequency, THz represents terahertz, and Phase represents phase) In the embodiment of the present invention, by changing the conductivity of the phase change material vanadium dioxide 4, the switching of the projection and reflection states can be achieved. When the conductivity is 0 Siemens, at the communication window frequency of 0.22 THz, the corresponding Fig.12 In the transmission state shown in the figure, the projection coefficient amplitude reaches 0.9, and the reflection and absorption amplitudes are both 0.2. As the conductivity increases, the transmittance gradually decreases and the reflectivity increases. When the conductivity increases to 1.1×105 Siemens, the corresponding Fig.13 In the high reflection state shown, the transmission and absorption amplitudes are both below 0.2, while the reflection coefficient amplitude reaches above 0.9; in addition, when the conductivity is 2×104 Siemens, the corresponding Fig.14 , it still shows a high reflection state at 0.22THz. It can be found that at 0.19THz, the amplitudes of the transmission and reflection coefficients are both around 0.25, and the amplitude of the absorption coefficient reaches 0.8. The metasurface shows an absorption state for the incident terahertz beam. This shows that the conversion of the two states of transmission and reflection is achieved at the same frequency; within a certain width, the conversion of the three states of transmission, absorption and reflection is achieved.

[0094] See also Figures 15 to 17 According to another embodiment of the present invention, a double-layer transmission terahertz Huygens metasurface is provided, which is composed of a cross structure 1, an ultraviolet quartz substrate 2, a Jerusalem cross structure 3 and vanadium dioxide 4. Specifically, the thickness of the ultraviolet quartz substrate 2 is 150 microns, the thickness of the vanadium dioxide 4 is 200 nanometers, the cross structure 1 is located on the top of the ultraviolet quartz substrate 2, the Jerusalem cross structure 3 is located at the bottom of the ultraviolet quartz substrate 2, and the vanadium dioxide 4 is located at the terminal of the Jerusalem cross structure 3.

[0095] In summary, with the help of the above technical solutions of the present invention, the double-layer transmission terahertz Huygens metasurface control method and metasurface proposed by the present invention innovatively combine phase change materials, so that the metasurface unit with a single function can show different characteristics in different states, and compared with the single metasurface unit structure, a very meaningful exploration is made in the dynamic terahertz beam control method, which increases the efficiency of control. The present invention adds vanadium dioxide 4 to the bottom terminal of the metasurface unit, which can realize the high modulation depth conversion of beam transmission and reflection by temperature control, and realizes the terahertz beam focusing effect with a focal length of 2 cm for 2-bit and 3-bit pixels by designing different geometric dimensions and relative positions of the structure.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-layer transmission terahertz Huygens metasurface control method, characterized in that: The control method includes: Obtain arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, perform phase result simulation operation based on the arm length parameters, and determine the phase resolution of the metasurface according to the simulation results; The metasurface phase analysis and data analysis modeling technology is used to analyze the distribution of discrete phase setting values ​​on the metasurface, and the metasurface terahertz beam focusing control is performed based on the distribution results.

2. A double-layer transmission terahertz Huygens metasurface control method according to claim 1, characterized in that: The step of obtaining arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, and performing a phase result simulation operation based on the arm length parameters, and determining the phase resolution of the metasurface according to the simulation results includes: Obtain arm length parameters of the cross structure and the Jerusalem cross structure of the metasurface, and collect the terminal length of the Jerusalem cross structure; According to the simulation operation requirements, the terminal length is kept unchanged, the arm length parameters are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is determined according to the phase change; According to the simulation operation requirements, the arm length parameters of the Jerusalem cross structure are kept unchanged, the arm length parameters of the cross structure and the terminal length are adjusted, the phase change of the metasurface is analyzed based on the adjustment and simulation results, and the transmission coefficient amplitude is determined according to the phase change; The optical path of electromagnetic waves from various positions on the metasurface to any position is analyzed according to the phase change and the superlens. The focusing state is analyzed using the optical path results to obtain the focal length. The phase resolution requirement relationship of the metasurface is set based on the focal length and the Fermat principle.

3. A double-layer transmission terahertz Huygens metasurface control method according to claim 2, characterized in that: The phase resolution requirement relationship is: In the formula, represents the phase difference, x and y represent the lateral center distance and longitudinal center distance from any point on the metasurface to the metasurface, λ represents the wavelength of the incident electromagnetic wave in free space, f represents the focal length, Indicates the correction phase.

4. A double-layer transmission terahertz Huygens metasurface control method according to claim 3, characterized in that: The method of analyzing the distribution of discrete phase setting values ​​on the metasurface by using metasurface phase analysis and data analysis modeling technology, and performing metasurface terahertz beam focusing control processing based on the distribution results includes: Set the focal length and wavelength of the incident electromagnetic wave in free space, as well as the metasurface period and array size, and write the code using data analysis modeling techniques and metasurface phase resolution requirements; The distribution of discrete phase thresholds on the metasurface is analyzed using codes and set numerical values, and the theoretical distribution of discrete phases is obtained based on the distribution. Constructing a simulated metasurface structure at the same position as the electromagnetic field simulation software, and using data analysis modeling technology and the electromagnetic field simulation software to translate the simulated metasurface structure to a position corresponding to the discrete phase theory distribution, to obtain a constructed superlens array; The beam focusing situation is analyzed according to the superlens array and electromagnetic field simulation software, and the phase range is adjusted based on the analysis results to perform metasurface terahertz beam focusing control processing.

5. A double-layer transmission terahertz Huygens metasurface control method according to claim 4, characterized in that: The process of analyzing the beam focusing condition according to the superlens array and the electromagnetic field simulation software and adjusting the phase range based on the analysis result to perform the metasurface terahertz beam focusing control processing includes: Based on the superlens array, dual electric and dual magnetic boundary conditions are set in the electromagnetic field simulation software, and the waveguide port is set with a linearly polarized plane wave for simulation operation, and the beam focusing of the beam transmission superlens array is observed; According to beam focusing, the arm lengths of the cross structure and the Jerusalem cross structure of the metasurface are regulated, the phase range is expanded using the regulated arm lengths, and the discrete phase is changed based on the phase range expansion result to increase the number of simulated metasurface structures; The added results are used to regenerate the superlens array, which is combined with electromagnetic field simulation software to analyze the beam focusing situation and complete the control processing of the metasurface terahertz beam focusing.

6. A double-layer transmission terahertz Huygens metasurface control method, characterized in that: The control method includes: Obtain the ambient temperature of the metasurface, change the properties of vanadium dioxide based on the ambient temperature results, connect the Jerusalem cross structure to form Huygens conditions according to the state results, and regulate the transmission state of the metasurface; Initialize the conductivity of vanadium dioxide, analyze the action state of vanadium dioxide based on the conductivity, and combine the action state with numerical simulation technology to determine the switching trend of the projection and reflection states of the metasurface to perform metasurface control operations.

7. A double-layer transmission terahertz Huygens metasurface control method according to claim 6, characterized in that: Initializing the conductivity of vanadium dioxide, analyzing the action state of vanadium dioxide based on the conductivity, and combining the action state with numerical simulation technology to determine the switching trend of the projection and reflection states of the super surface to perform the super surface control operation includes: Initializing the conductivity of vanadium dioxide, determining the transmission state of the metasurface, and recording the transmission coefficient amplitude and absorption amplitude of the metasurface based on the transmission state as the action state of vanadium dioxide; The conductivity of vanadium dioxide is gradually increased based on numerical simulation technology, and the transmission change trend of the metasurface is determined during the increase process. The transmission coefficient amplitude and absorption amplitude are analyzed using the transmission change trend. Based on the analysis results and the transmission change trend, the switching trend of the metasurface projection and reflection states is determined, and the switching trend is used to change the conductivity of vanadium dioxide to perform metasurface regulation operations.

8. The double-layer transmission terahertz Huygens metasurface control method according to claim 7, characterized in that: When the conductivity of the vanadium dioxide is 0 Siemens, the reflection and absorption amplitudes of the metasurface are both 0.2, and the projection coefficient amplitude is 0.9; The electrical conductivity of the vanadium dioxide is 1.1×10 5 When Siemens, the reflection and absorption amplitudes of the metasurface are both less than 0.2, and the projection coefficient amplitude is greater than 0.9; The electrical conductivity of vanadium dioxide is 2×10 4 Siemens, the reflection and absorption amplitudes of the metasurface are both 0.25, and the projection coefficient amplitude is 0.

8.

9. A double-layer transmissive terahertz Huygens metasurface, used to implement the control method of the double-layer transmissive terahertz Huygens metasurface according to any one of claims 1 to 5 or claims 6 to 8, characterized in that: The metasurface consists of a cross structure, an ultraviolet quartz substrate, a Jerusalem cross structure and vanadium dioxide.

10. The double-layer transmissive terahertz Huygens metasurface according to claim 9, characterized in that: The thickness of the ultraviolet quartz substrate is 150 micrometers, and the thickness of the vanadium dioxide is 200 nanometers.

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