A tunable electromagnetically induced transparent metamaterial sensor chip

Abstract

This solution provides a tunable electromagnetically induced transparent metamaterial sensor chip, comprising: at least one array of sensor units, wherein each sensor unit comprises a graphene layer and a dielectric layer from top to bottom, with two identical cloud resonators arranged alternately on the graphene layer. Each cloud resonator is designed to be cloud-shaped with horizontal and curved strips connected end to end. The patterned graphene structure enables flexible frequency adjustment, and has the advantages of high sensitivity, specific detection, structural optimizability, and clear mechanism, effectively overcoming the shortcomings of traditional sensors.

Description

Technical Field

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

[0002] Electromagnetically induced transparency (EIT) refers to the phenomenon in which, at specific frequencies, the transmittance of electromagnetic waves increases significantly due to nonlinear effects in the medium, thereby creating a transparent window. This phenomenon can be widely used in sensing, optical storage, communications, and other fields. However, its excitation conditions are demanding. With the advent of metamaterials, research has found that a similar EIT effect can be stimulated in terahertz metamaterials, greatly reducing the requirements for experimental conditions. As a result, metamaterial sensors have begun to emerge. With their unique electromagnetic properties and controllability, metamaterial sensors have demonstrated unprecedented application potential in many fields, including biomedical testing, environmental monitoring, and food safety. EIT metamaterial sensors, in particular, have become a hot topic in sensor research due to their high sensitivity, high resolution, and ability to accurately detect tiny changes in physical quantities.

[0003] With the increasing demand for antibiotic detection, existing metamaterial sensors are mostly made of metal materials and cannot be adjusted once they are made. This greatly limits their flexibility and versatility in actual complex detection scenarios. Specifically, it can only realize the sensing and detection function of a single antibiotic at a specific, fixed frequency, and it is difficult to detect other antibiotics at other frequencies. In actual application scenarios, it is often necessary to face the detection needs of multiple antibiotics, 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 fixed-frequency detection model of a single antibiotic is obviously difficult to meet these diversified and complex actual needs, which has undoubtedly become 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 transparent metamaterial sensor chip, which achieves flexible frequency adjustment through a patterned graphene structure, and has the advantages of high sensitivity, specific detection, optimizable structure 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 of sensor units, 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 cloud-shaped with horizontal strips and curved strips connected end to end.

[0006] Compared with the existing technology, this technical solution has the following characteristics and beneficial effects:

[0007] 1. Flexible frequency adjustment: By changing the external bias voltage to adjust the graphene's Fermi level, the EIT window can be flexibly adjusted so that the sensor's peak can appear at different frequencies. This breaks through the limitation of traditional antibiotic sensors that cannot be flexibly adjusted after manufacture, and can meet the actual detection needs of different antibiotics at different frequencies.

[0008] 2. High-sensitivity detection: The sensor is sensitive to changes in the refractive index of the surrounding environment. In simulation analysis, when the refractive index of the object under test increases from 1.0 to 1.4 in steps of 0.1, linear fitting calculations show a sensitivity of 220GHz / RIU, a quality factor (Q) of 13.6, and a comprehensive performance index (FOM) of 9.84. This sensor has excellent sensing performance and can accurately detect tiny changes in physical quantities.

[0009] 3. Specific detection: Since 1 Thz is the characteristic fingerprint spectrum of chloramphenicol, the sensing unit has a transparent peak at 1.021 THz and a transmittance of 83.1%, which can specifically sense and detect chloramphenicol, meeting the needs of specific substance detection.

[0010] 4. Optimizable Structure: The sensor unit's structural parameters, such as the cloud resonator shape, coupling distance, ring segment radius, and dielectric plate thickness, are adjustable. For example, changing the coupling distance affects the redshift and amplitude variation of the EIT window, while adjusting the dielectric plate thickness can control the EIT window redshift while keeping the transmission amplitude virtually unchanged, facilitating optimization of sensor performance for different application scenarios.

[0011] 5. Clear Mechanism: The EIT effect of this sensor is based on bright-bright mode coupling. Both cloud resonators operate in bright mode and are directly excited by the incident field. The resulting interference field forms an EIT transparent window. The electric field energy diagram clearly illustrates the electric field distribution of each resonator when excited individually and collectively, providing a theoretical basis for further research and improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the structural diagram of the tunable electromagnetically induced transparent metamaterial sensor chip of this scheme.

[0013] Figure 2 The transmission curves of the three sensors are obtained by simulation and analysis.

[0014] Figure 3 It is the electric field energy diagram of the EIT effect at the three resonance point frequencies.

[0015] Figure 4 is the EIT window diagram at different coupling distances.

[0016] Figure 5 It is the EIT window diagram under different ring segment radii.

[0017] Figure 6 This is the EIT window diagram under different dielectric thicknesses.

[0018] Figure 7 It is the transmission curve of the metamaterial sensor under different refractive indices of the object to be measured.

[0019] Figure 8 It is a linear fitting diagram of the refractive index change of each EIT window relative to the surrounding test object.

[0020] Figure 9 is the Fermi level of graphene to obtain the peak map of the corresponding EIT transparency peak. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0022] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "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 accompanying 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.

[0023] Example 1

[0024] like Figure 1 As shown, this technical solution provides a tunable electromagnetically induced transparent metamaterial sensor chip, comprising:

[0025] At least one array of sensor units, each of which includes a graphene layer and a dielectric layer from top to bottom, with two identical cloud resonators arranged alternately on the graphene layer. Each cloud resonator is designed to be cloud-shaped with horizontal strips and curved strips connected end to end.

[0026] The two cloud resonators on each sensing unit of this scheme constitute the resonant part of the current sensor. The two cloud resonators act as bright modes to generate bright-bright coupling, and the two cloud resonators each generate an excited electric field to achieve superposition.

[0027] 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.

[0028] It's important to note that changes in the coupling distance between the two cloud resonators significantly affect the EIT window. This is because changes in the coupling distance alter the coupling of the resonant fields, which in turn affects the electric field distribution of the coupled fields. Generally speaking, as the coupling distance increases, the EIT window experiences a redshift, meaning the center frequency of the window moves toward lower frequencies and the window amplitude increases.

[0029] In some embodiments, the two cloud resonators are arranged at an angle relative to each other, that is, one cloud resonator is located at a diagonally opposite position to the other cloud resonator, and the two cloud resonators do not overlap.

[0030] 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.

[0031] In addition, the coupling distance between two cloud resonators refers to the shortest distance between the two cloud resonators.

[0032] Regarding the shape of the cloud resonator:

[0033] 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 at the head and tail are respectively connected to the horizontal bar.

[0034] In some embodiments, each circular ring segment is identical to divide the curved strip into three equal segments, thereby making the cloud resonator a symmetrical structure design.

[0035] Furthermore, the radius h of the open ring corresponding to each ring segment is 7.9-8.3 μm. Preferably, the radius of the open ring corresponding to each ring segment is 8 μm.

[0036] Furthermore, each ring segment is semicircular in shape.

[0037] In some embodiments, the width of the horizontal bars and the curved bars of each cloud resonator is the same, both being 1.9 to 2.1 μm. Preferably, the width of the horizontal bars and the curved bars of each cloud resonator is 2 μm.

[0038] In some embodiments, the graphene layer has a thickness of 0.001 μm.

[0039] In some embodiments, the dielectric plate is made of quartz material, and the relative dielectric constant of the quartz material is 1.9.

[0040] In some embodiments, the dielectric plate has a thickness of 5 to 9 μm. Preferably, the dielectric plate has a thickness of 5 μm.

[0041] In some embodiments, the dielectric plate is a square with equal length and width. In this case, the side lengths Px and Py of the dielectric plate are 64µm. This configuration has the advantage of suppressing mutual interference between adjacent resonators. If the side lengths of the quartz dielectric plate are too small, the electromagnetic fields of adjacent units will interfere with each other, destroying the EIT effect. However, if the side lengths of the quartz dielectric plate are too large, the sensor's integration density will be reduced.

[0042] This solution can adjust the Fermi level of graphene and thus the EIT window by changing the external bias voltage, so that its peak can appear at other frequencies, thereby achieving flexible adjustment of the antibiotics to be tested. This overcomes the disadvantage that traditional antibiotic sensors cannot be flexibly adjusted once they are manufactured. This device provides a solution for flexible detection of antibiotics.

[0043] 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, 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.

[0044] In some embodiments, each sensing unit has a transparency peak at 1.021 THz and a transmittance of 83.1%. Given that 1 THz is a characteristic fingerprint spectrum of chlortetracycline, the sensing unit can be used for specific sensing and detection of chlortetracycline.

[0045] Example 2

[0046] In order to study and verify the performance of the tunable electromagnetically induced transparent metamaterial sensor chip designed in this scheme, a simulation environment is set up for performance testing:

[0047] The metamaterial sensor was simulated using CST Studio Suite electromagnetic simulation software. The EIT-like metamaterial sensor's boundary conditions in the x and y directions were set to the unit cell boundary, and the z direction to the open (add space) boundary. This simulated an infinitely large metamaterial periodic array. A THz plane wave incident in the -z direction was selected as the excitation source, and the simulation frequency range was set to 0.3-1.4 THz.

[0048] Parameter design of tunable electromagnetically induced transparent metamaterial sensor chip:

[0049] The dielectric plate is made of quartz, and the thickness d of the dielectric plate is 5µm. The side lengths of the dielectric plate in the x and y directions are represented by Px and Py, respectively, Px=64µm, Py=64µm, the coupling distance s=2.8µm between the two cloud resonators, the width of the horizontal bar and the curved bar of each cloud resonator is 2µm, the radius of the open circular ring corresponding to the three circular segments on the curved segment is 8µm, and the thickness of the cloud resonator is 0.001µm.

[0050] (1) EIT mechanism analysis:

[0051] The sensor with only the cloud resonator in the lower left corner is called URR, the sensor with only the cloud resonator in the upper right corner is called LRR, and the sensor with both the cloud resonator in the lower left corner and the cloud resonator in the upper right corner is called EIT-like sensor of this scheme. The transmission curves of the three sensors are obtained by simulation and analysis as shown in the following figure. Figure 2 As shown, the electric field energy diagram of the EIT effect at the three resonance point frequencies is obtained as follows Figure 3 shown.

[0052] Depend on Figure 2 It can be seen that when the URR is simulated alone, a strong resonance is generated at 1.043THz, while when the LRR is simulated alone, it is excited at 1.035THz. When the URR and LRR are combined, the EIT-like shows a transparency peak at 1.021THz, and its transmittance is 83.1%. It can be seen that the electromagnetically induced transparency window generated by the sensor of this scheme is bright-bright mode coupling. In this sensor, the excitation of the two cloud resonators is relatively strong. Both cloud resonators can be directly excited by the incident field, so 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 a clear EIT transparency window. It should be noted that since 1Thz is the characteristic fingerprint peak of chloramphenicol, the sensor of this scheme can achieve specific sensing and detection of chloramphenicol.

[0053] Depend on Figure 3 It can be seen that Figure 3 (a) is the electric field distribution diagram of URR when it is excited alone. It can be seen that it is strongly excited and is in bright mode. Figure 3 (b) shows the electric field distribution when LRR is excited alone. It is also strongly excited and is also in bright mode. Figure 3 Figure (c) shows the electric field distribution when the two are simulated together. It can be seen that when the two are coupled, a bright-bright mode-like EIT effect is excited, and the electric field distribution is symmetrical. The electric field energy of the URR is mainly distributed in the rings on both sides, while the electric field energy of the LRR is mainly distributed in the upper right ring. The coupling of the two electric fields greatly enhances the field strength in the proximity of the two waves. In the principle of wave superposition, when the peaks or troughs of two waves reach the same frequency at the same time, destructive interference occurs, and the interference wave produces the maximum amplitude.

[0054] (2) Influence of coupling distance s:

[0055] The sensors with coupling distances s of 2.8µm, 3.5µm, 4.2µm, 4.9µm and 6.6µm were designed for simulation and the EIT window diagrams at different coupling distances were obtained as shown in the figure below. Figure 4 shown.

[0056] Depend on Figure 4 It can be seen that as the coupling distance s increases, the EIT window red-shifts and the amplitude increases. In addition, it can be seen that when the coupling distance s is 2.8µm, the EIT resonance peak is sharper, that is, the Q value is higher, the sensing performance is better, and the transmittance is higher. At the same time, the resonance peak position is also near the chlortetracycline fingerprint spectrum of 1THz.

[0057] (4) Influence of the ring segment radius h:

[0058] The sensors with h of 7.9µm, 8.0µm, 8.1µm, 8.2µm and 8.3µm were designed for simulation and the EIT window diagrams under different annular segment radii h were obtained as shown in the figure below. Figure 5 shown.

[0059] Depend on Figure 5 It can be seen that as h increases, the EIT window blue-shifts and the window amplitude decreases. Preferably, the performance is best when h is 8.1µm or 8.1µm, at which time the Q value is higher, the sensing performance is better, the transmittance is higher, and the resonance peak position is also near the chlortetracycline fingerprint spectrum at 1THz.

[0060] (5) Influence of dielectric plate thickness d:

[0061] The sensors with dielectric plate thickness d of 5µm, 6µm, 7µm, 8µm and 9µm were designed for simulation and the EIT window diagrams under different dielectric plate thickness d were obtained as shown in the figure below. Figure 5 shown

[0062] Depend on Figure 6 It can be seen that as d increases, the EIT window redshifts, while the transmission amplitude remains almost unchanged. Preferably, when the dielectric plate thickness d is 5µm, the EIT resonance peak is sharper, indicating a higher Q value, better sensing performance, and higher transmittance. The resonance peak is also located near the chlortetracycline fingerprint spectrum at 1THz.

[0063] (6) Sensor performance characterization:

[0064] Metamaterial-based EIT sensors can achieve a frequency shift in the EIT window peak by changing the refractive index of the object being measured. Therefore, the performance of the sensor depends on its sensitivity to the refractive index of the surrounding environment. Sensitivity, quality factor Q, and FOM are usually used to characterize the performance of the sensor.

[0065] Regarding the sensitivity S index, this index represents the relationship between the change in the refractive index of the object under test on the sensor surface and the window frequency shift. In experimental measurements, changes in the concentration of the object under test will cause changes in the refractive index. The commonly used unit of sensitivity is GHz / RIU. The specific formula is as follows:

[0066]

[0067] is the change in refractive index, The frequency shift of the transparent window corresponding to the change of the refractive index of the object to be measured.

[0068] 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:

[0069]

[0070] is the center frequency of the transparent window, and FWHM is the full width at half-wave of the transparent window peak.

[0071] Regarding the FOM indicator, this indicator is a comprehensive indicator of sensor performance and can be used to compare the performance of multiple sensors. The calculation formula of FOM is:

[0072] .

[0073] In order 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 test object with a thickness of 3µm was set on the surface of the designed metamaterial sensor. By changing its refractive index, the change of the transmission curve of the metamaterial sensor was studied. The refractive indices of the test object were 1, 1.1, 1.2, 1.3 and 1.4 respectively. The results are shown in the figure below. Figure 7As shown in , the linear fitting diagram of the refractive index change of each EIT window relative to the surrounding test object is obtained as shown in Figure 8 As shown in the figure, as the refractive index increases from 1.0 to 1.4 in steps of 0.1, the transmission window undergoes a frequency shift, with its resonant peak frequencies reaching 0.9116, 0.9369, 0.9534, 0.9776, and 0.9996 THz, respectively. Linear fitting calculations indicate a sensitivity of 220 GHz / RIU, a Q value of 13.6, and a FOM of 9.84, demonstrating excellent sensing performance.

[0074] (7) Characterization of sensor tunability:

[0075] The tunability of the EIT metamaterial antibiotic sensor was analyzed by adjusting the Fermi level of graphene to obtain the corresponding peak of the EIT transparency peak. Figure 9 As shown, it can be seen that when the Fermi level Ef of graphene gradually increases, that is, from 0.9eV to 1.1eV by 0.05eV, the peak of the EIT window moves to high frequency, and the peak frequencies are 0.93THz, 0.95THz, 0.97THz, 0.99THz, and 1.01THz, respectively. Its transmittance increases slightly, and the transmittance of the left and right valleys decreases, among which the decrease in the right valley is more obvious.

[0076] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0077] The above embodiments merely illustrate several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A tunable electromagnetically induced transparent metamaterial sensor chip, characterized in that: include: At least one array of sensor units, each comprising a graphene layer and a dielectric layer from top to bottom, the dielectric plate being made of quartz. Two identical, alternating cloud resonators are formed on the graphene layer. The two cloud resonators are tilted relative to each other, do not overlap, and have a coupling distance of 2.8 to 6.6 µm. Each cloud resonator is designed to be in the shape of a cloud, with horizontal and curved bars connected end to end. The curved bar is composed of three connected circular segments, and the two circular segments at the head and tail are respectively connected to the horizontal bar. The two cloud resonators act as bright modes to produce bright-bright coupling, and the two cloud resonators each generate an excited electric field to achieve superposition; 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 0.9eV to 1.15eV with an amplitude of 0.05eV each time, the corresponding peak frequencies of the EIT transparency peak are 0.93THz, 0.95THz, 0.97THz, 0.99THz, 1.01THz, and 1.0121THz.

2. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: Each circular segment is identical to divide the bending strip into three equal segments, and the y-circle segment radius of the open circular ring corresponding to each circular segment is 7.9-8.3 μm.

3. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 1, characterized in that: The thickness of the dielectric plate is 5~9µm.

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

5. 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, both 2µm.

6. The tunable electromagnetically induced transparent metamaterial sensor chip according to claim 5, 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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