A hollow all-dielectric quasi-continuous domain bound state terahertz metamaterial sensor

Abstract

The present application relates to a kind of hollow full dielectric quasi-continuous domain bound state terahertz metamaterial sensor, belong to terahertz sensing technical field.The present application aims to solve the problems of complex structure, high dielectric loss, low quality factor and sensitivity of existing terahertz sensor.The technical scheme is: the sensor is composed of periodic array unit, each unit includes square hollow ring and rectangular bar inlaid around different length, uses full dielectric material and excites quasi-continuous domain bound state mode through structure asymmetry design.It has the beneficial effects of simple and stable structure, low preparation cost, extremely low loss and ultra-high quality factor, can produce double resonance peak, is extremely sensitive to refractive index change, has high sensitivity, strong environmental adaptability, and is suitable for high-precision material detection.

Description

Technical Field

[0001] This invention belongs to the field of terahertz sensing technology and relates to a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies between 0.1 and 10 terahertz, and their spectral position lies between microwaves and infrared light waves. This band possesses both the penetrating properties of microwaves and the spectral resolution of optical bands, exhibiting unique advantages such as low energy, large bandwidth, and high spectral resolution. It can realize the fingerprint spectral identification of material characteristics and has important application prospects in wireless communication, security detection, biomedicine, and materials characterization.

[0003] Metamaterials are artificially designed periodic structural arrays with subwavelength scales, capable of acquiring extraordinary physical properties not found in natural materials, and are important carriers for electromagnetic wave manipulation. Resonance with a high quality factor is crucial for enhancing light-matter interactions and achieving high-sensitivity sensing. Currently, research on terahertz quasi-continuous bound-state metasurfaces mostly employs metallic structures, but the inherent high ohmic and dielectric losses of metallic materials make it difficult to achieve extremely high quality factor resonances. In contrast, all-dielectric metasurface sensors possess lower optical losses and superior sensing potential. However, existing terahertz metamaterial sensors generally suffer from complex structures, high fabrication costs, limited resonance quality factors, and sensing responses concentrated at a single frequency point, making it difficult to meet the practical detection requirements of multi-band, high-sensitivity applications.

[0004] Bound states in the continuum (BIC) are eigenmodes that coexist with continuous radiation waves while remaining localized, and can theoretically achieve an infinitely large quality factor. However, in practical applications, the ideal BIC mode is difficult to realize due to perturbations such as material loss and processing errors. It is usually transformed into a quasi-BIC mode with a finite lifetime but an ultra-high quality factor. Constructing metasurface sensors based on the quasi-BIC mechanism provides a new technical approach for achieving ultra-sensitive sensing. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a terahertz metamaterial sensor in a hollow all-dielectric quasi-continuous domain bound state.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A hollow, all-dielectric quasi-continuous domain bound state terahertz metamaterial sensor, comprising multiple array units in... x direction and yThe array is arranged in a periodic pattern, and each array unit consists of a hollow rectangular structure and four rectangular strips inlaid around it, wherein at least two of the rectangular strips are of different lengths.

[0007] Furthermore, the hollow rectangular structure is a square hollow ring.

[0008] Furthermore, the array unit is a subwavelength structure.

[0009] Furthermore, the outer ring side length of the square hollow ring P The value range is 300μm~320μm, and the value range of the inner ring side length M of the square hollow ring is 200μm~220μm.

[0010] Furthermore, the thickness of the array unit H The value range is 200μm~220μm.

[0011] Furthermore, the array unit is made of high resistivity silicon.

[0012] Furthermore, the lengths of the two rectangular strips are G , G The value range is 70μm~90μm, and the lengths of the other two rectangular strips are... L , L The value range is 75μm~95μm.

[0013] The sensing method based on the hollow all-dielectric quasi-continuous domain bound state terahertz metamaterial sensor includes the following steps: immersing the sensor in the object to be tested, incident a terahertz wave perpendicularly onto the sensor, obtaining the transmission response curve of the sensor, and determining the refractive index of the object to be tested based on the resonant peak frequency in the transmission response curve.

[0014] Furthermore, the sensor excites at least one quasi-continuous bound-state resonance peak in the transmission response curve, and the resonance peak frequency f satisfies a linear relationship with the refractive index n of the analyte. ,in, This is the resonant peak frequency shift. Let S be the change in refractive index, and S be the sensitivity.

[0015] Furthermore, the quality factor of the sensor ,in, f is the resonant peak frequency, and FWHM is the full width at half maximum (FWHM) of the resonant peak.

[0016] The beneficial effects of this invention are as follows: First, in terms of structure and fabrication, this invention abandons the traditional solid substrate and complex multi-layer stacking design required for sensors, and adopts a one-piece hollow all-dielectric structure. This novel and simple structure significantly simplifies the configuration of the sensor unit, greatly reduces the process difficulty and manufacturing cost of micro-nano fabrication, and improves the overall stability of the structure.

[0017] Secondly, regarding materials and working mechanisms, the use of all-dielectric materials effectively avoids the inherent ohmic loss problem of metal structures, achieving extremely low dielectric loss. By introducing structural asymmetry, the ideal continuous-domain bound state mode is successfully transformed into a directly exciteable quasi-continuous-domain bound state mode. This design enables the sensor to excite sharp resonance peaks of high-quality factors and generate a double-resonance peak response, thereby greatly enhancing the localization capability of terahertz wave energy and the intensity of photomatter interaction.

[0018] Furthermore, in terms of sensing performance, the extremely high quality factor results in an extremely narrow resonant linewidth, significantly improving the sensor's frequency selectivity and spectral resolution. The dual-resonant-peak design enhances the ability to distinguish different analytes and the reliability of detection. Simultaneously, the substrate-free hollow structure allows the sensor to be directly immersed in the analyte, greatly increasing the sensing volume and the contact area with the analyte, thereby achieving extremely high refractive index detection sensitivity.

[0019] Furthermore, in terms of practicality and reliability, the all-dielectric material possesses excellent chemical stability, enabling the sensor to maintain stable operation over long periods in complex environments. Its resonant characteristics are insensitive to the polarization state of the incident terahertz wave, reducing the requirements for the detection system and facilitating practical integration and application. This invention comprehensively improves the performance of terahertz sensors from structural, material, and mechanistic perspectives, effectively solving technical bottlenecks in existing technologies such as low quality factor, insufficient sensitivity, complex structure, and weak environmental adaptability, demonstrating significant practical application value and industrialization prospects.

[0020] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the unit three-dimensional structure of a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. Figure 2 This is a top view of a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. Figure 3 This is a side view of a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. Figure 4 The terahertz metamaterial sensor of the hollow all-dielectric quasi-continuous domain bound state BIC provided in the embodiment of the present invention has a symmetrical structure formed by rectangular strips of equal length embedded around it; Figure 5 The terahertz metamaterial sensor of the hollow all-dielectric quasi-continuous domain bound state BIC provided in the embodiment of the present invention has an asymmetric structure formed by rectangular strips of unequal lengths embedded around it. Figure 6 The relationship between the frequency variation of the high-frequency resonance peak and the refractive index of the analyte in a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention; Figure 7 The relationship between the frequency variation of the low-frequency resonance peak and the refractive index of the analyte in a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention; Figure 8 The linear fitting results of the high-frequency resonance peak and low-frequency resonance peak of a terahertz metamaterial sensor of hollow all-dielectric quasi-continuous domain bound state BIC provided in the embodiments of the present invention under the condition of perpendicular terahertz wave incidence, are given for different refractive indices of the analyte. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] Figure 1 This is a schematic diagram of the unit three-dimensional structure of a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. It is a hollow rectangular ring structure with rectangular strips inlaid around the perimeter.

[0026] Figure 2 This is a top view of a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. The length of the outer side of the rectangular ring. The inner side length of the rectangular ring. To extend the length of the rectangular strip, The length of the rectangular strip protruding on the left and top sides.

[0027] Figure 3 This is a side view of a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in an embodiment of the present invention. The thickness of the array structure.

[0028] Figure 4 The transmission coefficient of a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention is shown in the case where rectangular strips of equal length are embedded around the perimeter to form a symmetrical structure. Figure 5 The transmission coefficient of a terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention is shown in the case where the rectangular strips embedded around the sensor have unequal lengths, forming an asymmetric structure, thus constituting a QBIC. Figure 6 The relationship between the frequency variation of the high-frequency resonance peak and the refractive index of the analyte in a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention; Figure 7The relationship between the frequency variation of the low-frequency resonance peak and the refractive index of the analyte in a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state BIC provided in this embodiment of the invention; Figure 8 The linear fitting results of the high-frequency resonance peak and low-frequency resonance peak of a terahertz metamaterial sensor of hollow all-dielectric quasi-continuous domain bound state BIC provided in the embodiments of the present invention under the condition of perpendicular terahertz wave incidence, are given for different refractive indices of the analyte.

[0029] Please see Figures 1 to 8 This is a terahertz metamaterial sensor with an all-dielectric hollow quasi-continuous domain bound state (BIC).

[0030] Example 1 This embodiment provides a detailed description of a terahertz metamaterial sensor based on a fully dielectric hollow quasi-continuous bound state (BIC) proposed in this invention.

[0031] like Figure 1 As shown, the hollow all-dielectric quasi-continuous domain bound state terahertz metamaterial sensor in this embodiment is composed of multiple cubic array units surrounded by rectangular strips of different lengths arranged periodically in the x and y directions. Each array unit is made of silicon.

[0032] In this embodiment, the length direction of the sensor array, composed of several sensing units, is defined as the x-direction, and the width direction as the y-direction. The openings of all array units point to and are parallel to the x-direction, and the vertical axes of all array units point to the y-direction. All sensor array units are arranged periodically along the x and y directions, resulting in a metamaterial sensor operating in the 0.26–0.29 THz band.

[0033] Preferably, such as Figure 2 As shown, in this embodiment, the outer ring side lengths of the rectangular ring structure of a single array unit in the x and y directions are denoted as . Its range is 300μm to 320μm, preferably 310μm; the inner ring side length of a single array unit is denoted as... Its range is 200μm to 220μm, preferably 210μm.

[0034] Preferably, in this embodiment, the length of the rectangular strips inlaid in the rectangular ring of a single array unit is denoted as . Its range is 70μm to 90μm, preferably 80μm; the length of the rectangular strips protruding on the left and top sides of a single array unit is denoted as... Its range is 75μm to 95μm, preferably 85μm.

[0035] Preferably, such as Figure 3As shown, the thickness of the dielectric layer of a single array unit in this embodiment is denoted as . Its range is 200μm to 220μm, preferably 210μm.

[0036] Preferably, the all-dielectric hollow quasi-continuous bound state (QBIC) terahertz metamaterial sensor of the present invention uses lossy silicon (Si) as the core material for its entire structure. This silicon material has a stable relative permittivity of 11.9 in the terahertz band and extremely low dielectric loss. It also possesses excellent mechanical properties and mature micro / nano fabrication technology, enabling precise adaptation to the fabrication requirements of hollow structures and differentiated rectangular strips in the device. Crucially, silicon material exhibits extremely high sensitivity to changes in the refractive index and thickness of the analyte, accurately capturing minute parameter changes related to the analyte. This characteristic is essential for the high-precision measurement requirements of terahertz metamaterial sensors, providing a core material guarantee for achieving high-sensitivity sensing in the device.

[0037] like Figure 4 and Figure 5 The figures show the transmission response curves of the sensor under conditions of no structural symmetry disruption (corresponding to BIC mode) and disrupted structural symmetry disruption (corresponding to QBIC mode), respectively. Figure 4 The transmission curve is the one corresponding to the continuous domain bound state (BIC). Figure 5 The transmission curves show the quasi-continuous bound state (QBIC) configuration. As can be seen from the curves, after breaking the symmetry through structural design and obtaining the QBIC mode, the number of resonance peaks in the transmission curve increases from one to two, and the newly added low-frequency resonance peak has an extremely sharp shape. This experimental result further confirms the successful realization of the quasi-continuous bound state (QBIC) and verifies its excellent resonance performance, providing experimental support for high Q-value and high-sensitivity sensing devices.

[0038] like Figure 6 and Figure 7 The figures shown are the transmission response curves of the sensor when sensing and detecting objects with different refractive indices. Figure 6 The corresponding trend of high-frequency resonance peaks. Figure 7 The curves show the changing trend of the low-frequency resonant peak. As the refractive index of the object under test increases, the sensor's resonant frequency exhibits a significant redshift. All the above response curves were obtained through simulation using CST software. The simulation frequency range was set to 0.25–0.31 THz. A plane wave perpendicularly incident device unit structure was used, with the electric field direction parallel to the x-axis. A perfectly matched layer was set along the z-axis, and periodic boundary conditions were applied along the x and y axes to ensure the accuracy and reliability of the simulation results.

[0039] Figure 8In this study, the correlation between the resonant frequency of the terahertz metamaterial sensor in the hollow all-dielectric quasi-continuous domain bound state BIC and the refractive index of the analyte was further explored. The fitting curves showed that the two have a significant linear inverse relationship, i.e., the resonant absorption frequency shifts... Variation with refractive index And decrease.

[0040] Generally speaking, quality factor It is an important indicator for evaluating the frequency selectivity performance of a resonant system, reflecting the sharpness of the resonant peak in the frequency domain and the relative magnitude of energy loss. Its specific definition is... The ratio of the resonant frequency to the full width at half maximum (FWHM), i.e., where The frequency representing the resonance peak, This represents the frequency bandwidth corresponding to when the amplitude drops to half of the peak value. Based on this definition, in the metamaterial sensor proposed in this embodiment, the quality factor corresponding to the high resonance peak is calculated to be... The quality factor corresponding to the low resonance peak The calculation results show that the sensor exhibits a high quality factor at both resonant frequency points. This further demonstrates its excellent frequency selectivity and low resonant energy loss.

[0041] On the other hand, sensitivity It is a key parameter for evaluating a sensor's ability to respond to changes in refractive index in the external environment, and is commonly used to measure the detection performance of resonant sensors. It is defined as follows: The ratio of the resonant frequency shift to the change in refractive index, i.e., expressed in GHz / RIU, where This represents the frequency shift caused by a unit change in refractive index. The unit represents the change in refractive index. Based on experimental data, the sensitivity of the metamaterial sensor in this embodiment at the high resonance peak is... GHz / RIU, at the low resonance peak GHz / RIU. The high sensitivity value indicates that the sensor has a significant response to small changes in refractive index, demonstrating that the present invention has good detection performance and practical potential in sensing applications.

[0042] In summary, the hollow all-dielectric quasi-continuous bound state (QBIC) terahertz metamaterial sensor described in this invention features a simple and novel overall structural design. It abandons the complex structural units and multi-layer stacking processes of traditional sensors, and leverages the mature micro-nano fabrication characteristics of silicon to effectively reduce fabrication costs and process difficulty, fully meeting the core requirement of high cost-effectiveness in sensor design. Furthermore, thanks to the excellent dielectric properties of silicon and the unique QBIC structural design, this sensor possesses a quality factor exceeding 2000 and excellent sensing sensitivity. It can accurately capture minute changes in parameters such as the refractive index of the analyte, significantly improving the sensing performance and detection accuracy of the device. This effectively solves the technical pain points of low quality factor and insufficient sensitivity in existing terahertz sensors, demonstrating good practical application value and industrialization prospects.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A terahertz metamaterial sensor with a hollow, all-dielectric quasi-continuous domain bound state, characterized in that: The sensor consists of multiple array units. x direction and y The array is arranged in a periodic pattern, and each array unit consists of a hollow rectangular structure and four rectangular strips inlaid around it, wherein at least two of the rectangular strips are of different lengths.

2. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 1, characterized in that: The hollow rectangular structure is a square hollow ring.

3. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 2, characterized in that: The array unit is a subwavelength structure.

4. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 3, characterized in that: The outer ring side length of the square hollow ring P The value range is 300μm~320μm, and the value range of the inner ring side length M of the square hollow ring is 200μm~220μm.

5. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 4, characterized in that: The thickness of the array unit H The value range is 200μm~220μm.

6. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 5, characterized in that: The array unit is made of high resistivity silicon.

7. The terahertz metamaterial sensor with a hollow all-dielectric quasi-continuous domain bound state according to claim 6, characterized in that: The lengths of the two rectangular strips are G , G The value range is 70μm~90μm, and the lengths of the other two rectangular strips are... L , L The value range is 75μm~95μm.

8. A sensing method based on a terahertz metamaterial sensor of a hollow all-dielectric quasi-continuous domain bound state according to any one of claims 1 to 7, characterized in that: The process includes the following steps: immersing the sensor in the object to be tested, incident a terahertz wave perpendicularly onto the sensor, obtaining the transmission response curve of the sensor, and determining the refractive index of the object to be tested based on the resonant peak frequency in the transmission response curve.

9. The sensing method according to claim 8, characterized in that: The sensor excites at least one quasi-continuous bound-state resonance peak in the transmission response curve, and the resonance peak frequency f satisfies a linear relationship with the refractive index n of the analyte. ,in, This is the resonant peak frequency shift. Let S be the change in refractive index, and S be the sensitivity.

10. The sensing method according to claim 9, characterized in that: The quality factor of the sensor ,in, f is the resonant peak frequency, and FWHM is the full width at half maximum (FWHM) of the resonant peak.

Images