Multi-resonance terahertz metasurface sensor

Abstract

The invention provides a multi-resonance terahertz metasurface sensor, and relates to the technical field of biosensing, the multi-resonance terahertz metasurface sensor comprises a high-resistance substrate, a dielectric layer and a resonance layer which are stacked in sequence, the resonance layer is provided with metasurface units periodically distributed on the dielectric layer, and each metasurface unit comprises a first metal body and a second metal body which are equal in thickness; the two first metal bodies are arranged in a bilateral symmetry mode, each first metal body is provided with a vertical section and two transverse straight sections, one transverse straight section is perpendicularly connected with the upper end of the vertical section, the other transverse straight section is perpendicularly connected with the middle of the vertical section, all the transverse straight sections are located between the two vertical sections, and the second metal bodies and the first metal bodies are arranged in a vertically spaced mode. The second metal body is provided with a semicircular ring section with an upward opening, the outer side of the second metal body is aligned with the outer sides of the two vertical sections, and four different harmonic peaks can be generated when terahertz electromagnetic waves are incident to the metasurface unit. Through combined sensing of the four resonance peaks, comparison and matching of multi-resonance-point data can be realized, so that high-precision and high-sensitivity detection is realized.

Description

Technical Field

[0001] This invention relates to the field of biosensing technology, and in particular to a multi-resonant terahertz metasurface sensor. Background Technology

[0002] Terahertz metasurface sensors are sensing devices based on metasurface structures. Their principle lies in utilizing the electromagnetic response of artificially designed subwavelength structures to terahertz waves to achieve sensing functionality. When terahertz waves irradiate the metasurface, they induce currents and charge distributions on its structure. Changes in the surrounding environment modulate these charge and current distributions, thereby altering the metasurface's resonant characteristics, such as its resonant frequency or intensity. By detecting changes in the resonant characteristics within the terahertz wave spectrum, subtle changes in the environment can be indirectly sensed.

[0003] Currently, single-resonant metasurface structures are commonly used in the field of terahertz sensing. These structures are typically analyzed using equivalent circuit models, where the structural gaps are equivalent to capacitance, and the ring current path of the metal pattern is equivalent to inductance. Together, they determine a dominant ground-state resonant frequency. In the terahertz band, these sensors often exhibit only a single and significant main absorption peak.

[0004] However, because it relies on a single resonance peak for information extraction, its sensing signal source is singular and susceptible to measurement noise, environmental interference, and system drift, leading to decreased detection accuracy and reliability. Furthermore, the single-resonant structure has limited response sensitivity to minute changes in electromagnetic parameters caused by the analyte, making it difficult to achieve highly robust sensing. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a multi-resonant terahertz metasurface sensor, which improves sensing sensitivity and anti-interference capability by supporting multi-resonant collaborative operation.

[0006] According to an embodiment of the present invention, a multi-resonant terahertz metasurface sensor includes a high-resistivity substrate, a dielectric layer, and a resonant layer. The dielectric layer is disposed on the high-resistivity substrate, and the resonant layer is disposed on the dielectric layer. The resonant layer has metasurface units periodically distributed on the dielectric layer. Each metasurface unit includes two first metal bodies and a second metal body of equal thickness. The two first metal bodies are symmetrically arranged horizontally. Each first metal body has a vertical segment and two parallel horizontal segments of equal length. One of the horizontal segments is perpendicularly connected to the end of the vertical segment away from the second metal body, and the other horizontal segment is perpendicularly connected to the end of the vertical segment away from the second metal body. The vertical segments are vertically connected at the middle, and all the horizontal segments are located between two vertical segments. The second metal body is arranged vertically and vertically with the two first metal bodies. The second metal body has a semi-circular ring segment. The axis of symmetry of the semi-circular ring segment coincides with the axis of symmetry of the two first metal bodies. The opening of the semi-circular ring segment faces upward, and the outer sides of the two ends of the opening of the semi-circular ring segment are respectively aligned with the opposite sides of the two vertical segments. When terahertz electromagnetic waves are incident on the metasurface unit, four different resonance peaks can be generated, and the four resonance peaks exhibit different frequency shift characteristics in response to changes in the surface dielectric environment.

[0007] The multi-resonant terahertz metasurface sensor according to embodiments of the present invention has at least the following beneficial effects: by sequentially setting a dielectric layer and a metal resonant layer on a high-resistivity substrate, and setting periodically arranged metasurface units in the resonant layer, and setting the metasurface units in a special configuration of two "F"-shaped symmetrical first metal bodies and one "U"-shaped second metal body, in the terahertz band, the resonators formed by the two "F"-shaped first metal bodies and the resonators formed by the "U"-shaped second metal bodies can use their respective fundamental mode resonances and near-field coupling to excite four independent resonance peaks in the terahertz frequency band. Finally, through the different frequency shift characteristics of the four resonance peaks in response to changes in the surface dielectric environment, high-precision joint analysis and cross-verification can be achieved. Compared with the single-resonant metasurface structure, it can effectively suppress the defects of a single signal source being susceptible to measurement noise, environmental disturbances and system drift, thereby improving the sensor's sensing sensitivity and anti-interference ability, and can be applied to fields such as biomolecular detection and material recognition.

[0008] According to some embodiments of the present invention, the thickness of the first metal body and the second metal body is 0.5 μm, the distance between the first metal body and the second metal body is 4 μm, the distance between the two first metal bodies is 10 μm, the length of the vertical segment is 30 μm, the width of the horizontal segment is 8 μm, the outer diameter of the semicircular ring segment is 30 μm, and the inner diameter of the semicircular ring segment is 22 μm.

[0009] According to some embodiments of the present invention, the electrical conductivity of both the first metal body and the second metal body is 4.561 × 10⁻⁶. 7 S / m.

[0010] According to some embodiments of the present invention, the regions of the high-resistivity substrate and the dielectric layer corresponding to each of the metasurface units are square.

[0011] According to some embodiments of the present invention, the high-resistivity substrate is a silicon substrate.

[0012] According to some embodiments of the present invention, the dielectric constant of the silicon substrate is 11.9, the side length of the region of the silicon substrate corresponding to each metasurface unit is 100 μm, and the thickness of the silicon substrate is 3 μm.

[0013] According to some embodiments of the present invention, the dielectric layer is a silicon dioxide dielectric layer.

[0014] According to some embodiments of the present invention, the dielectric constant of the silicon dioxide dielectric layer is 3.75, the side length of the region of the silicon dioxide dielectric layer corresponding to each metasurface unit is 100 μm, and the thickness of the silicon dioxide dielectric layer is 0.5 μm.

[0015] According to some embodiments of the present invention, the frequency of the terahertz electromagnetic wave is 0.1THz to 3THz, and the frequencies of the four resonant peaks are 1.756THz, 2.113THz, 2.382THz and 2.858THz, respectively.

[0016] According to some embodiments of the present invention, the sensitivity of the multi-resonant terahertz metasurface sensor is 230 GHz / RIU to 350 GHz / RIU.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and some of these additional aspects and advantages will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a multi-resonant terahertz metasurface sensor according to an embodiment of the present invention; Figure 2 This is an isometric view of a metasurface unit in one embodiment of the present invention; Figure 3 This is a side view of a metasurface unit in one embodiment of the present invention; Figure 4 This is a top view of a metasurface unit in one embodiment of the present invention; Figure 5 This is the transmission spectrum of a multi-resonant terahertz metasurface sensor in one embodiment of the present invention when there is no analyte on its surface; Figure 6 This is a surface current distribution diagram corresponding to each resonance peak on the surface of a multi-resonance terahertz metasurface sensor according to an embodiment of the present invention; Figure 7 This is an electric field distribution diagram corresponding to each resonance peak on the surface of a multi-resonance terahertz metasurface sensor according to an embodiment of the present invention; Figure 8 This is a terahertz spectrum of a multi-resonant terahertz metasurface sensor with a constant refractive index of the surface analyte at different thicknesses, according to an embodiment of the present invention. Figure 9 This is a terahertz spectrum of the refractive index change of a multi-resonant terahertz metasurface sensor with a constant surface analyte thickness, as shown in one embodiment of the present invention. Explanation of key component symbols: 1. High-resistivity substrate; 2. Dielectric layer; 3. First metal body; 31. Vertical segment; 32. Horizontal segment; 4. Second metal body; 5. Metasurface unit; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0021] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0022] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] Reference Figures 1 to 4 The multi-resonant terahertz metasurface sensor of this invention includes a high-resistivity substrate 1, a dielectric layer 2, and a resonant layer.

[0024] The high-resistivity substrate 1 has an extremely low intrinsic carrier concentration and very low conductivity, resulting in very weak absorption and reflection of terahertz waves, thus minimizing energy loss of the incident terahertz waves. Simultaneously, the high-resistivity substrate 1 provides robust mechanical support for the dielectric layer 2 and the resonant layer above it.

[0025] Dielectric layer 2 is deposited on high-resistivity substrate 1, and resonant layer is deposited on dielectric layer 2. In the equivalent circuit model, the resonant layer and the underlying high-resistivity substrate 1 form a parallel-plate capacitor, and dielectric layer 2 is the insulating medium of this capacitor. Its dielectric constant and thickness directly determine the capacitance value and are one of the key parameters for controlling the resonant frequency.

[0026] The resonant layer has metasurface units 5 periodically distributed on the dielectric layer 2. Through the specific geometric configuration and arrangement of the metasurface units 5, when terahertz electromagnetic waves are incident on the metasurface units 5, they can resonate at four specific frequencies, which are manifested as four different resonance peaks in the spectrum.

[0027] Specifically, the metasurface unit 5 includes two first metal bodies 3 of equal thickness and one second metal body 4. The two first metal bodies 3 are symmetrically arranged from left to right. Each first metal body 3 has a vertical segment 31 and two parallel horizontal segments 32 of equal length. One horizontal segment 32 is perpendicularly connected to the upper end of the vertical segment 31, and the other horizontal segment 32 is perpendicularly connected to the middle of the vertical segment 31. All horizontal segments 32 are located between the two vertical segments 31. The second metal body 4 is arranged vertically and vertically spaced from the lower ends of the two first metal bodies 3. The second metal body 4 has a semi-circular ring segment. The axis of symmetry of the semi-circular ring segment coincides with the axis of symmetry of the two first metal bodies 3. The opening of the semi-circular ring segment faces upward, and the outer sides of the two ends of the opening of the semi-circular ring segment are respectively aligned with the outer sides of the opposite ends of the two vertical segments 31.

[0028] In some embodiments, the position and sensitivity of the resonance peak can be optimized by adjusting the geometric parameters of the metasurface unit 5. Specifically, based on the LC equivalent circuit model theory, the resonance point can be flexibly controlled by changing the main factor affecting the initial resonance frequency (the size of the metasurface sensor structural unit).

[0029] Reference Figure 3 and Figure 4 The thickness t3 of the first metal body 3 and the second metal body 4 is both set to 0.5 μm, the distance d between the first metal body 3 and the second metal body 4 is set to 4 μm, the distance m between the two first metal bodies 3 is set to 10 μm, the outer diameter r1 of the semicircular ring segment is set to 30 μm, the inner diameter r2 of the semicircular ring segment is set to 22 μm, the length L1 of the vertical segment 31 is set to 30 μm, and the width k of the horizontal segment 32 is set to 8 μm.

[0030] In some embodiments, the electrical conductivity of both the first metal body 3 and the second metal body 4 is 4.561 × 10⁻⁶. 7 S / m.

[0031] Reference Figures 2 to 4 In some embodiments, the regions of the high-resistivity substrate 1 and dielectric layer 2 corresponding to each metasurface unit 5 are square.

[0032] In some embodiments, the high-resistivity substrate 1 is a silicon substrate with a dielectric constant of 11.9. The selection of geometric parameters is based on... Figure 4 The side length 'a' of the silicon substrate region corresponding to each metasurface unit 5 is set to 100 μm, as referenced. Figure 3 The thickness t1 of the silicon substrate is set to 3 μm.

[0033] In some embodiments, the dielectric layer 2 is a silicon dioxide dielectric layer.

[0034] In some embodiments, the dielectric constant of the silicon dioxide dielectric layer is 3.75. For the selection of geometric parameters, refer to... Figure 4 The side length 'a' of the silica dielectric layer corresponding to each metasurface unit 5 is set to 100 μm, as referenced. Figure 3 The thickness t2 of the silica dielectric layer is set to 0.5 μm.

[0035] It should be noted that the specific geometric parameters of the aforementioned terahertz metasurface sensor structure were obtained through simulation calculations using electromagnetic simulation software. Specifically, periodic unit cell boundary conditions were set in the x and y directions, and open boundary conditions were set in the z direction.

[0036] In some embodiments, the frequency of the terahertz electromagnetic wave is 0.1THz to 3THz.

[0037] Reference Figure 5 The figure shows the transmission spectrum of the terahertz metasurface sensor in its initial state without any analyte. The transmission coefficient is a relative ratio, characterizing the metasurface's ability to transmit terahertz waves. As can be seen from the figure, four independent absorption peaks appear in the 0.1 THz to 3 THz frequency range, with resonant frequencies of [missing values]. , , , The corresponding half-height and full width are 0.09 and 0.09 respectively. 0.045 0.02 0.04 The quality factor Q is calculated according to formula (1): (1) in, The resonant frequency, The full width at half maximum (FWHM) of the resonance peak; The calculated quality factor Q values ​​are 20, 47, 119, and 71, respectively.

[0038] It should be noted that the quality factor (Q) represents the resonant characteristics of a sensor, and the Q value affects the sensor's sensitivity and resolution. As the Q value increases, the amplitude of the resonant peak increases, and the peak becomes sharper, resulting in higher sensor sensitivity. Furthermore, the Q value is directly proportional to the sensor's resolution; a larger Q value corresponds to a larger resolution.

[0039] Figure 6 The diagram shows the current vector distribution at four independent resonant frequencies. Figure 7 The figures show the electric field distribution at four independent resonant frequencies. From the two figures, it can be seen that the surface current at 1.756 THz, 2.113 THz, and 2.858 THz exhibits a circulating current pattern. The resulting magnetic dipoles and the electric dipoles formed by the highly concentrated electric field create typical LC resonances. At 2.382 THz, the surface current is mainly concentrated at the "gap" and "metal arm" of the structure, exhibiting obvious asymmetry and localization. The electric field shows significant field strength concentration, which is usually the result of interference between bright and dark modes, thus forming a unique Fano resonance. This hybrid resonant mode has a unique optical response.

[0040] Reference Figure 8 The figure shows the terahertz spectrum of a terahertz metasurface sensor when the thickness h of the analyte varies from 0 μm to 6 μm (in 2 μm steps) under analyte conditions, with the refractive index n=2. The amplitude is the absolute physical quantity describing the intensity of the transmitted wave. As can be seen from the figure, with the gradual increase of thickness h, the resonant frequencies of each resonance peak gradually shift to the left, and the corresponding frequency shift decreases. Therefore, when studying the sensitivity of the terahertz metasurface sensor, the thickness h of the analyte can be set to 4 μm to reduce the influence of the analyte thickness on the sensor sensitivity. The sensing sensitivity of a terahertz metasurface sensor can be obtained by calculating the change in resonant frequency with respect to the dielectric constant (usually manifested as a change in refractive index). Specifically, the sensitivity S can be calculated using formula (2): (2) in, This represents the change in resonant frequency. This represents the change in the refractive index of the analyzed material; It should be noted that the high sensitivity of terahertz metasurface sensors means that the sensors can respond keenly to minute changes in environmental parameters, which directly determines the sensor's detection limit and practical value. In practical applications, the response of metasurfaces to changes in refractive index usually exhibits a resonant redshift phenomenon. As the refractive index of the measured medium increases, the resonant frequency shifts towards lower frequencies. The physical mechanism of this redshift phenomenon stems from the electromagnetic coupling between the metasurface resonant unit and the surrounding medium: when the refractive index of the surrounding medium increases, the propagation phase velocity of electromagnetic waves in the medium decreases, the equivalent wavelength shortens, causing the resonance condition to be satisfied at a lower frequency, thus triggering a redshift of the resonant frequency.

[0041] Reference Figure 9 The figure shows the terahertz spectrum of the analyte on a terahertz metasurface sensor with a constant thickness h of 4 μm, as the refractive index n of the analyte changes from 1.0 to 2.0 (step size 0.5). The amplitude is the absolute physical quantity describing the intensity of the transmitted wave. As can be seen from the figure, the resonant frequencies of each resonance peak are highly sensitive to changes in the refractive index n of the analyte. Linear fitting calculations show that... , , , At these locations, the sensitivity values ​​S reach 236 GHz / RIU, 257 GHz / RIU, 234 GHz / RIU, and 350 GHz / RIU, respectively, far exceeding the sensitivity of most traditional single-resonant metasurface structure sensors.

[0042] In summary, the terahertz metasurface sensor provided in this application has four resonant peaks. By observing the different frequency shift characteristics exhibited by the four resonant peaks in response to changes in the surface dielectric environment, high-precision joint analysis and cross-validation can be achieved. Compared with single-resonant metasurface structures, it can effectively suppress the defects of single signal sources being susceptible to measurement noise, environmental disturbances, and system drift, thereby improving the sensor's sensing sensitivity and anti-interference ability. It can be applied to fields such as biomolecular detection and material identification.

[0043] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A multi-resonant terahertz metasurface sensor, characterized in that, include: High-resistivity substrate; A dielectric layer is deposited on the high-resistivity substrate; A resonant layer is deposited on the dielectric layer. The resonant layer has metasurface units periodically distributed on the dielectric layer. Each metasurface unit includes two first metal bodies and a second metal body of equal thickness. The two first metal bodies are symmetrically arranged from left to right. Each first metal body has a vertical segment and two parallel horizontal segments of equal length. One of the horizontal segments is perpendicularly connected to the end of the vertical segment away from the second metal body, and the other horizontal segment is perpendicularly connected to the middle of the vertical segment. All the horizontal segments are located between the two vertical segments. The second metal body is arranged vertically and vertically spaced from the two first metal bodies. The second metal body has a semi-circular ring segment. The axis of symmetry of the semi-circular ring segment coincides with the axis of symmetry of the two first metal bodies. The opening of the semi-circular ring segment faces upward, and the outer sides of the two ends of the opening of the semi-circular ring segment are respectively aligned with the opposite sides of the two vertical segments. When terahertz electromagnetic waves are incident on the metasurface unit, four different resonance peaks are generated, and the four resonance peaks exhibit different frequency shift characteristics in response to changes in the surface dielectric environment.

2. The multi-resonant terahertz metasurface sensor according to claim 1, characterized in that, The thickness of the first metal body and the second metal body is 0.5 μm, the distance between the first metal body and the second metal body is 4 μm, the distance between the two first metal bodies is 10 μm, the length of the vertical segment is 30 μm, the width of the horizontal segment is 8 μm, the outer diameter of the semicircular ring segment is 30 μm, and the inner diameter of the semicircular ring segment is 22 μm.

3. The multi-resonant terahertz metasurface sensor according to claim 2, characterized in that, The electrical conductivity of both the first and second metal bodies is 4.561 × 10⁻⁶. 7 S / m.

4. The multi-resonant terahertz metasurface sensor according to claim 2, characterized in that, The regions of the high-resistivity substrate and the dielectric layer corresponding to each metasurface unit are square.

5. The multi-resonant terahertz metasurface sensor according to claim 4, characterized in that, The high-resistivity substrate is a silicon substrate.

6. The multi-resonant terahertz metasurface sensor according to claim 5, characterized in that, The silicon substrate has a dielectric constant of 11.9, the side length of the silicon substrate region corresponding to each metasurface unit is 100 μm, and the thickness of the silicon substrate is 3 μm.

7. The multi-resonant terahertz metasurface sensor according to claim 4, characterized in that, The dielectric layer is a silicon dioxide dielectric layer.

8. The multi-resonant terahertz metasurface sensor according to claim 7, characterized in that, The dielectric constant of the silicon dioxide dielectric layer is 3.75, the side length of the region of the silicon dioxide dielectric layer corresponding to each metasurface unit is 100 μm, and the thickness of the silicon dioxide dielectric layer is 0.5 μm.

9. The multi-resonant terahertz metasurface sensor according to claim 1, characterized in that, The frequency of the terahertz electromagnetic wave is 0.1THz to 3THz, and the frequencies of the four resonant peaks are 1.756THz, 2.113THz, 2.382THz and 2.858THz, respectively.

10. The multi-resonant terahertz metasurface sensor according to claim 1, characterized in that, The sensitivity of the multi-resonant terahertz metasurface sensor is 230 GHz / RIU to 350 GHz / RIU.

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