A transmission type terahertz absorption structure and a preparation method thereof

Abstract

The embodiment of the present application discloses a kind of transmission type terahertz absorption structure and preparation method thereof.Transmission type terahertz absorption structure includes at least one transmission type terahertz absorption composite film layer, transmission type terahertz absorption composite film layer includes substrate and the metal grating layer, insulating layer and graphene layer that are sequentially stacked in substrate side;Wherein metal grating layer and graphene layer are electrically connected with external power supply.The technical scheme of the embodiment of the present application is based on electromagnetic wave theory and the electrical properties of graphene, by additional voltage control Fermi level of graphene, adjust the absorption of absorption structure to terahertz, make the terahertz wave that pass through the present absorption structure have different intensity information under the influence of external voltage, play the role of switch, and have the advantages of active regulation, real-time control, accurate control, suitable for terahertz spectrum imaging analysis, single-pixel imaging and spectrum measurement etc.

Description

Technical Field

[0001] This invention relates to the field of terahertz wave modulation technology, and in particular to a transmission-type terahertz absorption structure and its preparation method. Background Technology

[0002] Terahertz waves, with a frequency range between 0.1 THz and 10 THz, are electromagnetic waves whose frequency classification lies between millimeter waves and infrared radiation, and whose energy classification lies between electrons and photons. They possess characteristics such as short wavelength (0.03 mm to 3 mm), large bandwidth, strong penetration, low photon energy, and high resolution, making them extremely promising for applications in data transmission, biomedicine, new materials research, aerospace science, and Earth environmental science.

[0003] Terahertz technology has made continuous progress in recent years, but there are still many areas for improvement in the field of terahertz absorbers, such as the active modulation performance of the absorber, the timeliness of modulation, and the controllability of modulation. Existing terahertz absorbers generally adopt a reflective structure, which needs to reflect the incident terahertz wave signal back for absorption, thus generating a certain reflection loss, resulting in the absorption efficiency needing to be improved. Summary of the Invention

[0004] This invention provides a transmission-type terahertz absorption structure and its preparation method. Based on electromagnetic wave theory and the electrical properties of graphene, the transmission-type terahertz absorption structure adjusts the absorption degree of terahertz by controlling the Fermi level of graphene through an applied voltage. This allows the terahertz wave passing through the absorption structure to have different intensity information under the influence of the applied voltage, thus acting as a switch. It also has the advantages of active regulation, real-time regulation, and precise control, and is suitable for fields such as terahertz spectral imaging analysis, single-pixel imaging, and spectral measurement.

[0005] According to one aspect of the present invention, a transmissive terahertz absorption structure is provided, comprising at least one transmissive terahertz absorption composite film layer, wherein the transmissive terahertz absorption composite film layer comprises a substrate and a metal grating layer, an insulating layer and a graphene layer sequentially stacked on one side of the substrate;

[0006] The metal grating layer and the graphene layer are electrically connected to an external power source.

[0007] Optionally, the substrate includes a silicon dioxide substrate, the metal grating layer includes an aluminum grating, the insulating layer includes aluminum oxide, and the graphene layer includes monolayer graphene.

[0008] Optionally, the stripe width of the aluminum grating is 34μm~40μm, and the ratio of the stripe width to the grating period is 0.51~0.54.

[0009] Optionally, the metal grating layer includes a grating region and an external power supply soldering region. The grating region includes a metal grating, and the external power supply soldering region includes a metal layer. The metal layer is connected to all the grating lines of the metal grating.

[0010] Optionally, the transmissive terahertz absorption structure includes at least two stacked transmissive terahertz absorption composite film layers to achieve multi-level absorption modulation of terahertz waves.

[0011] Optionally, the graphene layer is electrically connected to the positive terminal of the external power supply, and the metal grating layer is electrically connected to the negative terminal of the external power supply.

[0012] According to another aspect of the present invention, a method for preparing a transmission-type terahertz absorption structure is provided, comprising:

[0013] Provide substrate;

[0014] A metal grating layer is formed on one side of the substrate;

[0015] An insulating layer is formed on the side of the metal grating layer that faces away from the substrate;

[0016] A graphene layer is formed on the side of the insulating layer opposite to the substrate;

[0017] The metal grating layer and the graphene layer are electrically connected to an external power source.

[0018] Optionally, the metal grating layer includes an aluminum grating, and the metal grating layer is formed on one side of the substrate, comprising:

[0019] An aluminum layer is grown on one side of the substrate;

[0020] The aluminum grating is formed on the aluminum layer using a photolithography process.

[0021] Optionally, the metal grating layer includes a grating area and an external power supply bonding area. When forming the aluminum grating using a photolithography process, the mask used includes a grating pattern and an external power supply area. The grating pattern includes a grating pattern corresponding to the aluminum grating, and the external power supply area completely blocks the exposure beam.

[0022] Optionally, electrically connecting the metal grating layer and the graphene layer to an external power source includes:

[0023] The graphene layer is electrically connected to the positive terminal of the external power source;

[0024] The metal grating layer is electrically connected to the negative terminal of the external power supply.

[0025] The transmissive terahertz absorption structure provided in this invention includes at least one transmissive terahertz absorption composite film layer. This film layer comprises a substrate and, sequentially, a metal grating layer, an insulating layer, and a graphene layer stacked on one side of the substrate. The metal grating layer and the graphene layer are electrically connected to an external power source. By controlling the Fermi level of the graphene with an applied voltage, the absorption of terahertz waves by the composite film layer is adjusted, allowing the terahertz waves transmitted through the composite film layer to exhibit different intensity information under the influence of the applied voltage. This acts as a switch and possesses the advantages of active modulation, real-time modulation, and precise controllability, making it suitable for fields such as terahertz spectral imaging analysis, single-pixel imaging, and spectral measurement.

[0026] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a transmission terahertz absorption structure provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of a metal grating layer in a transmission terahertz absorption structure provided in an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of another transmission-type terahertz absorption structure provided in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram illustrating the carrier changes before and after applying voltage to the transmissive terahertz absorption composite film layer provided in an embodiment of the present invention.

[0032] Figure 5 This is a diagram showing the change in the Fermi level of the graphene layer after applying voltage stimulation, provided in an embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the performance test of a transmission-type terahertz absorption structure provided in an embodiment of the present invention;

[0034] Figure 7 A schematic flowchart illustrating a method for preparing a transmission-type terahertz absorption structure according to an embodiment of the present invention;

[0035] Figure 8 This is a schematic diagram of a mask plate provided in an embodiment of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] Figure 1 This is a schematic diagram of a transmission-type terahertz absorption structure provided for an embodiment of the present invention. (Reference) Figure 1 The transmissive terahertz absorption structure includes at least one transmissive terahertz absorption composite film layer 10. The transmissive terahertz absorption composite film layer 10 includes a substrate 11 and a metal grating layer 12, an insulating layer 13 and a graphene layer 14 sequentially stacked on one side of the substrate 11; wherein the metal grating layer 12 and the graphene layer 14 are electrically connected to an external power supply 20.

[0039] It is understood that the substrate 11, metal grating layer 12, insulating layer 13, and graphene layer 14 in the terahertz absorption composite film layer 10 provided in this embodiment of the invention are in close contact and stacked. Figure 1 The individual film layers are schematically separated to illustrate the structure of each layer.

[0040] In one embodiment, optionally, the substrate 11 includes a silicon dioxide substrate, the metal grating layer 12 includes an aluminum grating, the insulating layer 13 includes aluminum oxide, and the graphene layer 14 includes a monolayer of graphene.

[0041] The silica substrate has good transmittance to terahertz waves and is stable, which can prevent the aluminum in the aluminum grating from being oxidized. The insulating layer 13 is made of aluminum oxide, which not only has an insulating effect, but also avoids the introduction of other impurity elements, thus ensuring the stability of the terahertz absorption composite film.

[0042] An aluminum grating is a type of metal grating that can alter the spatial distribution of terahertz waves during transmission. Due to the interference effect of the grating, the wavelengths that can pass through the grating are filtered by the grating period *d*, resulting in enhanced light intensity. Furthermore, the metal grating can directly enhance the interaction between graphene and terahertz waves, thereby increasing the absorption of terahertz waves. Aluminum is also a good material for fabricating terahertz gratings because it is soft, has a low melting point, is easy to vapor-deposit, and is readily etched in photolithography processes.

[0043] Graphene is a novel high-performance material composed of regularly arranged six-membered carbon rings. Compared to conventional semiconductor materials, it exhibits outstanding electrochemical properties. Graphene has strong electrical conductivity, with an electron mobility exceeding 1500 cm⁻¹ under normal conditions. 2 V -1 s -1 Furthermore, the Fermi level of graphene can be controllably altered through various stimuli, such as light irradiation, applied voltage, and chemical doping. Due to the change in the Fermi level, the electromagnetic properties of graphene change, and this change is continuously controllable over a wide spectral range. This characteristic makes graphene commonly used in optoelectronic devices. In recent years, microstructures fabricated using the unique electrochemical properties of graphene have shown great promise for applications in the infrared and terahertz bands.

[0044] The technical solution of this invention controls the Fermi level of graphene by applying an external voltage, adjusts the absorption of terahertz waves by the composite film, and makes the terahertz waves passing through the composite film have different intensity information under the influence of the external voltage, thus playing the role of a switch. It has the advantages of active regulation, real-time regulation, and precise controllability, and is applicable to fields such as terahertz spectral imaging analysis, single-pixel imaging, and spectral measurement.

[0045] Furthermore, the advantages of the transmission-type terahertz absorption structure provided in this embodiment of the invention compared to the traditional reflection-type absorption structure are as follows:

[0046] 1) Broadband absorption capability. Transmissive terahertz absorption structures can achieve broadband absorption capability in the terahertz band, and can be used to absorb all terahertz wave signals within the frequency range without frequency tuning or adjustment. In contrast, reflective terahertz absorption structures have narrowband absorption capability and can only absorb terahertz wave signals within a specific frequency range.

[0047] 2) It has a high absorption rate. The transmission-type terahertz absorption structure disclosed in the embodiments of the present invention has a high absorption rate, which can effectively absorb terahertz wave signals and avoid signal reflection and leakage.

[0048] 3) Easy to prepare and process. The transmission-type terahertz absorption structure disclosed in the embodiments of this invention is typically prepared using common materials such as metals, graphite, and polymers. The preparation process is simple, the cost is low, and it is easy to process into samples of various shapes and sizes. For example, the vapor deposition machines and electron beam vapor deposition machines used to process aluminum gratings and aluminum oxide insulating layers are domestically mature technologies, and the preparation is relatively simple. In contrast, the reflection-type terahertz absorption structure requires the use of materials that can produce strong reflections, usually metals or conductive polymers. These materials may interfere with the terahertz signal, affecting the detection and transmission of the terahertz signal. Moreover, the reflection-type terahertz absorber requires fine geometry and surface structure, and the preparation of such a structure is relatively difficult, requiring the use of precise processes and equipment.

[0049] 4) Adjustable absorption capacity. The absorption capacity of a transmission-type terahertz absorption structure can be adjusted and optimized by factors such as the geometry, thickness, and composition of the material, offering greater design flexibility. Since a reflection-type terahertz absorber needs to reflect the incident terahertz wave signal back for absorption, a certain amount of reflection loss occurs, resulting in lower absorption efficiency compared to a transmission-type terahertz absorption structure.

[0050] 5) Applicable to various terahertz systems. Transmission-type terahertz absorption structures can be widely used in systems such as terahertz imaging, terahertz communication, and terahertz spectroscopy, playing an important role in improving the detection sensitivity of terahertz signals, suppressing noise interference, and protecting receivers. Reflection-type terahertz absorption structures are typically used in specific terahertz systems, such as scenarios where the terahertz source and detector are located on the same side of the absorption structure. They may not be suitable for some systems requiring large-area scanning and detection.

[0051] In summary, the transmission-type terahertz absorption structure disclosed in this invention is a terahertz wave absorbing material with broad application prospects. It has advantages such as broadband absorption, high absorption rate, and easy preparation and processing, and makes up for the disadvantages of traditional reflection-type terahertz absorption structures, such as high preparation difficulty, narrow-band absorption, reflection loss, and material limitations. It plays an important role in promoting the application and development of terahertz systems.

[0052] Optionally, the stripe width of the aluminum grating is 34μm~40μm, and the ratio of the stripe width to the grating period is 0.51~0.54.

[0053] For example, in one embodiment, the terahertz absorption composite film is composed of a 500 μm thick silicon dioxide substrate, a 200 nm thick aluminum grating layer, a 500 nm thick aluminum oxide layer, and a single layer of graphene, stacked sequentially. This terahertz absorption composite film has two adjustment functions: by adjusting the grating size, the received terahertz wave can be selected; by adjusting the applied voltage to the graphene layer and the aluminum grating layer, the electron mobility and Fermi level of the graphene can be adjusted within a very short time interval, changing the transmission and reflection coefficients of the graphene layer for terahertz light, thereby affecting the intensity of the transmitted terahertz light. These two methods combined achieve both the selection of the terahertz band and the adjustment of the transmission intensity.

[0054] In practice, the structural performance was optimized using the commercial full-wave numerical simulation software Microwave Studio (CST). In the simulation, the conductivity of the aluminum layer was 3.56 × 10⁻⁶. 7 The parameters of graphene are described by the Kubo formula, with a relaxation time of 20 fs and a Fermi level variation range of 0–0.8 eV, which is simulable for graphene produced by chemical vapor deposition (CVD). After optimization, the optimal grating size is a fringe width of 34 μm–40 μm and a fringe width to period ratio of 0.51–0.54.

[0055] Figure 2 This is a schematic diagram of the metal grating layer in a transmission-type terahertz absorption structure provided in an embodiment of the present invention. (Reference) Figure 2 Optionally, the metal grating layer 12 includes a grating region 111 and an external power supply soldering region 112. The grating region 111 includes a metal grating, and the external power supply soldering region 112 includes a metal layer. The metal layer is connected to all the grating lines of the metal grating.

[0056] The external power supply welding area 112 includes an unetched solid metal layer to facilitate a stable connection with the external power supply and avoid poor contact and welding loss that may occur when welding on the surface of the metal grating.

[0057] In other embodiments, optionally, the transmissive terahertz absorption structure includes at least two stacked transmissive terahertz absorption composite film layers for achieving multi-level absorption modulation of terahertz waves.

[0058] For example, taking a two-layer transmissive terahertz absorption composite film layer as an example, Figure 3 This is a schematic diagram of another transmission-type terahertz absorption structure provided in an embodiment of the present invention. The multi-level tuning of the transmission-type terahertz absorption structure disclosed in this embodiment of the present invention has the following advantages:

[0059] High precision: Multi-level adjustment can break down the adjustment process into multiple steps, each of which only requires adjustment of a small range, thus achieving higher precision.

[0060] Good stability: Through multi-level adjustment, the system can be made more stable, reducing the interference of sudden changes and unstable factors, and improving the robustness of the system.

[0061] Wide adjustment range: Multi-level adjustment can expand the adjustment range. By superimposing multiple steps, a wider range of adjustment can be achieved.

[0062] Fast adjustment speed: Through multi-level adjustment, the adjustment speed can be accelerated, the adjustment time can be reduced, and the efficiency can be improved.

[0063] Easy to implement: Multi-level adjustment is relatively simple to implement. It can be done by breaking down the entire adjustment process into multiple steps and completing them step by step.

[0064] Furthermore, compared to traditional reflective terahertz absorption structures, the limitations of reflective structures mean that the terahertz emitter and receiver must be placed on the same side, and the terahertz light source cannot strike the reflective structure perpendicularly; the incident light must be at a certain angle to the horizontal plane. This reflective structure prevents reflective absorbers from achieving two-level or even multi-level tuning. In contrast, the terahertz absorption structure disclosed in this invention has two-level or even multi-level tuning capabilities. The terahertz emitter and receiver can be placed on opposite sides of the structure, and multiple layers can be placed between the receiver and the emitter. Each layer independently limits the absorption rate of the terahertz light, and the final absorption rate of the terahertz light is the sum of the absorption effects of the two layers.

[0065] In summary, multi-level adjustment has advantages such as high precision, good stability, wide adjustment range, fast adjustment speed, and ease of implementation. Its application in the terahertz absorption field can significantly improve the modulation effect.

[0066] Optional, continue to refer to Figure 1 The graphene layer 14 is electrically connected to the positive electrode of the external power supply 20, and the metal grating layer 12 is electrically connected to the negative electrode of the external power supply 20.

[0067] Since the graphene layer 14 and the metal grating layer 12 need to be connected to the positive and negative terminals of the external power supply 20 respectively, this structure can be regarded as a special type of capacitor. For example, Figure 4 This is a schematic diagram illustrating the change in charge carriers before and after applying voltage to the transmissive terahertz absorption composite film layer provided in an embodiment of the present invention. (Reference) Figure 4 Before being powered by an external power source, the charge carriers in the composite membrane are randomly distributed. After stimulation, the anions in the structure tend to be distributed towards the positive electrode, and the cations in the structure tend to move towards the negative electrode. This change occurs instantaneously when the power is applied. This characteristic enables the real-time control feature designed in the embodiments of the present invention.

[0068] In this embodiment, the monolayer graphene is generated by CVD, and its Fermi level variation range covers the range of 0-0.8 eV required by the embodiments of the present invention. In CST, it can be regarded as a two-dimensional plane with no height. Figure 5 The graph shows the change in the Fermi level of the graphene layer after applying voltage stimulation, as provided in an embodiment of the present invention. Figure 5 When graphene is stimulated by a voltage, its surface Fermi level changes with the intensity of the applied voltage, affecting the graphene's conductivity and absorptivity. In practice, a terahertz receiver can be placed on the side of a silicon dioxide substrate away from the metal grating layer to receive terahertz light modulated by the composite film layer and compare it with the incident light.

[0069] The Fermi level is the highest occupied electron energy level at 0 K (absolute zero). In materials such as semiconductors and metals, the Fermi level lies between the valence band and the conduction band, and is an important reference indicator for electron flow in conductors. The Fermi level is generally considered as the threshold energy of free electrons within a conductor; electrons below the Fermi level are filled, while those above are in an unfilled state.

[0070] The quasi-Fermi level is an energy level reached by electrons and holes in dynamic equilibrium under non-equilibrium conditions, where their concentrations are equal. In semiconductors and other materials, the quasi-Fermi level is commonly used to describe the state of externally excited or injected electrons or holes. In semiconductor devices, the location of the quasi-Fermi level has a crucial influence on the direction and magnitude of electron or hole flow.

[0071] Graphene is a single-layer honeycomb lattice structure composed of carbon atoms, possessing excellent electrical, thermal, and mechanical properties. Graphene is a zero-bandgap half-metal, with its conduction band and valence band intersecting; therefore, at zero temperature, its Fermi level is located at the intersection of the conduction and valence bands.

[0072] Under the influence of an applied electric field or chemical modification, the charge carrier concentration in graphene changes, and the Fermi level position shifts accordingly. At this point, the concept of a quasi-Fermi level is introduced to describe the situation where the electron and hole concentrations are no longer equal. The position of the quasi-Fermi level is related to factors such as the applied electric field strength and the doping concentration of the material, affecting the electrical properties and applications of graphene materials.

[0073] Figure 6 This is a schematic diagram illustrating the performance testing of a transmission-type terahertz absorption structure provided in an embodiment of the present invention. (Refer to...) Figure 6By gradually increasing the external voltage, the Fermi level of graphene was gradually adjusted from 0 eV to 0.8 eV. The figure shows the absorption coefficient of the transmission terahertz absorption structure as a function of frequency for a grating with a fringe width P = 40 μm and a fringe gap W = 30 μm, at Fermi levels of 0.25 eV, 0.5 eV, and 0.75 eV, respectively. As can be seen from the figure, the absorption coefficient of the model provided in this embodiment of the invention for terahertz light gradually increases with the gradual increase of the graphene Fermi level, verifying the feasibility of the device concept. This embodiment of the invention provides a practical approach for controllably adjustable terahertz absorbers.

[0074] The transmissive terahertz absorption structure disclosed in this invention realizes rapid feedback to voltage stimulation and completes effective and controllable modulation and absorption of terahertz light waves. It is a very significant performance optimization of terahertz absorption structures in terms of active controllability, control timeliness, and control precision.

[0075] Figure 7 This is a schematic flowchart illustrating a method for preparing a transmission-type terahertz absorption structure according to an embodiment of the present invention. This method is used to prepare the transmission-type terahertz absorption structure provided in the above embodiment. (Refer to...) Figure 7 The preparation method includes:

[0076] S110 provides a substrate.

[0077] The substrate can be a material with high transmittance to terahertz waves, such as a silicon dioxide substrate. In specific implementation, the substrate can include: a pure, scratch-free silicon dioxide sheet with a thickness of 500μm and a diameter of 2 inches, which is sequentially washed with water, cleaned with acetone, cleaned with isopropanol, and dried to obtain a silicon dioxide substrate with clean and uncontaminated upper and lower surfaces.

[0078] S120. A metal grating layer is formed on one side of the substrate.

[0079] Optionally, the metal grating layer includes an aluminum grating, and the metal grating layer is formed on one side of the substrate, comprising:

[0080] An aluminum layer is grown on one side of the substrate;

[0081] In practice, a 200nm thick aluminum layer can be grown on the surface of a silicon dioxide substrate using a thermal evaporation machine. Note that the other surface must be protected to prevent scratches and wear during the evaporation process.

[0082] An aluminum grating is formed on an aluminum layer using photolithography.

[0083] Photolithography is a crucial step in fabricating the aluminum grating in this embodiment of the invention. The photolithography steps required in this embodiment are as follows: cleaning the film, pre-baking, coating with photoresist, drying the photoresist, alignment, exposure, development, hardening, etching, and resist removal. The basic principle of photolithography is that photoresist denatures after exposure to light, acquiring corrosion resistance. A photomask with a pre-designed pattern is aligned with the film using a photolithography machine and exposed. The photoresist in the exposed area acquires corrosion resistance. Because the corrosion resistance of different parts of the photoresist varies, the photoresist in the exposed area is not washed away by the developer during the development stage. The properties of the unexposed photoresist remain unchanged and are not left on the metal structure surface after development. The etching stage involves placing the hardened film in a prepared etching solution (usually a balanced acid solution). During etching, the metal structure covered by the denatured photoresist is preserved, while the uncovered metal structure is peeled off. After etching, the film is cleaned and then undergoes a resist removal and drying process. The designed photolithographic pattern is retained on the metal surface, completing the entire photolithography process. In this embodiment, since the grating needs to be electrically connected to an external power supply, optionally, the metal grating layer includes a grating region and an external power supply bonding region. When forming the aluminum grating using photolithography, the mask used includes a grating pattern and an external power supply region. The grating pattern includes a grating design corresponding to the aluminum grating, and the external power supply region completely blocks the exposure beam. For example, Figure 8 This is a schematic diagram of a photomask provided in an embodiment of the present invention. The photomask includes a grating pattern 100 and an external power supply area 200. During photolithography, the silicon dioxide substrate covered with an aluminum layer is processed according to the above-described procedure to obtain a photomask with an aluminum grating pattern 100. Figure 8 The photomask shown has a grating pattern with virtually no errors. Simulation results indicate that the optimal combination of gratings is a fringe width P = 40 μm and a fringe gap W = 30 μm.

[0084] S130. An insulating layer is formed on the side of the metal grating layer that is away from the substrate.

[0085] The insulating layer can be aluminum oxide, for example, by electroplating a 500nm thick layer of aluminum oxide onto the surface of an aluminum grating using an electron beam evaporation machine.

[0086] S140. A graphene layer is formed on the side of the insulating layer away from the substrate.

[0087] In practice, a wet transfer method can be used to transfer a single layer of graphene onto the surface of the insulating layer. This results in the entire structure, from bottom to top, consisting of a silicon substrate, an aluminum grating, aluminum oxide, and graphene.

[0088] S150. Electrically connect the metal grating layer and the graphene layer to an external power source.

[0089] Optionally, the metal grating layer and the graphene layer are electrically connected to an external power source, including:

[0090] The graphene layer is electrically connected to the positive terminal of an external power source;

[0091] The metal grating layer is electrically connected to the negative terminal of an external power supply.

[0092] The transmission terahertz absorption structure prepared in this embodiment of the invention has the advantages of clear structure and significant modulation effect, and has extremely high potential value in the fields of terahertz spectral imaging analysis, single-pixel imaging and spectral measurement.

[0093] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A transmission-type terahertz absorption structure, characterized in that, It includes at least one transmissive terahertz absorption composite film layer, wherein the transmissive terahertz absorption composite film layer includes a substrate and a metal grating layer, an insulating layer and a graphene layer stacked sequentially on one side of the substrate; The metal grating layer and the graphene layer are electrically connected to an external power source, the graphene layer is electrically connected to the positive terminal of the external power source, and the metal grating layer is electrically connected to the negative terminal of the external power source. The substrate includes a silicon dioxide substrate, the metal grating layer includes an aluminum grating, the insulating layer includes aluminum oxide, and the graphene layer includes a single layer of graphene. The terahertz absorption structure is a transmission design, and the Fermi level of the graphene is controlled by an external voltage to adjust the absorption of terahertz waves by the composite film layer, so that the terahertz waves transmitted through the composite film layer have different intensity information under the influence of the external voltage. The transmissive terahertz absorption structure includes at least two stacked transmissive terahertz absorption composite film layers, which are used to achieve multi-level absorption modulation of terahertz waves.

2. The transmission-type terahertz absorption structure according to claim 1, characterized in that, The aluminum grating has a stripe width of 34μm to 40μm, and the ratio of the stripe width to the grating period is 0.51 to 0.

54.

3. The transmission-type terahertz absorption structure according to claim 1, characterized in that, The metal grating layer includes a grating region and an external power supply soldering region. The grating region includes a metal grating, and the external power supply soldering region includes a metal layer. The metal layer is connected to all the grating lines of the metal grating.

4. A method for preparing the transmission-type terahertz absorption structure according to any one of claims 1 to 3, characterized in that, include: Provide substrate; A metal grating layer is formed on one side of the substrate; An insulating layer is formed on the side of the metal grating layer that faces away from the substrate; A graphene layer is formed on the side of the insulating layer opposite to the substrate; The metal grating layer and the graphene layer are electrically connected to an external power source.

5. The method for preparing the terahertz absorption structure according to claim 4, characterized in that, The metal grating layer includes an aluminum grating, and is formed on one side of the substrate, comprising: An aluminum layer is grown on one side of the substrate; The aluminum grating is formed on the aluminum layer using a photolithography process.

6. The method for preparing the terahertz absorption structure according to claim 5, characterized in that, The metal grating layer includes a grating area and an external power supply bonding area. When the aluminum grating is formed using a photolithography process, the mask used includes a grating pattern and an external power supply area. The grating pattern includes a grating pattern corresponding to the aluminum grating, and the external power supply area completely blocks the exposure beam.

7. The method for preparing the terahertz absorption structure according to claim 4, characterized in that, Electrically connecting the metal grating layer and the graphene layer to an external power source includes: The graphene layer is electrically connected to the positive terminal of the external power source; The metal grating layer is electrically connected to the negative terminal of the external power supply.

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