A graphene fano resonance based terahertz sensor and a method for regulating and application thereof

Abstract

The application relates to a graphene Fano resonance-based terahertz sensor and a regulation method and application thereof, and relates to the technical field of sensor devices.The terahertz sensor comprises a substrate layer, a dielectric layer and a graphene layer, the graphene layer comprises at least one unit structure arranged on the dielectric layer, the unit structure comprises two long graphene strips arranged in parallel at intervals and four short graphene strips arranged between the two long graphene strips, the four short graphene strips are symmetrically arranged at two ends of the two long graphene strips, and the outer ends of the short graphene strips are flush with the end portions of the long graphene strips.The application combines Fano resonance with a graphene terahertz sensor, utilizes electric dipole resonance caused by the action of an electric field and a magnetic field, generates a Fano resonance phenomenon, effectively reduces radiation loss through the action of destructive interference between bright and dark modes, and improves the Q value of the sensor.The terahertz sensor has good sensing performance and has important application potential in the fields of biomedicine and sample detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensor devices, in particular to a graphene Fano resonance based terahertz sensor and a method for regulating and application thereof. BACKGROUND

[0002] Terahertz waves are located in a specific region of the electromagnetic spectrum, with frequencies between infrared light and microwaves, and wavelengths between 0.1 and 1 millimeters, known as the "terahertz gap". In recent years, terahertz waves have shown great potential for application in many fields due to their unique characteristics such as strong penetration, significant interaction with matter, and no ionizing radiation. Metamaterials are a type of artificially synthesized periodic sub-wavelength structure electromagnetic material with optical properties beyond the scope of traditional natural materials. Optical devices designed from metamaterials have been widely used in terahertz technology, breaking the limitations of most traditional materials that cannot produce strong electromagnetic responses in the terahertz band, and greatly changing the traditional methods of regulating terahertz waves.

[0003] Graphene is a two-dimensional material composed of a single layer of carbon atoms, with excellent electrical and optical properties. Graphene has extremely high transparency in the visible light range, with only 2.3% light absorption, allowing the graphene surface to achieve total internal reflection. Moreover, graphene can excite surface plasmon resonance (SPR) in the terahertz band, which can enhance the interaction between terahertz waves and graphene, resulting in a localized electromagnetic field enhancement effect. By changing the bias voltage of graphene, the Fermi level of graphene can be adjusted, changing the frequency of SPR and achieving dynamic tunability of the resonance peak. In addition, graphene itself has high carrier mobility, which means it can quickly respond to changes in external electromagnetic fields. Compared to optical devices made of noble metals, graphene has better tunability and lower damping loss, allowing terahertz sensors to achieve higher quality factors and thus improve sensing performance. These characteristics make graphene have wide application potential in terahertz sensing.

[0004] Some graphene-based terahertz sensors have been disclosed in the prior art, such as Chinese invention patent CN117007186A entitled "Graphene-based metamaterial dual-frequency terahertz sensor", and CN118258788A entitled "Tunable graphene metamaterial three-frequency terahertz refractive index sensor". However, the sensing performance of current terahertz sensors still needs to be further improved.

[0005] Fano resonance is a quantum interference effect caused by the interaction between discrete states and continuous states. In plasmonic structures, two characteristic resonance modes can be excited: narrow-band subradiation (dark state) resonance and wide-band super-radiation (bright state) resonance mode. By interference between resonance modes, Fano line type can be produced, causing resonance enhancement of terahertz waves, transparent window formation and nonlinear optical effect generation, thereby improving the sensitivity and quality factor of the sensor. In addition, Fano resonance has a local field enhancement response, which can change the frequency, amplitude or phase of the resonance peak by sensing changes in the dielectric environment around the structure and weak interactions in the measured sample, and has a unique advantage in designing high-sensitivity terahertz sensors. However, there are few reports on the preparation of terahertz sensors based on graphene and Fano resonance in the prior art. SUMMARY

[0006] The present application aims to provide a graphene Fano resonance-based terahertz sensor and its regulation method and application. By combining Fano resonance with graphene terahertz sensors, the sensing performance of the terahertz sensor is further improved.

[0007] In order to achieve the above-mentioned purpose, the specific scheme adopted by the present application is as follows: a graphene Fano resonance-based terahertz sensor, comprising a substrate layer, a dielectric layer and a graphene layer, the graphene layer comprising at least one unit structure arranged on the dielectric layer, the unit structure comprising two long graphene strips arranged in parallel and four short graphene strips arranged between the two long graphene strips, the four short graphene strips being symmetrically arranged at both ends of the two long graphene strips, and the outer ends of the short graphene strips being flush with the end portions of the long graphene strips.

[0008] As a further optimization of the above technical solution, the number of unit structures is multiple, the surface of the dielectric layer is divided into multiple graphene strip arrangement areas arranged in an array along the X and Y directions, each graphene strip arrangement area is a square, and each graphene strip arrangement area is provided with one unit structure, and the long graphene strips of all unit structures are distributed in the same direction.

[0009] As a further optimization of the above technical solution, the number of unit structures is four, and the unit structures are arranged in an array along the X and Y directions on the surface of the dielectric layer, and the long graphene strips of two unit structures arranged along the length direction of the long graphene strips are continuous.

[0010] As a further optimization of the above technical solution, the Fermi energy level of the graphene is 0.3ev-1.0ev.

[0011] As a further optimization of the above technical solution, the material of the substrate layer is a metal film.

[0012] As a further optimization of the above technical solution, the material of the dielectric layer is polyalkylene cycloolefin copolymer.

[0013] A regulation method of a terahertz sensor based on graphene Fano resonance, by changing the structural parameters of long graphene strips and short graphene strips, or by changing the Fermi energy level of graphene through an external bias voltage, the absorption frequency of the sensor to terahertz waves is adjusted.

[0014] The structural parameters include: long graphene strip length L1, short graphene strip width L2, long graphene strip distance from the center point S1, short graphene strip distance from the center point S2, and short graphene strip spacing g.

[0015] A regulation method of a terahertz sensor based on graphene Fano resonance, by changing the thickness of the measured object and / or using different refractive index measured objects, the absorption spectrum and sensing performance of the sensor are adjusted.

[0016] A sensing performance evaluation method of a terahertz sensor based on graphene Fano resonance, the sensing performance includes quality factor (Quality, Q), sensitivity (Sensitivity, S) and quality factor FOM value (Figure Of Merit, FOM).

[0017] The quality factor is represented by formula (1):

[0018]

[0019] Wherein f represents the resonance frequency of the resonance peak, and FWHM represents the full width at half maximum of the resonance peak.

[0020] The sensitivity is represented by formula (2):

[0021]

[0022] Wherein, Δf is the frequency shift of the resonance peak; Δn is the change amount of the refractive index, and the unit is THz / RIU (Refractive Index Unit, RIU).

[0023] The quality factor FOM value is obtained by combining formula (1) and (2), and the FOM value is represented by formula (3):

[0024]

[0025] An application of a terahertz sensor based on graphene Fano resonance in detecting biomolecules, the measured object is applied to the surface of the graphene strip.

[0026] Compared with the prior art, the beneficial effects of the present application are as follows:

[0027] The application combines Fano resonance with a graphene terahertz sensor, utilizes electric dipole resonance caused by electric field and magnetic field action, generates Fano resonance phenomenon, effectively reduces radiation loss through destructive interference between bright and dark modes, and improves the Q value of the sensor.

[0028] The terahertz sensor of the application generates two narrow-band absorption peaks in the frequency range of 3-9 THz, realizes the sensing effect of terahertz waves, has simple structure, can be actively tuned, has wide regulation and control range, has good sensing performance, and has important application potential in biomedical and sample detection.

[0029] The application can enhance the flexibility and application range of the sensor by regulating the Fermi energy level of graphene.

[0030] The highest sensing sensitivity of the application can reach 1.548 THz / RIU, compared with the existing terahertz metamaterial refractive index sensor, effectively solving the problem of low sensitivity. The sensor proposed in the application not only has superior performance, but also can reduce detection cost. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the three-dimensional structure of the terahertz sensor in embodiment 1 of the application;

[0032] Figure 2 is a schematic diagram of the top view of a unit structure in the application;

[0033] Figure 3 is a schematic diagram of the three-dimensional structure of the terahertz sensor in embodiment 2 of the application;

[0034] Figure 4 is an absorption spectrum diagram of a terahertz sensor based on graphene Fano resonance in the application under different polarizations;

[0035] Figure 5 is an electric field and current schematic diagram of a terahertz sensor based on graphene Fano resonance in the application at a terahertz frequency of 6.1 THz;

[0036] Figure 6 is an absorption spectrum diagram of a terahertz sensor based on graphene Fano resonance in the application under different Fermi energy levels;

[0037] Figure 7 is an absorption spectrum diagram of a terahertz sensor based on graphene Fano resonance in the application under different structure parameters;

[0038] Figure 8 is an absorption spectrum diagram of a terahertz sensor based on graphene Fano resonance in the application under different thicknesses of the measured object;

[0039] Figure 9 This is the absorption spectrum of a terahertz sensor based on graphene Fano resonance under different refractive indices of the analyte according to the present invention.

[0040] Figure reference numerals: 1. Substrate layer, 2. Dielectric layer, 3. Long graphene strip, 4. Short graphene strip, 5. Au electrode. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of the present invention should be understood as prior art known or should be known by those skilled in the art.

[0042] Example 1

[0043] like Figure 1 , 2 As shown, the present invention discloses a terahertz sensor based on graphene Fano resonance, comprising a substrate layer 1, a dielectric layer 2 disposed on the substrate layer 1, and a graphene layer disposed on the dielectric layer 2. The graphene layer and the dielectric layer 2 are tightly bonded together, and the graphene layer includes a unit structure disposed on the dielectric layer.

[0044] Both substrate layer 1 and dielectric layer 2 are square with a side length of P, where P = 11 μm.

[0045] The unit structure includes two parallel and spaced long graphene strips 3 and four short graphene strips 4 disposed between the two long graphene strips 3. The two long graphene strips 3 are the same size, and the four short graphene strips 4 are the same size. The four short graphene strips 4 are symmetrically disposed at both ends of the two long graphene strips 3, and the outer ends of the short graphene strips 4 are flush with the ends of the long graphene strips 3.

[0046] For ease of understanding, we define the center of the square dielectric layer 2 as the center point, the length of the long graphene strip 3 as L1, the width of the short graphene strip 4 as L2, the distance between the long graphene strip 3 and the center point as S1, the distance between the short graphene strip 4 and the center point as S2, the spacing between the two short graphene strips 4 located at the same end of the long graphene strip 3 as g, and the outer end of the short graphene strip 4 as the end furthest from the center point.

[0047] The sensor's geometric parameters are:

[0048] L1=11μm, L2=1μm, g=0.8μm, S1=2μm, S2=5μm.

[0049] The Fermi level of graphene is 0.3 eV to 1.0 eV.

[0050] Substrate layer 1 has a conductivity σ = 2.21 × 10⁻⁶. 7The layer structure is made of a metal thin film with a specific material of gold, and the thickness of the substrate layer 1 is 0.2 μm, the substrate layer 1 is used for preventing the penetration of terahertz waves, and the full reflection effect of the terahertz waves can be realized by using gold as the substrate layer.

[0051] The medium layer 2 is a layer structure made of polyalkene copolymer (TOPAS), the relative dielectric constant of the medium layer 2 is 2.35, and the thickness of the medium layer is d = 9 μm. The medium layer has very low loss and dispersion in the terahertz region.

[0052] Embodiment 2

[0053] The application discloses a terahertz sensor based on graphene Fano resonance, which comprises a substrate layer 1, a medium layer 2 arranged on the substrate layer 1 and a graphene layer arranged on the medium layer 2, the graphene layer and the medium layer 2 are closely attached, and the graphene layer comprises a plurality of unit structures arranged on the medium layer 2.

[0054] The surface of the medium layer 2 is divided into a plurality of array-distributed graphene strip setting areas along the X and Y directions, adjacent graphene strip setting areas are connected, each graphene strip setting area is a square, and one unit structure is arranged in each graphene strip setting area.

[0055] The unit structure comprises two long graphene strips 3 arranged in parallel at intervals and four short graphene strips 4 arranged between the two long graphene strips 3, the two long graphene strips 3 are of the same size, the four short graphene strips 4 are of the same size, the four short graphene strips 4 are symmetrically arranged at two ends of the two long graphene strips 3, and the outer end of the short graphene strip 4 is flush with the end of the long graphene strip 3.

[0056] Specifically, in the embodiment, as shown in the figure, Figure 3 four unit structures are arranged on the medium layer 2 and array-distributed on the surface of the medium layer 2 along the X and Y directions, the length direction of the long graphene strip 3 is the Y direction, in the two unit structures arranged along the length direction of the long graphene strip 3, the two long graphene strips 3 are continuous, and the two short graphene strips 4 close to each other are also continuous.

[0057] As shown in the figure, Figure 2 for the convenience of understanding, the center of the square graphene strip setting area is set as a center point, the side length of the graphene setting area is P, P = 11 μm, the length of the long graphene strip 3 is L1, the width of the short graphene strip 4 is L2, the distance between the long graphene strip 3 and the center point is S1, the distance between the short graphene strip 4 and the center point is S2, the spacing between the two short graphene strips 4 at the same end of the long graphene strip 3 is g, and the outer end of the short graphene strip 4 is the end far away from the center point.

[0058] The geometric parameters of the sensor are as follows:

[0059] L1=11μm, L2=1μm, g=0.8μm, S1=2μm, S2=5μm.

[0060] The Fermi energy of the graphene is 0.3ev~1.0ev.

[0061] The substrate layer 1 is made of a metal film with conductivity σ=2.21×10 7 S / m, and the specific material is gold, and the thickness of the substrate layer 1 is 0.2μm, and the substrate layer 1 is used to prevent terahertz waves from penetrating, and gold is used as the substrate layer, so that the full reflection effect of the terahertz wave can be realized.

[0062] The dielectric layer 2 is made of a layer structure of polyalkene copolymer (TOPAS), the relative dielectric constant of the dielectric layer 2 is 2.35, and the thickness of the dielectric layer is d=9μm. In the terahertz region, it has very low loss and dispersion.

[0063] Embodiment 3

[0064] The application discloses a kind of based on the regulation and control method of terahertz sensor of graphene Fano resonance, by changing the size of different structure of graphene pattern layer, or, by external bias voltage change Fermi energy of graphene, to adjust the absorption frequency of sensor to terahertz wave.

[0065] Specifically, by changing the structure parameters of the long graphene band 3 and the short graphene band 4, the absorption frequency of the sensor to the terahertz wave is adjusted.

[0066] The structure parameters include: long graphene band length L1, short graphene band width L2, long graphene band and center point distance S1, short graphene band and center point distance S2, and short graphene band spacing g.

[0067] As shown in Figure 1 As shown in the figure, Fermi energy of graphene is changed by external bias voltage, Au electrode 5 is connected to long graphene band 3 and short graphene band 4, Au electrode 5 is long strip-shaped, and is perpendicular to long graphene band 3, Figure 1 Wherein Vg represents external bias voltage,

[0068] In the terahertz wave band, the carrier concentration of graphene is affected by Fermi energy and carrier scattering rate. The Fermi energy of graphene can be changed by applying external bias voltage, which can be shown as follows:

[0069]

[0070] n s represents carrier concentration, V biased External bias voltage (V g in the figure), the capacitance of a0 structure model, according to the formula, the higher the bias voltage, the higher the Fermi energy of graphene.

[0071] Furthermore, the modulation method of the terahertz sensor based on graphene Fano resonance of the present invention can also achieve the adjustment of the absorption spectrum and sensing performance of the sensor by changing the thickness of the analyte and using analytes with different refractive indices.

[0072] In the sensor of this invention, different types of analyte samples are attached to the graphene surface of the sensor during sensing, and the degree of resonance peak shift is compared to achieve sensing and analysis of the analytes.

[0073] The sensor performance was studied using the full-wave electromagnetic simulation software Lumerical FDTD Solutions. Periodic boundary conditions were set in the X and Y directions, and a perfectly matched layer (PML) boundary condition was set in the Z direction.

[0074] like Figure 4 As shown, Figure 4 When the polarization angles are 0° and 90°, these correspond to the TM and TE modes, respectively. In the TM mode, the resonance condition is met, resulting in Fano resonance. In the TE mode, resonance peaks are generated at 7.1 THz and 9.7 THz through the interaction between graphene and terahertz waves, but these peaks differ significantly from those generated in the TM mode. This is because the designed sensor structure is not highly symmetrical (it should be noted that "not highly symmetrical" in this invention means that within the same unit structure of the sensor, the two long graphene strips have the same size, and the four short graphene strips have the same size, but the sizes of the long and short graphene strips are inconsistent, resulting in a sensor structure that is not rotationally symmetrical). Therefore, the resonances generated differ when facing electric field polarization in different directions. Thus, this invention primarily focuses on the TM mode.

[0075] like Figure 5 As shown, Figure 5 In the figure, (a) represents the electric field component in the X direction of the bright mode; (b) represents the electric field component in the X direction of the dark mode; (c) represents the electric field distribution of the complete graphene structure; and (d) represents the current distribution at a terahertz frequency of 6.1 THz.

[0076] like Figure 5 As shown in (a), when the polarization electric field direction of the incident plane wave is in the positive X-axis direction, for short graphene strips, a large number of opposite charges accumulate at both ends of the short graphene strips, exhibiting typical characteristics of electric dipole resonance. This indicates that the short graphene strips can directly and strongly couple with the incident electromagnetic wave, and this coupled resonance state is defined as a bright mode. For long graphene strips, they cannot be directly excited by the incident electromagnetic wave near this frequency point, therefore their surface has almost no electric field distribution, such as... Figure 5(b) shows, so it is defined as dark mode. The electric field distribution of the sensor structure designed by the present application is shown in Figure 5 (c) shows, the left and right edges of the short graphene band gather a large number of opposite charges, and a strong electric field is generated around it. A small part of the opposite charges also accumulates on the long graphene band, but the electric field formed is extremely weak. Combined with the electric field distribution shown in Figure 5 (d) shows the current distribution, it can be observed that the surface current is mainly concentrated on the short graphene band, and a small amount of surface current is also distributed on the long graphene band, and the overall current propagates in the negative direction of the X axis. Therefore, it can be seen that the long graphene band which originally did not occur electromagnetic response is excited to produce resonance, and surface current is generated on its surface, while the resonance of the short graphene band with the electric field generated by the terahertz wave is suppressed, and the resonance strength is weakened. Secondly, due to the close distance between the two substructures and the similar resonance frequency, through near-field coupling, the long graphene band also generates a resonance under the excitation of the electric dipole resonance generated by the short graphene band. Because the two structures are excited in different sequences, there is a certain phase difference, and through interference cancellation, the resonance of the short graphene band is suppressed, and the local electric field of the long graphene band is enhanced, finally the left and right ends of the short graphene band excite strong surface electric field distribution, that is, dipole oscillation, thereby reducing the radiation loss, and making the absorption spectrum show Fano line type. This is consistent with the distribution characteristics of the electric field, and also explains the reason for the formation of the Fano resonance peak.

[0077] The terahertz sensor of the present application is provided with a plurality of graphene bands of different sizes, and a typical asymmetric Fano resonance peak is generated through the interference action between the graphene bands. This is because Fano resonance describes the resonance response of two modes to the incident (excitation) light after coupling and interference, which is generally manifested as an asymmetric line in the scattering spectrum or extinction spectrum. An independent resonance response spectrum is a symmetrical Lorentz shape, when two modes interact, the spectrum is not simply an intensity superposition, because the phase responses of the two resonances are different. The line shape of the Fano resonance comes from the interference of two scattering amplitudes, one is the scattering of the continuous state (related to the background), and the other is the excitation of the discrete state (related to the resonance). The energy of the resonance state must be within the energy range of the continuous state (i.e. the background), and the effect will occur. Near the resonance energy, the amplitude of the background scattering usually changes very slowly with energy, but the amplitude and phase of the resonance scattering change quite rapidly, resulting in the occurrence of asymmetry.

[0078] As shown in Figure 6As shown, when the Fermi level is tuned between 0.3 eV and 1.0 eV, the resonance peaks all exhibit a blue shift. This is because light absorption is related to electronic transitions. As the Fermi level moves to higher energy levels, electrons can absorb the energy of photons and transition to even higher energy levels. At this point, the resonance peak shifts towards higher energy (shorter wavelengths), resulting in a blue shift. Therefore, in practical applications, adjusting the Fermi level of graphene can enable the sensor to operate within the desired frequency range.

[0079] like Figure 7 As shown, Figure 7 In the image, (a) represents the absorption spectrum after the length of the long graphene band increases, and (b) represents the absorption spectrum after the bandwidth of the short graphene band increases.

[0080] As shown in (a) and (b), as parameter L1 gradually increases, the dual-frequency resonance peak generated by the incident wave undergoes a redshift. This is because the change in graphene length leads to an increase in the equivalent inductance of the structure surface, thus causing the resonance peak to redshift. However, when parameter L1 = 11 μm, the structure produces a Fano resonance peak because the electric fields of the long and short graphene bands interfere, forming a Fano resonance. Similarly, as parameter L2 increases, the Fano resonance peak appears at L2 = 1 μm. As L2 increases further, the Fano resonance phenomenon disappears, and the dual-frequency resonance peak gradually redshifts.

[0081] Figure 7 In the diagram, (c) represents the absorption spectrum of the long graphene band with an increased distance from the center point, and (d) represents the absorption spectrum of the short graphene band with an increased distance from the center point.

[0082] As shown in (c) and (d), the Fano resonance only occurs when the structural parameters are at specific values. With changes in parameter S1, the resonance peak redshifts, and the absorption rate gradually increases. At S1 = 2 μm, the Fano resonance effect occurs, and the absorption rate reaches its maximum. As S1 gradually increases, the Fano resonance effect disappears, transforming into a single resonance peak. The resonance peak frequency continues to redshift, and the absorption rate gradually decreases until only the electric field of the short graphene bands interacts with the terahertz waves. With an increase in parameter S2, the resonance peak undergoes a slight blue shift. At S2 = 5 μm, a phase abruptly occurs, forming the Fano resonance peak at 6.1 THz.

[0083] Figure 7 In the diagram, (e) represents the absorption spectrum after the spacing between short graphene bands is increased, and (f) represents the absorption spectrum after the dielectric layer is increased.

[0084] As shown in (e), when analyzing parameter g, it can be found that the modulation depth of the Fano resonance window increases with the increase of g, but the absorptivity of the resonance peak decreases after a certain value, and the resonance peak undergoes a redshift. Therefore, by analyzing the influence of structural parameters on sensor performance, it can be concluded that the formation of Fano resonance is related to the electric field coupling between graphenes, and can only be generated under specific structural parameters, requiring the satisfaction of corresponding Fano resonance conditions. As shown in (f), with the increase of parameter d, the absorptivity of the Fano resonance peak gradually increases, and the frequency of the resonance peak undergoes a blueshift. However, after d = 9 μm, the absorptivity gradually decreases, and the frequency shift of the resonance frequency gradually decreases. Therefore, the thickness of the dielectric layer is not necessarily better the thicker it is. Increasing the thickness of the dielectric layer within a certain range allows terahertz waves to undergo multiple reflections and refractions within the structure, enhancing the interaction between the metamaterial and the terahertz waves. After the thickness reaches a certain value, impedance matching is formed, at which point the absorptivity of the resonance peak is the highest. Subsequently, as the thickness continues to increase, the propagation path of the terahertz waves within the structure becomes longer, the propagation loss increases, and therefore the absorptivity continuously decreases.

[0085] like Figure 8 As shown in (a), a layer of the analyte is coated on the top layer of the sensor, with the refractive index of the analyte fixed at 1.5. Comparing the absorption spectrum without the analyte on the sensor surface, the resonant frequency of the absorption spectrum with the analyte exhibits a significant redshift, with a frequency shift of approximately 0.9 THz. This indicates that the structure is highly sensitive to changes in the external dielectric environment. The curve showing the relationship between the analyte thickness and the degree of resonant peak shift is shown in Figure [image missing]. Figure 8 As shown in (b), the black solid line in the figure represents the curve of the change in the thickness of the object under test versus the frequency shift, and the red solid line represents the fitting curve of the simulation data. The results show that the simulation data and the exponential fitting curve are in good agreement. When the thickness of the object under test increases, the frequency shift of the resonance peak shows an exponential decreasing trend, and the frequency shift gradually approaches 0 after the thickness exceeds 2 μm. Therefore, after the thickness exceeds 2 μm, the influence of the thickness on the sensor performance can be ignored.

[0086] like Figure 9 As shown in (a), with a fixed analyte thickness of 2 μm, the resonance peak exhibits a redshift of 1.18 THz as the refractive index of the analyte increases. Therefore, this sensor is highly sensitive to changes in the external dielectric environment. The linear relationship between frequency and refractive index is shown in Figure [Figure number missing]. Figure 9 As shown in (b), the frequency increases linearly with the increase of refractive index. A linear fit is performed between the two, and the slope of the fitted curve represents the sensor's sensitivity. The fitted curve shows that the sensor's sensitivity remains constant, thus indicating good stability. Based on formulas (1) to (3), the sensor sensitivity of this invention is obtained as S = 1.548 THz / RIU, Q = 31.05, and FOM = 8.1 RIU.-1 .

[0087] The prepared terahertz sensor realizes good refractive index detection performance and has important application potential in biomedical and sample detection.

[0088] In the biomedical field, the weak interaction (such as hydrogen bond, van der Waals force, etc.) between biological macromolecules such as proteins, DNA / RNA, lipids and sugars is just located in the terahertz (THz) frequency range. The refractive index of most biological macromolecules usually varies in the range of 1.4 to 2.0, and when the terahertz wave interacts with these biological macromolecules, resonance effect will occur, and the characteristic resonance peak can be used to detect the slight change of the structure and composition of the substance, which provides a new method for analyzing cell structure and medical diagnosis. Secondly, when the terahertz wave interacts with biological tissues or cells, it will inevitably interact with a large number of water molecules therein. Since the stretching and bending vibration modes of hydrogen bonds between water molecules are in the terahertz wave band (the strongest resonance frequencies are 5.6 THz and 1.5 THz, respectively), these vibration modes will be excited and cause resonance phenomenon, resulting in significant absorption of water to terahertz wave. In addition, different contents of bases in DNA and RNA will cause resonance absorption in the entire terahertz frequency band, and the frequency points are located between 2 THz and 8 THz, so the sensor designed by the present application can be used for detection of biological molecules.

[0089] When the terahertz sensor of the present application is used to detect biological molecules, a sample containing biological molecules is coated on the surface of the graphene strip as the measured object.

[0090] The above-mentioned embodiments are only preferred embodiments of the present application, and do not limit the scope of the present application. Therefore, equivalent changes or modifications made according to the structure, features and principles described in the patent scope of the present application should be included in the patent scope of the present application.

Claims

1. A terahertz sensor based on graphene Fano resonance, comprising a substrate layer (1), a dielectric layer (2), and a graphene layer, characterized in that, The graphene layer includes at least one unit structure disposed on the dielectric layer (2). The unit structure includes two long graphene strips (3) disposed in parallel and spaced apart, and four short graphene strips (4) disposed between the two long graphene strips (3). The four short graphene strips (4) are symmetrically disposed at both ends of the two long graphene strips (3), and the outer ends of the short graphene strips (4) are flush with the ends of the long graphene strips (3).

2. The terahertz sensor based on graphene Fano resonance according to claim 1, characterized in that, The number of unit structures is multiple. The surface of the dielectric layer (2) is divided into multiple arrayed graphene strip setting areas along the X and Y directions. Each graphene strip setting area is square. Each graphene strip setting area is set with one of the unit structures. The long graphene strips (3) of all unit structures are distributed in the same direction.

3. A terahertz sensor based on graphene Fano resonance according to claim 1, characterized in that, The number of unit structures is 4, and they are arrayed on the surface of the dielectric layer (2) along the X and Y directions. The long graphene strips (3) of the two unit structures are continuous along the length direction of the long graphene strips (3).

4. A terahertz sensor based on graphene Fano resonance according to claim 1, characterized in that, The Fermi level of graphene is .

5. A terahertz sensor based on graphene Fano resonance according to claim 1, characterized in that, The substrate (1) is made of a metal thin film.

6. A terahertz sensor based on graphene Fano resonance according to claim 1, characterized in that, The medium layer (2) is made of polycyclic olefin copolymer.

7. A method for controlling a terahertz sensor based on graphene Fano resonance as described in any one of claims 1-6, characterized in that, By changing the structural parameters of the long graphene band (3) and the short graphene band (4), or by changing the Fermi level of graphene by applying an external bias voltage, the absorption frequency of terahertz waves by the sensor can be adjusted. The structural parameters include: the length L1 of the long graphene strip (3), the width L2 of the short graphene strip (4), the distance S1 between the long graphene strip (3) and the center point, the distance S2 between the short graphene strip (4) and the center point, and the spacing g of the short graphene strip (4).

8. A method for controlling a terahertz sensor based on graphene Fano resonance as described in any one of claims 1-6, characterized in that, The absorption spectrum and sensing performance of the sensor can be adjusted by changing the thickness of the analyte and / or using analytes with different refractive indices.

9. An application of a terahertz sensor based on graphene Fano resonance as described in any one of claims 1-6 in the detection of biomolecules, characterized in that, The analyte was coated onto the surface of the graphene tape.

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