All-dielectric terahertz metasurface based on inverted D-shaped column structure and preparation method

Abstract

The invention discloses an all-dielectric terahertz metasurface based on an inverted D-shaped column structure and a preparation method, and belongs to the technical field of terahertz metasurfaces. According to the preparation method provided by the invention, the silicon dioxide layer is used as the protective layer, so that the silicon wafer can be effectively prevented from being oxidized or corroded in the subsequent processing process; through the steps of spin coating of a photoresist layer, baking, placement of a mask plate, exposure, development and the like, a pattern of an inverted D-shaped column structure is formed on a silicon wafer, deep reactive ion etching is performed on the silicon wafer by utilizing etching reaction gas, the inverted D-shaped column structure is formed on the silicon wafer, in-plane rotational symmetry of the all-dielectric terahertz metasurface is broken, and the dielectric performance of the all-dielectric terahertz metasurface is improved. Quasi-continuous domain bound state resonance with a higher Q value and an extremely narrow resonance line width is obtained, and active and flexible tuning of formant frequency and the Q value can be realized by controlling the asymmetry of the structure. And the photoresist layer is effectively removed by using the plasma gas, so that the cleanliness and the integrity of the all-dielectric terahertz metasurface are ensured.

Description

Technical Field

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

[0002] Terahertz metasurfaces, ultrathin planar arrangements of subwavelength resonators of different materials, shapes, and sizes, have broad application prospects in holography, sensing detection, enhanced light emission, chiral effects, and nonlinear optics. However, due to the existence of radiation losses, conventional terahertz metasurfaces can only excite resonances with relatively low Q values, which greatly limits the performance of terahertz optoelectronic devices and metadevices that require strong light-matter interactions.

[0003] Traditional terahertz metasurface designs are often limited by radiation loss problems, making it difficult to improve the resonant Q value, which directly affects the performance of the device in high-sensitivity detection, efficient energy conversion, etc. Although the continuous domain bound state (especially the symmetry-protected type) is a unique non-radiative eigenstate, it provides a new idea for solving this problem - it is located above the light cone, and although the frequency is embedded in the continuous spectrum of the radiation wave, it remains completely orthogonal to the radiation spectrum, thereby avoiding radiation loss. However, the key to achieving this ideal state lies in symmetry breaking, and how to accurately control the degree of symmetry breaking on the all-dielectric terahertz metasurface to produce quasi-continuous domain bound state resonance with high Q value and extremely narrow line width is still a major problem facing current technology. In addition, the size characteristics of the all-dielectric terahertz metasurface (usually between tens and hundreds of microns) further increase the difficulty of technical implementation. Since it is almost impossible to grow such a thick dielectric material directly on the substrate, most of the current high-Q value resonance designs based on the terahertz quasi-continuous domain bound state have to abandon the substrate or use a suspended structure, which not only increases the complexity and cost of manufacturing, but also may introduce additional 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 need to overcome urgently. Summary of the invention

[0005] The purpose of the present invention is to provide an all-dielectric terahertz metasurface based on an inverted D-type 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: A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure comprises the following steps: Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains after cleaning and perform drying treatment 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 on the photoresist layer after baking, the mask having an inverted D-type pattern, exposing and developing the photoresist layer with the mask placed thereon, and obtaining a silicon wafer having an inverted D-type pattern; Step 4: bonding the silicon wafer with the inverted D-shaped pattern to a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with the quartz substrate using an etching reaction gas to obtain an etched silicon wafer with an inverted D-type column structure; remove the photoresist layer of the silicon wafer using plasma gas to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0007] Furthermore, in step 1, the water stains are blown dry after cleaning and the drying process is specifically as follows: nitrogen is used to blow dry the water stains on the silicon wafer, and the dried silicon wafer is placed on a hot plate for baking at a baking temperature of 100-120° and a baking time of 3-7 minutes.

[0008] Furthermore, the protective silicon dioxide layer is deposited to a thickness of 1.5-2.5 μm.

[0009] Further, in step 3, the thickness of the spin-coated photoresist layer is 3~5 μm; the spin-coating speed is 3500~4500 rad / 30 s; the baking temperature of the baked photoresist layer is 110~130°, and the baking time is 3~10 min; the photoresist layer with the mask placed on it is exposed and developed, specifically: the photoresist layer with the mask placed on it is exposed using ultraviolet light with a luminous intensity of 9.6 candela, the exposure time is 20~40 seconds, and the development time is 3~5 minutes.

[0010] Furthermore, 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.

[0011] Further, 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.

[0012] Furthermore, in step 5, the plasma gas is one or more of oxygen, nitrogen and argon.

[0013] The present invention also provides an all-dielectric terahertz metasurface based on an inverted D-type column 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 closely attached to the upper surface of the dielectric substrate, and the dielectric coating layer covers the dielectric metasurface; 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.

[0014] 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.

[0015] 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.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are: The invention provides a preparation method of an all-dielectric terahertz supersurface based on an inverted D-type column 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, which can effectively prevent a silicon wafer from being oxidized or corroded during subsequent processing; a pattern of an inverted D-type column structure is formed on a silicon wafer through the steps of spin coating a photoresist layer, baking, placing a mask, exposing and developing, etc., and the silicon wafer is subjected to deep reactive ion etching by using an etching reaction gas to form an inverted D-type column structure on the silicon wafer, thereby breaking the in-plane rotational symmetry of the all-dielectric terahertz supersurface, obtaining a quasi-continuous domain bound state resonance with a higher Q value and an extremely narrow resonance linewidth, and realizing active and flexible tuning of the resonance peak frequency and the Q value 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 supersurface.

[0017] 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 a terahertz wave is vertically incident on the structure, compared with a traditional terahertz metasurface, it can excite a quasi-continuous domain bound state resonance, providing a high Q value and an 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

[0018] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic 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.

[0019] Figure 1 It is a schematic diagram of the three-dimensional structure of an all-dielectric terahertz metasurface when the in-plane symmetry is not broken; Figure 2 It is a schematic diagram of a two-dimensional unit cell of an all-dielectric terahertz metasurface based on an inverted D-type pillar structure of the present invention that breaks the in-plane structural symmetry; Figure 3 This is a scanning electron microscope image of an all-dielectric terahertz metasurface based on an inverted D-type pillar structure of the present invention; Figure 4 This is a physical picture of an all-dielectric terahertz metasurface based on an inverted D-type column structure of the present invention; Figure 5 It is a line graph of the Q value of the resonance mode in the momentum space of an all-dielectric terahertz metasurface based on an inverted D-type pillar structure of the present invention; Figure 6 It is a transmission spectrum of an all-dielectric terahertz metasurface based on an inverted D-type column structure of the present invention under vertical incidence of a terahertz wave when the in-plane structural symmetry is broken; Figure 7 It is a flow chart of a method for preparing an all-dielectric terahertz supersurface based on an inverted D-type column structure according to the present invention.

[0020] Among them, 1 is a dielectric substrate; 2 is a dielectric metasurface; 3 is a dielectric coating layer; ΔR is the asymmetry factor; R1 is the radius of the inverted D-type 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

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 here can be arranged and designed in various different configurations.

[0022] 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 claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] 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, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0025] In addition, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0027] See also Figure 7 , a method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure, comprising the following steps: Step 1: Clean the double-sided polished silicon wafer, blow dry the water stains after cleaning and perform drying treatment 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 on the photoresist layer after baking, the mask having an inverted D-type pattern, exposing and developing the photoresist layer with the mask placed thereon, and obtaining a silicon wafer having an inverted D-type pattern; Step 4: bonding the silicon wafer with the inverted D-shaped pattern to a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with the quartz substrate using an etching reaction gas to obtain an etched silicon wafer with an inverted D-type column structure; remove the photoresist layer of the silicon wafer using plasma gas to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0028] The preparation 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, 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 the steps of spin coating a photoresist layer, baking, placing a mask, exposing and developing, and the like; the silicon wafer is subjected to deep reactive ion etching using an etching reaction gas to form an inverted D-type column 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, and 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.

[0029] 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 min.

[0030] Specifically, the deposition thickness of the protective silicon dioxide layer is 1.5-2.5 μm.

[0031] Specifically, in step 3, the thickness of the spin-coated photoresist layer is 3-5 μm; the spin-coating speed is 3500-4500 rad / 30 s; the baking temperature of the baked photoresist layer is 110-130°, and the baking time is 3-10 min; 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 20-40 seconds, and the development time is 3-5 min.

[0032] 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.

[0033] 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.

[0034] Specifically, in step 5, the plasma gas is one or more of oxygen, nitrogen and argon.

[0035] 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-type column 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; 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.

[0036] 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.

[0037] 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 resonance wavelength of the dielectric metasurface 2 .

[0038] The all-dielectric terahertz metasurface based on the inverted D-type pillar 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 a terahertz wave is vertically incident on the structure, compared with a traditional terahertz metasurface, it can excite a quasi-continuous domain bound state resonance, providing a high Q value and an 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.

[0039] When an electromagnetic wave in the terahertz band is vertically incident on the metasurface structure, the conditions for the formation of a perfect continuous domain bound state 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 state 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.

[0040] Embodiment 1 A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure is specifically implemented according to the following steps: Step 1, cleaning a double-sided polished silicon wafer with a crystal orientation of 100, and drying it with nitrogen; During cleaning, the substrate was first soaked in acetone, then ultrasonically cleaned for 10 minutes, and after the substrate was taken out, it was ultrasonically cleaned in anhydrous ethanol for 10 minutes, then rinsed with plasma water, and finally the silicon wafer was cleaned with distilled water; Step 2, depositing a protective silicon dioxide layer on the silicon wafer using a plasma enhanced chemical vapor deposition process; Step 3, spin-coating a photoresist layer on the protective silicon dioxide layer, and baking it, and then placing a mask on the photoresist layer, the mask having an inverted D-shaped pattern; AZ4620 photoresist was used for spin coating, where the spin coating speed was 4000 rpm / 30s and the spin coating thickness was 4 μm. After coating, it was placed on a hot plate, set at 100 degrees and baked for 3 minutes; Step 4, exposing the photoresist layer with a UV exposure machine, setting the light intensity to 9.6 candela, and the exposure time to 25 seconds; then developing with a 3038 positive photoresist developer, the development time is 3 minutes, and finally obtaining a silicon wafer with an inverse D-type pattern; 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; Step 6, using deep reactive ion etching technology, a mixed gas of C4F8 and SF6 is used to etch the silicon wafer, the flow rates of C4F8 and SF6 are set to 200 sccm and 400 sccm, respectively, and the etching depth is 100 μm; then, dry stripping is performed with oxygen plasma gas to remove the remaining photoresist to obtain a periodic all-dielectric structure, and then an all-dielectric terahertz metasurface based on a double-symmetric protected quasi-continuum bound state is obtained.

[0041] By adopting 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 resonance frequency and Q value of the bound state in the quasi-continuous domain, wherein the asymmetry factor is the difference between the radius of the inverted D-shaped column structure and the vertical distance from the center of its circle to the straight edge of the inverted D-shaped column structure.

[0042] 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 incident on the structure vertically, 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.

[0043] See also Figure 6By 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 resonance peak increases. α As the asymmetry factor increases, the resonance frequencies of the two quasi-continuous domain bound states are red-shifted or blue-shifted, respectively, and the line width of the resonance gradually widens. 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, line width and Q value.

[0044] Embodiment 2 An all-dielectric terahertz metasurface based on an inverted D-type column 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 closely attached to the upper surface of the dielectric substrate 1, and the dielectric coating layer 3 covers 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; 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, both of which are equal to the resonant wavelength of the dielectric metasurface 2.

[0045] See also Figure 5 The Q value distribution line diagram along the high symmetry direction in momentum space shows that the wave vectors of the two resonant 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 symmetry-protected continuous domain bound states.

[0046] Embodiment 4 A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure comprises the following steps: Step 1: clean the double-sided polished silicon wafer, use nitrogen to blow dry the water stains on the silicon wafer, place the dried silicon wafer on a hot plate and bake it at a temperature of 100° for 3 min 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, wherein the deposition thickness of the protective silicon dioxide layer is 1.5 μm, thereby obtaining a silicon wafer with a protective silicon dioxide layer; Step 3: Spin-coat a photoresist layer on the protective silicon dioxide layer of the silicon wafer, the thickness of the spin-coated photoresist layer is 3-5 μm, and the spin-coating speed is 3500 rad / 30 s; bake the photoresist layer, the baking temperature is 110°, and the baking time is 3 min; after baking, place a mask on the photoresist layer, the mask has an inverted D-type pattern, and use ultraviolet light with a luminous intensity of 9.6 candela to expose the photoresist layer with the mask, the exposure time is 20 seconds, and the development time is 3 min, to obtain a silicon wafer with an inverted D-type pattern; 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 under UV light with an irradiance of 2.5 W cm −2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with the quartz substrate using etching reaction gas, wherein the etching reaction gas is 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; remove the photoresist layer of the silicon wafer by plasma gas, wherein the plasma gas is oxygen, to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0047] Embodiment 5 A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure comprises the following steps: 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; Step 2: Depositing a protective silicon dioxide layer on the dried silicon wafer using a plasma enhanced chemical vapor deposition process, wherein the deposition thickness of the protective silicon dioxide layer is 2.5 μm, thereby obtaining a silicon wafer with a protective silicon dioxide layer; Step 3: Spin-coat 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; bake the photoresist layer, the baking temperature is 130°, and the baking time is 10 min; after baking, place a mask on the photoresist layer, the mask has an inverted D-type pattern, and use ultraviolet light with a luminous intensity of 9.6 candela to expose the photoresist layer with the mask, the exposure time is 40 seconds, and the development time is 5 min, to obtain a silicon wafer with an inverted D-type pattern; 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 under UV light with an irradiance of 2.5 W cm −2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with the quartz substrate using etching reaction gas, wherein the etching reaction gas is 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; remove the photoresist layer of the silicon wafer by plasma gas, wherein the plasma gas is nitrogen, to obtain an all-dielectric terahertz metasurface based on the inverted D-type column structure.

[0048] Embodiment 6 A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column structure comprises the following steps: 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 min 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, wherein the deposition thickness of the protective silicon dioxide layer is 2 μm, thereby obtaining a silicon wafer with a protective silicon dioxide layer; Step 3: Spin-coat 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; bake the photoresist layer, the baking temperature is 120°, and the baking time is 7 min; after baking, place a mask on the photoresist layer, the mask has an inverted D-type pattern, and use ultraviolet light with a luminous intensity of 9.6 candela to expose the photoresist layer with the mask, the exposure time is 30 seconds, and the development time is 4 min, to obtain a silicon wafer with an inverted D-type pattern; 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 under UV light with an irradiance of 2.5 W cm−2 , exposure time 10 minutes, to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with a quartz substrate using an etching reaction gas, wherein the etching reaction gas is 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 an etched silicon wafer with an inverted D-type column structure; remove the photoresist layer of the silicon wafer 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.

[0049] Finally, it should be noted that the above-listed embodiments exist only as one or more specific forms of expression of the technical solution of the present invention. Their purpose is to clearly explain the concept, principle and application of the present invention through specific examples, and it is by no means intended to limit the protection scope of the present invention to these specific embodiments. In fact, the real value of the present invention lies in the technical ideas and innovations it proposes, rather than its form of expression or means of implementation.

[0050] For ordinary technicians in the relevant technical field, after in-depth reading and understanding of the technical solution of the present invention, they are fully capable of making various forms of changes, modifications or equivalent substitutions 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 changed 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.

[0051] In addition, with the continuous progress and development of technology, new technical means and methods continue to emerge, which also provides broad space for further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and extensions based on the existing technology. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are also protected by patent rights.

Claims

1. A method for preparing an all-dielectric terahertz metasurface based on an inverted D-type column 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 perform drying treatment 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 plate on the photoresist layer after baking, wherein the mask plate has an inverted D-type pattern, exposing and developing the photoresist layer on which the mask plate is placed, and obtaining a silicon wafer having an inverted D-type pattern; Step 4: bonding the silicon wafer with the inverted D-shaped pattern to a quartz substrate and exposing it to ultraviolet light to obtain a silicon wafer with a quartz substrate; Step 5: Perform deep reactive ion etching on the silicon wafer with the quartz substrate using an etching reaction gas to obtain an etched silicon wafer with an inverted D-type column structure; remove the photoresist layer of the silicon wafer using 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-type pillar structure according to claim 1, characterized in that: In step 1, the water stains are blown away after cleaning and the drying treatment is specifically: nitrogen is used to blow away the water stains on the silicon wafer, and the dried silicon wafer is placed on a hot plate for baking at a baking temperature of 100-120° for 3-7 min.

3. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-type pillar structure according to claim 1, characterized in that: The protective silicon dioxide layer was 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-type pillar structure according to claim 1, characterized in that: In step 3, the thickness of the spin-coated photoresist layer is 3~5 μm; the spin-coating speed is 3500~4500 rad / 30s; the baking temperature of the baked photoresist layer is 110~130°, and the baking time is 3~10 min; the photoresist layer with the mask placed is exposed and developed, specifically: the photoresist layer with the mask placed is exposed using ultraviolet light with a luminous intensity of 9.6 candela, the exposure time is 20~40 seconds, and the development time is 3~5 min.

5. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-type pillar structure according to claim 1, characterized in that: 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.

6. The method for preparing an all-dielectric terahertz metasurface based on an inverted D-type pillar structure according to claim 1, characterized in that: 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-type 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-type column structure, characterized in that: Prepared by the method described in any one of claims 1 to 7, 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 tightly 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-type 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-type 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 resonance wavelength of the dielectric metasurface (2).

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