Multiband terahertz absorber based on stacked graphene structures

Abstract

The application claims a kind of multiband terahertz absorber based on laminated graphene structure, which is a laminated stack structure.The positive terminal of external power supply is connected to two layers of graphene, and the negative terminal is connected to a gold reflection layer.The Fermi energy level of graphene is controlled by voltage.The structure parameters of each layer, graphene and dielectric layer material characteristics are set.The absorber forms multiple absorption peaks in the 1~5 THz frequency band, with a peak absorption rate of over 90%.At 1.60 THz, a narrowband absorption of 93% is achieved, and at 2.54~4.28 THz, a broadband absorption with a relative bandwidth of 51% is achieved.The normalized equivalent impedance at the resonance frequency point is nearly perfectly matched with the free space impedance.The absorber also has good polarization angle insensitivity, with only slight absorption performance attenuation within an incident angle range of 0~60°.The absorption characteristics can also be adjusted by adjusting the key geometric parameters.The application can simultaneously achieve narrowband and broadband absorption, with excellent absorption performance, and is suitable for interference signal filtering in terahertz communication systems.

Description

Technical Field

[0001] This invention belongs to the field of terahertz communication technology, specifically to a multi-band terahertz absorber based on a stacked graphene structure. Background Technology

[0002] Terahertz waves (THz) are electromagnetic waves with a frequency range of 0.1-10 THz, bridging the microwave and infrared regions of the electromagnetic spectrum. Terahertz waves possess advantages such as low photon energy, a wide spectral range, and high penetrability, attracting increasing attention in fields such as communication, imaging, and security detection. Therefore, terahertz waves have broad application prospects in communication, medical testing, national defense, and optoelectronic information science.

[0003] One of the most important applications of terahertz waves is terahertz communication technology. A terahertz communication system includes subsystems such as transceiver links and channels. The role of the terahertz transceiver system is to mix, filter, and amplify terahertz signals of different frequencies. Terahertz absorbers play a crucial role in terahertz communication systems. Currently, the materials used in designing terahertz metasurface absorbers mainly include conventional materials such as metals, polyimide (PI), and silicon dioxide (SiO2). In recent years, due to the unique electromagnetic response of graphene, it has become one of the important materials for improving absorber performance and has attracted increasing attention from researchers. However, currently studied metamaterial terahertz absorbers can only absorb, filter, and suppress interference in specific narrowband or broadband applications, rarely achieving combined absorption effects. Therefore, designing terahertz absorbers using graphene materials that can achieve multi-band absorption will become one of the future research hotspots. The shortcomings of existing technologies are as follows: Most metamaterial terahertz absorbers currently only have specific operating modes, and can only obtain single narrowband absorption peaks, multiple narrowband absorption peaks, or broadband absorption peaks, but cannot achieve a combined absorption effect of all three, that is, simultaneous multi-peak absorption and broadband absorption. In contrast, multi-band terahertz absorbers based on stacked graphene structures can simultaneously achieve narrowband and broadband absorption, with a relatively large bandwidth, and have strong application value in terahertz detectors, terahertz communication, and terahertz imaging.

[0004] A search revealed application publication number CN114498070A, which discloses a terahertz dual-band tunable absorber based on a graphene-dielectric-metal structure. This absorber, from bottom to top, consists of a metal layer, an intermediate dielectric layer, and a top U-shaped graphene pattern. The top U-shaped graphene pattern is periodically arranged in the x and y directions. The bottom metal film, intermediate dielectric layer, and top U-shaped graphene layer are bonded together. Terahertz absorbers often employ a single metal or conventional dielectric structure, generally suffering from problems such as a single operating frequency band and narrow absorption bandwidth. They can only achieve single-narrowband, multi-narrowband, or broadband absorption, making it difficult to simultaneously achieve a combination of multi-peak narrowband and broadband absorption effects. Furthermore, such devices have fixed resonant modes, poor tunability, complex structures, and low integration, failing to meet the practical application requirements of terahertz communication, imaging, and detection systems for wide-band, multi-functional, and dynamically tunable devices. Summary of the Invention

[0005] In terahertz communication systems, terahertz absorbers can absorb noise and interference signals at both the transmitting and receiving ends, thus filtering out interference signals. However, currently researched metamaterial terahertz absorbers can only absorb, filter, and suppress interference for specific narrowband or broadband applications, rarely achieving a combined absorption effect. Therefore, to address the above problems, a multi-band terahertz absorber and method based on a stacked graphene structure is proposed. The technical solution of this invention is as follows:

[0006] A multi-band terahertz absorber based on a stacked graphene structure is disclosed. The absorber has a layered stacked structure, consisting of, from top to bottom, a tetraelliptical cross-shaped graphene layer, a silicon dioxide upper dielectric layer, a cross-shaped grooved graphene layer, a silicon dioxide lower dielectric layer, and a gold reflective layer. The positive terminal of an external power supply is electrically connected to the top tetraelliptical cross-shaped graphene layer and the middle cross-shaped grooved graphene layer, respectively, while the negative terminal is electrically connected to the bottom gold reflective layer. The Fermi level of the graphene is controlled by adjusting the voltage of the external power supply. The tetraelliptical cross-shaped graphene layer serves as the top layer for absorbing terahertz waves, achieving absorption in a specific frequency band. The absorption and electromagnetic response of terahertz waves is one of the main absorbing units. The upper dielectric layer of silicon dioxide serves as a spacer medium, supporting the top graphene structure, providing an electromagnetic transmission channel and adjusting the resonant spacing. The cross-shaped grooved graphene layer serves as the lower dielectric support layer, separating the middle graphene layer from the bottom reflective layer and optimizing the overall electromagnetic resonance characteristics. The lower dielectric layer of silicon dioxide serves as the lower dielectric support layer, separating the middle graphene layer from the bottom reflective layer and optimizing the overall electromagnetic resonance characteristics. Finally, the gold reflective layer serves as a metal reflective substrate, preventing the transmission of terahertz waves and reflecting the transmitted waves back to the upper structure to enhance the absorption efficiency.

[0007] Furthermore, the structure of the tetraelliptical cross graphene layer is composed of four elliptical structures arranged in a 45° cross pattern.

[0008] Furthermore, the absorber unit structure has a period of 8 μm, the major semi-axis of the top graphene ellipse is 3.6 μm, and the minor semi-axis is 3 μm; the length of the cross groove inside the middle graphene layer is 1 μm and the width is 0.42 μm; the thickness of the SiO2 upper dielectric layer is 0.68 μm; the thickness of the SiO2 lower dielectric layer is 12 μm; and the thickness of the bottom gold layer is 0.2 μm.

[0009] Furthermore, the relative permittivity of both the upper and lower silicon dioxide dielectric layers is 3.9; the relaxation time of the graphene material used in the tetraelliptic cross-graphene layer and the cross-groove graphene layer is 0.6 ps, with the Fermi level of the tetraelliptic cross-graphene layer set to 0.58 eV and the Fermi level of the cross-groove graphene layer set to 0.2 eV.

[0010] Furthermore, the absorber forms multiple absorption peaks in the 1-5 THz frequency range, with the maximum peak absorption rate being greater than or equal to 90%; it achieves narrowband absorption at the 1.60 THz frequency point with an absorption rate of 93%; and it achieves broadband absorption in the 2.54-4.28 THz frequency range, with an effective absorption bandwidth of 1.74 THz at the 70% absorption threshold and a relative bandwidth of 51%, and absorption rates greater than 90% at the 2.82 THz, 3.33 THz, and 4.07 THz frequencies.

[0011] Furthermore, at the resonant frequencies of 1.60 THz, 2.82 THz, 3.33 THz, and 4.07 THz, the real part of the normalized equivalent impedance of the absorber is close to 1, and the imaginary part is close to 0.

[0012] Furthermore, the absorber has polarization angle insensitivity characteristics, and the absorption curve remains unchanged as a whole within the polarization angle range of 0-60°; the frequency of the low-frequency narrowband absorption peak remains unchanged within the incident angle range of 0-60°.

[0013] The advantages and beneficial effects of this invention are as follows:

[0014] The innovation of this invention is mainly reflected in the overall technical solution of the stacked graphene structure, the combination of multiple resonant units, and the multi-band narrowband and broadband composite absorption mechanism, corresponding to the multi-layer graphene resonant structure, the layered combination of the dielectric layer and the metal substrate, the periodic array arrangement and key size parameters as defined in the independent claims.

[0015] The combination of the aforementioned structure, parameters, and materials is not a conventional technical approach. First, traditional metamaterial absorbers mostly employ single-layer resonant units, making it difficult to achieve the simultaneous coexistence of multi-peak narrowband and broadband absorption through simple stacking. Second, the electromagnetic coupling between graphene layers is complex, and there is no readily available design paradigm for the coordinated matching of the number of layers, spacing, geometry, and Fermi level. Finally, existing technologies generally treat narrowband and broadband absorption as mutually exclusive structures. This invention breaks through this conventional thinking, achieving composite absorption through multi-layer resonant mode coupling, and the overall solution possesses non-obviousness. Attached Figure Description

[0016] Figure 1 Figure 1 shows a preferred embodiment of the terahertz absorber structure and voltage connection method provided by the present invention.

[0017] Figure 2. Absorption curve of the absorber.

[0018] Figure 3. Normalized equivalent impedance diagram of the absorber.

[0019] Figure 4. Electric field distribution of the top and middle layers at the absorption frequency of the terahertz absorber.

[0020] Figure 5. Current distribution at each frequency point in the top, middle and bottom layers.

[0021] Figure 6. Scanning analysis diagram of key geometric parameters of the absorber.

[0022] Figure 7. Absorption curves of the absorber at different incident angles theta and polarization angles phi. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. The described embodiments are merely some embodiments of the present invention.

[0024] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0025] like Figure 1As shown, the basic structure of the absorber consists of patterned two-dimensional graphene material on the top layer, with a graphene film inserted between the two dielectric layers. After optimization, it can achieve multi-band absorption of terahertz waves with even better absorption performance. The absorber structure, from top to bottom, consists of a four-elliptical cross-shaped graphene layer, a silicon dioxide (SiO2) dielectric layer, a cross-shaped grooved graphene layer, a SiO2 dielectric layer, and a gold reflective layer. The gold material has a high conductivity, the dielectric layer material is SiO2 with a relative permittivity of 3.9, the relaxation time of the graphene material is set to 0.6 ps, the Fermi level of the top graphene layer is set to 0.58 eV, and the Fermi level of the second graphene layer is set to 0.2 eV. The specific parameters of the absorber are as follows: the period of the unit structure P = 8 μm, the major semi-axis r1 = 3.6 μm, and the minor semi-axis r = 3 μm of the top graphene ellipse. The length of the cross-shaped groove inside the middle graphene layer is d=1 μm, and the width is w=0.42 μm. The thickness of the first part of the SiO2 dielectric layer is h1=0.68 μm, and the thickness of the second part of the SiO2 dielectric layer is h2=12 μm. The thickness of the bottom gold layer is h3=0.2 μm. The positive terminal of the power supply is connected to the top and middle graphene layers, and the negative terminal is connected to the bottom metal substrate. The Fermi level of the graphene is simulated by controlling the voltage.

[0026] As shown in Figure 2, the simulation results exhibit multiple absorption peaks in the 1-5 THz frequency range, with a peak absorption rate exceeding 90%. A relatively wide effective absorption bandwidth is formed below the 70% absorption threshold, and narrowband absorption is achieved at 1.60 THz with an absorption rate of 93%. Broadband absorption is also achieved in the relatively high frequency range of 2.54-4.28 THz, with a bandwidth of 1.74 THz for absorption rates greater than 70%. Calculations show that the relative bandwidth can reach 51%, and there are three frequency points with absorption rates greater than 90%, namely f2=2.82 THz, f3=3.33 THz, and f4=4.07 THz.

[0027] Figure 3 shows the normalized equivalent impedance diagram of the absorber. Based on impedance matching theory, a detailed analysis can be performed at each frequency point. The black solid line represents the real part of the normalized impedance, and the red dashed line represents the imaginary part. In the figure, the blue dashed line represents the horizontal lines for the equivalent impedance of 0 and 1, and the pink rectangular areas represent the real and imaginary parts of each absorption frequency. It can be seen that the real and imaginary curves corresponding to four frequency points roughly intersect the blue curve, meaning the real part is close to 1 and the imaginary part is close to 0. Furthermore, at non-frequency points, the real part of the normalized equivalent impedance is neither 1 nor 0. Therefore, it can be concluded that the normalized equivalent impedance of the absorber achieves almost perfect matching with the free-space impedance at the resonant frequencies f1-f4, at which point the absorption rate can approach 100%.

[0028] Figure 4This diagram shows the electric field distribution of the top and middle layers at the absorption frequency of the terahertz absorber. At the absorption peak f1, the electric field distribution on the surface of the top graphene layer is relatively uniform, distributed around the perimeter of the top graphene layer, indicating that this frequency mainly excites electric dipole resonance. Simultaneously, a significant localized electric field enhancement phenomenon appears in the central region of the middle graphene layer, indicating a relatively strong electric field coupling between the upper and lower graphene layers. This coupling effectively confines the terahertz wave within the multilayer structure and dissipates it through the ohmic loss of the graphene. Therefore, the high absorption rate at the absorption peak f1 mainly originates from the combined effect of electric dipole resonance and interlayer capacitive coupling.

[0029] Figure 4 (b) and Figure 4 (f) shows the electric field distribution in the top and middle layers at the absorption peak f2. The electric field is more significant at the edge of the graphene film in the top layer, with obvious charge accumulation. Meanwhile, multiple discrete high electric field intensity points can be observed on the middle graphene layer, indicating that equivalent LC hybrid resonances are excited at this frequency. The superposition of electric dipole resonances and LC resonances enhances the dissipation of terahertz wave energy within the absorber structure, thus achieving a high absorption rate at the absorption peak f2 as well.

[0030] At the third absorption peak f3, as Figure 4 (c) and Figure 4 As shown in (g), in the top-layer graphene resonant structure, the electric field is mainly concentrated at the upper and lower ends. The electric field distribution in the middle graphene layers exhibits complex, discrete high-field-intensity points, indicating that higher-order multipole resonant modes are excited at these frequencies, and high-frequency broadband absorption is primarily generated by these higher-order resonant modes. Furthermore, resonant behavior similar to a Fabry-Perot cavity is generated between the dielectric layers in the multilayer structure. The superposition of multiple resonant mechanisms (including higher-order LC resonance and Fabry-Perot cavity resonance) ensures a good match between the equivalent impedance and free-space impedance in this frequency band, which is crucial for the formation of broadband absorption.

[0031] Figure 4 (d) and Figure 4 (h) shows the electric field distribution in the top and middle layers at the absorption peak f4. Both the top and middle graphene layers exhibit significant discretization and asymmetry, characteristic of typical high-order surface plasmon resonance modes, thus significantly enhancing the ohmic loss in the graphene layers. Simultaneously, the multiple scattering effect within the dielectric cavity further promotes energy dissipation, enabling this absorber structure to maintain a high absorption rate even at relatively high terahertz frequencies.

[0032] from Figure 5As can be seen from the electric field distribution diagram at the absorption peak f1, the surface current in the top layer of graphene is generally distributed downwards, exhibiting a relatively uniform current distribution characteristic, indicating that electric dipole resonance is mainly excited at the f1 frequency point. At the same time, the current direction in the middle graphene layer is significantly different from that in the top layer, with reverse current appearing in local areas, while the induced current direction in the bottom metal is basically opposite to that in the top layer of graphene.

[0033] The formation of a reverse current between the top graphene and the bottom metal creates a closed current loop, which in turn excites a significant magnetic response within the dielectric layer, forming a typical low-order magnetic resonance. This effectively suppresses the reflection of terahertz waves in the structure and dissipates energy through the ohmic loss of the graphene, enabling the absorber to achieve a high absorption rate at f1.

[0034] At the absorption peak f2, the current in the top graphene film exhibits a significant non-uniform distribution, with enhanced current density in localized areas, demonstrating a strong charge accumulation effect. Multiple current convergence regions appear in the middle graphene layer, indicating that the middle layer contributes significantly to the resonance at this frequency. Meanwhile, the induced current in the bottom metal layer maintains an anti-polarity relationship with the top graphene layer, exhibiting an electric dipole resonance mode. This resonance mode significantly improves the dissipation loss in the graphene, ultimately achieving high absorption.

[0035] like Figure 5 The third column shows the current distribution of each layer at absorption peak f3. The current distribution in all three layers exhibits a more complex morphology. The current direction in the top graphene layer shows multiple current oscillation regions, while a distinct vortex-like current distribution forms in the middle graphene layer. The induced current in the bottom metal layer maintains an upward current distribution pattern, forming multiple closed current loops together with the upper graphene layer. This multi-loop current structure corresponds to the superposition excitation of multiple magnetic resonances, effectively broadening the impedance matching frequency band. The synergistic effect of higher-order current modes and magnetic resonance causes electromagnetic energy to be dissipated step by step within the structure, which is one of the key physical mechanisms for the formation of broadband high absorption.

[0036] At the highest absorption frequency f4, the current distribution in the top and middle graphene layers exhibits significant irregularities, with strong regional variations in current direction, indicating a high-order oscillation mode. Simultaneously, the induced current in the bottom metal layer maintains an inverse relationship with the top graphene layer, forming a stable magnetic resonance response. In the high-frequency range, the strong localized current density on the graphene surface significantly enhances its ohmic losses. Multiple scattering and coupling within the multilayer structure further extend the propagation path of electromagnetic energy, maintaining high absorption efficiency at this frequency, while the superposition and coupling of multiple absorption peaks create broadband absorption.

[0037] Figure 6 shows the sweep parameter analysis of key geometric parameters of the absorber. As the unit cell period parameter p increases from 7.5 μm to 9.5 μm, the absorber maintains multiple high-absorption-rate absorption peaks within the 0-5 THz range, exhibiting stable overall absorption performance. With increasing p, the frequency of the narrowband absorption peak in the low-frequency range shifts slightly towards lower frequencies, and the absorptivity gradually decreases. In the mid-to-high frequency range, the absorptivity of absorption peak f2 gradually decreases, and its frequency gradually shifts towards higher frequencies, while absorption peak f4 maintains a relatively high absorptivity. The overall broadband absorption rate greater than 80% also gradually degrades. This is mainly due to the period parameter p altering the equivalent capacitance and inductance of the unit cell structure, thereby changing the LC resonance condition.

[0038] Figure 6 (b) illustrates the effect of the thickness h2 of the lower dielectric layer on the absorption performance. It can be seen that as h2 increases, the frequency of the low-frequency narrowband absorption peak shifts slightly lower, and the absorption rate gradually increases, but simultaneously, the separation between the narrowband and the high-frequency broadband gradually deteriorates. For the mid-to-high frequency absorption peaks, their peak value and bandwidth change significantly. When h2 is small, the coupling between the upper and lower graphene layers is strong, resulting in absorption peaks with good absorption performance; as h2 increases, the interlayer coupling gradually weakens, and some absorption peaks split or decrease in peak value. This indicates that h2 plays a crucial role in regulating the coupling strength between the two graphene layers and the high-frequency absorption bandwidth.

[0039] Further analysis was conducted on the absorption performance when the thickness h1 of the upper dielectric layer varied within the range of 0.60-0.70 μm, such as... Figure 6 As shown in (c). The results indicate that, overall, the variation of h1 has little impact on the absorption performance of the absorber, and has a small effect on the frequency shift and absorptivity of the low-frequency narrowband absorption peak. Under suitable h1 conditions, the absorber achieves near-perfect absorption at multiple frequency points, indicating that a reasonable upper dielectric layer thickness helps to improve the overall absorption efficiency.

[0040] For terahertz absorbers, wide-angle absorption performance is one of the important characteristics for practical applications. Figure 7 The effect of different polarization angles and incident angles on the absorber.

[0041] Figure 7 (a) illustrates the effect of different polarization angles (0-60°) on the absorber performance when the incident angle is fixed at 0°. It can be observed that the absorption curves remain largely unchanged overall under different polarization angles, with the positions of the low-frequency and relatively high-frequency absorption peaks remaining essentially constant, and only slight variations in absorbance occurring in certain frequency bands. This effect is primarily due to the high geometric symmetry of the unit cell structure involved, making it insensitive to changes in polarization angle.

[0042] Similarly, under the condition of a fixed polarization angle of 0°, as the incident angle increases from 0° to 60°, such as Figure 7 As shown in (b), the absorber maintains a relatively constant frequency at its narrow-band absorption peak in the low-frequency range, but the absorption intensity gradually decreases. Simultaneously, in the relatively high-frequency range, a certain degree of absorptivity decay and a slight frequency shift occur in the broadband portion, but a relatively high absorptivity is still maintained at absorption peaks f2 and f4. In summary, this absorber structure exhibits good polarization angle insensitivity, but its absorption performance degrades when the incident angle is too large.

[0043] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions.

[0044] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] The above embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A multi-band terahertz absorber based on a stacked graphene structure, characterized in that, The absorber has a layered stacked structure, consisting of, from top to bottom, a tetraelliptical cross-shaped graphene layer, a silicon dioxide upper dielectric layer, a cross-shaped grooved graphene layer, a silicon dioxide lower dielectric layer, and a gold reflective layer. The positive terminal of the external power supply is electrically connected to the top tetraelliptical cross-shaped graphene layer and the middle cross-shaped grooved graphene layer, while the negative terminal is electrically connected to the bottom gold reflective layer. By adjusting the voltage of the external power supply, the Fermi level of the graphene can be controlled. The tetraelliptical cross-shaped graphene layer serves as the top layer for terahertz wave absorption, achieving absorption and electromagnetic response of terahertz waves in a specific frequency band. The graphene layer is one of the main absorbing units. The upper dielectric layer of silica serves as a spacer medium, supporting the top graphene structure, providing an electromagnetic transmission channel and adjusting the resonant spacing. The cross-shaped grooved graphene layer serves as the lower dielectric support layer, separating the middle graphene layer from the bottom reflective layer and optimizing the overall electromagnetic resonance characteristics. The lower dielectric layer of silica serves as the lower dielectric support layer, separating the middle graphene layer from the bottom reflective layer and optimizing the overall electromagnetic resonance characteristics. Finally, the gold reflective layer serves as a metal reflective substrate, preventing terahertz wave transmission and reflecting the transmitted wave back to the upper structure to enhance absorption efficiency.

2. The multi-band terahertz absorber based on a stacked graphene structure according to claim 1, characterized in that, The structure of the tetraelliptical cross graphene layer is composed of four elliptical structures arranged in a 45° cross pattern.

3. The multi-band terahertz absorber based on a stacked graphene structure according to claim 2, characterized in that, The absorber unit structure has a period of 8 μm, the major semi-axis of the top graphene ellipse is 3.6 μm, and the minor semi-axis is 3 μm; the length of the cross groove inside the middle graphene layer is 1 μm and the width is 0.42 μm; the thickness of the SiO2 upper dielectric layer is 0.68 μm; the thickness of the SiO2 lower dielectric layer is 12 μm; and the thickness of the bottom gold layer is 0.2 μm.

4. The multi-band terahertz absorber based on a stacked graphene structure according to claim 1, characterized in that, The relative permittivity of both the upper and lower dielectric layers of silicon dioxide is 3.9; the relaxation time of the graphene material used in the tetraelliptical cross-shaped graphene layer and the cross-shaped groove graphene layer is... The Fermi level is 0.6 ps, where the Fermi level of the four-elliptical cross-shaped graphene layer is set to 0.58 eV and the Fermi level of the cross-shaped grooved graphene layer is set to 0.2 eV.

5. The multi-band terahertz absorber based on a stacked graphene structure according to any one of claims 1 to 4, characterized in that, The absorber forms multiple absorption peaks in the 1-5 THz frequency range, with the maximum peak absorption rate being greater than or equal to 90%; it achieves narrowband absorption at 1.60 THz with an absorption rate of 93%; and it achieves broadband absorption in the 2.54-4.28 THz frequency range, with an effective absorption bandwidth of 1.74 THz at the 70% absorption threshold and a relative bandwidth of 51%, and absorption rates greater than 90% at 2.82 THz, 3.33 THz, and 4.07 THz.

6. The multi-band terahertz absorber based on a stacked graphene structure according to any one of claims 1 to 4, characterized in that, At the resonant frequencies of 1.60 THz, 2.82 THz, 3.33 THz, and 4.07 THz, the real part of the normalized equivalent impedance of the absorber is close to 1, and the imaginary part is close to 0.

7. The multi-band terahertz absorber based on a stacked graphene structure according to any one of claims 1 to 4, characterized in that, The absorber is polarization angle insensitive; the absorption curve remains unchanged throughout the 0-60° polarization angle range; and the frequency of the low-frequency narrowband absorption peak remains unchanged within the 0-60° incident angle range.

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