Tunable electromagnetic induction transparent metamaterial sensing chip

Abstract

The scheme provides a tunable electromagnetic induction transparent metamaterial sensing chip, which comprises at least one sensing unit arranged in an array, each sensing unit comprises a graphene layer and a dielectric layer from top to bottom, two same cloud resonators arranged at intervals are formed on the graphene layer, and the dielectric layer is arranged between the two cloud resonators. Each cloud resonator is designed to be in a cloud shape formed by connecting a transverse strip and a bent strip end to end, flexible frequency adjustment is achieved through a patterned graphene structure, the sensor has the advantages of being high in sensitivity, specific in detection, optimizable in structure and clear in mechanism, and the defects of a traditional sensor are effectively overcome.

Description

Technical Field

[0001] The present invention relates to the field of metamaterial sensor design, and particularly to a tunable electromagnetically induced transparency metamaterial sensing chip. Background Art

[0002] The electromagnetically induced transparency (EIT) effect refers to the phenomenon that at a specific frequency, due to the nonlinear effect in the medium, the transmittance of electromagnetic waves increases significantly, thereby generating a transparent window. It can be widely applied in the fields of sensing, optical storage, communication, etc. However, its excitation conditions are harsh. With the proposal of metamaterials, it has been found that the quasi-electromagnetically induced transparency effect can be excited in terahertz metamaterials, and the requirements for experimental conditions are greatly reduced. Therefore, metamaterial sensors have begun to emerge. Relying on their unique electromagnetic properties and tunability, metamaterial sensors have shown unprecedented application potential in many fields such as biomedical detection, environmental monitoring, and food safety. Among them, EIT metamaterial sensors have become one of the hot research directions in the field of sensors due to their advantages such as high sensitivity, high resolution, and the ability to accurately detect small physical quantity changes.

[0003] With the increasing demand for antibiotic detection, most of the existing metamaterial sensors are made of metal materials and cannot be adjusted once fabricated, which greatly limits their application flexibility and universality in actual complex detection scenarios. Specifically, they can only achieve the sensing and detection function of a single antibiotic at a specific and fixed frequency, and it is difficult to detect other antibiotics at other frequencies. In actual application scenarios, however, the detection requirements for multiple antibiotics are often faced, such as the analysis of different antibiotic components in compound drugs in the medical field, or the sequential detection of multiple antibiotic residues in the field of food safety monitoring. The mode of detecting a single antibiotic at a fixed frequency obviously cannot meet these diversified and complex actual needs, which undoubtedly becomes a key factor restricting the further large-scale practical application of this sensor. Summary of the Invention

[0004] The purpose of the present invention is to provide a tunable electromagnetically induced transparency metamaterial sensing chip, which realizes flexible frequency adjustment through a patterned graphene structure, and has the advantages of high sensitivity, specific detection, structural optimization, and clear mechanism, effectively overcoming the defects of traditional sensors.

[0005] To achieve the above objectives, the present invention provides a tunable electromagnetically induced transparent metamaterial sensor chip, comprising: at least one array-arranged sensor unit, wherein each sensor unit comprises a graphene layer and a dielectric layer from top to bottom, and two identical cloud resonators arranged alternately are formed on the graphene layer, and each cloud resonator is designed to be in the shape of a cloud with horizontal strips and curved strips connected end to end.

[0006] Compared with the prior art, this technical solution has the following characteristics and beneficial effects: 1. Flexible frequency adjustment: By changing the external bias voltage to adjust the Fermi level of graphene, the EIT window can be flexibly adjusted so that the peak of the sensor can appear at different frequencies. This breaks through the limitation that traditional antibiotic sensors cannot be flexibly adjusted after they are manufactured, and can meet the detection needs of different antibiotics at different frequencies in actual detection.

[0007] 2. High-sensitivity detection: The sensor is sensitive to changes in the refractive index of the surrounding environment. In the simulation analysis, when the refractive index of the object to be measured increases from 1.0 to 1.4 in steps of 0.1, the linear fitting calculation shows that its sensitivity is 220GHz / RIU, the quality factor Q is 13.6, and the comprehensive performance index FOM is 9.84. It has good sensing performance and can achieve accurate detection of tiny changes in physical quantities.

[0008] 3. Specific detection: Since 1Thz is the characteristic fingerprint spectrum of chloramphenicol, the sensor unit has a transparent peak at 1.021THz and a transmittance of 83.1%, which can specifically sense and detect chloramphenicol to meet the needs of specific substance detection.

[0009] 4. The structure can be optimized: The structural parameters of the sensing unit, such as the shape of the cloud resonator, coupling distance, ring segment radius, dielectric plate thickness, etc., can be adjusted. For example, changing the coupling distance will affect the red shift and amplitude change of the EIT window, and adjusting the thickness of the dielectric plate can control the red shift of the EIT window and keep the transmission amplitude almost unchanged, which is convenient for optimizing sensor performance according to different application scenarios.

[0010] 5. Clear mechanism: The EIT effect of this sensor is based on bright-bright mode coupling. Both cloud resonators are bright modes and can be directly excited by the incident field. The interference field generated by the coupling after excitation forms an EIT transparent window. The electric field energy diagram clearly shows the electric field distribution of each resonator when it is excited individually and together, providing a theoretical basis for further research and improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a structural diagram of the tunable electromagnetically induced transparent metamaterial sensor chip of this scheme.

[0012] Figure 2 The transmission curves of the three sensors are obtained by simulating and analyzing the three sensors.

[0013] Figure 3 It is the electric field energy diagram of the EIT effect at three resonance point frequencies.

[0014] Figure 4 It is the EIT window diagram under different coupling distances.

[0015] Figure 5 It is the EIT window diagram under different annular segment radii.

[0016] Figure 6 It is the EIT window diagram under different dielectric thickness.

[0017] Figure 7 It is a transmission curve diagram of the metamaterial sensor under different refractive indices of the object to be tested.

[0018] Figure 8 It is a linear fitting diagram of the refractive index change of each EIT window relative to the surrounding test object.

[0019] Figure 9 is the Fermi level of graphene to obtain the corresponding peak of the EIT transparency peak. DETAILED DESCRIPTION

[0020] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0021] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0022] Embodiment 1 like Figure 1 As shown, the technical solution provides a tunable electromagnetically induced transparent metamaterial sensor chip, comprising: At least an array arrangement of sensing units, where each sensing unit includes a graphene layer and a dielectric layer from top to bottom. Two identical and alternately arranged cloud resonators are formed on the graphene layer, and each cloud resonator is designed to be in the shape of a cloud formed by connecting a horizontal bar and a curved bar end to end.

[0023] The two cloud resonators on each sensing unit of this solution constitute the resonant part of the current sensor. The two cloud resonators are respectively used as bright modes to generate bright-bright coupling, and the excited electric fields generated by the two cloud resonators are superimposed.

[0024] Specifically, the two cloud resonators are staggered, and the coupling distance is 2.8 - 6.6 µm. Preferably, the coupling distance s between the cloud couplers is 2.8 µm.

[0025] It should be noted that the change in the coupling distance between the two cloud resonators has a significant impact on the EIT window. This is because the change in the coupling distance will cause the coupling of the resonant fields to change, thereby affecting the electric field distribution of the coupling field. Generally speaking, when the coupling distance becomes larger, the EIT window will show a red shift phenomenon, that is, the center frequency of the window moves towards the low-frequency direction, and the amplitude of the window will increase.

[0026] In some embodiments, the two cloud resonators are arranged relatively obliquely, that is, one cloud resonator is located at the diagonal position of the other cloud resonator, and the two cloud resonators do not overlap.

[0027] Specifically, one cloud resonator on each sensing unit is located at the lower left of the dielectric plate, and the other cloud resonator is located at the upper right of the dielectric plate; or one cloud resonator is located at the upper left of the dielectric plate, and the other cloud resonator is located at the lower right of the dielectric plate.

[0028] In addition, the coupling distance between the two cloud resonators refers to the closest distance between the two cloud resonators.

[0029] Regarding the shape of the cloud resonator: Each cloud resonator is designed to be in the shape of a cloud formed by connecting a horizontal bar and a curved bar end to end, where the curved bar is composed of three connected circular ring segments spliced together, and the two circular ring segments at the head and tail are respectively connected to the horizontal bar.

[0030] In some embodiments, each circular ring segment is the same to divide the curved bar into three equal segments, so that the cloud resonator is designed with a symmetric structure.

[0031] Furthermore, the radius h of the circular ring segment corresponding to each circular ring segment of the open circular ring is 7.9 - 8.3 µm. Preferably, the radius of the open circular ring corresponding to each circular ring segment is 8 µm.

[0032] Furthermore, each circular ring segment is in the shape of a semi-circle.

[0033] In some embodiments, the widths of the horizontal bars and the curved bars of each cloud resonator are the same, both being 1.9 - 2.1 µm. Preferably, the widths of the horizontal bars and the curved bars of each cloud resonator are 2 µm.

[0034] In some embodiments, the thickness of the graphene layer is 0.001 µm.

[0035] In some embodiments, the dielectric plate is made of quartz material, and the relative dielectric constant of the quartz material is 1.9.

[0036] In some embodiments, the thickness of the dielectric plate is 5 - 9 µm. Preferably, the thickness of the dielectric plate is 5 µm.

[0037] In some embodiments, the dielectric plate is a square with equal length and width. At this time, the side lengths Px and Py of the dielectric plate are 64 µm. The advantage of such a setting is that it can suppress the mutual interference between adjacent resonators. If the side length of the quartz dielectric plate is too small, the electromagnetic fields of adjacent units will interfere with each other, destroying the EIT effect; while if the side length of the quartz dielectric plate is too large, the sensor integration will also be reduced.

[0038] This solution can adjust the Fermi level of graphene by changing the external bias voltage, thereby adjusting the EIT window so that its peak can appear at other frequencies, realizing flexible adjustment of the antibiotic to be measured, overcoming the disadvantage that traditional antibiotic sensors cannot be flexibly adjusted once made. This device provides a solution for the flexible detection of antibiotics.

[0039] In some embodiments, the Fermi level of graphene is changed to change the peak frequency of the EIT transparency peak of the sensor. When the Fermi level of graphene increases from 0.9 eV to 1.15 eV in increments of 0.05 eV each time, the corresponding peak frequencies of the EIT transparency peak are 0.93 THz, 0.95 THz, 0.97 THz, 0.99 THz, 1.01 THz, and 1.021 THz.

[0040] In some embodiments, each sensing unit has a transparency peak at 1.021 THz, and the transmittance is 83.1%. Since 1 Thz is the characteristic fingerprint spectrum of chlortetracycline, this sensing unit can be used for specific sensing detection of chlortetracycline.

[0041] Embodiment 2 In order to study and verify the performance of the tunable electromagnetic induced transparency metamaterial sensing chip designed in this solution, this solution sets up a simulation environment for performance testing: The simulation environment is as follows: The CST Studio Suite electromagnetic simulation software is used to complete the simulation of the metamaterial sensor. During the simulation, the boundary conditions of the EIT-like metamaterial sensor unit in the x and y directions are set as unit cell boundaries, and the z direction is set as an open (add space) boundary to simulate an infinite periodic array of metamaterials. The incident direction of the THz plane wave is selected as -z as the excitation source, and the simulation frequency band is set to 0.3 - 1.4 THz.

[0042] Parameter design of the tunable electromagnetic induced transparency metamaterial sensing chip: The dielectric plate is made of quartz, and the thickness d of the dielectric plate is 5 µm. The side lengths of the dielectric plate in the x and y directions are represented by Px and Py respectively, Px = 64 µm, Py = 64 µm. The coupling distance s between the two cloud resonators is 2.8 µm. The widths of the horizontal and curved bars of each cloud resonator are 2 µm. The radius of the open ring corresponding to the three circular ring segments on the curved section is 8 µm. The thickness of the cloud resonator is 0.001 µm.

[0043] (1)Analysis of the EIT mechanism: The sensor with only the cloud resonator in the lower left corner is designed as URR, the sensor with only the cloud resonator in the upper right corner is designed as LRR, and the sensor of this scheme with both the cloud resonator in the lower left corner and the cloud resonator in the upper right corner is designed as EIT-like. The transmission curves of the three sensors are obtained through simulation and analysis as shown in Figure 2 shown, and the electric field energy diagrams at the three resonance point frequencies of the EIT effect are obtained as shown in Figure 3 shown.

[0044] As can be seen from Figure 2 , when URR is simulated alone, a strong resonance occurs at 1.043 THz, while when LRR is simulated alone, it is excited at 1.035 THz. When URR and LRR are combined in EIT-like, a transparency peak appears at 1.021 THz, and its transmittance is 83.1%. It can be seen that the electromagnetic induced transparency window generated by the sensor of this scheme is a bright-bright mode coupling. In this sensor, the excitation of the two cloud resonators is relatively strong, and both cloud resonators can be directly excited by the incident field. Therefore, both are bright modes. After the two cloud resonators are excited as a whole, the interference field generated by the coupling between the two cloud resonators forms an obvious EIT transparency window. It should be noted that since 1 THz is the characteristic fingerprint peak of chlortetracycline, the sensor of this scheme can achieve specific sensing detection of chlortetracycline.

[0045] As can be seen from Figure 3 , Figure 3In (a), it is the electric field distribution diagram of URR when excited alone. It can be seen that it is strongly excited and is in the bright mode; Figure 3 In (b), it is the electric field distribution diagram of LRR when excited alone. It is also strongly excited and is also in the bright mode; Figure 3 In (c), it is the electric field distribution diagram when both are simulated together. It can be seen that when the two are coupled, the bright-bright mode-like EIT effect is excited, and its electric field distribution is a symmetric mode. The electric field energy of URR is mainly distributed on the two side rings, and the electric field energy of LRR is mainly distributed on the upper right ring. The coupling of the two electric field energies greatly enhances the field strength at the approaching positions. In the superposition principle of waves, the wave crests or wave troughs of two waves reach the same frequency at the same time, resulting in destructive interference, and the interference wave will produce the maximum amplitude.

[0046] (2) Influence of the coupling distance s: Sensors with coupling distances s designed to be 2.8 µm, 3.5 µm, 4.2 µm, 4.9 µm, and 6.6 µm respectively are simulated to obtain the EIT window diagrams at different coupling distances as Figure 4 shown.

[0047] As Figure 4 can be seen, it can be seen that as the coupling distance s increases, the EIT window shows a red shift and the amplitude increases. In addition, it can be seen that when the coupling distance s is 2.8 µm, the EIT resonance peak is sharper, that is, the Q value is higher, the sensing performance is better, the transmittance is higher, and the resonance peak position is also near the 1 THz chlortetracycline fingerprint spectrum.

[0048] (4) Influence of the radius h of the circular ring segment: Sensors with h designed to be 7.9 µm, 8.0 µm, 8.1 µm, 8.2 µm, and 8.3 µm respectively are simulated to obtain the EIT window diagrams at different radii h of the circular ring segment as Figure 5 shown.

[0049] As Figure 5 can be seen, as h increases, the EIT window shows a blue shift and the window amplitude decreases. Preferably, the performance is the best when h is 8.1 µm or 8.1 µm. At this time, the Q value is higher, the sensing performance is better, the transmittance is higher, and the resonance peak position is also near the 1 THz chlortetracycline fingerprint spectrum.

[0050] (5) Influence of the thickness d of the dielectric plate: Sensors with the thickness d of the dielectric plate designed to be 5 µm, 6 µm, 7 µm, 8 µm, and 9 µm respectively are simulated to obtain the EIT window diagrams at different thicknesses d of the dielectric plate as Figure 5 shown As Figure 6It can be seen that as d increases, the EIT window exhibits a red shift, and the transmission amplitude remains almost unchanged. Preferably, when the thickness d of the dielectric plate is 5 µm, the EIT resonance peak is sharper, that is, the Q value is higher, the sensing performance is better, the transmittance is higher, and at the same time, the resonance peak position is also near the fingerprint spectrum of chlortetracycline at 1 THz.

[0051] (6)Performance characterization of the sensor: The EIT sensor based on metamaterials can achieve a frequency shift of the EIT window peak by changing the refractive index of the analyte. Therefore, the performance of the sensor depends on the sensitivity to the refractive index of the surrounding environment. Usually, three values, namely sensitivity, quality factor Q, and FOM, are used to characterize the performance of the sensor.

[0052] Regarding the sensitivity S index, this index represents the relationship between the change in the refractive index of the analyte on the sensor surface and the frequency shift of the window. In experimental measurements, the change in the analyte concentration will cause a change in the refractive index. The common unit of sensitivity is GHz / RIU, and the specific formula is as follows:

[0053] is the change in refractive index, is the frequency shift of the transparent window corresponding to the change in the refractive index of the analyte.

[0054] Regarding the quality factor Q index, this index represents the resonance characteristics of the sensor. The sharper the peak at the transparent window, the higher the corresponding Q value. A high Q value can overcome a large amount of electromagnetic wave radiation loss. The Q value calculation formula is:

[0055] is the center frequency of the transparent window, and FWHM is the full width at half maximum of the transparent window peak.

[0056] Regarding the FOM index, this index is a comprehensive index of the sensor performance and can be used for comparing the performance of multiple sensors. The calculation formula of FOM is: .

[0057] To explore the sensitivity index, the sensing performance of the tunable EIT metamaterial antibiotic sensor was simulated and analyzed. During the simulation, a layer of analyte with a thickness of 3 µm was set on the surface of the designed metamaterial sensor, and the change in the transmission curve of the metamaterial sensor was studied by changing its refractive index. The refractive indices of the analyte were 1, 1.1, 1.2, 1.3, and 1.4 respectively. The obtained result graph is as shown in Figure 7 shown, and the linear fitting graph of the refractive index change of each EIT window with respect to the surrounding analyte is as shown in Figure 8As shown, it can be seen that when the refractive index increases from 1.0 to 1.4 with a step of 0.1, the transmission window undergoes frequency shift, and the resonant peak frequencies are 0.9116, 0.9369, 0.9534, 0.9776, 0.9996 THz respectively. Through linear fitting calculation, the sensitivity of this sensor is obtained as 220 GHz / RIU, the Q value is 13.6, and the FOM is 9.84, showing good sensing performance.

[0058] (7) Characterization of the tunability of the sensor: Analyze the tunability of the EIT metamaterial antibiotic sensor, and adjust the Fermi level of graphene to obtain the peak value of the corresponding EIT transparency peak. The results are as Figure 9 shown. It can be seen that when the Fermi level Ef of graphene gradually increases, that is, from 0.9 eV to 1.1 eV with a step of 0.05 eV, the peak value of the EIT window moves to higher frequencies, and the peak frequencies are 0.93 THz, 0.95 THz, 0.97 THz, 0.99 THz, 1.01 THz respectively. Its transmittance slightly increases, and the transmittances of the left and right valleys decrease, with the decrease of the right valley being more obvious.

[0059] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as within the scope described in this specification.

[0060] The above embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be understood as a limitation to the scope of this application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

Claims

1. A tunable electromagnetically induced transparent metamaterial sensor chip, characterized in that: include: At least one array of sensor units, wherein each sensor unit comprises a graphene layer and a dielectric layer from top to bottom, two identical cloud resonators arranged alternately are formed on the graphene layer, and each cloud resonator is designed to be in the shape of a cloud with horizontal strips and curved strips connected end to end.

2. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The two cloud resonators are staggered and the coupling distance is 2.8~6.6µm.

3. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The two cloud resonators are arranged to be relatively inclined, and the two cloud resonators do not overlap.

4. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: Each cloud resonator is designed to be in the shape of a cloud with horizontal bars and curved bars connected end to end, wherein the curved bar is composed of three connected circular segments, and the two circular segments located at the head and the tail are respectively connected to the horizontal bar.

5. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 4, characterized in that: Each circular ring segment is identical to divide the bending strip into three equal segments, and the y-circular ring segment radius of the open circular ring corresponding to each circular ring segment is 7.9~8.3µm.

6. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The dielectric plate is made of quartz and has a thickness of 5~9µm.

7. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The thickness of the graphene layer is 0.001µm.

8. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The width of the horizontal and curved strips of each cloud resonator is the same, 2µm.

9. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The Fermi level of graphene is changed to change the peak frequency of the EIT transparent peak of the sensor. When the Fermi level of graphene increases from 0.9eV to 1.15eV in increments of 0.05eV each time, the corresponding peak frequencies of the EIT transparent peak are 0.93THz, 0.95THz, 0.97THz, 0.99THz, 1.01THz, and 1.0121THz.

10. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 9, characterized in that: When the sensing unit shows a transparent peak at 1.021 THz, it is used for specific sensing and detection of chlortetracycline.

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