A full-dielectric terahertz metasurface based on inverse-d-shaped post structure and preparation method thereof

Abstract

The application discloses a kind of full dielectric terahertz super surface based on inverted D-shaped column structure and preparation method, belong to terahertz super surface technical field.The preparation method provided by the present application uses silica layer as protective layer, which can effectively prevent silicon wafer from being oxidized or corroded during subsequent processing;By spin coating photoresist layer, baking, placing mask, exposure and development, etc., the pattern of inverted D-shaped column structure is formed on the silicon wafer, and the silicon wafer is etched by using etching reaction gas, forming inverted D-shaped column structure on the silicon wafer, breaking the in-plane rotational symmetry of full dielectric terahertz super surface, obtaining quasi-continuous domain bound state resonance with higher Q value and extremely narrow resonance line width, and by controlling the size of structure asymmetry, the resonance peak frequency and Q value can be actively and flexibly tuned;The use of plasma gas effectively removes the photoresist layer, ensuring the cleanliness and integrity of the full dielectric terahertz super surface.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz metasurfaces, and in particular to an all-dielectric terahertz metasurface based on an inverted D-shaped column structure. Background Art

[0002] Terahertz metasurfaces, ultrathin planar arrangements of subwavelength resonators of varying materials, shapes, and sizes, hold great promise for applications in holography, sensing, enhanced light emission, chiral effects, and nonlinear optics. However, due to radiative losses, conventional terahertz metasurfaces can only excite resonances with relatively low Q values, significantly limiting the performance of terahertz optoelectronic devices and metadevices requiring strong light-matter interactions.

[0003] Conventional terahertz metasurface designs are often limited by radiative losses, making it difficult to improve resonant Q. This directly impacts device performance in areas such as high-sensitivity detection and efficient energy conversion. Continuum bound states (particularly symmetry-protected ones) offer a novel approach to addressing this issue as unique non-radiative eigenstates. These states reside above the light cone, and while their frequencies are embedded in the continuum spectrum of the radiated wave, they remain completely orthogonal to it, thus avoiding radiative losses. However, achieving this ideal state relies on symmetry breaking. Precisely controlling the degree of symmetry breaking on all-dielectric terahertz metasurfaces to generate high-Q quasi-continuum bound state resonances with extremely narrow linewidths remains a significant technical challenge. Furthermore, the dimensional characteristics of all-dielectric terahertz metasurfaces (typically ranging from tens to hundreds of microns) further complicate implementation. Because growing such thick dielectric materials directly on substrates is nearly impossible, most current high-Q resonant designs based on terahertz quasi-continuum bound states forgo substrates or resort to suspended structures, which not only increases fabrication complexity and cost but also introduces potential stability and durability issues.

[0004] Therefore, how to break the in-plane symmetry of the metasurface that supports the symmetry-protected continuous domain bound state while maintaining substrate support, thereby stimulating quasi-continuous domain bound state resonance with extremely high Q value and extremely narrow resonance linewidth, has become a technical problem that technicians in this field urgently need to overcome. Summary of the Invention

[0005] The purpose of the present invention is to provide an all-dielectric terahertz metasurface based on an inverted D-shaped column structure and a preparation method thereof, so as to overcome the problem in the prior art that the Q value is difficult to improve while maintaining the substrate.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure comprises the following steps:

[0008] Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains after cleaning and dry it to obtain a dried silicon wafer;

[0009] Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma enhanced chemical vapor deposition process to obtain a silicon wafer with a protective silicon dioxide layer;

[0010] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, baking the photoresist layer, placing a mask having an inverted D-shaped pattern on the photoresist layer after baking, exposing and developing the photoresist layer with the mask, and obtaining a silicon wafer having an inverted D-shaped pattern;

[0011] Step 4: Bonding the silicon wafer with the inverted D-shaped pattern onto a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate;

[0012] Step 5: Deep reactive ion etching is performed on the silicon wafer with the quartz substrate using an etching reaction gas to obtain a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0013] Furthermore, in step 1, the water stains are blown away after cleaning and the drying process is specifically as follows: nitrogen is used to blow away the water stains on the silicon wafer, and the dried silicon wafer is placed on a hot plate and baked at a baking temperature of 100~120° and a baking time of 3~7 minutes.

[0014] Furthermore, the protective silicon dioxide layer is deposited to a thickness of 1.5 to 2.5 μm.

[0015] Furthermore, in step 3, the thickness of the spin-coated photoresist layer is 3 to 5 μm; the spin-coating speed is 3500 to 4500 rad / 30 s; the baking temperature of the photoresist layer is 110 to 130°, and the baking time is 3 to 10 min; the photoresist layer with the mask placed thereon is exposed and developed, specifically: ultraviolet light with a luminous intensity of 9.6 candela is used to expose the photoresist layer with the mask placed thereon, the exposure time is 20 to 40 seconds, and the development time is 3 to 5 minutes.

[0016] Furthermore, in step 4, the thickness of the quartz substrate is 300-500 μm; the light irradiance during exposure under ultraviolet light is 2.5 W cm −2 , exposure time 10 minutes.

[0017] Furthermore, in step 5, the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm.

[0018] Furthermore, in step 5, the plasma gas is one or more of oxygen, nitrogen and argon.

[0019] The present invention also provides an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure, which is prepared by the above method and includes N×N unit cell structures periodically arranged along the x and y directions. Each unit cell structure includes a dielectric substrate, a dielectric coating layer and a dielectric metasurface. The dielectric metasurface is tightly attached to the upper surface of the dielectric substrate, and the dielectric coating layer covers the dielectric metasurface.

[0020] Among them, the dielectric metasurface is a silicon wafer with an inverted D-shaped column structure, the dielectric substrate is a quartz substrate, and the dielectric coating layer is air.

[0021] Furthermore, the radius of the dielectric metasurface is 2.6 times its height; the periodicity is specifically: the distance between the centers of any two adjacent dielectric metasurfaces is 3 times their height.

[0022] Furthermore, the thickness of the dielectric substrate is equal to the thickness of the dielectric cladding layer, and both are equal to the resonant wavelength of the dielectric metasurface.

[0023] Compared with the prior art, the present invention has the following positive effects:

[0024] The present invention provides a preparation method of an all-dielectric terahertz metasurface based on an inverted D-type pillar structure. The method does not require stacking of multiple layers of materials, is easy to prepare, and is not easily oxidized or corroded. Specifically, a silicon dioxide layer is used as a protective layer to effectively prevent a silicon wafer from being oxidized or corroded during subsequent processing. A pattern of the inverted D-type pillar structure is formed on a silicon wafer through the steps of spin coating a photoresist layer, baking, placing a mask, exposing and developing. The silicon wafer is subjected to deep reactive ion etching using an etching reaction gas to form the inverted D-type pillar structure on the silicon wafer, thereby breaking the in-plane rotational symmetry of the all-dielectric terahertz metasurface and obtaining a quasi-continuous domain bound state resonance with a higher Q value and an extremely narrow resonance linewidth. Active and flexible tuning of the resonance peak frequency and the Q value can be achieved by controlling the size of the structural asymmetry. The use of plasma gas effectively removes the photoresist layer, thereby ensuring the cleanliness and integrity of the all-dielectric terahertz metasurface.

[0025] The present invention also provides an all-dielectric terahertz metasurface based on an inverted D-type column structure, which has a simple geometric structure and includes N×N unit cell structures periodically arranged along the x and y directions. Each unit cell structure includes a dielectric substrate, a dielectric coating layer and a dielectric metasurface. When the terahertz wave is vertically incident on the structure, compared with the traditional terahertz metasurface, it can excite quasi-continuous domain bound state resonance, providing a high Q value and extremely narrow resonance linewidth. At the same time, since the structure is transparent to terahertz radiation, the transmittance of the structure can be directly obtained from the transmission spectrum, which provides convenience for the performance testing and application of the metasurface. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 This is a schematic diagram of the three-dimensional structure of an all-dielectric terahertz metasurface without breaking the in-plane symmetry;

[0028] Figure 2 This is a schematic diagram of a two-dimensional unit cell of an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure of the present invention that breaks the in-plane structural symmetry;

[0029] Figure 3 This is a scanning electron microscope image of an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to the present invention;

[0030] Figure 4 This is a physical picture of an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to the present invention;

[0031] Figure 5 It is a line graph of the Q value of the resonant mode in the momentum space of an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure of the present invention;

[0032] Figure 6 It is the transmission spectrum of the all-dielectric terahertz metasurface based on the inverted D-shaped pillar structure of the present invention under vertical incidence of terahertz waves when the in-plane structural symmetry is broken;

[0033] Figure 7 This is a flow chart of a method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure according to the present invention.

[0034] Among them, 1 is the dielectric substrate; 2 is the dielectric metasurface; 3 is the dielectric cladding layer;

[0035] ΔR is the asymmetry factor; R1 is the radius of the inverted D-shaped column structure; p is the distance between the centers of any two adjacent dielectric metasurfaces; H is the thickness of the dielectric coating layer; and h is the height of the dielectric metasurface. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0039] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] Furthermore, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0042] See also Figure 7 A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type pillar structure comprises the following steps:

[0043] Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains after cleaning and dry it to obtain a dried silicon wafer;

[0044] Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma enhanced chemical vapor deposition process to obtain a silicon wafer with a protective silicon dioxide layer;

[0045] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, baking the photoresist layer, placing a mask having an inverted D-shaped pattern on the photoresist layer after baking, exposing and developing the photoresist layer with the mask, and obtaining a silicon wafer having an inverted D-shaped pattern;

[0046] Step 4: Bonding the silicon wafer with the inverted D-shaped pattern onto a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate;

[0047] Step 5: Deep reactive ion etching is performed on the silicon wafer with the quartz substrate using an etching reaction gas to obtain a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0048] This preparation method does not require stacking multiple layers of materials, is easy to prepare, and is not easily oxidized or corroded. Specifically: a silicon dioxide layer is used as a protective layer, which can effectively prevent the silicon wafer from being oxidized or corroded during subsequent processing; a pattern of an inverted D-type column structure is formed on the silicon wafer through steps such as spin coating a photoresist layer, baking, placing a mask, exposing and developing, and deep reactive ion etching is performed on the silicon wafer using an etching reaction gas to form an inverted D-type column structure on the silicon wafer, breaking the in-plane rotational symmetry of the all-dielectric terahertz metasurface, and obtaining a quasi-continuous domain bound state resonance with a higher Q value and an extremely narrow resonance linewidth, and by controlling the size of the structural asymmetry, active and flexible tuning of the resonance peak frequency and Q value can be achieved; the use of plasma gas effectively removes the photoresist layer, ensuring the cleanliness and integrity of the all-dielectric terahertz metasurface.

[0049] Specifically, in step 1, the water stains are blown away after cleaning and the drying process is specifically as follows: the water stains on the silicon wafer are blown away with nitrogen, and the dried silicon wafer is placed on a hot plate and baked at a baking temperature of 100-120° for 3-7 minutes.

[0050] Specifically, the protective silicon dioxide layer is deposited to a thickness of 1.5 to 2.5 μm.

[0051] Specifically, in step 3, the thickness of the spin-coated photoresist layer is 3 to 5 μm; the spin-coating speed is 3500 to 4500 rad / 30 s; the baking temperature of the photoresist layer is 110 to 130°, and the baking time is 3 to 10 min; the photoresist layer with the mask placed thereon is exposed and developed, specifically: ultraviolet light with a luminous intensity of 9.6 candela is used to expose the photoresist layer with the mask placed thereon, the exposure time is 20 to 40 seconds, and the development time is 3 to 5 min.

[0052] Specifically, in step 4, the thickness of the quartz substrate is 300-500 μm; the light irradiance for exposure under ultraviolet light is 2.5 W cm −2 , exposure time 10 minutes.

[0053] Specifically, in step 5, the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm.

[0054] Specifically, in step 5, the plasma gas is one or more of oxygen, nitrogen and argon.

[0055] See also Figure 1 Based on the same inventive concept, the present invention also provides an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure, which is prepared by the above method and includes N×N unit cell structures periodically arranged along the x and y directions. Each unit cell structure includes a dielectric substrate 1, a dielectric coating layer 3 and a dielectric metasurface 2. The dielectric metasurface 2 is tightly attached to the upper surface of the dielectric substrate 1, and the dielectric coating layer 3 covers the dielectric metasurface 2.

[0056] The dielectric metasurface 2 is a silicon wafer with an inverted D-shaped column structure, the dielectric substrate 1 is a quartz substrate, and the dielectric coating layer 3 is air.

[0057] Specifically, the radius of the dielectric metasurface 2 is 2.6 times its height; the periodicity is specifically: the distance between the centers of any two adjacent dielectric metasurfaces 2 is 3 times their height.

[0058] Specifically, the thickness of the dielectric substrate 1 is equal to the thickness of the dielectric cladding layer 3 , and both are equal to the resonant wavelength of the dielectric metasurface 2 .

[0059] The all-dielectric terahertz metasurface based on the inverted D-shaped column structure provided by the present invention has a simple geometric structure and includes N×N unit cell structures periodically arranged along the x and y directions. Each unit cell structure includes a dielectric substrate 1, a dielectric coating layer 3 and a dielectric metasurface 2. When the terahertz wave is vertically incident on the structure, compared with the traditional terahertz metasurface, it can excite quasi-continuous domain bound state resonance, providing a high Q value and extremely narrow resonance linewidth. At the same time, since the structure is transparent to terahertz radiation, the transmittance of the structure can be directly obtained from the transmission spectrum, which provides convenience for the performance testing and application of the metasurface.

[0060] When electromagnetic waves in the terahertz band are incident vertically on the metasurface structure, the conditions for the formation of perfect continuous domain bound states are met, and two symmetric protected continuous domain bound states with Q values ​​tending to infinity are excited at the center point Γ of the momentum space. After breaking the structural symmetry of the metasurface, a coupling channel is constructed between the perfect continuous domain bound states and the incident electromagnetic wave, and the two symmetric protected continuous domain bound states are transformed into quasi-continuous domain bound states with extremely narrow resonance linewidths.

[0061] Example 1

[0062] A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure is specifically implemented according to the following steps:

[0063] Step 1: Cleaning a double-sided polished silicon wafer with a crystal orientation of 100 and drying it with nitrogen;

[0064] During cleaning, the substrate was first soaked in acetone and then ultrasonically cleaned for 10 minutes. After the substrate was removed, it was ultrasonically cleaned in anhydrous ethanol for 10 minutes, followed by rinsing with plasma water, and finally the silicon wafer was cleaned with distilled water.

[0065] Step 2: depositing a protective silicon dioxide layer on the silicon wafer using a plasma enhanced chemical vapor deposition process;

[0066] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer and baking it, and then placing a mask having an inverted D-shaped pattern on the photoresist layer;

[0067] AZ4620 photoresist was spin-coated at a speed of 4000 rpm for 30 s and a thickness of 4 μm. After coating, the substrate was placed on a hot plate at 100°C and baked for 3 minutes.

[0068] Step 4: Expose the photoresist layer using a UV exposure machine with a light intensity of 9.6 candelas and an exposure time of 25 seconds; then develop the layer using a 3038 positive photoresist developer for 3 minutes, ultimately obtaining a silicon wafer with an inverted D-shaped pattern.

[0069] Step 5: Use Norland Optical Adhesive 85 UV-curable polymer adhesive to directly bond the silicon wafer with the photoresist layer to the quartz substrate. −2 Exposure to ultraviolet light for 10 minutes;

[0070] In step 6, the silicon wafer is etched using a mixture of C4F8 and SF6 gas through deep reactive ion etching technology. The flow rates of C4F8 and SF6 gases are set to 200 sccm and 400 sccm, respectively, and the etching depth is 100 μm. Then, oxygen plasma gas is used for dry stripping to remove the remaining photoresist to obtain a periodic all-dielectric structure, thereby obtaining an all-dielectric terahertz metasurface based on a bisymmetric protected quasi-continuous domain bound state.

[0071] By using this preparation method, the degree of symmetry breaking of the terahertz metasurface structure can be changed by changing the asymmetry factor of the mask, thereby achieving active and on-demand adjustment of the quasi-continuous domain bound state resonance frequency and Q value, wherein the asymmetry factor is the difference between the radius of the inverted D-shaped column structure and the vertical distance from its center to the straight edge of the inverted D-shaped column structure.

[0072] See also Figure 2 It can be seen that by breaking the in-plane rotational symmetry of the terahertz metasurface, the symmetry-protected continuous domain bound state is transformed into a quasi-continuous domain bound state. When the terahertz wave is vertically incident on the structure, the quasi-continuous domain bound state resonance can be excited, providing a high Q value and extremely narrow resonance linewidth. At the same time, since the structure is transparent to terahertz radiation, the transmittance of the structure can be directly obtained from the transmission spectrum.

[0073] See also Figure 6 By changing the asymmetry factor of the mask in Example 1, an all-dielectric terahertz metasurface based on an inverted D-type column structure with three asymmetry factors is obtained. The three asymmetry factors are ΔR=0, 15, and 40μm, respectively. The transmittance curve of the corresponding all-dielectric terahertz metasurface is obtained through the transmission spectrum. When the asymmetry factor ΔR is zero, no resonance peak appears in the spectrum, and the two symmetrically protected continuous domain bound states on the surface do not couple with external electromagnetic waves; when the asymmetry factor ΔR is greater than zero, the two symmetrically protected continuous domain bound states supported by the all-dielectric terahertz metasurface are transformed into quasi-continuous domain bound states with extremely narrow linewidth. As the asymmetry factor increases, the two symmetrically protected continuous domain bound states supported by the all-dielectric terahertz metasurface are transformed into quasi-continuous domain bound states with extremely narrow linewidth. α As the asymmetry factor increases, the resonance frequencies of the two quasi-continuous domain bound states red-shift or blue-shift, respectively, and the line width of the resonance gradually broadens. These results show that by finely controlling the asymmetry factor α The size of the bound state resonance in the quasi-continuum domain can be actively tuned to adjust the frequency, linewidth and Q value.

[0074] Example 2

[0075] An all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure, comprising N×N unit cell structures periodically arranged along the x and y directions, each unit cell structure comprising a dielectric substrate 1, a dielectric coating layer 3, and a dielectric metasurface 2. The dielectric metasurface 2 is tightly attached to the upper surface of the dielectric substrate 1, and the dielectric coating layer 3 covers the dielectric metasurface 2.

[0076] The dielectric metasurface 2 is a silicon wafer with an inverted D-shaped column structure, the dielectric substrate 1 is a quartz substrate, and the dielectric coating layer 3 is air.

[0077] See also Figure 3 and Figure 4 , the height h of the dielectric metasurface 2 is 100 μm, the radius R=260 μm, the center distance between any two adjacent dielectric metasurfaces 2 is 300 μm, the thickness of the dielectric substrate 1 is equal to the thickness of the dielectric cladding layer 3, and both are equal to the resonant wavelength of the dielectric metasurface 2.

[0078] See also Figure 5 From the Q value distribution line diagram along the high symmetry direction in momentum space, it can be concluded that the wave vectors of the two resonance modes in momentum space are k =0 is divergent and exceeds 10 to the eighth power, indicating that the all-dielectric metasurface 2 can support two symmetric protected continuous domain bound states.

[0079] Example 4

[0080] A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure comprises the following steps:

[0081] Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains on the silicon wafer with nitrogen, place the dried silicon wafer on a hot plate and bake it at 100° for 3 minutes to obtain a dried silicon wafer;

[0082] Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma-enhanced chemical vapor deposition process. The protective silicon dioxide layer is deposited to a thickness of 1.5 μm to obtain a silicon wafer with a protective silicon dioxide layer.

[0083] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, with a thickness of 3-5 μm and a spin-coating speed of 3500 rad / 30 s; baking the photoresist layer at a baking temperature of 110° for 3 minutes; after baking, placing a mask having an inverted D-shaped pattern on the photoresist layer, and exposing the photoresist layer with the mask using ultraviolet light with a luminous intensity of 9.6 candela for 20 seconds and a development time of 3 minutes, thereby obtaining a silicon wafer having an inverted D-shaped pattern;

[0084] Step 4: Bond the silicon wafer with the inverse D-shaped pattern to a quartz substrate with a thickness of 300 μm and expose it to UV light with an irradiance of 2.5 W cm −2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate;

[0085] Step 5: Deep reactive ion etching is performed on the silicon wafer with a quartz substrate using etching reaction gases, wherein the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm, thereby obtaining a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas, wherein the plasma gas is oxygen, thereby obtaining an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0086] Example 5

[0087] A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure comprises the following steps:

[0088] Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains on the silicon wafer with nitrogen, place the dried silicon wafer on a hot plate and bake it at a temperature of 120° for 7 minutes to obtain a dried silicon wafer;

[0089] Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma-enhanced chemical vapor deposition process. The protective silicon dioxide layer is deposited to a thickness of 2.5 μm to obtain a silicon wafer with a protective silicon dioxide layer.

[0090] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, the thickness of the spin-coated photoresist layer is 5 μm, and the spin-coating speed is 4500 rad / 30 s; baking the photoresist layer at a baking temperature of 130° for 10 minutes; after baking, placing a mask having an inverted D-shaped pattern on the photoresist layer, and exposing the photoresist layer with the mask using ultraviolet light with a luminous intensity of 9.6 candela for 40 seconds and a development time of 5 minutes, thereby obtaining a silicon wafer having an inverted D-shaped pattern;

[0091] Step 4: Bond the silicon wafer with the inverse D-shaped pattern to a quartz substrate with a thickness of 500 μm and expose it to UV light with an irradiance of 2.5 W cm −2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate;

[0092] Step 5: Deep reactive ion etching is performed on the silicon wafer with a quartz substrate using etching reaction gases, wherein the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm, thereby obtaining a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas, wherein the plasma gas is nitrogen, thereby obtaining an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0093] Example 6

[0094] A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure comprises the following steps:

[0095] Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains on the silicon wafer with nitrogen, place the dried silicon wafer on a hot plate and bake it at a temperature of 110° for 5 minutes to obtain a dried silicon wafer;

[0096] Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma-enhanced chemical vapor deposition process. The protective silicon dioxide layer is deposited to a thickness of 2 μm, thereby obtaining a silicon wafer with a protective silicon dioxide layer.

[0097] Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, the thickness of the spin-coated photoresist layer is 4 μm, and the spin-coating speed is 4000 rad / 30 s; baking the photoresist layer at a baking temperature of 120° for 7 minutes; after baking, placing a mask having an inverted D-shaped pattern on the photoresist layer, and exposing the photoresist layer with the mask using ultraviolet light with a luminous intensity of 9.6 candela for 30 seconds and a development time of 4 minutes, thereby obtaining a silicon wafer having an inverted D-shaped pattern;

[0098] Step 4: Bond the silicon wafer with the inverse D-shaped pattern to a quartz substrate with a thickness of 400 μm and expose it to UV light with an irradiance of 2.5 W cm −2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate;

[0099] Step 5: Deep reactive ion etching is performed on the silicon wafer with a quartz substrate using etching reaction gases, wherein the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm, to obtain a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas, wherein the plasma gas is nitrogen and argon, to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0100] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of the present invention. Their purpose is to clearly illustrate the concept, principles, and application of the present invention through specific examples, and is in no way intended to limit the scope of protection of the present invention to these specific embodiments. In fact, the true value of this invention lies in its technical ideas and innovations, not in its form of expression or implementation.

[0101] For ordinary technicians in the relevant technical field, after thoroughly reading and understanding the technical solutions of the present invention, they are fully capable of making various forms of changes, modifications or equivalent replacements to the specific implementation methods of the invention based on their own professional knowledge and skills. These changes may include but are not limited to: adjusting the value range of technical parameters, optimizing algorithm processes to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as these modified technical solutions still substantially maintain the technical features claimed for protection by the original invention, that is, they can still achieve the core functions and effects of the present invention, then these changes should be deemed to fall within the scope of protection of the pending claims of the present invention.

[0102] Furthermore, with the continuous advancement and development of technology, new technical means and methods continue to emerge, providing ample room for further improvement and perfection of the present invention. Therefore, the scope of protection of the present invention should also include reasonably foreseeable improvements and extensions based on existing technologies. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be considered equivalent to the present invention and equally protected by patent rights.

Claims

1. A method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure, characterized in that: The following steps are involved: Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains after cleaning and dry it to obtain a dried silicon wafer; Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma enhanced chemical vapor deposition process to obtain a silicon wafer with a protective silicon dioxide layer; Step 3: Spin-coating a photoresist layer on the protective silicon dioxide layer of the silicon wafer, baking the photoresist layer, placing a mask having an inverted D-shaped pattern on the photoresist layer after baking, exposing and developing the photoresist layer with the mask placed thereon, and obtaining a silicon wafer having an inverted D-shaped pattern; Step 4: Bonding the silicon wafer with the inverted D-shaped pattern onto a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate; Step 5: Deep reactive ion etching is performed on the silicon wafer with the quartz substrate using an etching reaction gas to obtain a silicon wafer with an inverted D-type column structure after etching; the photoresist layer of the silicon wafer is removed by plasma gas to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

2. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, wherein: In step 1, the water stains are blown away after cleaning and the drying process is specifically as follows: the water stains on the silicon wafer are blown away with nitrogen, and the dried silicon wafer is placed on a hot plate and baked at a baking temperature of 100-120° for 3-7 minutes.

3. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, wherein: The protective silicon dioxide layer is deposited to a thickness of 1.5–2.5 μm.

4. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, wherein: In step 3, the thickness of the spin-coated photoresist layer is 3 to 5 μm; the spin-coating speed is 3500 to 4500 rad / 30 seconds; the baking temperature of the photoresist layer is 110 to 130 degrees, and the baking time is 3 to 10 minutes; the photoresist layer with the mask placed thereon is exposed and developed, specifically: the photoresist layer with the mask placed thereon is exposed using ultraviolet light with a luminous intensity of 9.6 candela, the exposure time is 20 to 40 seconds, and the development time is 3 to 5 minutes.

5. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, wherein: In step 4, the thickness of the quartz substrate is 300-500 μm; the light irradiance during exposure under ultraviolet light is 2.5 W cm −2 , exposure time 10 minutes.

6. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, wherein: In step 5, the etching reaction gases are C4F8 gas and SF6 gas, wherein the flow rate of C4F8 gas is 200 sccm, the flow rate of SF6 gas is 400 sccm, and the etching depth is 100 μm.

7. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 1, characterized in that: In step 5, the plasma gas is one or more of oxygen, nitrogen and argon.

8. An all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure, characterized in that: Prepared by the method described in any one of claims 1 to 7 above, comprising N×N unit cell structures periodically arranged along the x and y directions, each unit cell structure comprising a dielectric substrate (1), a dielectric coating layer (3) and a dielectric metasurface (2), the dielectric metasurface (2) being closely attached to the upper surface of the dielectric substrate (1), and the dielectric coating layer (3) coating the dielectric metasurface (2); The dielectric metasurface (2) is a silicon wafer with an inverted D-shaped column structure, the dielectric substrate (1) is a quartz substrate, and the dielectric coating layer (3) is air.

9. The all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 8, characterized in that: The radius of the dielectric metasurface (2) is 2.6 times its height; the periodicity is specifically: the distance between the centers of any two adjacent dielectric metasurfaces (2) is 3 times their height.

10. The all-dielectric terahertz metasurface based on an inverted D-shaped pillar structure according to claim 8, characterized in that: The thickness of the dielectric substrate (1) is equal to the thickness of the dielectric cladding layer (3), and both are equal to the resonant wavelength of the dielectric metasurface (2).

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