Frequency-tunable frequency-polarization dual-mode vo2 millimeter wave / terahertz metasurface unit

Abstract

The application discloses a frequency-polarization dual-mode VO2 millimeter wave / terahertz super surface unit with adjustable frequency, mainly solves the problems of single function and uncontrollable of the existing super surface unit, and avoids the problems of complex vanadium dioxide excitation mode and high precision requirement of the existing vanadium dioxide excitation mode. The unit comprises a ground plate (1) and a substrate (2), and the substrate is coated with an open ring (3), a polarization switch (4), a frequency perturbation switch (5) and a discrete patch ring (6) respectively. The polarization switch (4) and the open ring (3) form a complete circular ring, and the outer radius is smaller than the inner radius of the frequency perturbation switch (5). The width range of the discrete patch ring (6) is within the width range of the frequency perturbation switch (5). The application can realize the function of regulating two electromagnetic characteristics by one unit, and can realize the unit function by heating the unit as a whole, and can be used for terahertz communication, millimeter wave communication and 6G communication.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and more specifically relates to a frequency-tunable, frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit in the field of wireless communication technology. This invention can be used in the design of novel dual-mode tunable metasurface units. Background Technology

[0002] Metasurface units are artificially designed subwavelength electromagnetic structures with unique physical properties. The electromagnetic properties of a metasurface unit are determined by both its subwavelength structure and the material. Therefore, different electromagnetic properties and device functions can be generated through structural design and material selection. Besides altering the unit's function by changing its physical structure, there are also methods that utilize special material properties to actively regulate the modal functions of metasurface units by changing the external environment, including temperature, light, and electrical modulation methods. Metasurface designs based on phase change materials (including graphene, liquid crystals, and vanadium dioxide) can simultaneously achieve the modulation of multimodal functional electromagnetic properties. Phase change materials exhibit an intermolecular transition (IMT) characteristic under external excitation, during which their conductivity changes by several orders of magnitude. However, in practical communication applications, to improve the system integration of the transmitter, it is desirable for metasurface units to have multiple tunable functions. Most existing metasurface unit functions lack tunability. Furthermore, to adapt to practical application scenarios, it is desirable for phase change materials to be easily excited. Existing phase change material excitation technologies are relatively complex and not suitable for routine application.

[0003] In their paper "Design and Analysis of a Metasurface Terahertz Dual-Band Linear Polarization Converter" (Laser Optoelectronics. Prog., vol. 60, no. 19, p. 1930002, 2023), Pan Wu et al. disclosed a reflective dual-mode tunable metasurface unit. The artificial metallic microstructure on this metasurface unit consists of nested inner and outer rings. The inner and outer rings, with different structural sizes, have different resonant points and operating bandwidths. Their superposition enables coupling between frequency bands, broadening the operating frequency band and achieving linear polarization conversion of electromagnetic waves within two bands. However, this metasurface unit still has shortcomings. Its function is limited by the fixed metallic structure, lacking tunability and failing to achieve multi-dimensional tunable control of electromagnetic waves.

[0004] Benwen Chen et al. disclosed a vanadium dioxide-based erasable terahertz metasurface unit in their paper "Programmable Terahertz Metamaterials with Non-Volatile Memory" (Laser & Photonics Reviews, vol. 16, no. 4, p. 2100472, Apr. 2022). This metasurface unit has three operating states: when excited by pump light, it is in an "information writing" state; when electrically heated, it is in an "information memory" state; and when it cools naturally to room temperature, the information is erased, restoring the initial state. However, this metasurface unit still has shortcomings. Pump light excitation requires high precision and sophisticated experimental equipment, making it complex for practical applications and lacking the conditions for routine use. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by proposing a frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit. This addresses the problem of existing metasurface units having limited functionality and being untunable. A novel metasurface unit structure is proposed to improve the equivalent conductivity of some structures within the metasurface unit, thus avoiding the problems of complex and high-precision excitation methods required by existing vanadium dioxide excitation methods.

[0006] The underlying concept for achieving the objective of this invention is as follows: The top layer of the metasurface unit is composed of a combination of a metal structure and a vanadium dioxide structure. The metal open ring has a linear polarization conversion function. The activation or deactivation of the vanadium dioxide polarization switch controls the on / off state of the metal open ring. When the vanadium dioxide polarization switch is not activated, the metal open ring operates normally to achieve electromagnetic wave linear polarization conversion. When the vanadium dioxide polarization switch is activated to the metallic state, the two ends of the metal open ring are connected, and the polarization conversion function is shielded. The vanadium dioxide frequency perturbation switch, acting as a perturbation structure, gradually activates the vanadium dioxide frequency perturbation switch, causing the inner ring to maintain its linear polarization conversion state while gradually shifting its operating frequency band. By combining the inner and outer structures, the metasurface unit acts as a polarization conversion switch. By simultaneously activating the inner and outer vanadium dioxide, the metasurface unit generates a polarization conversion effect and shifts its operating frequency band. When the vanadium dioxide is activated to the metallic state, the entire metasurface unit is shielded, losing both its polarization conversion and operating frequency band shifting functions. This achieves the function of controlling two electromagnetic properties with a single metasurface unit. This solves the problem of existing metasurface units having only one function or being unable to adjust their function. The metal embellishment structure consists of several uniformly discrete metal patches symmetrical about the origin. Due to its symmetry about the origin, it has virtually no impact on the overall electromagnetic properties of the metasurface unit. After the vanadium dioxide frequency perturbation switch is embedded in the metal, its equivalent conductivity increases. Compared to the unembedded metal, stimulating the vanadium dioxide frequency perturbation switch at this point yields a higher equivalent conductivity, resulting in a more significant frequency shift effect. In this case, the difference in equivalent conductivity between the inner and outer rings does not require precise partitioned pump light excitation but is generated by the metal embellishment structure itself. Therefore, simply heating the entire metasurface unit to excite the vanadium dioxide is sufficient to achieve the operating frequency shift function of the metasurface unit. This solves the problem in existing technologies where precise pump light excitation of vanadium dioxide is required for the metasurface unit to function properly.

[0007] The metasurface unit of the present invention includes a ground plane and a substrate sequentially coated on the metasurface unit, and an open ring, a polarization switch, a frequency perturbation switch and a discrete patch ring are respectively coated on the substrate.

[0008] The polarization switch is located on the opening of the open ring, filling the space at the opening of the open ring to form a complete ring. The outer radius of the ring is smaller than the inner radius of the frequency perturbation switch, R1+R2<R3, where R1 is the inner radius of the ring formed by the open ring and the polarization switch, R2 is the width of the ring formed by the open ring and the polarization switch, and R3 is the inner radius of the frequency perturbation switch.

[0009] The polarization switch and the outer ring perturbation switch are made of vanadium dioxide.

[0010] The discrete patch ring is composed of multiple patches, all of which are evenly distributed at equal intervals and are symmetrical about the center point of the top surface of the substrate.

[0011] The discrete patch ring passes through and is partially embedded in the frequency perturbation switch, and the width of the discrete patch ring does not exceed the width of the frequency perturbation switch.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] First, this invention employs vanadium dioxide as the material in the polarization switch and outer ring perturbation switch structures. Utilizing the variable conductivity of vanadium dioxide, it achieves simultaneous control of the polarization and resonant frequency of electromagnetic waves (i.e., the operating frequency of the metasurface unit), realizing the function of controlling two electromagnetic properties with a single metasurface unit. This overcomes the shortcomings of existing metasurface units, which often have only one function or are not adjustable, giving this invention the advantage of being able to control both the polarization and resonant frequency of electromagnetic waves.

[0014] Secondly, this invention features a discrete patch ring structure, which enhances the equivalent conductivity of certain parts of the metasurface unit. This allows the metasurface unit to function simply by heating the entire metasurface unit to excite the vanadium dioxide. This overcomes the limitations of existing technologies that require precise pump light irradiation of the vanadium dioxide to function properly. This invention enables the normal functioning of the metasurface unit by heating the entire metasurface unit to excite the vanadium dioxide. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the metasurface unit structure in the millimeter-wave band of Embodiment 1 of the present invention;

[0016] Figure 2 This is a top view of the metasurface unit in the millimeter-wave band of Embodiment 1 of the present invention;

[0017] Figure 3 This is a schematic diagram of the metasurface unit structure in the terahertz band of Embodiment 2 of the present invention;

[0018] Figure 4 This is a top view of the metasurface unit in the terahertz band of Embodiment 2 of the present invention;

[0019] Figure 5 The simulation curve of the polarization conversion rate (PCR) as a function of frequency and vanadium dioxide conductivity in Example 1 of the present invention is shown.

[0020] Figure 6 This is a simulation curve of the polarization conversion rate PCR as a function of frequency and vanadium dioxide conductivity in Example 2 of the present invention;

[0021] Figure 7 This is a schematic diagram of the metasurface unit structure used in simulation experiment 3 of the present invention to verify the effect of discrete patch ring 6 on improving the equivalent conductivity of frequency perturbation switch 5 in the millimeter-wave band.

[0022] Figure 8 This is a top view of the metasurface unit used in simulation experiment 3 of this invention to verify the effect of the discrete patch ring 6 on the equivalent conductivity of the frequency perturbation switch 5 in the millimeter-wave band.

[0023] Figure 9 This is a simulation curve of the polarization conversion rate PCR as a function of frequency and vanadium dioxide conductivity in simulation experiment 3 of this invention.

[0024] Figure 10 This is a schematic diagram of the metasurface unit structure used in simulation experiment 4 of the present invention to verify the effect of the discrete patch ring 6 on the equivalent conductivity of the frequency perturbation switch 5 in the terahertz band.

[0025] Figure 11 This is a top view of the metasurface unit used in simulation experiment 4 of this invention to verify the effect of the discrete patch ring 6 on the equivalent conductivity of the frequency-enhancing perturbation switch 5 in the terahertz band.

[0026] Figure 12 This is a simulation curve of the polarization conversion rate PCR as a function of frequency and vanadium dioxide conductivity in simulation experiment 4 of this invention. Detailed Implementation

[0027] The present invention relates to a frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit, comprising a ground plane 1, a substrate 2, and an open ring 3, a polarization switch 4, a frequency perturbation switch 5, and a discrete patch ring 6 coated on the substrate 2.

[0028] The polarization switch 4 is located on the opening of the open ring 3, filling the space at the opening of the open ring 3 to form a complete ring. The outer radius of the ring is smaller than the inner radius of the frequency perturbation switch 5, R1+R2<R3, where R1 is the inner radius of the ring formed by the open ring 3 and the polarization switch 4, R2 is the width of the ring formed by the open ring 3 and the polarization switch 4, and R3 is the inner radius of the frequency perturbation switch 5.

[0029] The polarization switch 4 and the frequency perturbation switch 5 are made of vanadium dioxide.

[0030] The discrete patch ring 6 is composed of multiple patches, all of which are evenly distributed at equal intervals and are symmetrical about the center point of the top surface of the substrate 2.

[0031] The discrete patch ring 6 passes through and is partially embedded in the frequency perturbation switch 5, and the width of the discrete patch ring 6 does not exceed the width of the frequency perturbation switch 5.

[0032] The thickness t1 of the floor 1, the open ring 3, and the discrete patch ring 6 is equal in the millimeter-wave band and the terahertz band, and is the same as the thickness of the polarization switch 4 and the frequency perturbation switch 5, satisfying 0.2μm≤t1≤0.4μm.

[0033] The floor 1, open ring 3, and discrete patch ring 6 all employ conductivity σ > 1 × 10⁻⁶ in both the millimeter-wave and terahertz frequency bands. 7 Metallic materials with S / m.

[0034] The substrate 2 is square in both the millimeter-wave and terahertz frequency bands, and is made of any one of silicon, quartz, alumina, sapphire, or polyimide.

[0035] The width L of the substrate 2 in the millimeter-wave band is: 2(R3+R4)<L<4R1, and its thickness H<1mm.

[0036] The width L of the substrate 2 in the terahertz band is: 2(R3+R4)<L<4R1, and its thickness H<0.1mm.

[0037] The outer radius of the open ring 3 in the millimeter-wave and terahertz frequency bands is R1+R2<R3, R1≈0.1λ, the rotation angle φ satisfies 40°<φ<50°, and the opening angle α satisfies 70°<α<80°; where R2 is the width of the open ring 3, R3 is the inner radius of the frequency perturbation switch 5, and λ is the wavelength of the unit's working center frequency.

[0038] The polarization switch 4 and the frequency perturbation switch 5 are made of vanadium dioxide in the millimeter-wave and terahertz frequency bands, respectively, and their thickness t1 satisfies 0.2μm≤t1≤0.4μm.

[0039] The frequency perturbation switch 5 has an inner radius R3 < R5, an outer radius R5 + R6 < R3 + R4 < 0.5L, and an opening angle of 140° < α1 < 160° in the millimeter wave and terahertz bands, where R4 is the width of the frequency perturbation switch 5, R5 is the inner radius of the discrete patch ring 6, and R6 is the width of the discrete patch ring 6.

[0040] The overall shape of the discrete patch ring 6 can be any shape among circles and rectangles, and the shape of the patch can be any shape among arcs, rectangles, and circles.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] The present invention has two embodiments. The metasurface unit of Embodiment 1 operates in the millimeter-wave band, and the metasurface unit of Embodiment 2 operates in the terahertz band.

[0043] Example 1: Simulation of metasurface units operating in the millimeter-wave band.

[0044] Reference Figure 1 The overall diagram of the metasurface unit is shown below, which further describes the metasurface unit structure of Embodiment 1 of the present invention.

[0045] The metasurface unit of Embodiment 1 of the present invention includes a ground plane 1 and a substrate 2 sequentially coated on the metasurface unit. An open ring 3, a polarization switch 4, a frequency perturbation switch 5, and a discrete patch ring 6 are respectively coated on the substrate 2.

[0046] The polarization switch 4 is located at the opening of the open ring 3, forming a complete circle with the open ring 3. The outer radius of the circle formed by the polarization switch 4 and the open ring 3 is smaller than the inner radius of the frequency perturbation switch 5. The inner radius of the discrete patch ring 6 is slightly larger than the inner radius of the frequency perturbation switch 5, and the outer radius of the discrete patch ring 6 is slightly smaller than the outer radius of the frequency perturbation switch 5. The polarization switch and the outer ring perturbation switch are made of vanadium dioxide.

[0047] Figure 1 The light yellow cube is floor 1, located at the bottom of the metasurface unit. Its width L = 3500 μm and height 0.2 μm is made of metallic silver.

[0048] exist Figure 1 The gray semi-transparent cube in the middle layer of the metasurface unit is the substrate 2. It has the same width as the floor 1 and a height H = 600 μm. It is made of quartz.

[0049] Reference Figure 2 The top view of the metasurface unit further describes the metasurface unit structure of Embodiment 1 of the present invention.

[0050] Figure 2 The discrete patch ring 6 located on the outer side is composed of multiple short yellow arc patches. The short yellow arc patches are evenly distributed at fixed intervals of α3 = 5° to form a discrete yellow ring. Each patch in the discrete patch ring 6 covers an angle of α2 = 10°. The number of patches n = 24 in the discrete patch ring 6 is determined by (α2 + α3) * n = 360°. Its inner radius R5 = 1500 μm, width R6 = 100 μm, thickness is 0.2 μm, and the material is metallic silver.

[0051] Figure 2 The red, long, arc-shaped patch located on the outer side is the frequency perturbation switch 5. The part that overlaps with the discrete patch ring 6 is hollowed out. Its inner radius R3 = 1400 μm, width R4 = 300 μm, arc α1 = 150°, thickness 0.2 μm, and material is vanadium dioxide.

[0052] Figure 2 The solid yellow C-shaped open ring located on the inner side is open ring 3. The two ends of open ring 3 are broken at the solid red short arc patch. Its inner radius R1 = 900 μm, width R2 = 300 μm, and rotation angle... The opening angle α = 75°, the thickness is 0.2μm, and the material is metallic silver.

[0053] Figure 2 The solid red arc-shaped patch located on the inner side is the polarization switch 4, situated at the opening of the open ring 3, forming a complete circle with the open ring 3. It has a thickness of 0.2 μm, is made of vanadium dioxide, and has a dielectric constant of [missing value]. =10.7, the conductivity in the insulating state is 10 S / m. When excited by external temperature or laser irradiation, it exhibits a metallic state, with a maximum conductivity of 3 × 10. 5 S / m.

[0054] Example 2: Example 2 of the present invention is a metasurface unit structure operating in the terahertz frequency band.

[0055] Reference Figure 3 The overall diagram of the metasurface unit is shown below, which further describes the metasurface unit structure of Embodiment 2 of the present invention.

[0056] The metasurface unit of Embodiment 2 of the present invention includes a ground plane 1 and a substrate 2 sequentially coated on the metasurface unit. An open ring 3, a polarization switch 4, a frequency perturbation switch 5, and a discrete patch ring 6 are coated on the substrate 2. The polarization switch 4 is located at the opening of the open ring 3, forming a complete ring with the open ring. The outer radius of the ring formed by the polarization switch 4 and the open ring 3 is smaller than the inner radius of the frequency perturbation switch 5. The inner radius of the discrete patch ring 6 is slightly larger than the inner radius of the frequency perturbation switch 5, and the outer radius of the discrete patch ring 6 is slightly smaller than the outer radius of the frequency perturbation switch 5. The polarization switch 4 and the outer ring perturbation switch 5 are made of vanadium dioxide.

[0057] Figure 3 The middle floor 1 is a light yellow cube located at the bottom of the metasurface unit. Its width L = 200 μm and its height is 0.2 μm. It is made of metallic silver.

[0058] Figure 3 The intermediate substrate 2 is a gray semi-transparent cube located in the middle layer of the metasurface unit. Its width is the same as that of the ground plane 1, and its height H = 35 μm. It is made of quartz.

[0059] Reference Figure 4 The top view of the metasurface unit further describes the metasurface unit structure of Embodiment 2 of the present invention.

[0060] Figure 4 The outermost discrete patch ring 6 is composed of multiple short yellow arc patches, which are evenly distributed at fixed intervals of α3 = 5° to form a discrete yellow ring. Each patch in the discrete patch ring 6 covers an angle of α2 = 10°. The number of patches in the discrete patch ring 6, n = 24, is determined by (α2 + α3) * n = 360°. Its inner radius R5 = 85 μm, width R6 = 10 μm, thickness 0.2 μm, and material is metallic silver.

[0061] Figure 4 The red, long, arc-shaped patch located on the outer side is the frequency perturbation switch 5. The part that overlaps with the discrete patch ring 6 is hollowed out. Its inner radius R3 = 80 μm, width R4 = 20 μm, arc α1 = 150°, thickness 0.2 μm, and material is vanadium dioxide.

[0062] Figure 4 The solid yellow C-shaped open ring located on the inner side is open ring 3. The two ends of open ring 3 are broken at the solid red short arc patch. Its inner radius R1 = 55 μm, width R2 = 15 μm, and rotation angle... The opening angle α = 75°, the thickness is 0.2μm, and the material is metallic silver.

[0063] Figure 4 The solid red short arc-shaped patch located on the inner side is the polarization switch 4, situated at the opening of the open ring 3, forming a complete ring with the open ring 3. It has a thickness of 0.2 μm, is made of vanadium dioxide, and has a dielectric constant of [missing value]. =10.7, the conductivity in the insulating state is 10 S / m. When excited by external temperature or laser irradiation, it exhibits a metallic state, with a maximum conductivity of 3 × 10. 5 S / m.

[0064] The technical effects of the present invention will be further explained below with reference to simulation experiments.

[0065] 1. Simulation experimental conditions:

[0066] The software platform for the simulation experiment of this invention is: Windows 10 operating system and commercial simulation software HFSS_21.1.

[0067] 2. Simulation content and result analysis:

[0068] The present invention includes four simulation experiments, wherein simulation experiment 1 is the simulation result of Example 1, simulation experiment 2 is the simulation result of Example 2, simulation experiment 3 is a control experiment of simulation experiment 1, and simulation experiment 4 is a control experiment of simulation experiment 2.

[0069] Simulation Experiment 1 of this invention models and simulates the polarization conversion rate (PCR) of the metasurface unit of this invention in the millimeter-wave frequency band.

[0070] The simulation experiment 1 of this invention uses a Floquet port for simulation. Two pairs of master-slave boundaries are set to surround the metasurface unit of this invention. The simulation center frequency is set to 30 GHz, the maximum number of iterations is 20, the convergence accuracy is 0.02, the frequency sweep range is 20 GHz to 35 GHz, and the frequency sweep step size is 0.2 GHz.

[0071] Simulation Experiment 1 of this invention uses the metasurface unit structure described in Embodiment 1 of this invention. In the simulation, the conductivity σ1 of the polarization switch and the conductivity σ2 of the frequency polarization switch are set to four values: 1, 30000, 60000, and 300000, respectively. The polarization conversion efficiency (PCR) under the four conductivity conditions is plotted as follows: Figure 5 The four curves shown.

[0072] Simulation Experiment 2 of this invention models and simulates the polarization conversion rate (PCR) of the metasurface unit of this invention in the terahertz frequency band.

[0073] The simulation experiment 2 of this invention uses a Floquet port for simulation. Two pairs of master-slave boundaries are set to surround the metasurface unit of this invention. The simulation center frequency is set to 475 GHz, the maximum number of iterations is 20, the convergence accuracy is 0.02, the frequency sweep range is 350 GHz to 600 GHz, and the frequency sweep step size is 2.5 GHz.

[0074] Simulation Experiment 2 of this invention uses the metasurface unit structure described in Embodiment 2 of this invention. In the simulation, the conductivity σ1 of the polarization switch and the conductivity σ2 of the frequency polarization switch are set to four values: 1, 30000, 60000, and 300000, respectively. The polarization conversion efficiency (PCR) under the four conductivity conditions is plotted as follows: Figure 6 The four curves shown.

[0075] Simulation experiment 3 of this invention verifies whether the discrete patch ring 6 of the metasurface unit of this invention has the effect of improving the equivalent conductivity of the frequency perturbation switch 5 in the millimeter wave frequency band.

[0076] The overall structure and top-view structure of the metasurface unit used in simulation experiment 3 of this invention are as follows: Figure 7 and Figure 8 As shown, the discrete patch ring 6 was removed from the metasurface unit structure of Example 1, and the hollowed-out part of the frequency perturbation switch 5 was filled in. The purpose was to verify whether the discrete patch ring 6 of the metasurface unit can improve the equivalent conductivity of the frequency perturbation switch 5 in the millimeter-wave band.

[0077] In the simulation experiment, the conductivity σ1 of the polarization switch was set to four values: 1, 30000, 60000, and 300000. The conductivity σ2 of the frequency polarization switch was set to four values: 1000, 60000, 130000, and 350000. σ1 and σ2 were assigned one-to-one correspondences in sequence. The polarization conversion efficiency (PCR) under the four conductivity conditions was plotted together with the results of simulation experiment 1 as shown in the figure. Figure 9 The eight curves shown.

[0078] Simulation experiment 4 of this invention verifies whether the discrete patch ring 6 of the metasurface unit of this invention has the effect of improving the equivalent conductivity of the frequency perturbation switch 5 in the terahertz frequency band.

[0079] The overall structure and top-view structure of the metasurface unit used in simulation experiment 4 of this invention are as follows: Figure 10 and Figure 11 As shown, the discrete patch ring 6 was removed from the metasurface unit structure of Example 2, and the hollowed-out part of the frequency perturbation switch 5 was filled in. The purpose was to verify whether the discrete patch ring 6 of the metasurface unit played a role in improving the equivalent conductivity of the frequency perturbation switch 5 in the terahertz band.

[0080] In the simulation, the conductivity σ1 of the polarization switch was set to four values: 1, 30000, 60000, and 300000. The conductivity σ2 of the frequency polarization switch was set to four values: 5000, 40000, 100000, and 320000. σ1 and σ2 were assigned one-to-one correspondences in sequence. The polarization conversion efficiency (PCR) results for the four conductivity values ​​were plotted together with the results from simulation experiment 2 as shown in the figure. Figure 12 The eight curves shown.

[0081] The effects of the present invention will be further described below with reference to simulation results.

[0082] Figure 5 The figure shows the simulation results of simulation experiment 1. The horizontal axis represents frequency in GHz, the vertical axis represents PCR, the scale ranges from 0 to 1, and the curves show the changes in PCR with frequency and vanadium dioxide conductivity. σ1 and σ2 are the conductivity of the polarization switch and the frequency perturbation switch, respectively.

[0083] Depend on Figure 5 As can be seen, with the effective working range of polarization conversion rate PCR ≥ 0.8 as the standard, in the simulation results of Example 1 of this invention, as the conductivity of vanadium dioxide increases, the working frequency band shifts to lower frequencies, from 28.94 GHz to 31.58 GHz to 25.61 GHz to 26.92 GHz, and reaches a minimum of 25.29 GHz to 26.47 GHz. When vanadium dioxide reaches its maximum conductivity, the metasurface unit is completely shielded and loses its polarization conversion function.

[0084] Depend on Figure 5 As can be seen, compared with the frequency-polarization modulation metasurface units disclosed in the prior art, the metasurface unit designed in this invention has the function of polarization conversion in the millimeter-wave band and the operating frequency can be adjusted within a certain range, overcoming the shortcomings of existing metasurface units that have single function and non-adjustable operating frequency.

[0085] The prior art refers to:

[0086] Pan Wu et al. proposed a reflective dual-mode tunable metasurface unit in their paper “Design and Analysis of Metasurface Terahertz Dual-Band Linear Polarization Converter” (Laser Optoelectronics.Prog., vol.60, no.19, p.1930002, 2023).

[0087] Figure 6 The figure shows the simulation results of simulation experiment 2. The horizontal axis represents frequency in GHz, the vertical axis represents PCR, the scale is from 0 to 1, the curve is the curve of PCR as a function of frequency and vanadium dioxide conductivity, and σ1 and σ2 are the conductivity of polarization switch and frequency perturbation switch, respectively.

[0088] Depend on Figure 6 As can be seen, with the effective working range of polarization conversion rate PCR ≥ 0.8 as the standard, in the simulation results of simulation experiment 2 of this invention, as the conductivity of vanadium dioxide increases, the working frequency band shifts to lower frequencies, from 525.54 GHz to 481.06 GHz to 442.90 GHz to 429.12 GHz, and reaches a minimum of 438.31 GHz to 417.07 GHz. When vanadium dioxide reaches its maximum conductivity, the metasurface unit is completely shielded and loses its polarization conversion function.

[0089] Depend on Figure 6 As can be seen, compared with the frequency-polarization modulation metasurface units disclosed in the prior art, the metasurface unit designed in this invention has the function of polarization conversion in the terahertz band and the operating frequency can be adjusted within a certain range, overcoming the shortcomings of existing metasurface units that have single function and non-adjustable operating frequency.

[0090] The prior art refers to:

[0091] Pan Wu et al. proposed a reflective dual-mode tunable metasurface unit in their paper “Design and Analysis of Metasurface Terahertz Dual-Band Linear Polarization Converter” (Laser Optoelectronics.Prog., vol.60, no.19, p.1930002, 2023).

[0092] Figure 9The solid curve in the figure represents the simulation result curve of simulation experiment 3, and the dashed curve represents the simulation result curve of simulation experiment 1. The horizontal axis represents frequency in GHz, and the vertical axis represents PCR (partial conductivity), with a scale from 0 to 1. The curves show the variation of PCR with frequency and vanadium dioxide conductivity in different zones. σ1 and σ2 represent the conductivity of the polarization switch and the frequency perturbation switch, respectively. Simulations were performed with different conductivity settings for the polarization switch and the frequency perturbation switch, with the frequency perturbation switch having a higher conductivity. The difference in conductivity settings between the two switches was used to simulate and verify whether the discrete patch ring improves the conductivity of the frequency perturbation switch under the overall heating condition of the metasurface unit. The results of simulation experiment 3 were compared with those of simulation experiment 1 to verify whether the discrete patch ring improves the equivalent conductivity of the frequency perturbation switch.

[0093] Depend on Figure 9 As can be seen, the solid and dashed lines largely coincide, proving that the discrete patch ring improves the equivalent conductivity of the frequency perturbation switch. This allows the frequency perturbation switch to have a higher equivalent conductivity when the entire metasurface unit is heated. Heating the entire metasurface unit can differentially excite vanadium dioxide to achieve different conductivities, thereby realizing the function of shifting the operating frequency. Compared with the vanadium dioxide excitation methods disclosed in the prior art, the metasurface unit of this invention only requires heating the entire metasurface unit to achieve the frequency shifting function, overcoming the shortcomings of existing vanadium dioxide excitation methods which require complex and precise equipment such as accurate pump illumination.

[0094] The prior art refers to:

[0095] Benwen Chen et al. proposed a method for vanadium dioxide to be excited by pump light in their paper “Programmable Terahertz Metamaterials with Non-Volatile Memory” (Laser & Photonics Reviews, vol. 16, no. 4, p. 2100472, Apr. 2022).

[0096] Figure 12The solid line curve represents the simulation result curve of simulation experiment 4, and the dashed line curve represents the simulation result curve of simulation experiment 2. The horizontal axis represents frequency in GHz, and the vertical axis represents PCR (partial conductivity), with a scale from 0 to 1. The curves show the variation of PCR with frequency and vanadium dioxide conductivity. Different conductivity levels were set for the polarization switch and the frequency perturbation switch, with the frequency perturbation switch exhibiting higher conductivity, and simulations were performed. The difference in conductivity between the two switches was to simulate and verify whether the discrete patch ring improves the conductivity of the frequency perturbation switch under the overall heating condition of the metasurface unit. The results of simulation experiment 4 were compared with those of simulation experiment 2 to verify whether the discrete patch ring improves the equivalent conductivity of the frequency perturbation switch.

[0097] Depend on Figure 12 As can be seen, the solid and dashed lines largely overlap, proving that the discrete patch ring improves the equivalent conductivity of the frequency perturbation switch. The frequency perturbation switch exhibits higher equivalent conductivity when the entire metasurface unit is heated. Heating the entire metasurface unit allows for differential excitation of vanadium dioxide, resulting in different conductivities and thus enabling frequency shifting. Compared to existing vanadium dioxide excitation methods, the metasurface unit designed in this invention only requires heating the entire metasurface unit to achieve frequency shifting, overcoming the shortcomings of existing vanadium dioxide excitation techniques that require complex and precise pump illumination equipment.

[0098] The prior art refers to:

[0099] Benwen Chen et al. proposed a method for vanadium dioxide to be excited by pump light in their paper “Programmable Terahertz Metamaterials with Non-Volatile Memory” (Laser & Photonics Reviews, vol. 16, no. 4, p. 2100472, Apr. 2022).

Claims

1. A frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit, comprising a ground plane (1), a substrate (2), and an open ring (3), a polarization switch (4), a frequency perturbation switch (5), and a discrete patch ring (6) coated on the substrate (2), characterized in that: The polarization switch (4) is located on the opening of the open ring (3), filling the space at the opening of the open ring (3) to form a complete ring. The outer radius of the ring is smaller than the inner radius of the frequency perturbation switch (5), R1+R2<R3, R1 is the inner radius of the ring formed by the open ring (3) and the polarization switch (4), R2 is the width of the ring formed by the open ring (3) and the polarization switch (4), and R3 is the inner radius of the frequency perturbation switch (5). The polarization switch (4) and the frequency perturbation switch (5) are made of vanadium dioxide. The discrete patch ring (6) is composed of multiple patches, all of which are evenly distributed at equal intervals and are symmetrical about the center point of the top surface of the substrate (2). The discrete patch ring (6) passes through and is partially embedded in the frequency perturbation switch (5), and the width of the discrete patch ring (6) does not exceed the width of the frequency perturbation switch (5).

2. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The thickness t1 of the floor (1), the open ring (3), and the discrete patch ring (6) is equal in the millimeter-wave band and the terahertz band, and is the same as the thickness of the polarization switch (4) and the frequency perturbation switch (5), satisfying 0.2μm≤t1≤0.4μm.

3. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The floor (1), open ring (3), and discrete patch ring (6) all employ conductivity σ > 1 × 10⁻⁶ in both the millimeter-wave and terahertz frequency bands. 7 Metallic materials with S / m.

4. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The substrate (2) is square in both the millimeter-wave and terahertz frequency bands, and is made of any one of silicon, quartz, alumina, sapphire, or polyimide.

5. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The width L of the substrate (2) in the millimeter wave band is: 2(R3+R4)<L<4R1, and its thickness H<1mm.

6. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The width L of the substrate (2) in the terahertz band is: 2(R3+R4)<L<4R1, and its thickness H<0.1mm.

7. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The outer radius of the open ring (3) in the millimeter wave band and the terahertz band is R1+R2<R3, R1≈0.1λ, the rotation angle φ satisfies 40°<φ<50°, and the opening angle α satisfies 70°<α<80°; where R2 is the width of the open ring (3), R3 is the inner radius of the frequency perturbation switch (5), and λ is the wavelength of the unit's working center frequency.

8. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The polarization switch (4) and the frequency perturbation switch (5) are made of vanadium dioxide in the millimeter wave band and the terahertz band, and their thickness t1 satisfies 0.2μm≤t1≤0.4μm.

9. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The frequency perturbation switch (5) has an inner radius R3 < R5, an outer radius R5 + R6 < R3 + R4 < 0.5L, and an opening angle of 140° < α1 < 160° in the millimeter wave band and terahertz band. R4 is the width of the frequency perturbation switch (5), R5 is the inner radius of the discrete patch ring (6), and R6 is the width of the discrete patch ring (6).

10. The frequency-tunable frequency-polarized dual-mode VO2 millimeter-wave / terahertz metasurface unit according to claim 1, characterized in that, The overall shape of the discrete patch ring (6) can be any shape among circles and rectangles, and the shape of the patch can be any shape among arcs, rectangles, and circles.

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