Far-infrared silicon-based high-transmittance superstructure surface and design and processing method thereof

Abstract

This invention discloses a far-infrared silicon-based high-transmittance metasurface and its design and fabrication method, relating to the field of micro-nano optical devices. The metasurface employs a layered stacked structure with a porous meta-atomic array layer as the central layer. From the incident side to the emitted side, it consists of an upper antireflection film, an upper substrate layer, a porous meta-atomic array layer, a lower substrate layer, and a lower antireflection film. Both the upper and lower antireflection films include a first antireflection layer and a second antireflection layer arranged sequentially from the inside out. The porous meta-atomic array layer, the upper substrate layer, and the lower substrate layer are all made of single-crystal silicon. This invention improves the reflectivity of the 8-12μm far-infrared band to over 95% under lossless conditions by matching the equivalent refractive index of the interface through subwavelength structure design. The process route is simple, and the use of silicon-silicon bonding technology to encapsulate and protect the microstructure units of the metasurface enhances the stability of the metasurface in processing and application.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, and in particular to a far-infrared silicon-based high-transmittance metasurface and its design and fabrication method. Background Technology

[0002] With the development of planar optics, metasurfaces have emerged. Compared with traditional optical devices, metasurfaces have the ability to control phase, amplitude, and polarization, and also have advantages such as being thin, light, and easy to integrate, thus attracting widespread attention. They have great potential to replace traditional optical surfaces, especially in fields such as infrared imaging and detection.

[0003] However, the mismatch between the refractive index of the metasurface and the environment outside the upper and lower surfaces causes reflections that reduce the brightness of the image. On the other hand, stray light generated by multiple reflections leads to a decrease in image contrast. Currently, the transmittance of metasurfaces in the far-infrared broadband band is insufficient, and existing antireflection coating processes for metasurfaces typically involve placing the antireflection coating between the metasurface and the substrate or filling the metasurface before applying the antireflection coating. This requires equivalent refractive index analysis of the metasurface and complex design to obtain the antireflection coating, and the overall process difficulty and structural stability are still insufficient. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a far-infrared silicon-based high-transmittance metasurface and its design and processing method. By optimizing the structural design, material selection, and process route, high transmittance in the 8-12μm far-infrared band is achieved, while ensuring the structural stability and processing feasibility of the surface, thus meeting the high-performance application requirements of far-infrared optical systems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention proposes a far-infrared silicon-based high-transmittance metasurface with a working wavelength of 8-12 μm. The metasurface adopts a layered stacked structure with a porous meta-atom array layer as the central layer. From the incident side to the emitting side, the metasurface consists of an upper antireflection film layer, an upper substrate layer, a porous meta-atom array layer, a lower substrate layer, and a lower antireflection film layer. Both the upper and lower antireflection film layers include a first antireflection layer and a second antireflection layer arranged sequentially from the inside to the outside.

[0007] The porous meta-atom array layer, the upper substrate layer, and the lower substrate layer are all made of single-crystal silicon.

[0008] The porous meta-atom array layer comprises subwavelength porous microstructure units arranged in a tetragonal lattice, and the microstructure units do not require dielectric filling.

[0009] Furthermore, the thickness of the upper and lower substrate layers is 100-500 μm, and the thickness of the porous meta-atom array layer is 5-30 μm.

[0010] Furthermore, the first antireflection layer and the second antireflection layer are ZnSe layer and MgF2 layer, respectively.

[0011] Furthermore, the microstructure unit is a circular hole or a square hole with a period of 2.0-5.0 μm, a diameter of 0.8-2.0 μm for the circular hole, and a side length of 0.8-2.0 μm for the square hole.

[0012] Furthermore, the overall transmittance of the metasurface is greater than 94%, and the phase modulation of the microstructure unit in the working band covers 0-2π.

[0013] Secondly, this invention proposes a design method for a far-infrared silicon-based high-transmittance metasurface as described above, comprising the following steps:

[0014] S11: Single-crystal silicon is selected as the porous meta-atomic array layer and substrate material, and ZnSe and MgF2 are selected as antireflection film materials;

[0015] S12: Set the incident environment and the exit environment as parameters of the substrate layer, and adjust the parameters of the microstructure unit of the porous meta-atom array layer, including the hole size, unit period and thickness, wherein the hole size is the diameter of a circular hole or the side length of a square hole.

[0016] The parameters of the microstructure units were traversed within the range of aperture size 0.8μm-2μm, unit period 2μm-5μm, and thickness 10μm-20μm. The transmittance and phase response of the microstructure units were simulated, and a parameter-performance comparison table was formed.

[0017] S13: Select unit parameters with transmittance greater than 95% in the working band, arrange microstructure units according to phase requirements, and form a porous meta-atomic array layer. In the porous meta-atomic array layer, the unit period and thickness of the microstructure units are the same, and the pore size meets the phase requirements.

[0018] S14: Based on the far-infrared 8-12μm band, the thickness of the ZnSe layer and MgF2 layer in the antireflection coating is optimized with a center wavelength of 10 μm. The optimization target is set to a single-sided broadband transmittance of greater than 99.5% under normal incidence conditions.

[0019] S15: A substrate layer and an antireflection film layer are sequentially combined on both sides of the porous meta-atomic array layer to form a far-infrared silicon-based high-transmittance meta-surface.

[0020] Thirdly, the present invention proposes a method for processing a far-infrared silicon-based high-transmittance metasurface as described above, comprising the following steps:

[0021] S21: Clean the first silicon wafer;

[0022] S22: A silicon dioxide layer is grown on the first silicon wafer and a photoresist layer is spin-coated, and a silicon dioxide hard mask layer and a photoresist layer are sequentially formed on the first silicon wafer.

[0023] S23: Micro-nano structure patterns of metasurfaces are obtained by exposing and developing on a photoresist layer using electron beam direct writing or laser direct writing technology.

[0024] S24: ICP etching is used to transfer the micro-nano structure pattern to the silicon dioxide hard mask layer, and then deep silicon etching is used to form a porous meta-atom array layer;

[0025] S25: Remove the silicon dioxide hard mask layer and clean it to obtain an integrated porous meta-atom array layer and a lower substrate layer;

[0026] S26: Clean the second silicon wafer, align the second silicon wafer with the porous meta-atom array layer and perform silicon-silicon bonding;

[0027] S27: A double-sided antireflection coating is deposited on the bonded silicon wafer to obtain a far-infrared silicon-based high-transmittance metasurface.

[0028] As a preferred embodiment of the present invention, deep silicon etching is performed using the Bosch process, alternating between etching and passivation, with an etching depth of 5-30 μm.

[0029] As a preferred embodiment of the present invention, the silicon-silicon bonding is carried out in a vacuum environment, with an annealing temperature of 800-1000℃ and an annealing time of 0.5-2 hours.

[0030] As a preferred embodiment of the present invention, the thickness of the first silicon wafer and the second silicon wafer is 100-500 μm.

[0031] The beneficial effects of this invention are:

[0032] The far-infrared silicon-based high-transmittance metasurface provided by this invention effectively improves the transmittance of the metasurface in the far-infrared broadband band by using a layered stacking design with a porous metasurface atomic array layer as the core and combining it with an optimized ZnSe-MgF2 double-layer antireflection film system deposited on both sides of the metasurface. At the same time, the antireflection film design relies on mature film system optimization theory, and the processing can be connected with existing micro-nano manufacturing processes, which has the advantage of simple preparation. Moreover, the encapsulation protects the metasurface microstructure units, which can further ensure the long-term stability of the metasurface. The prepared metasurface can be used for far-infrared imaging and detection. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a far-infrared silicon-based high-transmittance metasurface provided by the present invention;

[0034] Figure 2 This is a cross-sectional view of a far-infrared silicon-based high-transmittance metasurface provided by the present invention;

[0035] Figure 3 This is a structural comparison diagram of the present invention and existing columnar metasurface antireflection solutions;

[0036] Figure 4 This is a schematic diagram of the porous meta-atomic array layer and microstructure unit in a metasurface;

[0037] Figure 5 This is a graph showing the transmittance-wavelength relationship of microstructure units in the far-infrared (8-12μm) band;

[0038] Figure 6 It is a graph showing the relationship between the transmittance and phase of the microstructure unit at various wavelengths;

[0039] Figure 7 This is a graph showing the relationship between the transmittance of the antireflection coating on the metasurface and wavelength, and the relationship between the overall transmittance and wavelength in the working wavelength range.

[0040] Figure 8 This is a flowchart of the design method for antireflection films on far-infrared silicon-based high-transmittance metasurfaces;

[0041] Figure 9 This is a schematic diagram of the fabrication process for far-infrared silicon-based high-transmittance metasurfaces;

[0042] Figure 10 This is a flowchart of the processing method for far-infrared silicon-based high-transmittance metasurfaces;

[0043] Explanation of reference numerals in the attached figures: 1 is the porous meta-atom array layer; 2a is the upper substrate layer; 2b is the lower substrate layer; 3a is the upper ZnSe layer; 3b is the lower ZnSe layer; 4a is the upper MgF2 layer; 4b is the lower MgF2 layer; 5 is the photoresist layer; 6 is the silicon dioxide layer; 7 is the photoresist layer with pattern after development; 8 is the silicon dioxide mask layer after etching. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention or the claims of this invention without creative effort should fall within the scope of protection of this invention.

[0045] This invention proposes a far-infrared silicon-based high-transmittance metasurface, with reference to... Figure 1 and Figure 2 It includes a layered stacked structure with a porous meta-atom array layer 1 as the core, which, from the incident side to the exit side, consists of: an upper antireflection film layer, an upper substrate layer 2a, a porous meta-atom array layer 1, a lower substrate layer 2b, and a lower antireflection film layer. Both the upper and lower antireflection film layers are, from the inside out, ZnSe and MgF2 layers, respectively defined as upper ZnSe layer 3a, upper MgF2 layer 4a, lower ZnSe layer 3b, and lower MgF2 layer 4b.

[0046] In a preferred embodiment, the porous meta-atom array layer has a thickness of 18 μm and is made of single-crystal silicon. The upper and lower substrate layers are both 300 μm thick single-crystal silicon layers with a refractive index of 3.42. The upper and lower antireflection coating layers have identical structures, both consisting of a ZnSe layer (refractive index 2.4) and a MgF2 layer (refractive index 1.38) from the inside out. The ZnSe layer has a thickness of 1040 nm, the MgF2 layer has a thickness of 1810 nm, and the total thickness is 2850 nm.

[0047] Traditional antireflection methods use cylindrical metasurfaces. After performing equivalent refractive index analysis on the metasurface, an antireflection coating is designed. If the refractive index difference between the metasurface and the air layer is large, an antireflection coating is added to the upper surface of the metasurface, such as... Figure 3 As shown in (a); if the refractive index difference between the metasurface and the substrate is large, an antireflection film is added to the lower surface of the metasurface, such as... Figure 3 As shown in (b); unlike traditional antireflection methods, the far-infrared silicon-based high-transmittance metasurface proposed in this invention is as follows: Figure 3 As shown in (c), a porous metasurface was used instead, and the upper and lower surfaces were replaced with silicon substrate layers. This eliminated the refractive index difference between the two surfaces, thus improving transmittance. Furthermore, the design avoided the potential collapse problem of columnar metasurface atoms and eliminated the need for a filling process, reducing the manufacturing complexity.

[0048] As a preferred implementation method, such as Figure 4 As shown, the porous meta-atomic array layer is composed of porous microstructure units. These microstructure units have a period p of 2.3 μm, a depth h of 18 μm, and a circular aperture diameter d of 800 nm-1600 nm. They are formed according to a tetragonal lattice arrangement without the need for dielectric filling. The circular apertures are relatively easy to fabricate and can be obtained using common fabrication methods. Alternatively, square or cross-shaped microstructure units can also be used. Using a subwavelength microstructure arrangement period achieves high diffraction efficiency and improves overall transmission efficiency. The use of a 18 μm deep microstructure effectively ensures the requirement of 2π phase coverage in the 8-12 μm wavelength range. Here, the period of the microstructure unit refers to the interval between the repeated arrangement of the tiny basic units in space.

[0049] For the transmittance characteristics of the preferred microstructure units, please refer to [link / reference]. Figure 5 .like Figure 5 As shown in (a), the microstructure unit with a diameter of 800 nm has a transmittance greater than 99% in the operating wavelength range. As the aperture increases, the equivalent refractive index changes, resulting in an FP-cavity resonant mode, and the overall transmittance fluctuates with wavelength; as... Figure 5 As shown in (b), the transmittance of the 1600 nm diameter microstructure unit fluctuates within the range of 95%-99% in the working wavelength band; the porous meta-atomic array layer is composed of several types of microstructure units, and the actual average transmittance is as follows. Figure 5 As shown in (c), the overall average transmittance is greater than 98% in the working band.

[0050] The relationship between the transmittance and phase of the microstructure unit selected in this embodiment can be found in [reference needed]. Figure 6 .like Figure 6 As shown in (a), (b), and (c), the microstructure units can cover 2π at wavelengths of 8μm, 10μm, and 12μm, and the transmittance is greater than 95%.

[0051] In a preferred embodiment, the antireflective coating layer consists of a ZnSe layer and a MgF2 layer. After optimization, this bilayer film system achieves a single-sided transmittance greater than 99.6% under normal incident conditions across the entire 8-12 μm wavelength range, effectively reducing reflection loss at the silicon-air interface. The transmittance of the antireflective coating is as follows: Figure 7 As shown in (a), for a single-crystal silicon substrate, the antireflection film is deposited on both sides, and the transmittance of the antireflection film is greater than 99%. In this scheme, considering the condition of no absorption loss, the transmittance after combining with the porous meta-atom array layer is as follows: Figure 7 As shown in (b), the overall transmittance is greater than 97% in the 8-12μm band.

[0052] The design method of the far-infrared silicon-based high-transmittance metasurface is as follows: Figure 8 As shown, it includes the following steps:

[0053] S11: Determination of material parameters

[0054] The materials and optical parameters of each functional layer are specified: the porous meta-atomic array layer, the upper substrate layer, and the lower substrate layer are all made of single-crystal silicon, with a refractive index of 3.42 in the 8-12μm band; the ZnSe material of the antireflection coating layer has a refractive index of 2.4, and the MgF2 material has a refractive index of 1.38; the incident environment and the exit environment are both set to air (refractive index of 1).

[0055] S12: Microstructure Element Parameter Simulation

[0056] The microstructure unit was simulated using the Rigorous Coupled Wave Analysis (RCWA) method. In the simulation model, the incident light was set to be normally incident 8-12μm broadband far-infrared light. The environmental parameters at the incident and emitting ends were matched with the material parameters of the substrate layer. The key parameters of the microstructure unit were adjusted: the diameter of the circular hole (0.8μm-2μm), the period of the microstructure unit (2μm-5μm), and the thickness of the porous meta-atomic array layer (10μm-20μm). These parameter combinations were iterated. The transmittance (amplitude response) and phase delay (phase response) of the microstructure unit under each set of parameters were obtained through simulation, and a parameter-performance comparison table was formed.

[0057] S13: High transmittance unit screening and array arrangement

[0058] Microstructure units with transmittance greater than 95% in the working wavelength range were selected from the parameter-performance comparison table. When the aperture diameter was 0.8-1.6 μm, the lattice period was 2.3 μm, and the array layer thickness was 18 μm, the average transmittance of the microstructure units in the 8-12 μm wavelength range was better than 98%, and the phase retardation could cover the 0-2π range, meeting the phase distribution requirements of the metasurface under broadband conditions. Subsequently, the microstructure units were arranged in a tetragonal lattice within a 7 mm × 7 mm plane to meet the phase requirements of the metasurface, forming a complete porous metaatomic atomic array layer. In this step, the microstructure units in the porous metaatomic atomic array layer had the same period and thickness, and the aperture was selected according to the phase requirements.

[0059] S14: Optimization of Anti-reflection Membrane Systems

[0060] Targeting the 8-12μm wavelength band, the center wavelength λ0 was set to 10μm. A single-crystal silicon substrate (300μm thick), identical to the substrate layer, was used for simulation. A ZnSe-MgF2 bilayer film model was constructed on the substrate. The initial film system was designed based on the λ0 / 4 theoretical design (λ0=10μm). With the optimization objective of achieving a single-sided average transmittance greater than 99.5% in the 8-12μm wavelength band, existing thin-film optics design software was used for iterative optimization, adjusting the ZnSe layer thickness to 1040nm and the MgF2 layer thickness to 1810nm. The optimized simulation results show that the film system achieves a single-sided average transmittance better than 99.6% in the 8-12μm wavelength band, meeting the target requirement.

[0061] S15: Overall structural assembly

[0062] Following the sequence of "upper antireflection coating layer (ZnSe 1040nm + MgF2 1810nm) - upper substrate layer (single-crystal silicon 300μm) - porous meta-atom array layer (single-crystal silicon, microstructure unit hole depth 18μm, hole diameter 0.8μm-1.6μm, unit period 2.3μm) - lower substrate layer (silicon 300μm) - lower antireflection coating layer (ZnSe 1040nm + MgF2 1810nm)," the simulation and physical assembly of each functional layer were completed to form a complete far-infrared silicon-based high-transmittance metasurface. Through overall optical simulation calculations, under conditions of no absorption loss, the comprehensive transmittance of this metasurface in the 8-12μm band is better than 97%.

[0063] like Figure 10 As shown, in some embodiments, the present invention provides a method for processing a far-infrared silicon-based high-transmittance metasurface, including the following steps, the visualization process of which is shown below. Figure 9 As shown.

[0064] S21: Silicon Wafer Cleaning

[0065] A 4-inch single-crystal silicon wafer (300μm thick, used to fabricate the lower substrate layer and the porous meta-atom array layer) was selected, and the wafer was sliced ​​to a size of 20mm×20mm. The RCA standard cleaning method was used to remove impurities and oxide layers.

[0066] S22: Silicon dioxide growth and photoresist spin coating

[0067] A silicon dioxide layer was grown on the cleaned silicon wafer surface using PECVD (plasma-enhanced chemical vapor deposition); then PMMA photoresist was spin-coated onto the silicon dioxide layer surface to form a uniform photoresist layer with a thickness of 270 nm; after spin-coating, the silicon wafer was placed in an oven and pre-baked at 180°C for 10 min.

[0068] S23: Graphic Exposure

[0069] The design pattern of the porous meta-atom array layer is introduced, and the photoresist layer is exposed area by area using an electron beam direct writing device to form a micro-nano pattern consistent with the design. The exposed silicon wafer is then placed in a developer to remove the photoresist in the exposed areas, at which point the photoresist layer forms a clear circular aperture array pattern.

[0070] S24: Etching Transfer and Deep Silicon Etching

[0071] The first step, ICP etching and transfer: The silicon wafer is placed in an ICP etching machine and etched for 60 seconds to transfer the circular hole pattern on the photoresist layer to the silicon dioxide hard mask layer;

[0072] The second step is deep silicon etching, which uses the Bosch process to alternate between etching (30 seconds) and passivation (20 seconds) for a total of 60 cycles. This transfers the circular hole pattern of the silicon dioxide mask into the silicon wafer, with an etching depth of 18 μm, forming a porous meta-atom array layer. After etching, SEM is used to inspect the etching depth, pattern accuracy, and sidewall perpendicularity to ensure that the structural accuracy requirements are met.

[0073] S25: Protective layer removal and cleaning

[0074] The silicon dioxide hard mask is removed by wet etching: the silicon wafer is immersed in BOE solution to remove the silicon dioxide mask layer and the native oxide layer on the surface; then the silicon wafer is cleaned again using the RCA standard cleaning process, while another 20mm×20mm single crystal silicon wafer (300μm thick, used to make the upper substrate layer) is cleaned. Oxygen cleaning is then performed to ensure the quality of subsequent bonding.

[0075] S26: Silicon-silicon bonding

[0076] The cleaned thin silicon wafer (upper substrate layer) is aligned with a silicon wafer (array layer + lower substrate layer) with a porous meta-atom array layer. The array layer is sandwiched between the upper and lower substrate layers. The silicon-silicon direct bonding is completed by annealing at 900°C for 1 hour in a vacuum environment.

[0077] S27: Double-sided anti-reflective coating

[0078] The bonded silicon wafer (upper substrate layer - array layer - lower substrate layer) is placed in an evaporation coating machine, and ZnSe layer and MgF2 layer are deposited sequentially on the upper and lower surfaces of the silicon wafer as antireflection films. After completion, the transmittance in the 8-12μm band is measured to ensure that it meets the design target. Thus, the fabrication of the far-infrared silicon-based high transmittance metasurface is completed.

[0079] Compared to existing technologies, the antireflection film provided by this invention only requires coating on both sides of the substrate. The coating does not affect the phase modulation of the microstructure units, significantly reducing the functional impact of traditional methods on the metasurface. Furthermore, the silicon wafer bonded to the surface of the metasurface effectively encapsulates and protects it, further ensuring its long-term stability.

[0080] Based on the above embodiments, the present invention provides a far-infrared silicon-based high-transmittance metasurface and its design and fabrication method, which effectively improves the transmittance of far-infrared (8-12μm) metasurfaces over a wide wavelength range. Furthermore, the design method is based on mature electromagnetic simulation theory and film system optimization algorithms, offering strong parameter controllability. Microstructure unit parameters and film thickness can be flexibly adjusted according to different metasurfaces. This anti-reflection design method is universal and practical. The fabrication scheme relies on mature micro-nano fabrication technologies such as electron beam direct writing, deep silicon etching, and silicon-silicon bonding, requiring no special equipment, exhibiting strong process compatibility, and facilitating industrial-scale mass production.

[0081] It should be noted that those skilled in the art will realize that the embodiments described herein are for the purpose of helping readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the scope of protection of the present invention.

Claims

1. A far-infrared silicon-based high-transmittance metasurface, operating in the 8-12 μm wavelength band, characterized in that, The metasurface adopts a layered stacked structure with a porous meta-atom array layer as the central layer. From the incident side to the exit side, it consists of an upper antireflection film layer, an upper substrate layer, a porous meta-atom array layer, a lower substrate layer, and a lower antireflection film layer. The upper and lower antireflection film layers each include a first antireflection layer and a second antireflection layer arranged sequentially from the inside to the outside. The porous meta-atom array layer, the upper substrate layer, and the lower substrate layer are all made of single-crystal silicon. The porous meta-atom array layer comprises subwavelength porous microstructure units arranged in a tetragonal lattice, and the microstructure units do not require dielectric filling. The overall transmittance of the metasurface is greater than 94%, and the phase modulation of the microstructure units covers 0-2π in the operating wavelength band; the fabrication method of the metasurface includes: S21: Clean the first silicon wafer; S22: A silicon dioxide layer is grown on the first silicon wafer and a photoresist layer is spin-coated, and a silicon dioxide hard mask layer and a photoresist layer are sequentially formed on the first silicon wafer. S23: Micro-nano structure patterns of metasurfaces are obtained by exposing and developing on a photoresist layer using electron beam direct writing or laser direct writing technology. S24: ICP etching is used to transfer the micro-nano structure pattern to the silicon dioxide hard mask layer, and then deep silicon etching is used to form a porous meta-atom array layer; S25: Remove the silicon dioxide hard mask layer and clean it to obtain an integrated porous meta-atom array layer and a lower substrate layer; S26: Clean the second silicon wafer, align the second silicon wafer with the porous meta-atom array layer and perform silicon-silicon bonding; S27: A double-sided antireflection coating is deposited on the bonded silicon wafer to obtain a far-infrared silicon-based high-transmittance metasurface.

2. The far-infrared silicon-based high-transmittance metasurface according to claim 1, characterized in that, The thickness of the upper and lower substrate layers is 100-500 μm, and the thickness of the porous meta-atom array layer is 5-30 μm.

3. The far-infrared silicon-based high-transmittance metasurface according to claim 1, characterized in that, The first antireflection layer and the second antireflection layer are ZnSe layer and MgF2 layer, respectively.

4. The far-infrared silicon-based high-transmittance metasurface according to claim 1, characterized in that, The microstructure unit is a circular or square hole with a period of 2.0-5.0 μm, a diameter of 0.8-2.0 μm for the circular hole, and a side length of 0.8-2.0 μm for the square hole.

5. The far-infrared silicon-based high-transmittance metasurface according to claim 1, characterized in that, Deep silicon etching employs the Bosch process, alternating between etching and passivation, with an etching depth of 5-30 μm.

6. The far-infrared silicon-based high-transmittance metasurface according to claim 1, characterized in that, The silicon-silicon bonding is carried out in a vacuum environment, with an annealing temperature of 800-1000℃ and an annealing time of 0.5-2 hours.

7. A design method for a far-infrared silicon-based high-transmittance metasurface as described in any one of claims 1-6, characterized in that, Includes the following steps: S11: Single-crystal silicon is selected as the porous meta-atomic array layer and substrate material, and ZnSe and MgF2 are selected as antireflection film materials; S12: Set the incident environment and the exit environment as parameters of the substrate layer, and adjust the parameters of the microstructure unit of the porous meta-atom array layer, including the hole size, unit period and thickness, wherein the hole size is the diameter of a circular hole or the side length of a square hole. The parameters of the microstructure units were traversed within the range of aperture size 0.8μm-2μm, unit period 2μm-5μm, and thickness 10μm-20μm. The transmittance and phase response of the microstructure units were simulated, and a parameter-performance comparison table was formed. S13: Select unit parameters with transmittance greater than 95% in the working band, arrange microstructure units according to phase requirements, and form a porous meta-atomic array layer. In the porous meta-atomic array layer, the unit period and thickness of the microstructure units are the same, and the pore size meets the phase requirements. S14: Based on the far-infrared 8-12μm band, the thickness of the ZnSe and MgF2 layers in the antireflection coating is optimized with a center wavelength of 10μm. The optimization target is set to a single-sided broadband transmittance of greater than 99.5% under normal incidence conditions. S15: A substrate layer and an antireflection film layer are sequentially combined on both sides of the porous meta-atomic array layer to form a far-infrared silicon-based high-transmittance meta-surface.

Images