Terahertz waveband chiral metasurface vortex focusing lens and terahertz dimming device

Abstract

The present application relates to the field of vortex beam modulation, and particularly discloses a chiral metasurface vortex focusing lens in a terahertz wave band and a terahertz light modulation device, comprising a substrate and a vortex focusing phase wave surface arranged on the substrate; the vortex focusing phase wave surface comprises array-arranged polarizing units, each of the polarizing units comprising a first strip-shaped column, a second strip-shaped column and a connecting column; the first strip-shaped column and the second strip-shaped column are parallel to each other, the connecting point of the connecting column and the first strip-shaped column is closer to the first direction end of the first strip-shaped column, and the connecting point of the connecting column and the second strip-shaped column is closer to the second direction end of the second strip-shaped column; the present application occupies a small space, is easy to integrate, has a low production material cost, shortens the path of terahertz waves in the chiral metasurface vortex focusing lens, reduces the loss in the modulation process, and can obtain a large circular dichroism through normal incidence or oblique incidence of circularly polarized light.

Description

Technical Field

[0001] This invention relates to the field of vortex beam modulation, and in particular to a chiral metasurface vortex focusing lens and a terahertz dimming device in the terahertz band. Background Technology

[0002] A vortex beam is a beam of light carrying an optical vortex and having an exp(imφ) phase distribution. Traditional vortex beam generation often relies on bulky and expensive devices, such as spiral phase plates, gratings, crystals, and liquid crystals, to control the polarization state of electromagnetic waves and achieve beam vortices. However, the components used in these methods are large in size and cannot meet the growing demand for device integration and miniaturization. At the same time, the current vortex beam generation devices are large and complex in structure, resulting in high production costs for related equipment. In addition, the long modulation optical path also leads to high losses during the dimming process.

[0003] In summary, how to provide a vortex beam modulation method that occupies little space, is easy to integrate, and takes into account both low cost and low loss is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a chiral metasurface vortex focusing lens and a terahertz dimming device in the terahertz band, so as to solve the problems of small space occupation, high cost and high loss in the existing terahertz band vortex beam modulation device.

[0005] To solve the above-mentioned technical problems, the present invention provides a chiral metasurface vortex focusing lens in the terahertz band, comprising a substrate and a vortex focusing phase wavefront disposed on the substrate;

[0006] The vortex focusing phase wavefront includes an array of polarizing units, each polarizing unit comprising a first strip-shaped column, a second strip-shaped column, and a connecting column.

[0007] The first strip-shaped column and the second strip-shaped column are parallel to each other. The connection point between the connecting column and the first strip-shaped column is closer to the first direction end of the first strip-shaped column, and the connection point between the connecting column and the second strip-shaped column is closer to the second direction end of the second strip-shaped column.

[0008] The inclination direction of the connecting column, the inclination direction of the line connecting the first direction end of the first strip column and the first direction end of the second strip column, and the inclination direction of the line connecting the second direction end of the first strip column and the second direction end of the second strip column are all the same.

[0009] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the first strip column, the second strip column, and the connecting column have the same width.

[0010] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the phase corresponding to the polarizing unit on the vortex focusing phase wavefront is determined by the following formula:

[0011]

[0012] in, λ is the phase of the target polarizing unit, λ is the incident wavelength of the terahertz wave to be tuned, f is the focal length, r is the distance from the target polarizing unit to the center of the vortex focusing phase wavefront, l is the integer of the preset orbital angular momentum state, and θ is the polar coordinate angle from the target polarizing unit to the center of the vortex focusing phase wavefront.

[0013] Optionally, in the aforementioned chiral metasurface vortex focusing lens in the terahertz band, the method for obtaining the equivalent refractive index and impedance of the vortex focusing phase wavefront includes:

[0014] Obtain the transmission coefficient and reflection coefficient of the vortex-focused phase wavefront;

[0015] The equivalent refractive index and impedance are determined by S-parameter inversion based on the transmission coefficient and the reflection coefficient.

[0016] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the width of the first strip column, the second strip column, and the connecting column ranges from 19 micrometers to 21 micrometers, including the endpoint values.

[0017] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the distance between the first strip column and the second strip column ranges from 3 micrometers to 43 micrometers, including the endpoint value.

[0018] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the angle between the connecting column and the vertical direction ranges from 5 degrees to 30 degrees, including the endpoint value.

[0019] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the lengths of the first strip column and the second strip column range from 20 micrometers to 68 micrometers, including the endpoint values.

[0020] Optionally, in the terahertz band chiral metasurface vortex focusing lens, the vortex focusing phase wavefront is an all-silicon structure obtained by etching.

[0021] A terahertz dimming device, the terahertz dimming device comprising a chiral metasurface vortex focusing lens in the terahertz band as described in any of the above.

[0022] The terahertz-band chiral metasurface vortex focusing lens provided by this invention includes a substrate and a vortex focusing phase wavefront disposed on the substrate; the vortex focusing phase wavefront includes an array of polarizing units, each polarizing unit including a first strip-shaped pillar, a second strip-shaped pillar, and a connecting pillar; the first strip-shaped pillar and the second strip-shaped pillar are parallel to each other, the connection point between the connecting pillar and the first strip-shaped pillar is closer to the first direction end of the first strip-shaped pillar, and the connection point between the connecting pillar and the second strip-shaped pillar is closer to the second direction end of the second strip-shaped pillar; the tilt direction of the connecting pillar, the tilt direction of the line connecting the first direction end of the first strip-shaped pillar and the first direction end of the second strip-shaped pillar, and the tilt direction of the line connecting the second direction end of the first strip-shaped pillar and the second direction end of the second strip-shaped pillar are all the same.

[0023] This invention utilizes a chiral metasurface structure as a vortex focusing lens to modulate terahertz vortex beams. The chiral metasurface structure occupies little space, is easy to integrate, has low material costs, and is significantly thinner than other types of dimming devices. This shortens the path of the terahertz wave through the chiral metasurface vortex focusing lens, reducing losses during modulation. It also achieves high circular dichroism by using either normal or oblique incident circularly polarized light. This invention also provides a terahertz dimming device with the aforementioned advantages. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0026] Figure 2 A partial structural orientation schematic diagram of a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0027] Figure 3 A partial structural schematic diagram of a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0028] Figure 4 A schematic diagram of electric field focusing for a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0029] Figure 5 A schematic diagram of the phase arrangement of a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention.

[0030] Figure 6 A schematic diagram of electric field focusing for another specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0031] Figure 7 A schematic diagram of the phase arrangement of another specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention.

[0032] Figure 8 A schematic diagram of the focusing path of a specific embodiment of the chiral metasurface vortex focusing lens in the terahertz band provided by the present invention;

[0033] In the accompanying drawings of each specification, the reference numerals include: substrate 10, polarizing unit 20, first strip column 21, second strip column 22, connecting column 23, first direction end A, and second direction end B. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The core of this invention is to provide a chiral metasurface vortex focusing lens in the terahertz band, and a schematic diagram of one specific embodiment is shown below. Figure 1 As shown, this is referred to as Specific Implementation Method 1, which includes a substrate 10 and a vortex focusing phase wavefront disposed on the substrate 10;

[0036] The vortex focusing phase wavefront includes an array of polarizing units 20, each polarizing unit 20 including a first strip-shaped column 21, a second strip-shaped column 22, and a connecting column 23.

[0037] The first strip column 21 and the second strip column 22 are parallel to each other. The connection point between the connecting column 23 and the first strip column 21 is closer to the first direction end A of the first strip column 21, and the connection point between the connecting column 23 and the second strip column 22 is closer to the second direction end B of the second strip column 22.

[0038] The inclination direction of the connecting column 23, the inclination direction of the line connecting the first direction end A of the first strip column 21 and the first direction end A of the second strip column 22, and the inclination direction of the line connecting the second direction end B of the first strip column 21 and the second direction end B of the second strip column 22 are all the same.

[0039] It should be noted that the first direction and the second direction in this application are two directions parallel to but opposite to the extension directions of the first strip column 21 and the second strip column 22. Accordingly, end A of the first direction, i.e., the corresponding strip column, is closer to the end facing the first direction in the top view, and end B of the second direction, i.e., the corresponding strip column, is closer to the end facing the second direction in the top view. Please refer to [reference needed]. Figure 2 , Figure 2 This is a schematic diagram of the first direction, the second direction, the first direction end A, and the second direction end B. Of course, the strip column diagram in the figure can be the first strip column 21 or the second strip column 22.

[0040] Specifically, the height of the polarizing unit 20 ( Figure 1 The range of H (represented in the text) is 190 micrometers to 210 micrometers, including endpoint values ​​such as any one of 190.0 micrometers, 202.5 micrometers, or 210.0 micrometers; the range of the grid period of the vortex-focused phase wavefront is 176 micrometers to 184 micrometers, including endpoint values ​​such as any one of 176.0 micrometers, 180.0 micrometers, or 184.0 micrometers.

[0041] The widths of the first strip column 21, the second strip column 22, and the connecting column 23 ( Figure 3 The range of the value (represented by w1) is 19 to 21 micrometers, including endpoint values ​​such as any one of 19.0 micrometers, 20.4 micrometers, or 21.0 micrometers. It should be noted that the widths of the first strip column 21, the second strip column 22, and the connecting column 23 can be the same or different. As a preferred embodiment, the widths of the first strip column 21, the second strip column 22, and the connecting column 23 are the same. Limiting the widths of these three to the same value can greatly simplify the production process and improve production efficiency.

[0042] The distance between the first strip column 21 and the second strip column 22 ( Figure 3 The range of (represented by l1) is from 3 micrometers to 43 micrometers, including endpoint values ​​such as any one of 3.0 micrometers, 23.8 micrometers, or 43.0 micrometers. The spacing between the two columns refers to the distance between the two columns along the vertical direction; correspondingly, the angle between the connecting column 23 and the vertical direction ( Figure 3 The range (denoted by θ) is from 5 degrees to 30 degrees, including endpoint values ​​such as 5.0 degrees, 12.3 degrees, or 30.0 degrees. The vertical direction is perpendicular to both the first and second directions; please refer to [reference needed]. Figure 2

[0043] In addition, the lengths of the first strip column 21 and the second strip column 22 ( Figure 3 (represented by w2 and w3 respectively) ranges from 20 micrometers to 68 micrometers, including endpoint values ​​such as any one of 20.0 micrometers, 46.6 micrometers or 68.0 micrometers.

[0044] It should be noted that the above and various parameter ranges are the optimal ranges obtained after a large number of theoretical calculations and practical tests, under the condition that effective modulation of electromagnetic waves has not been achieved in the terahertz band. In order to achieve vortex focusing in a specific band, the above parameters can be adjusted at the same time, and the optimal combination of each parameter can be determined through practical tests and other methods. Of course, corresponding adjustments can also be made according to the actual situation, which is not limited in this application.

[0045] In a preferred embodiment, the vortex focusing phase wavefront is an all-silicon structure obtained by etching. The all-silicon vortex focusing phase wavefront in this preferred embodiment can be obtained by etching the substrate silicon, which can greatly reduce production costs and provide high production efficiency. At the same time, the all-silicon structure can obtain higher surface transmittance and sensitivity, reduce losses in the dimming process, and further reduce raw material costs by not using technology as the material for the vortex focusing lens.

[0046] This invention proposes a high-efficiency metasurface vortex focusing lens, mainly based on the effective refractive index theory of planar waveguides. It designs a millimeter-wave thickness and a metasurface vortex lens capable of efficient vortex focusing. The designed metasurface vortex lens first converts the incident plane wave into vortex light with arbitrary orbital angular momentum, and then focuses the vortex light at a specified focal length to form an energy ring on the order of wavelength. Since the theoretical mechanism used can make full use of the incident energy other than absorption and reflection, coupled with point-by-point rather than region-by-region phase modulation of the target wavefront, the designed metasurface vortex lens can form an energy ring in the terahertz band.

[0047] The terahertz-band chiral metasurface vortex focusing lens provided by the present invention includes a substrate 10 and a vortex focusing phase wavefront disposed on the substrate 10; the vortex focusing phase wavefront includes an array of polarizing units 20, each polarizing unit 20 including a first strip-shaped pillar 21, a second strip-shaped pillar 22, and a connecting pillar 23; the first strip-shaped pillar 21 and the second strip-shaped pillar 22 are parallel to each other, the connection point of the connecting pillar 23 and the first strip-shaped pillar 21 is closer to the first direction end A of the first strip-shaped pillar 21, and the connection point of the connecting pillar 23 and the second strip-shaped pillar 22 is closer to the second direction end B of the second strip-shaped pillar 22; the tilt direction of the connecting pillar 23, the tilt direction of the line connecting the first direction end A of the first strip-shaped pillar 21 and the first direction end A of the second strip-shaped pillar 22, and the tilt direction of the line connecting the second direction end B of the first strip-shaped pillar 21 and the second direction end B of the second strip-shaped pillar 22 are all the same. This invention uses a chiral metasurface structure as a vortex focusing lens to modulate terahertz vortex beams. The chiral metasurface structure occupies little space, is easy to integrate, has low production material costs, and is much thinner than other types of dimming devices, which shortens the path of the terahertz wave in the chiral metasurface vortex focusing lens and reduces the loss during the modulation process. It can obtain a large circular dichroism by using circularly polarized light that is incident normally or obliquely.

[0048] The terahertz-band chiral metasurface vortex focusing lens of this invention converts incident circularly polarized light into vortex light with arbitrary orbital angular momentum by adjusting the phase value of the polarizing unit 20 in the chiral metasurface array, and focuses it at a specified focal length to form an energy ring in the terahertz band.

[0049] Specifically, the surface of the silicon substrate 10 is divided into a square grid of cells with a grid period P = 180 μm. The polarizing cells 20 have a height H = 200 μm, w1 = 20 μm, w2 = 67 μm, w3 = 67 μm, and l1 = 31 μm. Please refer to the overall structure. Figure 1 and Figure 3 Its characteristics are: it is composed of an all-silicon substrate 10 and all-silicon asymmetric H-shaped nanopillars (i.e., the polarizing unit 20 mentioned above). The nanopillars are arranged in an array on the substrate 10 according to the aforementioned square unit grid. By adjusting the structural dimensions of the H-shaped nanopillars, this invention changes the overall transmission coefficient and reflection coefficient of the polarizing unit 20, thereby controlling the equivalent dielectric constant and permeability of the polarizing unit 20, and thus modulating the phase accumulated by light during propagation in the polarizing unit 20. Generally speaking, the greater the difference in refractive index between the dielectric material and the surrounding environment material, the smaller the thickness of the unit structure can be. Therefore, high refractive index materials can also be used to reduce the thickness of the structure.

[0050] The method for obtaining the equivalent refractive index and impedance of the vortex-focused phase wavefront includes:

[0051] A1: Obtain the transmission coefficient and reflection coefficient of the vortex-focused phase wavefront.

[0052] A2: Based on the transmission coefficient and the reflection coefficient, the equivalent refractive index and impedance are determined by S-parameter inversion.

[0053] S-parameter inversion calculation is highly efficient, the algorithm is mature, and it is highly versatile. Of course, other technical means can also be selected according to the actual situation, and this invention does not limit them.

[0054] The Jones matrix is ​​a physical principle of chirality that reflects the spectral properties of a metasurface, described by its transmission rate and polarization ellipse, mean polarization rotation, and polarization conversion. These vectors can be completely determined by a frequency-dependent Jones matrix, which relates the complex amplitude of the incident wave to the transmitted field. The Jones matrix, also known as the T matrix, fully describes how light is transmitted through the metamaterial plate.

[0055] In the specific design of the metasurface vortex focusing lens, the x and y directions are set as periodic boundaries, and the z direction is set as an open boundary (that is, the thickness of the metasurface vortex focusing lens is not a primary consideration, as the inherent properties of the metasurface vortex focusing lens determine that its thickness is much smaller than that of other lens structures). For a specific implementation method in the x, y, and z directions, please refer to [reference needed]. Figure 1 The effect of plane wave excitation on the electromagnetic response under incident light was observed at the z-boundary near the substrate.

[0056] In Pancharatnam-Berry (PB) phase-based modulation, for example, a 31×31 chiral metasurface array is designed, consisting of a superposition of spherical and helical wavefronts. The helical wavefront is responsible for generating vortex beams with different orbital angular momentum, while the spherical wavefront is responsible for focusing the generated vortex beams to a specific position, forming a high-energy vortex focusing ring.

[0057] In a preferred embodiment, the phase corresponding to the polarizing unit on the vortex focusing phase wavefront is determined by the following formula (1):

[0058]

[0059] in, Let λ be the phase of the target polarizing unit, λ be the incident wavelength of the terahertz wave to be tuned, f be the focal length, r be the distance from the target polarizing unit to the center of the vortex focusing phase wavefront, l be the integer of the preset orbital angular momentum state, and θ be the polar coordinate angle from the target polarizing unit to the center of the vortex focusing phase wavefront. Of course, at this time, the in-plane coordinate +z is the propagation direction.

[0060] After a plane wave is incident perpendicularly onto a metasurface used for spiral focusing, the different field intensity distributions that evolve along the xy direction as the light propagates are shown. The orbital angular momentum number of the vortex beam is set to l = 1, and the focal length is set to f = 6 mm. It can be seen that when the incident light passes through the metasurface array, it is first converted into a vortex beam of the same size as the metasurface, and then focused into an increasingly concentrated ring (focusing effect diagram shown in the figure). Figure 4 In this case, the phase arrangement diagram of a metasurface vortex focusing lens with the expected OAM (orbital angular momentum) spiral mode is as follows: Figure 5 At a focal length of 6mm, when RCP (right-hand circularly polarized light) is incident and LCP (left-hand circularly polarized light) is emitted, the electric field in the xy direction produces a focusing effect; when the orbital angular momentum number of the vortex light is set to l=2, the phase arrangement diagram is as follows. Figure 6 As shown, at a focal length of 6mm in the +z direction, the electric field intensity in the xy direction produces a focusing effect (focusing effect diagram as shown). Figure 7 This indicates that the constructed wavefront phase modulation is very well-developed, resulting in high-quality vortex light, and further verifies the flexibility and advantages of this metasurface in manipulating light. Figure 8 The focusing path diagram for RCP and LCP transmission through the metasurface vortex focusing lens.

[0061] The present invention also provides a terahertz dimming device, the terahertz dimming device comprising a chiral metasurface vortex focusing lens in the terahertz band as described in any of the above. The terahertz-band chiral metasurface vortex focusing lens provided by the present invention includes a substrate 10 and a vortex focusing phase wavefront disposed on the substrate 10; the vortex focusing phase wavefront includes an array of polarizing units 20, each polarizing unit 20 including a first strip-shaped pillar 21, a second strip-shaped pillar 22, and a connecting pillar 23; the first strip-shaped pillar 21 and the second strip-shaped pillar 22 are parallel to each other, the connection point of the connecting pillar 23 and the first strip-shaped pillar 21 is closer to the first direction end A of the first strip-shaped pillar 21, and the connection point of the connecting pillar 23 and the second strip-shaped pillar 22 is closer to the second direction end B of the second strip-shaped pillar 22; the tilt direction of the connecting pillar 23, the tilt direction of the line connecting the first direction end A of the first strip-shaped pillar 21 and the first direction end A of the second strip-shaped pillar 22, and the tilt direction of the line connecting the second direction end B of the first strip-shaped pillar 21 and the second direction end B of the second strip-shaped pillar 22 are all the same. This invention uses a chiral metasurface structure as a vortex focusing lens to modulate terahertz vortex beams. The chiral metasurface structure occupies little space, is easy to integrate, has low production material costs, and is much thinner than other types of dimming devices, which shortens the path of the terahertz wave in the chiral metasurface vortex focusing lens and reduces the loss during the modulation process. It can obtain a large circular dichroism by using circularly polarized light that is incident normally or obliquely.

[0062] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0063] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] The foregoing has provided a detailed description of the chiral metasurface vortex focusing lens and terahertz dimming device in the terahertz band provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A chiral metasurface vortex focusing lens in the terahertz band, characterized in that, Includes a substrate and a vortex-focusing phase wavefront disposed on the substrate; The vortex focusing phase wavefront includes an array of polarizing units, each polarizing unit comprising a first strip-shaped column, a second strip-shaped column, and a connecting column. The first strip-shaped column and the second strip-shaped column are parallel to each other. The connection point between the connecting column and the first strip-shaped column is closer to the first direction end of the first strip-shaped column, and the connection point between the connecting column and the second strip-shaped column is closer to the second direction end of the second strip-shaped column. The inclination direction of the connecting column, the inclination direction of the line connecting the first direction end of the first strip column and the first direction end of the second strip column, and the inclination direction of the line connecting the second direction end of the first strip column and the second direction end of the second strip column are all the same. The line segment from the connection point between the connecting column and the first strip column to the second direction end of the first strip column forms an angle greater than 90 degrees with the connecting column.

2. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The first strip column, the second strip column, and the connecting column have the same width.

3. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The phase of the polarizing unit on the vortex focusing phase wavefront is determined by the following formula: ； in, Let λ be the phase of the target polarizing unit, and λ be the incident wavelength of the terahertz wave to be tuned. Let θ be the focal length, r be the distance from the target polarizing unit to the center of the vortex focusing phase wavefront, l be the integer of the preset orbital angular momentum state, and θ be the polar coordinate angle from the target polarizing unit to the center of the vortex focusing phase wavefront.

4. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The methods for obtaining the equivalent refractive index and impedance of the vortex-focused phase wavefront include: Obtain the transmission coefficient and reflection coefficient of the vortex-focused phase wavefront; The equivalent refractive index and impedance are determined by S-parameter inversion based on the transmission coefficient and the reflection coefficient.

5. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The width of the first strip column, the second strip column, and the connecting column ranges from 19 micrometers to 21 micrometers, including the endpoint values.

6. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The distance between the first strip column and the second strip column ranges from 3 micrometers to 43 micrometers, including the endpoint values.

7. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The angle between the connecting column and the vertical direction ranges from 5 degrees to 30 degrees, including the endpoint values.

8. The chiral metasurface vortex focusing lens in the terahertz band as described in claim 1, characterized in that, The lengths of the first and second strip-shaped columns range from 20 micrometers to 68 micrometers, including the endpoint values.

9. The chiral metasurface vortex focusing lens in the terahertz band as described in any one of claims 1 to 8, characterized in that, The vortex-focused phase wavefront is an all-silicon structure obtained through etching.

10. A terahertz dimming device, characterized in that, The terahertz dimming device includes a chiral metasurface vortex focusing lens in the terahertz band as described in any one of claims 1 to 9.

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