Terahertz wavelength multiplexing focusing lens based on metasurface

Abstract

The invention discloses a terahertz wavelength multiplexing focusing lens based on a metasurface, which relates to the technical field of optical devices, and is characterized in that each metasurface unit of the focusing lens comprises a first dielectric layer, a second antenna layer and a second dielectric layer, when the first antenna layer and the third antenna layer which are orthogonally arranged clamp the second antenna layer, a Fabry-Perot-like resonant cavity is formed; meanwhile, the opening angles of the C-shaped opening resonance rings and the C-shaped groove opening resonance rings in each metasurface unit are different, the C-shaped opening resonance rings can independently regulate and control the transmission phase at the first working wavelength, and the C-shaped groove opening resonance rings can independently regulate and control the transmission phase at the second working wavelength; therefore, independent regulation and control of a plurality of wavelengths can be realized at the same time, regulation and control of 360-degree transmission phases can be covered, the metasurface focusing device can be applied to terahertz wavelengths or other wavelengths or wave bands, and the application range of the metasurface focusing device is expanded.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and in particular to a terahertz wavelength multiplexing focusing lens based on a metasurface. Background Technology

[0002] Currently, numerous revolutionary devices based on metamaterials have been proposed and fabricated to enable various novel applications. For example, the emergence of negative refraction, high-resolution imaging, and photolithography has provided possibilities for innovation in various fields. However, the widespread application of metamaterials is severely limited by some insurmountable difficulties in manufacturing and material loss. The emergence of two-dimensional metasurfaces provides an effective solution to these limitations, which is attributed to their powerful ability to manipulate the wavefront of incident electromagnetic waves at the subwavelength scale. When the local phase distribution of the structural unit is appropriate, the properties of electromagnetic waves can be arbitrarily manipulated based on the generalized Snell's law and the generalized Fresnel equations. This enables electromagnetic waves to have wide applications in many fields, such as waveplates, flat lenses, super holograms, the generation of orbital angular momentum (OAM), and the broadband spin Hall effect.

[0003] Despite the widespread attention and research on metasurfaces, current research aims to achieve optimized performance within a single wavelength. To date, only a few studies have focused on constructing multi-band and broadband devices, including absorbers and polarization converters with fine dispersion management. To meet the development needs of fields such as optical integration, multifunctional detection, and multispectral analysis, metasurfaces capable of realizing different functions in different operating wavelengths are currently required.

[0004] Terahertz waves are electromagnetic waves with frequencies between 0.1 and 10 THz, corresponding to wavelengths of 30 to 3000 μm, falling between millimeter waves and far-infrared waves. The unique spectral position of terahertz waves gives them advantages such as low photon energy, rich spectral information, strong penetration ability, and large bandwidth, making them valuable for applications in communication, sensing, and beam manipulation. However, due to the inherent dielectric constant and permeability of natural materials, traditional transmissive and reflective terahertz functional devices (such as lenses and phase modulators) are usually made of materials such as high-density polyethylene, polytetrafluoroethylene, polymethylpentene, quartz, and sapphire. This results in devices that can usually only operate at a single wavelength or band, making it difficult to apply them at terahertz wavelengths or other wavelengths or bands, thus limiting the high-precision focusing and control of the devices. Summary of the Invention

[0005] This invention provides a terahertz wavelength multiplexing focusing lens based on a metasurface, which can solve the problem in the prior art that the formed devices can usually only work at a single wavelength or band, and are difficult to apply at terahertz wavelengths or other wavelengths or bands.

[0006] This invention provides a terahertz wavelength multiplexing focusing lens based on metasurfaces, comprising multiple alternating metasurface units; The metasurface unit consists of a first antenna layer, a first dielectric layer, a second antenna layer, a second dielectric layer, and a third antenna layer arranged sequentially from bottom to top. The second antenna layer has a circular hole inside, and a C-shaped opening resonant ring is provided inside the circular hole and on the top surface of the first dielectric layer. A C-shaped slot opening resonant ring is provided on the second antenna layer outside the circular hole, and the opening angles of the C-shaped opening resonant ring and the C-shaped slot opening resonant ring are different. The first antenna layer is disposed on the bottom surface of the first dielectric layer, and the third antenna layer is disposed on the top surface of the second dielectric layer. Both the first antenna layer and the third antenna layer are rectangular and orthogonally arranged. When the orthogonally arranged first and third antenna layers enclose the second antenna layer, they are used to enable the metasurface units to form a Fabry-Perot-like resonant cavity. The opening angles of the C-shaped opening resonator and the C-shaped slot opening resonator in each metasurface unit are different. The C-shaped opening resonator is used to control the transmission phase at the first working wavelength, and the C-shaped slot opening resonator is used to control the transmission phase at the second working wavelength.

[0007] Preferably, the C-shaped opening resonant ring within the metasurface unit has the same ring width as the C-shaped groove opening resonant ring.

[0008] Preferably, the first antenna layer, the second antenna layer, and the third antenna layer are all made of aluminum film. Both the first antenna layer and the third antenna layer are rectangular aluminum films of the same shape.

[0009] Preferably, both the first dielectric layer and the second dielectric layer are polyimide dielectric layers; The dielectric constant of the polyimide dielectric layer is 3.5, and the loss tangent is 0.0027.

[0010] Preferably, by adjusting the opening angle of the C-shaped open resonant ring within the metasurface unit and the orientation angle relative to the x-axis, the transmission phase of the metasurface unit at the first operating wavelength covers a range of 360°. By adjusting the opening angle of the C-groove resonant ring within the metasurface unit, as well as the orientation angle relative to the x-axis, the transmission phase of the metasurface unit at the second operating wavelength covers a range of 360°.

[0011] Preferably, when x-polarized light is incident on the metasurface unit, the third antenna layer receives the x-polarized light, and the x-polarized light is converted into y-polarized light by the second antenna layer. The first antenna layer receives the y-polarized light and emits it.

[0012] Preferably, the first operating wavelength controlled by the C-shaped slot resonant ring is 1.28 THz, and the second operating wavelength controlled by the C-shaped slot resonant ring is 0.55 THz.

[0013] This invention provides a terahertz wavelength multiplexing focusing lens based on a metasurface, which has the following advantages compared with the prior art: This invention configures each metasurface unit of the focusing lens as a five-layer structure, specifically, a first antenna layer and a third antenna layer sandwiching an inner first dielectric layer, a second antenna layer, and a second dielectric layer. The orthogonally arranged first and third antenna layers, when sandwiching the second antenna layer, form a Fabry-Perot-like resonant cavity. Simultaneously, the opening angles of the C-shaped aperture resonator and the C-shaped slot aperture resonator within each metasurface unit are different. The C-shaped aperture resonator can independently control the transmission phase at the first operating wavelength, and the C-shaped slot aperture resonator can independently control the transmission phase at the second operating wavelength, thereby simultaneously achieving independent control of multiple wavelengths. This allows for 360-degree transmission phase control, enabling applications at terahertz wavelengths or other wavelengths or bands, expanding the application range of metasurface focusing devices in multi-wavelength applications. Attached Figure Description

[0014] Figure 1 A schematic diagram of the overall unit structure of a terahertz wavelength multiplexing focusing lens based on a metasurface is provided for an embodiment of the present invention; Figure 2 A schematic diagram of the structure of an intermediate layer antenna based on a metasurface terahertz wavelength multiplexing focusing lens unit structure provided for an embodiment of the present invention; Figure 3 A schematic diagram of a rectangular aluminum film with a unit structure of a metasurface-based terahertz wavelength multiplexing focusing lens provided for an embodiment of the present invention; Figure 4 A schematic diagram of the phase response simulation results of an eight-level discrete unit of a metasurface-based terahertz wavelength multiplexing focusing lens under x-polarized incident light at λ1=545μm (0.55THz) provided for an embodiment of the present invention; Figure 5 A schematic diagram illustrating the phase response simulation results of an eight-level discrete unit of a metasurface-based terahertz wavelength multiplexing focusing lens under x-polarized incident light at λ2 = 234 μm (1.28 THz) according to an embodiment of the present invention. Figure 6 A schematic diagram illustrating the transmission amplitude simulation results of an eight-level discrete unit of a metasurface-based terahertz wavelength multiplexing focusing lens under x-polarized incident light at λ1=545μm (0.55THz) according to an embodiment of the present invention. Figure 7 A schematic diagram of the phase response simulation results of an eight-level discrete unit of a terahertz wavelength multiplexing focusing lens based on a metasurface under x-polarized incident light at λ2=234μm (1.28THz) provided for an embodiment of the present invention; Figure 8 This is a schematic diagram showing the phase distribution curves of a 4mm superlens with the same focal length, based on a metasurface and designed as a terahertz wavelength multiplexing focusing lens, at λ1=545μm (0.55THz) and λ2=234μm (1.28THz), as a function of distance from the lens center. Figure 9 A schematic diagram of the cross-polarized electric field simulated by normal incidence of bottom x-polarized light at λ1=545μm (0.55THz) in a terahertz wavelength multiplexing focusing lens based on a metasurface, provided for an embodiment of the present invention; Figure 10 A schematic diagram of the cross-polarized electric field simulated by normal incidence of bottom x-polarized light at λ2=234μm (1.28THz) in a terahertz wavelength multiplexing focusing lens based on a metasurface, provided for an embodiment of the present invention; Figure 11 A schematic diagram of the intensity distribution curve of a terahertz wavelength multiplexing focusing lens based on a metasurface, provided for an embodiment of the present invention; Among them: 1. First antenna layer, 2. First dielectric layer, 3. Second antenna layer, 4. Second dielectric layer, 5. Third antenna layer. Detailed Implementation

[0015] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0016] See Figure 1 This invention provides a terahertz wavelength multiplexing focusing lens based on a metasurface, comprising a first antenna layer 1, a first dielectric layer 2, a second antenna layer 3, a second dielectric layer 4, and a third antenna layer 5 arranged sequentially from bottom to top. Specifically, it adopts a three-layer composite structure design, consisting of upper and lower polyimide dielectric layers and an intermediate metal functional layer.

[0017] The first antenna layer 1 and the third antenna layer 5 are both rectangular metal films of the same size, with a length of 120 μm and a width of 60 μm.

[0018] The first antenna layer 1 is placed at the bottom of the unit structure along the y-axis, and the third antenna layer 5 is placed at the top of the unit structure along the x-axis, with the first antenna layer 1 and the third antenna layer 5 placed in an orthogonal position.

[0019] The second antenna layer 3 consists of a C-shaped open-ring resonator and a metal sheet with C-shaped slots and circular holes. The side length of the second antenna layer 3 is 120μm. The inner diameter of the C-shaped open-ring resonator is 20μm, the outer diameter is 25μm, and the width is 5μm. The inner diameter of the C-shaped slot is 50μm, the outer diameter is 55μm, and the width is 5μm. The radius of the circular hole is 39μm. The C-shaped open-ring resonator is placed at the center of the metal sheet with C-shaped slots and circular holes. The material used for the second antenna layer 3 is aluminum.

[0020] The thickness of the first antenna layer 1, the second antenna layer 3, and the third antenna layer 5 is 0.2 μm.

[0021] The first dielectric layer 2 and the second dielectric layer 4 have the same dimensions, with a side length of 120 μm and a thickness of 65 μm. The first dielectric layer 2 and the second dielectric layer 4 are both made of polyimide, with a dielectric constant of 3.5 and a loss tangent of 0.0027.

[0022] like Figure 2 As shown, a 200nm thick aluminum functional layer is embedded between two polyimide dielectric layers. This functional layer consists of a C-shaped slot resonator, a C-shaped groove resonator, and a circular hole. The aluminum layer has a C-shaped groove and a circular hole, with the C-shaped slot resonator located at the center of the circular hole. The C-shaped groove resonator is responsible for controlling the phase at 0.55THz, and the C-shaped slot resonator is responsible for controlling the phase at 1.28THz. The two resonator units are integrated in the same space and are not coupled to each other due to the presence of the circular hole. The opening angle, outer radius, and width of the C-shaped slot resonator (C-shaped groove resonator) are denoted as α1 (α2), r1 = 25μm (r2 = 55μm), and w1 = w2 = 5μm, respectively. The slot resonator antenna with different opening angles can produce different electromagnetic response characteristics, that is, produce different phase changes to the incident wave, and achieve 0-π phase coverage.

[0023] Based on the control mechanism of this type of symmetrical open-loop resonant antenna, it produces a phase change and polarization conversion effect on x-polarized incident light. The C-shaped open-loop resonant ring (C-shaped slot open-loop resonant ring) is oriented θ1 (θ2) along the x-axis. By changing the sign of the orientation (flipping it on the x-axis), an additional π phase shift is achieved. Thus, by simultaneously changing the opening angle and the orientation along the x-axis, a phase response coverage of 0-2π can be achieved, thereby satisfying the primary condition for the metasurface to achieve precise control of electromagnetic waves.

[0024] like Figure 3As shown, a rectangular aluminum grating (length P = 120 μm, width w = 60 μm, thickness 200 nm, conductivity = 3.72 × 10^7 S / m) is prepared on the surface of a polyimide dielectric layer (thickness 65 μm, dielectric constant ε = 3.5) placed along the x-direction; a rectangular aluminum grating is prepared on the surface of another polyimide dielectric layer placed along the y-direction, and the two rectangular aluminum gratings are orthogonal.

[0025] According to the theory of multiple interference, two orthogonal rectangular aluminum gratings and an intermediate layer form a Fabry-Perot-like cavity. Specifically, when x-polarized light is incident on the bottom rectangular grating (first antenna layer), it can pass smoothly because the polarization direction is perpendicular to the grating. Subsequently, after polarization conversion by the intermediate layer (second antenna layer), the converted y-polarized light and some unconverted x-polarized light are transmitted to the top rectangular grating (third antenna layer). Since the polarization direction of the y-polarized light is perpendicular to the direction of the top grating (third antenna layer), some y-polarized light will pass through the top grating (third antenna layer), while the x-polarized light will be blocked by the top grating (third antenna layer). Then, it returns to the intermediate layer (second antenna layer) and interacts with the bottom layer (first antenna layer). By repeating the above process for multiple reflections and transmissions, the incident x-polarized light is converted into y-polarized light as much as possible. Compared with the structure without orthogonal gratings, this effectively improves the cross-polarization transmittance of the metasurface.

[0026] To determine the transmission phase and amplitude of the metasurface, this invention employs CST MicrowaveStudio computer simulation technology to numerically simulate the unit cell structure; for example... Figure 1 The diagram shows an xyz coordinate system. The incident wave is defined as x-linearly polarized light, with the incident direction (wave vector K) along the positive z-axis. The electric field component (electric field E) is along the x-axis, and the magnetic field component (magnetic field H) is along the y-axis. Periodic boundary conditions are used in the x and y directions of the unit structure, while open-space boundary conditions are used in the z-direction. This invention records the phase and amplitude of simulated cross-polarized transmitted waves at two incident frequencies. See [link to documentation]. Figure 4 , Figure 5 It can be seen that the entire 360° phase shift can be approximated by eight-level phase modulation with a 45° phase interval, and the resonant ring with different opening angles corresponds to different phases.

[0027] During the design process, this invention selected four suitable open-loop resonators with a 45° phase spacing. By simply rotating the orientation of the first four open-loop resonators by 90°, the other four unit cells can be obtained. The detailed geometric parameters of the open-loop resonators are shown in Table 1. When the opening direction of the open-loop resonator is at 45° with the positive x-axis, the structure exhibits higher polarization conversion efficiency. Therefore, this invention fixes the orientation angle θ of the open-loop resonator to 45° and -45° to obtain smaller amplitude fluctuations.

[0028] Table 1. Opening angle and rotation angle of unit structure

[0029] like Figure 4 As shown, the simulated phase response at 0.55 THz under x-polarized incident light can be seen. It can be observed that the phase response is almost entirely independent of the variation in the C-groove open-circuit resonator (CSSRR). Figure 5 As shown, the simulated phase response at 1.28 THz under x-polarized incident light can be seen. It can be seen that the change of the C-shaped open-circuit resonator (CSRR) has almost no effect on the phase at 0.55 THz, and only responds at 1.28 THz. This is the fundamental reason why phase modulation can be achieved independently and decoupled at the two frequencies.

[0030] Cross-polarization and transmission amplitude of the same-polarity wave component at two wavelengths are as follows Figure 6 , Figure 7 As shown; Figure 6 The three two-dimensional curves represent the simulated cross-polarization transmission amplitude, co-polarization transmission amplitude, and cross-polarization transmission amplitude of the unit structure in this invention at an incident frequency of 0.55 THz, respectively. As can be seen from the figures, the average cross-polarization transmission amplitude of the unit structure in this invention is above 0.8, the average co-polarization transmission amplitude is less than 0.1, while the average cross-polarization transmission amplitude of the unit structure without gratings is only about 0.4; similarly, Figure 7 The three two-dimensional curves in the figure represent the cross-polarization transmission amplitude, the same-polarization transmission amplitude, and the cross-polarization transmission amplitude of the unit structure without the two orthogonal metal gratings simulated at an incident frequency of 1.28 THz, respectively. As can be seen from the figure, the average cross-polarization transmission amplitude of the unit structure in this invention is above 0.7, the average same-polarization transmission amplitude is less than 0.2, and the average cross-polarization transmission amplitude of the unit structure without gratings is less than 0.4.

[0031] The metasurface structure designed in this invention consists of 54 unit cells arranged along the x-axis (i.e., the electric field E direction), with a total length of 6480 μm. These 54 unit cells form a supercell arranged periodically along the y-axis (i.e., the magnetic field H direction). The dual-wavelength characteristics of the planar superlens were numerically verified using the commercial software CST Microwave Studio. In the simulation, a periodic boundary condition (PBC) was applied along the y-axis to repeat the metasurface structure in the y-direction. Open boundary conditions with vacuum spacers were added in both the ±x-direction, and a perfectly matched layer was applied in the z-direction. A normally incident x-polarized plane wave was used to excite the structure from the bottom of the metasurface, and the scattered y-polarized radiation was recorded.

[0032] like Figure 8 The image shows the digital phase distribution required for a superlens with a focal plane located at a focal length of f = 4 mm at two incident frequencies (0.55 THz and 1.28 THz) when the total number of cells (only 27 cells are shown due to symmetry) is 54. Figure 8 The left (right) part is the required phase and digitized phase when λ1=545μm (λ2=234μm).

[0033] like Figure 9 and Figure 10 The figure shows the transmission focusing field intensity distribution of the cross-polarization component (i.e., y-polarized light) of a metasurface focusing lens under x-polarized incident light, as simulated by the simulation. Figure 9 This indicates that the actual simulated focal length at 0.55THz is 4mm, consistent with the design value. The white dashed line in the figure represents the position of the actual simulated metasurface lens focal length. Figure 10 This indicates that at 1.28THz, the actual simulated focal length is 4mm, which is consistent with the design value, and the metasurface lens produces a good focusing effect on the transmission space side.

[0034] like Figure 11 As shown in the figure, the solid and dashed lines represent the normalized intensity distribution curves at the cross section of the transmission focusing point at 0.55THz and 1.28THz, respectively. This indicates that when the wavelength is 0.55THz, the half-width at half-maximum (FWHM) is 400μm and 0.73λ, which is smaller than the working wavelength and close to the diffraction limit, indicating a good focusing effect. When the wavelength is 1.28THz, the FWHM is 200μm and 0.84λ, which is smaller than the working wavelength and close to the diffraction limit, also confirming a good focusing effect.

[0035] This invention embeds an intermediate metal layer between two polyimide dielectric layers. This metal layer consists of a C-shape split-ring resonator (CSRR), a C-slot split-ring resonator (CSSRR), and an aluminum layer with a circular hole. A rectangular aluminum film is deposited on the upper surface of the upper polyimide dielectric layer and on the lower surface of the lower polyimide dielectric layer. The aluminum film is orthogonal to the top aluminum film. In the meta-atom, the two orthogonal metal strip gratings and the intermediate layer form a Fabry-Perot-like cavity. The C-shape split-ring resonator and the C-slot split-ring resonator in the intermediate metal layer respond to two different wavelengths and are not coupled to each other. This enables transmission focusing of incident light of two different wavelengths, solving the technical problem that metasurface focusing lenses can only work at a single wavelength or in the same band, and expanding the application range of metasurface focusing devices in multi-wavelength applications.

[0036] The superlens unit structure of this invention consists of two polyimide dielectric layers and three metal resonators (top, middle, and bottom). The middle metal resonator integrates two different resonant structures that independently respond to two different frequencies: 0.55 THz (545 μm) and 1.28 THz (234 μm). By changing the opening angle and rotation angle of the two different resonant structures—the C-shaped open resonator and the C-shaped slot open resonator—a complete phase response covering [0-2π] at both frequencies and an average cross-polarization transmittance higher than 0.7 are achieved. Orthogonal... The synergistic design of the grating layer and the resonant unit constructs a Fabry-Perot-like resonant enhancement effect, increasing the overall cross-polarization transmittance to over 75%. At the same time, the focused spot size in the 0.55THz and 1.28THz frequency bands is compressed to 493μm and 203μm, respectively, achieving subwavelength resolution. Moreover, the overall thickness is only λ / 4, realizing the miniaturization and integration of the terahertz system. It also has the advantages of simple structure, simple fabrication process and low manufacturing cost, while broadening the design ideas and application prospects of metasurfaces in multi-wavelength applications.

[0037] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A terahertz wavelength multiplexing focusing lens based on a metasurface, characterized in that, It includes multiple alternating metasurface units; The metasurface unit consists of a first antenna layer (1), a first dielectric layer (2), a second antenna layer (3), a second dielectric layer (4), and a third antenna layer (5) arranged from bottom to top. A circular hole is provided inside the second antenna layer (3). A C-shaped opening resonant ring is provided inside the circular hole and on the top surface of the first dielectric layer (2). A C-shaped slot opening resonant ring is provided on the second antenna layer (3) outside the circular hole. The opening angles of the C-shaped opening resonant ring and the C-shaped slot opening resonant ring are different. The first antenna layer (1) is disposed on the bottom surface of the first dielectric layer (2), and the third antenna layer (5) is disposed on the top surface of the second dielectric layer (4). Both the first antenna layer (1) and the third antenna layer (5) are rectangular and orthogonally arranged. When the orthogonally arranged first antenna layer (1) and third antenna layer (5) enclose the second antenna layer (3), they are used to form a Fabry-Perot resonant cavity for the metasurface unit. The opening angles of the C-shaped opening resonator and the C-shaped slot opening resonator in each metasurface unit are different. The C-shaped opening resonator is used to control the transmission phase at the first working wavelength, and the C-shaped slot opening resonator is used to control the transmission phase at the second working wavelength.

2. The terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, The C-shaped opening resonant ring within the metasurface unit has the same ring width as the C-shaped slot opening resonant ring.

3. The terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, The first antenna layer (1), the second antenna layer (3) and the third antenna layer (5) are all made of aluminum film; The first antenna layer (1) and the third antenna layer (5) are both rectangular aluminum films of the same shape.

4. A terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, Both the first dielectric layer (2) and the second dielectric layer (4) are made of polyimide dielectric layers; The dielectric constant of the polyimide dielectric layer is 3.5, and the loss tangent is 0.0027.

5. A terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, By adjusting the opening angle of the C-shaped open resonator within the metasurface unit and the orientation angle relative to the x-axis, the transmission phase of the metasurface unit at the first operating wavelength covers a range of 360°. By adjusting the opening angle of the C-groove resonant ring within the metasurface unit, as well as the orientation angle relative to the x-axis, the transmission phase of the metasurface unit at the second operating wavelength covers a range of 360°.

6. A terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, When x-polarized light is incident on the metasurface unit, the third antenna layer (5) receives the x-polarized light. The x-polarized light is converted into y-polarized light by the second antenna layer (3). The first antenna layer (1) receives the y-polarized light and emits it.

7. A terahertz wavelength multiplexing focusing lens based on a metasurface according to claim 1, characterized in that, The first operating wavelength controlled by the C-shaped slot resonant ring is 1.28 THz, and the second operating wavelength controlled by the C-shaped slot resonant ring is 0.55 THz.

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