Folding-type continuous domain bound state photonic crystal super surface sensing device and method

Abstract

This invention proposes a sensing device based on a folded continuous-domain bound-state all-dielectric crystal metasurface, comprising a terahertz emitter, an all-dielectric photonic crystal metasurface, and a terahertz receiver. The all-dielectric photonic crystal metasurface sensing device has a periodic aperture array structure on its surface, and in the x-direction, it forms a supercell periodic modulation structure through alternating large and small apertures, achieving Brillouin zone folding in the x-direction. When an incident terahertz pulse emitted by the terahertz emitter perpendicularly irradiates the all-dielectric photonic crystal metasurface, the transmitted terahertz pulse formed after interaction is received by the terahertz detector. When the all-dielectric photonic crystal metasurface is excited by a terahertz wave, the local electric field enhancement effect formed by the periodic aperture array structure at the edge and inside of its pores passively captures and enriches sample molecules of the tested solution sample in the hot spot region within the pores. This invention improves the detection sensitivity and operational convenience for trace samples.

Description

Technical Field

[0001] This invention relates to the field of terahertz sensing technology, and in particular to a sensing device and method based on a folded continuous domain bound state all-dielectric crystal metasurface, specifically a sensing device and method based on a folded continuous domain bound state all-dielectric photonic crystal metasurface. Background Technology

[0002] Terahertz waves, due to their sensitivity to the rotational vibrational modes of biomolecules, have shown great potential in fields such as biomedicine, environmental monitoring, and safety detection. However, the relatively long wavelength of terahertz waves is mismatched with the size of microscopic biomolecules, resulting in weak interactions with matter and low detection sensitivity, especially limiting their ability to detect trace samples. Based on this limitation, metamaterials—subwavelength structures arranged periodically—have emerged.

[0003] In recent years, terahertz sensing technology based on metamaterials and photonic crystals has become a research hotspot. Among them, continuous domain bound states (BICs) are considered an ideal mechanism for achieving high-sensitivity sensing due to their theoretically infinite quality factor and strong field localization ability. However, existing BIC implementations mostly rely on symmetry breaking or structural perturbations, and their Q-values ​​are limited by metal ohmic losses, substrate effects, and structural fabrication precision, making it difficult to achieve a balance between ultra-high Q-values ​​and high sensitivity. Furthermore, traditional terahertz sensing devices often require external energy to drive sample enrichment, which is complex to operate and prone to introducing interference. Therefore, developing an all-dielectric terahertz sensing platform that requires no external drive, enables passive molecule capture, and possesses ultra-high Q-values ​​and high sensitivity has significant scientific research value and application prospects. Summary of the Invention

[0004] This invention proposes a sensing device and method for a folded continuous domain bound state all-dielectric crystal metasurface, which can achieve an ultra-high Q value BIC mode through the Brillouin zone folding mechanism. Combined with passive molecular capture technology, it improves the detection sensitivity and ease of operation for trace samples.

[0005] The present invention adopts the following technical solution.

[0006] A sensing device based on a folded continuous-domain bound-state all-dielectric crystal metasurface employs an all-dielectric photonic crystal. The sensing device includes a terahertz transmitter, an all-dielectric photonic crystal metasurface, and a terahertz receiver. The all-dielectric photonic crystal metasurface sensing device is made of single-crystal silicon material, and its surface has a periodically arranged array of square holes. In the x-direction, a supercell periodic modulation structure is formed by alternating large and small holes, thereby realizing Brillouin zone folding in the x-direction.

[0007] When the incident terahertz pulse (2) emitted by the terahertz transmitter (1) is perpendicularly irradiated on the metasurface of the all-dielectric photonic crystal, the transmitted terahertz pulse (6) formed after interaction is received by the terahertz detector (7).

[0008] The periodically arranged square hole array structure is a periodic hole array structure that supports continuous domain bound state modes. When the all-dielectric photonic crystal metasurface is excited by terahertz waves, the periodic hole array structure forms a strong local electric field enhancement effect at the edge and inside of its cavity, causing the sample molecules of the tested solution sample to be passively captured and enriched in the hot spot region inside the cavity.

[0009] The all-dielectric photonic crystal metasurface is made of single-crystal silicon material (5), and its specific structure is as follows: Figure 2 and Figure 3 As shown. Figure 2 The original structure before size modulation is shown, featuring a periodically arranged array of square holes, all with a diameter of 80 μm, and lattice periods of 140 μm and 120 μm in the x and y directions, respectively. Figure 3 The structure after size modulation of the present invention is shown. A supercell periodic modulation with alternating large and small holes is introduced in the x-direction, wherein the size of the large hole (3) is 80 μm and the size of the small hole (4) is 64 μm, the period in the x-direction is expanded to 280 μm, while the period in the y-direction remains unchanged at 120 μm, and the silicon wafer thickness is 200 μm. This periodic size modulation realizes the Brillouin zone folding effect in the x-direction.

[0010] The periodic aperture array structure of the all-dielectric photonic crystal metasurface consists of square through-holes. Geometric perturbation is introduced into the original 80 μm square holes in the x direction (i.e., the period is 140), which doubles the period in the x direction, while the lattice period in the y direction remains unchanged. The perturbation results in periods of 280 and 120 μm, through-hole sizes of 80 μm and 64 μm, and a silicon wafer thickness of 200 μm.

[0011] The aforementioned all-dielectric photonic crystal metasurface, with its periodic square hole structure, can form a continuous domain bound state under terahertz wave excitation and serve as a microcavity carrier for capturing the sample to be tested.

[0012] The microcavity carrier is prepared by multiple photolithography and deep silicon etching processes. Specifically, firstly, on the surface of the silicon wafer, a blind hole array with the same depth but periodically alternating hole diameters is processed by photolithography and deep silicon etching processes. Subsequently, based on this structure, all blind holes are etched into through holes by the same process again, and finally a fully dielectric photonic crystal metasurface with a supercell structure is formed.

[0013] The sensing device excites a continuous domain bound state based on Brillouin zone folding in the guiding model by terahertz waves under y-polarization. The magnetic field component of the bound state at the Γ point is oddly symmetric about a specific symmetry plane of the periodic hole array structure cavity, thus achieving ultra-high Q value resonance.

[0014] The sensing device uses conventional symmetry-broken continuous domain bound states excited under terahertz wave x-polarization to compare sensing performance.

[0015] The quality factor Q of the continuous domain bound state based on Brillouin zone folding is modulated by the structural size of the periodic aperture array cavity. Satisfying Relationship: ,in It is the ratio of the difference between the two holes to the larger hole.

[0016] A method for operating a sensing device for a folded continuous domain bound state all-dielectric crystal metasurface, used in the sensing device for the folded continuous domain bound state all-dielectric crystal metasurface described above, the method comprising the following steps;

[0017] Step S1: First, under terahertz wave excitation, the continuous domain bound state mode supported by the periodic hole array structure of the all-dielectric photonic crystal metasurface forms a local electric field enhancement effect at the edge and inside of the hole cavity. Then, the sample to be tested is dropped onto the surface of the photonic crystal metasurface in the form of a solution. Utilizing this local electric field effect, without the need to apply an external energy source, the sample molecules are passively captured and enriched in the hot spot region inside the hole cavity.

[0018] The test sample includes, but is not limited to, biomolecular solutions (such as amino acid solutions) or other trace liquid samples with specific refractive index characteristics;

[0019] Step S2: Terahertz waves are incident perpendicularly on the photonic crystal metasurface to excite the continuous domain bound states of the guided model based on Brillouin zone folding under y-polarization, and the transmission spectrum is collected by a terahertz detector.

[0020] Step S3: Analyze the shift in the resonance peak frequency in the spectrum and obtain the normalized sensing sensitivity of the photonic crystal metasurface sensing device according to the mathematical formula.

[0021] The passive capture process in step S1 is as follows: the sample solution permeates along the microfluidic channels formed by the pore array. After the solvent evaporates, the solute is squeezed and fixed in the pore wall and pore cavity under the action of surface tension.

[0022] In step S3, the formula used to calculate the normalized sensing sensitivity is:

[0023]

[0024] in It is the change in resonant frequency before and after loading the sample. The initial resonant frequency, This represents the change in the sample's refractive index.

[0025] A characterization method based on folded continuous-domain bound state all-dielectric crystal metasurfaces is used to evaluate the performance of the aforementioned sensing device. The characterization method includes: measuring the transmission spectrum of the sensing metasurface under γ-polarized wave incident light, extracting the center frequency of the resonance peak, and calculating its quality factor Q value using the Fano fitting formula; measuring the frequency shift of the resonance peak by changing the refractive index of the medium covering the surface of the sensing metasurface, and calculating its refractive index sensitivity Sn.

[0026] The step of calculating the quality factor Q using Fano fitting includes: fitting the resonance peaks in the transmission spectrum using a Fano line-shape function, wherein the Fano line-shape function is expressed as:

[0027]

[0028] in This is the background offset constant. For amplitude factor, It is the resonant peak angular frequency. It is the total damping ratio of resonance, which is related to the resonance linewidth, i.e., the resonance linewidth. These are the Fano fitting parameters used to determine the asymmetry of the resonance curve. The resonance linewidth is obtained through fitting. Then, according to the formula Calculate the quality factor Q value of the continuous domain bound state resonance;

[0029] The characterization method also includes, on the same sensing metasurface, comparing the Q value and sensitivity of a conventional symmetry-broken BIC excited by x-polarized wave incident and a Brillouin zone folded BIC excited by y-polarized wave incident, in order to quantitatively evaluate the performance advantages of the Brillouin zone folding path.

[0030] This invention proposes a terahertz photonic crystal metasurface sensing device and method based on folded continuous-domain bound states. The device comprises a terahertz emitter, an all-dielectric photonic crystal metasurface, and a terahertz receiver, belonging to the field of terahertz refractive index sensing and molecular detection. It aims to solve the problems of limited quality factor due to ohmic losses in metals and the inability to utilize the terahertz electric field penetrating into the substrate. The device is made of single-crystal silicon material with a periodically arranged array of square holes on its surface. By introducing alternating large and small holes in the supercell periodic modulation along the x-direction, Brillouin zone folding is achieved, folding the quasi-guided mode at the original x-point to the Γ-point, forming a folded continuous-domain bound state with ultra-high Q value, enabling high-sensitivity detection of the sample refractive index. Simultaneously, a traditional symmetry-broken BIC is excited by x-polarization for performance comparison. This invention also utilizes the local electric field within the holes to achieve passive molecule trapping, improving detection sensitivity. The device proposed in this invention has a simple structure, mature fabrication process, and high quality factor and sensing sensitivity.

[0031] The advantages of this invention are:

[0032] (1) This invention utilizes an innovative Brillouin zone folding mechanism to effectively fold the traditional guided mode located at point X to point Γ, forming a folded continuous domain bound state with an ultra-high quality factor. The measured first-order Q value reaches 3219, which is an order of magnitude higher than that of the traditional symmetry-broken BIC. This all-dielectric silicon-based structure completely avoids the inherent ohmic losses of metallic materials, which not only significantly improves the sensing sensitivity but also significantly enhances the long-term stability and reliability of the device.

[0033] (2) The high local electric field naturally formed in the cavity of the photonic crystal is used to realize the automatic enrichment and precise positioning of sample molecules. The sample solution spontaneously permeates into the hot spot area inside the cavity through capillary action and surface tension. During the solvent evaporation process, the solute molecules are efficiently concentrated. The whole process does not require external energy drive or complex control system, which significantly simplifies the operation process and reduces the detection cost, while ensuring the best interaction between the sample and the sensing area.

[0034] (3) Two independent working modes, y-polarized folded BIC and x-polarized traditional BIC, are integrated on the same sensing platform, providing users with an intuitive performance comparison and evaluation system. This platform has excellent parameter adjustment flexibility, and the resonance characteristics can be optimized by adjusting structural parameters such as aperture size and period to adapt to the detection needs of different frequency bands and samples. The device adopts standard micro-nano fabrication technology, with simple structure and mature fabrication, and has good scalability and practical application potential. Attached Figure Description

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] Appendix Figure 1 This is a schematic diagram of the sensing device of the present invention;

[0037] Appendix Figure 2 Detailed structural diagram of the photonic crystal metasurface before size modulation;

[0038] Appendix Figure 3 Detailed diagram of the structure after size modulation of the metasurface of a photonic crystal;

[0039] Appendix Figure 4 A schematic diagram of the band structure for the first Brillouin zone folding mechanism;

[0040] Appendix Figure 5 A comparison of the transmission spectra of a y-polarized folded BIC and a conventional BIC;

[0041] Appendix Figure 6 A comparison of the electric field enhancement factors between y-polarized folded BICs and conventional BICs;

[0042] Appendix Figure 7 This is a comparison of the normalized sensitivity of a y-polarized folded BIC and a traditional BIC.

[0043] In the diagram: 1-Terahertz transmitter; 2-Incident terahertz pulse; 3-Large aperture; 4-Small aperture; 5-Single crystal silicon material; 6-Transmitted terahertz pulse; 7-Terahertz detector. Detailed Implementation

[0044] As shown in the figure, the sensing device of the folded continuous domain bound state all-dielectric crystal metasurface adopts an all-dielectric photonic crystal. The sensing device includes a terahertz transmitter, an all-dielectric photonic crystal metasurface, and a terahertz receiver. The all-dielectric photonic crystal metasurface sensing device is made of single-crystal silicon material. Its surface has a periodically arranged square hole array structure, and in the x-direction, a supercell periodic modulation structure is formed by alternating large and small holes to realize Brillouin zone folding in the x-direction.

[0045] When the incident terahertz pulse 2 emitted by the terahertz transmitter 1 is perpendicularly irradiated on the all-dielectric photonic crystal metasurface, the transmitted terahertz pulse 6 formed after interaction is received by the terahertz detector 7.

[0046] The periodically arranged square hole array structure is a periodic hole array structure that supports continuous domain bound state modes. When the all-dielectric photonic crystal metasurface is excited by terahertz waves, the periodic hole array structure forms a strong local electric field enhancement effect at the edge and inside of its cavity, causing the sample molecules of the tested solution sample to be passively captured and enriched in the hot spot region inside the cavity.

[0047] The all-dielectric photonic crystal metasurface is made of single-crystal silicon material 5, and its specific structure is as follows: Figure 2 and Figure 3As shown. Figure 2 The original structure before size modulation is shown, featuring a periodically arranged array of square holes, all with a diameter of 80 μm, and lattice periods of 140 μm and 120 μm in the x and y directions, respectively. Figure 3 The structure after implementing size modulation according to the present invention is shown. A supercell periodic modulation with alternating large and small apertures is introduced in the x-direction, where the size of large aperture 3 is 80 μm, the size of small aperture 4 is 64 μm, the period in the x-direction is expanded to 280 μm, while the period in the y-direction remains unchanged at 120 μm, and the silicon wafer thickness is 200 μm. This periodic size modulation achieves the Brillouin zone folding effect in the x-direction.

[0048] The periodic aperture array structure of the all-dielectric photonic crystal metasurface consists of square through-holes. Geometric perturbation is introduced into the original 80 μm square holes in the x direction (i.e., the period is 140), which doubles the period in the x direction, while the lattice period in the y direction remains unchanged. The perturbation results in periods of 280 and 120 μm, through-hole sizes of 80 μm and 64 μm, and a silicon wafer thickness of 200 μm.

[0049] The aforementioned all-dielectric photonic crystal metasurface, with its periodic square hole structure, can form a continuous domain bound state under terahertz wave excitation and serve as a microcavity carrier for capturing the sample to be tested.

[0050] The microcavity carrier is prepared by multiple photolithography and deep silicon etching processes. Specifically, firstly, on the surface of the silicon wafer, a blind hole array with the same depth but periodically alternating hole diameters is processed by photolithography and deep silicon etching processes. Subsequently, based on this structure, all blind holes are etched into through holes by the same process again, and finally a fully dielectric photonic crystal metasurface with a supercell structure is formed.

[0051] The sensing device excites a continuous domain bound state based on Brillouin zone folding in the guiding model by terahertz waves under y-polarization. The magnetic field component of the bound state at the Γ point is oddly symmetric about a specific symmetry plane of the periodic hole array structure cavity, thus achieving ultra-high Q value resonance.

[0052] The sensing device uses conventional symmetry-broken continuous domain bound states excited under terahertz wave x-polarization to compare sensing performance.

[0053] The quality factor Q of the continuous domain bound state based on Brillouin zone folding is modulated by the structural size of the periodic aperture array cavity. Satisfying Relationship: ,in It is the ratio of the difference between the two holes to the larger hole.

[0054] A method for operating a sensing device for a folded continuous domain bound state all-dielectric crystal metasurface, used in the sensing device for the folded continuous domain bound state all-dielectric crystal metasurface described above, the method comprising the following steps;

[0055] Step S1: First, under terahertz wave excitation, the continuous domain bound state mode supported by the periodic hole array structure of the all-dielectric photonic crystal metasurface forms a local electric field enhancement effect at the edge and inside of the hole cavity. Then, the sample to be tested is dropped onto the surface of the photonic crystal metasurface in the form of a solution. Utilizing this local electric field effect, without the need to apply an external energy source, the sample molecules are passively captured and enriched in the hot spot region inside the hole cavity.

[0056] The test sample includes, but is not limited to, biomolecular solutions (such as amino acid solutions) or other trace liquid samples with specific refractive index characteristics;

[0057] Step S2: Terahertz waves are incident perpendicularly on the photonic crystal metasurface to excite the continuous domain bound states of the guided model based on Brillouin zone folding under y-polarization, and the transmission spectrum is collected by a terahertz detector.

[0058] Step S3: Analyze the shift in the resonance peak frequency in the spectrum and obtain the normalized sensing sensitivity of the photonic crystal metasurface sensing device according to the mathematical formula.

[0059] The passive capture process in step S1 is as follows: the sample solution permeates along the microfluidic channels formed by the pore array. After the solvent evaporates, the solute is squeezed and fixed in the pore wall and pore cavity under the action of surface tension.

[0060] In step S3, the formula used to calculate the normalized sensing sensitivity is:

[0061]

[0062] in It is the change in resonant frequency before and after loading the sample. The initial resonant frequency, This represents the change in the sample's refractive index.

[0063] A characterization method based on folded continuous-domain bound state all-dielectric crystal metasurfaces is used to evaluate the performance of the aforementioned sensing device. The characterization method includes: measuring the transmission spectrum of the sensing metasurface under γ-polarized wave incident light, extracting the center frequency of the resonance peak, and calculating its quality factor Q value using the Fano fitting formula; measuring the frequency shift of the resonance peak by changing the refractive index of the medium covering the surface of the sensing metasurface, and calculating its refractive index sensitivity Sn.

[0064] The performance evaluation of the sensing device is as follows: Figure 5-7 As shown. Figure 5 The transmission spectra of the y-polarized folded BIC and the conventional BIC are compared. The center frequency of the resonance peak is extracted from the transmission spectrum, and its quality factor Q value is calculated by Fano fitting formula.

[0065] The step of calculating the quality factor Q using Fano fitting includes: fitting the resonance peaks in the transmission spectrum using a Fano line-shape function, wherein the Fano line-shape function is expressed as:

[0066]

[0067] in This is the background offset constant. For amplitude factor, It is the resonant peak angular frequency. It is the total damping ratio of resonance, which is related to the resonance linewidth, i.e., the resonance linewidth. These are the Fano fitting parameters used to determine the asymmetry of the resonance curve. The resonance linewidth is obtained through fitting. Then, according to the formula Calculate the quality factor Q value of the continuous domain bound state resonance;

[0068] According to the formula Calculations show that the first-order Q factor of the folded BIC is 3219 and the second-order Q factor is 563; the first-order Q factor of the traditional BIC is 227 and the second-order Q factor is 111.

[0069] The characterization method also includes, on the same sensing metasurface, comparing the Q value and sensitivity of a conventional symmetry-broken BIC excited by x-polarized wave incident and a Brillouin zone folded BIC excited by y-polarized wave incident, in order to quantitatively evaluate the performance advantages of the Brillouin zone folding path.

[0070] Example:

[0071] like Figure 1 As shown, a sensing device based on a folded continuous-domain bound-state all-dielectric photonic crystal metasurface includes, from top to bottom, a terahertz emitter 1, an all-dielectric photonic crystal metasurface, and a terahertz detector 7. The incident terahertz pulse 2 emitted by the terahertz emitter 1 is perpendicularly incident on the all-dielectric photonic crystal metasurface, and the transmitted terahertz pulse 6 after interaction is received by the terahertz detector 7.

[0072] The all-dielectric photonic crystal metasurface is made of single-crystal silicon material 5, and its specific structure is as follows: Figure 2 and Figure 3 As shown. Figure 2The original structure before size modulation is shown, featuring a periodically arranged array of square holes, all with a diameter of 80 μm, and lattice periods of 140 μm and 120 μm in the x and y directions, respectively. Figure 3 The structure after implementing size modulation according to the present invention is shown. A supercell periodic modulation with alternating large and small apertures is introduced in the x-direction, where the size of large aperture 3 is 80 μm, the size of small aperture 4 is 64 μm, the period in the x-direction is expanded to 280 μm, while the period in the y-direction remains unchanged at 120 μm, and the silicon wafer thickness is 200 μm. This periodic size modulation achieves the Brillouin zone folding effect in the x-direction.

[0073] The working principle of the sensing device is as follows: Figure 4 As shown, by introducing periodic size modulation in the x-direction of an all-dielectric photonic crystal metasurface, Brillouin zone folding is achieved, folding the quasi-guided mode at the original X point to the Γ point, forming a folded continuous-domain bound state with ultra-high Q value. This device utilizes terahertz waves to excite this BIC mode under y-polarization to achieve highly sensitive detection of the sample's refractive index; simultaneously, a conventional symmetry-broken BIC is excited under x-polarization for performance comparison.

[0074] The all-dielectric photonic crystal metasurface is prepared by multiple photolithography and deep silicon etching processes. First, an array of blind holes with the same depth but periodically alternating apertures is processed on the surface of a silicon wafer. Then, it is etched again to form through holes, thus forming an all-dielectric photonic crystal metasurface with a supercell structure.

[0075] During sample sensing and detection, in the constructed terahertz transmission detection system, the prepared all-dielectric photonic crystal metasurface is fixed between the terahertz emitter 1 and the terahertz detector 7. The system is then activated, and the terahertz pulse 2 emitted by the terahertz emitter 1 is transmitted through a transmission method, allowing the terahertz wave to react with the all-dielectric photonic crystal metasurface before being emitted again. The detected transmitted terahertz pulse 7 signal is then transmitted to the data acquisition system. Specific detection steps include:

[0076] Step S1: Under terahertz wave excitation, the continuous domain bound state mode supported by the periodic hole array structure of the all-dielectric photonic crystal metasurface forms a strong local electric field enhancement effect, i.e., hot spot region, at the edge and inside of the hole cavity. The sample to be tested is dropped onto the surface of the photonic crystal metasurface in the form of a solution. Utilizing the spontaneously formed high local electric field, without the need for an external energy source, the sample solution permeates along the microfluidic channels formed by the hole array. After the solvent evaporates, the solute is squeezed and fixed to the hole wall and inside the hole cavity under the action of surface tension.

[0077] Step S2: Terahertz waves are incident perpendicularly on the photonic crystal metasurface to excite the continuous domain bound states of the guided model based on Brillouin zone folding under y-polarization, and the transmission spectrum is collected by a terahertz detector.

[0078] Step S3: By analyzing the shift in the resonance peak frequency in the spectrum, the normalized sensing sensitivity of the photonic crystal metasurface sensing device is obtained according to the mathematical formula.

[0079] The performance evaluation of the sensing device is as follows: Figure 5-7 As shown. Figure 5 The transmission spectra of the y-polarized folded BIC and the conventional BIC are compared. The center frequency of the resonance peak is extracted from the transmission spectrum, and its quality factor Q value is calculated by Fano fitting formula.

[0080] Figure 6 The figure shows a comparison of the electric field enhancement factors of the folded BIC and the conventional BIC under y-polarization, demonstrating that the folded BIC has a stronger electric field localization capability. Figure 7 This is a comparison of the normalized sensitivities of a folded BIC and a conventional BIC under y-polarization. The first-order and second-order normalized refractive index sensitivities driven by the folded BIC are 0.192 RIU. -1 And 0.153 RIU -1 The sensitivity of the first-order and second-order normalized refractive index driven by the traditional symmetry-broken type is only 0.048 RIU. -1 and 0.053 RIU -1 The foldable BIC is about 3 to 4 times larger than the traditional BIC.

Claims

1. A sensing device using a folded continuous-domain bound-state all-dielectric crystal metasurface, employing an all-dielectric photonic crystal, characterized in that: The sensing device includes a terahertz transmitter, an all-dielectric photonic crystal metasurface, and a terahertz receiver; the all-dielectric photonic crystal metasurface sensing device has a periodic hole array structure on its surface, and forms a supercell periodic modulation structure in the x-direction by alternating large and small holes, thereby realizing Brillouin zone folding in the x-direction. When the incident terahertz pulse (2) emitted by the terahertz transmitter (1) is perpendicularly irradiated on the metasurface of the all-dielectric photonic crystal, the transmitted terahertz pulse (6) formed after interaction is received by the terahertz detector (7). The periodic hole array structure is a periodic hole array structure that supports continuous domain bound state modes. When the all-dielectric photonic crystal metasurface is excited by terahertz waves, the local electric field enhancement effect formed by the periodic hole array structure at the edge and inside of its cavity causes the sample molecules of the tested solution sample to be passively captured and enriched in the hot spot region within the cavity.

2. The sensing device of the folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 1, characterized in that: The periodic aperture array structure of the all-dielectric photonic crystal metasurface consists of square through holes. In the design of the periodic aperture array structure, a geometric perturbation is introduced into the original square holes in the x-direction to double the period in the x-direction, while the lattice period in the y-direction remains unchanged.

3. The sensing device based on the folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 1, characterized in that: The aforementioned all-dielectric photonic crystal metasurface, with its periodic square hole structure, can form a continuous domain bound state under terahertz wave excitation and serve as a microcavity carrier for capturing the sample to be tested. The microcavity carrier is prepared by multiple photolithography and deep silicon etching processes. Specifically, firstly, on the surface of the silicon wafer, a blind hole array with the same depth but periodically alternating hole diameters is processed by photolithography and deep silicon etching processes. Subsequently, based on the blind aperture array structure, all blind apertures in the blind aperture array were etched into through-holes to form a fully dielectric photonic crystal metasurface with a supercell structure.

4. The sensing device of the folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 1, characterized in that: The sensing device excites a continuous domain bound state based on Brillouin zone folding in the guiding model by terahertz waves under y-polarization. The magnetic field component of the bound state at the Γ point is oddly symmetric about a specific symmetry plane of the periodic hole array structure cavity, thus achieving ultra-high Q value resonance. The sensing device uses conventional symmetry-broken continuous domain bound states excited under terahertz wave x-polarization to compare sensing performance.

5. The sensing device for a folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 4, characterized in that: The quality factor Q of the continuous domain bound state based on Brillouin zone folding is modulated by the structural size of the periodic aperture array cavity. Satisfying Relationship: ,in It is the ratio of the difference between the two holes to the larger hole.

6. A method for operating a sensing device for a folded continuous-domain bound-state all-dielectric crystal metasurface, used in the sensing device for a folded continuous-domain bound-state all-dielectric crystal metasurface as described in any one of claims 1, 2, 3, 4, and 5, characterized in that: The working method includes the following steps; Step S1: First, under terahertz wave excitation, the continuous domain bound state mode supported by the periodic hole array structure of the all-dielectric photonic crystal metasurface forms a local electric field enhancement effect at the edge and inside of the hole cavity. Then, the sample to be tested is dropped onto the surface of the photonic crystal metasurface in the form of a solution. Using the effect of the local electric field, the sample molecules are passively captured and enriched in the hot spot region inside the hole cavity. The sample to be tested includes a biomolecular solution or a trace liquid sample with specific refractive index characteristics; Step S2: Terahertz waves are incident perpendicularly on the photonic crystal metasurface to excite the continuous domain bound states of the guided model based on Brillouin zone folding under y-polarization, and the transmission spectrum is collected by a terahertz detector. Step S3: Analyze the shift in the resonance peak frequency in the spectrum and obtain the normalized sensing sensitivity of the photonic crystal metasurface sensing device according to the mathematical formula.

7. The operating method of the sensing device for the folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 6, characterized in that: The passive capture process in step S1 is as follows: the sample solution permeates along the microfluidic channels formed by the pore array. After the solvent evaporates, the solute is squeezed and fixed in the pore wall and pore cavity under the action of surface tension.

8. The operating method of the sensing device for the folded continuous-domain bound-state all-dielectric crystal metasurface according to claim 6, characterized in that: In step S3, the formula used to calculate the normalized sensing sensitivity is: in It is the change in resonant frequency before and after loading the sample. The initial resonant frequency, This represents the change in the sample's refractive index.

9. A sensing device based on a folded continuous-domain bound state all-dielectric crystal metasurface. A characterization method based on folded continuous-domain bound states is used to evaluate the performance of the sensing device as described in claim 1, characterized in that: The characterization method includes: measuring the transmission spectrum of the sensing metasurface under γ-polarized wave incident light, extracting the center frequency of the resonance peak, and calculating its quality factor Q value using the Fano fitting formula; measuring the frequency shift of the resonance peak by changing the refractive index of the medium covering the surface of the sensing metasurface, and calculating its refractive index sensitivity Sn.

10. The sensing device for the folded continuous-domain bound state all-dielectric crystal metasurface according to claim 9. The characterization method based on the folded continuous-domain bound state is characterized in that: The step of calculating the quality factor Q using Fano fitting includes: fitting the resonance peaks in the transmission spectrum using a Fano line-shape function, wherein the Fano line-shape function is expressed as: in This is the background offset constant. For amplitude factor, It is the resonant peak angular frequency. It is the total damping ratio of resonance, which is related to the resonance linewidth, i.e., the resonance linewidth. These are the Fano fitting parameters used to determine the asymmetry of the resonance curve. The resonance linewidth is obtained through fitting. Then, according to the formula Calculate the quality factor Q value of the continuous domain bound state resonance; The characterization method also includes, on the same sensing metasurface, comparing the Q value and sensitivity of a conventional symmetry-broken BIC excited by x-polarized wave incident and a Brillouin zone folded BIC excited by y-polarized wave incident, in order to quantitatively evaluate the performance advantages of the Brillouin zone folding path.

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