Terahertz X-type metasurface sensing device based on quasi-continuous bound state sensibilization

Abstract

The invention discloses a terahertz X-type metasurface sensing device based on quasi-continuous bound state sensibilization. The terahertz X-type metasurface sensing device comprises an ultrathin transparent medium substrate; the X-type patterned metal metasurface structure unit is deposited on the ultrathin transparent medium substrate; wherein each X-shaped patterned metal metasurface structure unit comprises a plurality of resonant bodies which are periodically arranged, and a metal connecting belt for connecting the adjacent resonant bodies; the resonance body is of an X-shaped structure composed of trapezoidal metal blades. The trapezoidal metal blades comprise upper blades and lower blades, and the symmetry of the X-shaped structure in the vertical direction is destroyed according to the height difference between the upper blades and the lower blades, so that the resonance mode of the resonance body is converted into a quasi-continuous domain bound state from a continuous domain bound state. The X-shaped structure provided by the invention is simple in design and easy to prepare, the provided detection sensitivity is higher than the sensitivity of the current terahertz metasurface device, and the technical problems that the current terahertz metasurface device is complex in structure and low in detection sensitivity can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of terahertz metamaterial sensing technology, and particularly relates to a terahertz X-type metasurface sensor based on quasi-continuous bound state enhancement. Background Technology

[0002] Metasurfaces, as artificial electromagnetic materials composed of periodically arranged subwavelength-scale resonant units, provide a highly controllable platform for the interaction between terahertz waves and matter, showing broad application prospects in fields such as biosensing, medical diagnosis, and environmental monitoring. In recent years, the introduction of the theory of bound states in the continuous (BIC) has opened up new avenues for the design of high-performance terahertz sensors. A BIC is a nonradiative bound state embedded in a continuous radiation spectrum, theoretically possessing an infinite quality factor and zero linewidth. By introducing structural perturbations to break its ideal symmetry, BICs can leak into observable quasi-bound states in the continuous (QBIC), generating significant localized electromagnetic field enhancement while maintaining a high Q factor, thereby greatly improving sensing sensitivity. However, existing QBIC metasurface sensors mostly rely on disrupting in-plane geometric symmetry (such as breaking lateral mirror symmetry, introducing rotational asymmetry, or constructing complex multi-unit coupled structures) to excite QBIC modes.

[0003] The aforementioned technical solutions have significant limitations in their implementation: on the one hand, the complex planar asymmetric structure design increases the difficulty of micro-nano fabrication processes, imposing stringent requirements on photolithography and alignment accuracy, resulting in high manufacturing costs and poor repeatability; on the other hand, existing symmetry-breaking methods struggle to achieve precise and controllable QBIC leakage rate adjustment, often accompanied by high radiation or ohmic losses, hindering further improvements in detection sensitivity. Therefore, developing a terahertz metasurface sensor device with a simple structure, easy fabrication, and precise QBIC mode control has become a critical issue urgently needing to be addressed in the field of metamaterial sensing technology. Summary of the Invention

[0004] This invention aims to address the shortcomings of existing QBIC metamaterial sensors by proposing a terahertz X-type metasurface sensor based on quasi-continuous bound state enhancement. By precisely controlling the ratio of the heights of the upper and lower trapezoidal metal blades (α=mn / m), the vertical symmetry of the X-type metal structural unit is disrupted, thereby modulating the plasma resonance mode from a continuous bound state to a quasi-continuous bound state mode. This results in an ultra-high detection sensitivity, which can be used in ultra-sensitive terahertz biosensing scenarios.

[0005] To address the aforementioned technical problems, this invention provides a terahertz X-type metasurface sensor based on quasi-continuous bound state sensitization, comprising: Ultra-thin transparent dielectric substrate; And X-shaped patterned metal metasurface structure units deposited on the ultrathin transparent dielectric substrate; The X-shaped patterned metal metasurface structure unit includes multiple resonators arranged in a periodic manner, and a metal connecting strip connecting adjacent resonators. The resonator is an X-shaped structure composed of trapezoidal metal blades; The trapezoidal metal blade includes an upper blade and a lower blade. The height difference between the upper blade and the lower blade disrupts the vertical symmetry of the X-shaped structure, causing the resonance mode of the resonator to change from a continuous domain bound state to a quasi-continuous domain bound state.

[0006] Preferably, the material of the ultrathin transparent dielectric substrate includes silicon dioxide and polyimide; The thickness of the ultrathin transparent dielectric substrate is 300 μm to 800 μm; The X-shaped patterned metallic metasurface structure unit is formed on the upper surface of the ultrathin transparent dielectric substrate.

[0007] Preferably, the material of the X-shaped patterned metal metasurface structure unit includes gold and silver; The thickness of the X-shaped patterned metallic metasurface structure unit is 0.1 μm to 0.5 μm; The structural period of the X-shaped patterned metal metasurface structural unit is 20 μm to 30 μm.

[0008] Preferably, the height m of the upper blade is 8 μm to 11 μm; The height n of the lower blade is 5 μm to 8 μm; The height ratio α between the upper blade and the lower blade is α = (mn) / m, and the value of the height ratio ranges from 0 to 0.9. The degree of damage to the vertical symmetry is quantitatively determined based on the height ratio.

[0009] Preferably, the upper transverse side length e of the upper blade is 3μm to 6μm; The upper oblique side length r1 of the upper blade is 10μm to 12μm; The upper oblique side length r2 of the upper blade is 10μm to 12μm.

[0010] Preferably, the lower oblique side length f1 of the lower blade is 8 μm to 10 μm. The lower oblique side length f2 of the lower blade is 7μm to 10μm.

[0011] Preferably, the long distance d between the two ends of the trapezoidal metal blade is 10μm to 15μm, the short distance w is 2μm to 5μm, and the distance u from the periodic frame is 5μm to 10μm; The width g of the metal connecting strip is 2μm to 5μm, and the thickness is 0.1μm to 0.5μm.

[0012] Preferably, the metal connecting strip is made of gold or silver; The metal connecting strip connects the trapezoidal metal blades of adjacent resonators to maintain the structural continuity of the periodic arrangement.

[0013] Preferably, under the excitation condition of terahertz wave vertical incidence, based on the degree of vertical symmetry disruption determined by the height ratio, the resonance mode of the resonator is coupled from the continuous domain bound state to the quasi-continuous domain bound state to form a corresponding resonance absorption peak.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention employs an X-type resonant structure composed of trapezoidal metal blades and utilizes the height difference between the upper and lower blades to precisely disrupt the vertical symmetry. This achieves a controllable transition from a continuous domain bound state to a quasi-continuous domain bound state using a minimally simplistic geometric modulation method. While reducing processing complexity and manufacturing costs, it achieves a detection sensitivity as high as 902 GHz / RIU, effectively solving the technical problems of processing difficulties and limited sensitivity caused by existing QBIC sensor devices that rely on complex planar asymmetric structures. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of a terahertz X-type metasurface sensor device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an X-type metasurface structure unit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the QBIC mechanism transition of the X-type metasurface structure according to an embodiment of the present invention; Figure 4 This is an electric field distribution diagram of the X-type metasurface structure unit according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the response of a terahertz X-type metasurface sensor device to changes in refractive index according to an embodiment of the present invention. Figure 6 This is a frequency shift fitting curve of the terahertz X-type metasurface sensor device according to an embodiment of the present invention; Figure 7This is a schematic diagram illustrating the response of a terahertz X-type metasurface sensor device to the thickness of the analyte according to an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] like Figure 1 and Figure 2 As shown, this embodiment provides a terahertz X-type metasurface sensor based on quasi-continuous bound state sensitization, comprising: Ultra-thin transparent dielectric substrate; And X-shaped patterned metallic metasurface structure units deposited on ultrathin transparent dielectric substrates; Among them, the X-type patterned metal metasurface structure unit includes multiple resonators arranged in a periodic manner, and a metal connecting strip connecting adjacent resonators; The resonator is an X-shaped structure composed of trapezoidal metal blades; The trapezoidal metal blade consists of an upper blade and a lower blade. The height difference between the upper and lower blades disrupts the vertical symmetry of the X-shaped structure, causing the resonance mode of the resonator to change from a continuous domain bound state to a quasi-continuous domain bound state.

[0019] This embodiment employs an X-shaped patterned metal metasurface structure unit composed of trapezoidal metal blades, and utilizes the height difference between the upper and lower blades to disrupt the vertical symmetry of the X-shaped structure. This enables the transformation of the resonance mode from a continuous domain bound state to a quasi-continuous domain bound state, generating an ultra-high local electromagnetic field enhancement effect. This overcomes the sensitivity bottleneck caused by radiation loss limitations in traditional metasurfaces.

[0020] Furthermore, the materials of the ultrathin transparent dielectric substrate include silicon dioxide and polyimide; The thickness of the ultrathin transparent dielectric substrate ranges from 300 μm to 800 μm; X-shaped patterned metallic metasurface structural units are formed on the upper surface of an ultrathin transparent dielectric substrate.

[0021] This embodiment selects silicon dioxide or polyimide as the ultrathin transparent dielectric substrate material and limits the substrate thickness to the range of 300μm to 800μm, which ensures effective transmission and low-loss transmission of terahertz waves. At the same time, it provides a stable physical support platform for the X-shaped patterned metal metasurface structure unit, ensuring the optical performance and mechanical stability of the sensor in the terahertz band.

[0022] Furthermore, the materials of the X-shaped patterned metal metasurface structural units include gold and silver; The thickness of the X-type patterned metallic metasurface structure unit is 0.1 μm to 0.5 μm; The structural period of the X-shaped patterned metallic metasurface structural unit is 20 μm to 30 μm.

[0023] This embodiment uses gold or silver as the material for the X-shaped patterned metal metasurface structure unit, and controls the structure thickness to 0.1μm to 0.5μm and the structure period to 20μm to 30μm, which significantly reduces ohmic loss, satisfies the subwavelength resonance condition, and ensures efficient excitation of plasma resonance and effective localization of electromagnetic energy.

[0024] Furthermore, the height m of the upper blade is 8 μm to 11 μm; The height n of the lower blades is 5 μm to 8 μm; The height ratio of the upper blade to the lower blade is α = (mn) / m, and the value of the height ratio ranges from 0 to 0.9. The degree of damage to the vertical symmetry is quantitatively determined based on the height ratio.

[0025] This embodiment achieves precise quantitative control over the degree of vertical symmetry disruption of the X-shaped structure by limiting the height m of the upper blade to 8μm to 11μm, the height n of the lower blade to 5μm to 8μm, and controlling the height ratio α=(mn) / m within the range of 0 to 0.9. This allows for the controllable leakage of the continuous domain bound state into the quasi-continuous domain bound state, resulting in a resonant mode with a high Q factor.

[0026] Furthermore, the upper transverse side length e of the upper blade is 3μm to 6μm; The upper oblique side length r1 of the upper blade is 10μm to 12μm; The upper oblique side length r2 of the upper blade is 10μm to 12μm.

[0027] In this embodiment, by setting the upper transverse side length e of the upper blade to 3μm to 6μm and the upper oblique side lengths r1 and r2 to 10μm to 12μm, the geometric configuration and current path of the upper blade are optimized, the resonant frequency and electric field distribution are effectively controlled, and the coupling efficiency with the incident terahertz wave is enhanced.

[0028] Furthermore, the lower oblique side length f1 of the lower blade is 8 μm to 10 μm. The lower oblique side length f2 of the lower blade is 7μm to 10μm.

[0029] In this embodiment, by setting the lower oblique side length f1 of the lower blade to 8μm to 10μm and f2 to 7μm to 10μm, a specific asymmetric trapezoidal structure is formed in combination with the size of the upper blade. This synergistically controls the geometric asymmetry of the X-shaped structure and optimizes the localization and enhancement effect of the electromagnetic field in the structure.

[0030] Furthermore, the long distance d between the two ends of the trapezoidal metal blade is 10μm to 15μm, the short distance w is 2μm to 5μm, and the distance u from the periodic frame is 5μm to 10μm; The width g of the metal connecting strip is 2μm to 5μm, and the thickness is 0.1μm to 0.5μm.

[0031] This embodiment precisely controls the electromagnetic coupling strength and spacing between adjacent resonators by limiting the long distance d at both ends of the trapezoidal metal blade to 10μm to 15μm, the short distance w to 2μm to 5μm, and the distance u from the periodic frame to 5μm to 10μm. It also limits the width g of the metal connecting band to 2μm to 5μm and the thickness to 0.1μm to 0.5μm. This maintains the continuity of the periodic structure and ensures the lattice periodicity conditions required for the stable formation of the quasi-continuous domain bound state.

[0032] Furthermore, the materials used for the metal connecting strips include gold and silver; The trapezoidal metal blades of adjacent resonators are connected by metal connecting strips to maintain the structural continuity of the periodic arrangement.

[0033] This embodiment uses gold or silver as the material for the metal connecting strip to connect the trapezoidal metal blades of adjacent resonators. While maintaining the continuity of the periodic arrangement structure, it reduces the resistance loss at the structural connection and enhances the mechanical stability and electric field conduction consistency of the overall structure.

[0034] Furthermore, under the excitation condition of terahertz waves perpendicularly incident, based on the degree of vertical symmetry disruption determined by the height ratio, the resonance mode of the resonator is coupled from a continuous domain bound state to a quasi-continuous domain bound state to form a corresponding resonance absorption peak.

[0035] In this embodiment, under the excitation condition of terahertz wave vertical incidence, the degree of vertical symmetry destruction determined by the height ratio is used to couple the resonant mode of the resonator from a continuous domain bound state to a quasi-continuous domain bound state, forming a sharp resonant absorption peak. This achieves a detection sensitivity of up to 902 GHz / RIU, enabling the sensor to produce a significant frequency shift response to minute changes in the surface optical refractive index.

[0036] As a preferred implementation, the terahertz X-type metasurface sensor based on quasi-continuous bound state sensitization proposed in this embodiment includes: an ultrathin transparent dielectric substrate and X-type patterned metal metasurface structural units, with adjacent X-type metal structural units connected by a metal strip. The X-type metasurface patterned structure includes several unit cells. For any unit cell, there are several resonators arranged periodically and independently on the transparent dielectric substrate; for any adjacent resonator, there are four trapezoidal metal blades and a strip-shaped metal strip.

[0037] Furthermore, the ultrathin transparent substrate is made of either silicon dioxide or polyimide, with a thickness ranging from 300 to 800 μm.

[0038] Furthermore, the X-shaped patterned metal metasurface structural unit is made of either gold or silver, with a thickness ranging from 0.1 to 0.5 μm and a structural period p width of 20 to 30 μm.

[0039] Furthermore, the single X-shaped patterned metallic metasurface structural unit consists of four trapezoidal metal blades. The upper horizontal side length *e* of each trapezoidal metal blade is 3–6 μm, the upper oblique side lengths *r1* and *r2* are 10–12 μm, and the height *m* is 8–11 μm. The lower oblique side lengths *f1* and *f2* are 8–10 μm, and the height *n* is 5–8 μm. The long distance *d* between the two ends of each trapezoidal metal blade is 10–15 μm, the short distance *w* is 2–5 μm, and the distance *u* from the periodic boundary is 5–10 μm.

[0040] Furthermore, the metal connecting strip is made of gold or silver, with a width g of 2~5 μm and a thickness of 0.1~0.5 μm.

[0041] Furthermore, such as Figure 3 As shown, when the refractive index of air is equal to 1, a terahertz wave is incident perpendicularly on the surface structure of the metamaterial. By adjusting the ratio α = (mn) / m of the heights of the upper and lower trapezoidal metal blades, the vertical symmetry of the X-shaped metal structural unit is disrupted, achieving modulation of the resonance mode from a continuous domain bound state to a quasi-continuous domain bound state mode. This generates a QBIC signal peak, which in turn produces an ultra-high local electromagnetic field enhancement effect, such as... Figure 4 As shown.

[0042] like Figure 5As shown, changing the optical refractive index (n=1-2) of the terahertz metamaterial sensor surface causes a significant blue shift in the QBIC signal peak. Since different concentrations of target analytes deposited on the sensor surface lead to varying degrees of change in the optical refractive index, the quasi-continuous bound-state sensitized terahertz X-type metasurface sensor proposed in this embodiment can achieve ultrasensitive quantitative determination of target analytes.

[0043] like Figure 6 As shown, the quasi-continuous bound state-enhanced terahertz X-type metasurface sensor proposed in this embodiment outputs a linear response to changes in refractive index. Under the excitation of terahertz waves perpendicularly incident, a terahertz resonance absorption peak is generated. By changing the optical refractive index (n=1-2) of the sensor surface, the terahertz resonance absorption peak undergoes a blue shift, resulting in a detection sensitivity of 902 GHz / RIU.

[0044] like Figure 7 As shown, the quasi-continuous bound-state enhanced terahertz X-type metasurface sensor proposed in this embodiment can measure target molecular layers of different thicknesses. Assuming a target analyte with an optical refractive index of 1.3 is deposited on the sensor surface, as the target molecular layer thickness is gradually adjusted from 0 μm to 10 μm, the QBIC signal peak exhibits varying degrees of blue shift. It is readily apparent that the magnitude of the QBIC signal peak change is quite significant, indicating that the terahertz metamaterial sensor proposed in this embodiment possesses good detectability.

[0045] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A terahertz X-type metasurface sensor based on quasi-continuous bound state sensitization, characterized in that, include: Ultra-thin transparent dielectric substrate; And X-shaped patterned metal metasurface structure units deposited on the ultrathin transparent dielectric substrate; The X-shaped patterned metal metasurface structure unit includes multiple resonators arranged in a periodic manner, and a metal connecting strip connecting adjacent resonators. The resonator is an X-shaped structure composed of trapezoidal metal blades; The trapezoidal metal blade includes an upper blade and a lower blade. The height difference between the upper blade and the lower blade disrupts the vertical symmetry of the X-shaped structure, causing the resonance mode of the resonator to change from a continuous domain bound state to a quasi-continuous domain bound state.

2. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The ultrathin transparent dielectric substrate is made of materials including silicon dioxide and polyimide; The thickness of the ultrathin transparent dielectric substrate is 300 μm to 800 μm; The X-shaped patterned metallic metasurface structure unit is formed on the upper surface of the ultrathin transparent dielectric substrate.

3. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The X-shaped patterned metal metasurface structure unit is made of gold and silver; The thickness of the X-shaped patterned metallic metasurface structure unit is 0.1 μm to 0.5 μm; The structural period of the X-shaped patterned metal metasurface structural unit is 20 μm to 30 μm.

4. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The height m of the upper blade is 8μm to 11μm; The height n of the lower blade is 5 μm to 8 μm; The height ratio α between the upper blade and the lower blade is α = (mn) / m, and the value of the height ratio ranges from 0 to 0.

9. The degree of damage to the vertical symmetry is quantitatively determined based on the height ratio.

5. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The upper transverse side length e of the upper blade is 3μm to 6μm; The upper oblique side length r1 of the upper blade is 10μm to 12μm; The upper oblique side length r2 of the upper blade is 10μm to 12μm.

6. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The lower oblique side length f1 of the lower blade is 8μm to 10μm. The lower oblique side length f2 of the lower blade is 7μm to 10μm.

7. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The long distance d between the two ends of the trapezoidal metal blade is 10μm to 15μm, the short distance w is 2μm to 5μm, and the distance u from the periodic frame is 5μm to 10μm; The width g of the metal connecting strip is 2μm to 5μm, and the thickness is 0.1μm to 0.5μm.

8. The terahertz X-type metasurface sensor according to claim 1, characterized in that, The metal connecting strip is made of materials including gold and silver; The metal connecting strip connects the trapezoidal metal blades of adjacent resonators to maintain the structural continuity of the periodic arrangement.

9. The terahertz X-type metasurface sensor according to claim 1, characterized in that, Under the excitation condition of terahertz wave vertical incidence, based on the degree of vertical symmetry disruption determined by the height ratio, the resonance mode of the resonator is coupled from the continuous domain bound state to the quasi-continuous domain bound state to form a corresponding resonance absorption peak.

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