Reconfigurable coupled dynamic perfect absorption metasurface based on self-folding BIC

Abstract

The invention provides a reconstructible coupled dynamic perfect absorption metasurface based on a self-folding BIC. The reconstructible coupled dynamic perfect absorption metasurface comprises a metal backboard, a dielectric substrate, a metal resonance unit cell and a phase change material bridging module. The conductivity of the phase change material is regulated and controlled through external excitation, dynamic switching of the metasurface between a symmetric protection BIC mode and a symmetric breaking quasi BIC (QBIC) mode can be achieved, and coupling between a self-folding QBIC mode and a loss mode is induced. Under specific conditions, the system reaches a critical coupling state, dynamic perfect absorption of a terahertz frequency band is realized, and high absorption rate and high modulation depth are achieved. The device has the advantages of dynamic adjustability, high absorption efficiency, high response speed and the like, and is suitable for the fields of terahertz intelligent spectrum management, real-time biosensing, programmable quantum information processing and the like.

Description

Technical Field

[0001] This invention relates to the fields of terahertz photonics and dynamic metasurfaces, specifically to a dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BICs. Background Technology

[0002] In recent years, bound states in the continuum (BIC), as a non-radiative electromagnetic mode existing in the radiation continuum, have shown great potential in fields such as sensing, filtering, lasers, and nonlinear optics due to their ultra-high quality factor (Q) and strong field localization characteristics. The realization of traditional BICs typically relies on the strict symmetry of the structure or fine-tuning of parameters, such as symmetry-protected BICs and accidental BICs; however, once their function is fixed, it is difficult to dynamically control. Although technologies such as microelectromechanical systems (MEMS) can achieve structural reconfiguration, their complexity and reliability limit practical applications.

[0003] In 2023, a Brillouin zone folding-based BIC mechanism was proposed, which transforms guided modes into BICs in the radiation domain through band folding. This not only enhances the robustness and Q-value sustainability of the modes but also provides a new platform for light-matter interactions. However, existing research largely relies on passive perturbation to achieve the degradation of BICs to quasi-BICs (QBICs), lacking dynamic control capabilities and limiting their application in real-time reconfigurable devices.

[0004] In the terahertz field, BIC-based devices such as narrowband filters, sensors, and absorbers are mostly single-mode designs. While they can achieve efficient frequency selection, they struggle to meet the demands for wide spectrum, dynamic response, and synergistic effects of multiple physical effects in complex electromagnetic environments. Although multimode coupling mechanisms (such as electromagnetically induced transparency, Fano resonance, and singularities) can generate new physical phenomena and functions, research on dynamically reconfigurable multimode coupling is still in its early stages.

[0005] The emergence of phase change materials such as vanadium dioxide (VDC) has provided new avenues for dynamic control. Their reversible insulator-metal phase transition characteristics under external field excitation make them ideal materials for realizing dynamic metasurfaces. However, how to utilize vanadium dioxide to achieve dynamic coupling between BIC and multiple modes, and further realize functions such as efficient and tunable absorption, remains a current research challenge and a cutting-edge direction. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention proposes a reconfigurable coupled dynamic perfect absorbing metasurface unit based on a self-folding BIC. By using a phase change material bridging module to achieve dynamic symmetry breaking, the self-folding BIC and loss modes are controllably coupled, achieving efficient dynamic absorption in the terahertz band. This overcomes the limitations of traditional single-mode BIC devices, which have limited functionality and rigid response, and provides a new solution for terahertz intelligent control and sensing.

[0007] To achieve the above objectives, this invention proposes a reconfigurable coupled dynamic perfect absorbing metasurface unit based on self-folding BICs, comprising:

[0008] Metal back panel;

[0009] A dielectric substrate is disposed on one side of the metal backing plate;

[0010] A metal resonant unit cell is disposed on the other side of the dielectric substrate. Each metal resonant unit cell consists of a pair of metal resonant ring units arranged in a mirror-symmetrical manner along the x-axis direction. The metal resonant unit cells are spaced apart along the x-axis direction.

[0011] A phase change material bridging module is disposed on the dielectric substrate and bridges the metal resonant unit cell. The conductivity of the phase change material bridging module can be continuously adjusted between the insulating state and the metallic state by external excitation.

[0012] The metasurface unit has a period of P in the y-direction, and its effective period in the x-direction switches between P and 2P depending on the state of the phase change material bridging module.

[0013] When the phase change material bridging module is in an insulating state, adjacent metasurface units maintain electromagnetic decoupling in the x-direction, and the effective period in the x-direction is P;

[0014] When the phase change material bridging module is in a metallic state, adjacent metasurface units form electromagnetic coupling in the x-direction through the phase change material bridging module, and the effective period in the x-direction becomes 2P.

[0015] Furthermore, the metal backplate is a metal layer with a thickness of 100-300 nanometers;

[0016] The dielectric substrate is made of sapphire, quartz or alumina, with a relative permittivity of 4-12 and a thickness of 100-200 micrometers;

[0017] The metal resonant ring unit is a U-shaped, C-shaped, or open ring structure with a thickness of 100-300 nanometers and a linewidth of 10-30 micrometers. The spacing between the pair of metal resonant ring units is 10-40 micrometers.

[0018] The period P is 100-200 micrometers.

[0019] Furthermore, the phase change material bridging module uses vanadium dioxide, tungsten dioxide, or GST phase change material, with a width of 10-30 micrometers;

[0020] The conductivity of the insulating state is less than 10. 2 S / m, the conductivity of the metallic state is greater than S / m;

[0021] The external excitation is either thermal or electrical. The temperature range of the thermal excitation is 20-100℃, and the voltage range of the electrical excitation is 1-10V.

[0022] Furthermore, the metal resonant ring unit is a short-arm U-shaped structure, including two long arms and one short arm. The long arms are parallel to the x-axis, the short arms are parallel to the y-axis, and the opening faces the y-axis direction.

[0023] The openings of the pair of metal resonant ring units are arranged facing each other.

[0024] A dynamic perfect absorbing metasurface based on reconfigurable coupling of self-folding BICs is used to realize the aforementioned dynamic perfect absorbing metasurface unit based on reconfigurable coupling of self-folding BICs.

[0025] The metasurface units are arranged in an array on a two-dimensional plane;

[0026] The metasurface units have an arrangement period of P in the y-direction and an arrangement period of 2P in the x-direction. The phase change material bridging modules of two adjacent metasurface units are connected to their respective metal resonant unit cells.

[0027] Furthermore, when the conductivity of the phase change material bridging module is less than 10... 3 At S / m, the structure of the metasurface maintains mirror symmetry and supports a lossless folded BIC mode at the Γ point in the Brillouin zone.

[0028] When the conductivity of the phase change material bridging module is greater than At S / m, the phase change material bridging module introduces C2 rotational symmetry breaking, transforming the folded BIC mode into a folded quasi-BIC mode with radiation loss.

[0029] Furthermore, by adjusting the conductivity of the phase change material bridging module... The coupling strength between the folded quasi-BIC mode and the loss mode can be continuously adjusted within the range of S / m.

[0030] Furthermore, under the condition of normal incidence of terahertz waves and electric field polarization along the y-direction, when the conductivity of the phase change material bridging module is... Within the S / m range, the folded quasi-BIC mode and the loss mode reach a critical coupling state, achieving perfect absorption with an absorption rate greater than 85% in the 0.3-0.5THz frequency range.

[0031] Furthermore, the absorption peak frequency of the perfect absorption is inversely proportional to the period P. By adjusting the period P within the range of 100-200 micrometers, the absorption peak frequency can be tuned within the range of 0.3-0.6 THz.

[0032] Under a fixed period, by adjusting the conductivity of the phase change material bridging module, the absorption rate can be continuously controlled within the range of 10%-99%, with a modulation depth greater than 70%.

[0033] Furthermore, in the application of terahertz intelligent control, the conductivity of the phase change material bridging module is dynamically adjusted through external excitation to achieve real-time switching of the terahertz wave absorption state, applicable to at least one of the following scenarios:

[0034] Dynamic spectrum management and absorption modulation in the terahertz band;

[0035] Terahertz biosensing and chemical sensing based on absorption peak shift;

[0036] Programmable absorption control in terahertz quantum information processing.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. This invention provides a dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BICs, solving the technical problem of the fixed function and inability to dynamically control traditional BIC metasurfaces. The phase change material can continuously and reversibly switch between insulating and metallic states under external excitation, enabling dynamic reconfiguration of the metasurface's effective period between P and 2P. This achieves the active conversion from folded BIC modes to folded quasi-BIC modes, breaking the limitation of traditional BIC devices relying on fixed structural perturbations.

[0039] 2. This invention provides a dynamically perfect absorbing metasurface based on reconfigurable coupling of a self-folding phase change material (BIC), achieving efficient perfect absorption and high modulation depth in the terahertz band. By continuously adjusting the conductivity of the phase change material, the radiation loss and dissipation loss of the system can be precisely matched, achieving near-perfect terahertz wave absorption under critical coupling conditions. Compared with traditional single-mode quasi-BIC structures, the dual-mode coupling mechanism of this invention has a faster response speed and more flexible control capability, enabling dynamic switching of absorption states and absorption intensities according to actual needs.

[0040] 3. This invention provides a dynamically perfect absorbing metasurface based on a reconfigurable coupling of self-folding BICs, exhibiting good universality over a wide range of periodic parameters. By synergistically controlling the geometric parameters and the conductivity of the phase change material, perfect absorption can be achieved at different frequencies, demonstrating excellent designability and scalability. The overall structural unit design is simple and easy to fabricate, and its size can be scaled up to different bands such as microwave, infrared, and visible light, providing an effective technical path for realizing multifunctional terahertz dynamic devices. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a side view (yz section) of the dynamic perfect absorbing metasurface unit structure based on self-folding BIC of the present invention.

[0043] Figures 2(a) and (b) are schematic diagrams and front views of the dynamic perfect absorbing metasurface unit realized by reconfigurable coupling based on self-folding BIC according to the present invention.

[0044] Figure 3(a) is a schematic diagram of the principle of band self-folding to form BIC. The dashed line in the figure represents the light cone boundary. The upper inset shows the schematic process of the metasurface period changing abruptly from 2P to P due to the structural perturbation introduced by the vanadium dioxide phase change material. Γ represents the center of the structure, and X1 and X represent the structural boundaries with periods of 2P and P, respectively.

[0045] Figure 3(b) is a schematic diagram of the process of dynamically adjusting the folded BIC to the folded QBIC and finally achieving perfect absorption, where dot symbols represent loss modes and star symbols represent folded BIC modes.

[0046] Figure 4(a) shows the electric field distribution of the metasurface unit of the present invention with a period P of 121 micrometers, where the left and right sub-figures show the electric field distribution in the folded BIC mode and the loss mode, respectively.

[0047] Figure 4(b) shows the evolution of the continuous reflection spectrum obtained by adjusting the conductivity of vanadium dioxide under the condition of normal incidence of y-polarized terahertz wave. The dashed line on the left represents the eigenfrequency of the loss mode, and the dashed line on the right represents the eigenfrequency of BIC.

[0048] Figure 4(c) shows the discrete reflection spectra at different conductivity levels, ranging from 10 S / m to 2 × 10⁻⁶. 5S / m shows the variation of resonance depth and linearity during the evolution from BIC to QBIC;

[0049] Figures 5(a) and 5(b) show the curves of Q quality factor and intrinsic frequency of the folded QBIC as a function of vanadium dioxide conductivity, respectively, for implementation case 1 with period P of 121 micrometers and P of 150 micrometers.

[0050] Figure 5(c) shows the curves of quality factor Q as a function of vanadium dioxide conductivity under different periods (P changes from 121 micrometers to 155 micrometers) in Implementation Case 1. The asterisks on the curves indicate the locations of inflection points.

[0051] Figure 5(d) shows the distribution trend of conductivity at the corresponding inflection point position in Implementation Case 1 as a function of period. The region where the inflection point disappears is the coupling region.

[0052] Figure 6(a) shows the corresponding implementation case 2 with a fixed conductivity of 9.2 × 10⁻⁶. 4 The curves showing the intrinsic frequencies of the folded BIC mode and the loss mode as a function of the period at S / m. The dashed line in the figure represents a period P of 139 micrometers.

[0053] Figure 6(b) shows the evolution of the simulation results of the absorption spectrum and the fitting of the time-domain coupled-mode theory with the change of conductivity in Implementation Case 2 with a period P of 139 micrometers.

[0054] Figure 6(c) shows the corresponding implementation case 2 with a fixed conductivity of 9.2 × 10⁻⁶. 4 At S / m, the reflection spectrum of multi-frequency absorption is achieved by adjusting the period. The white and black lines in the inset from bottom to top show the reflection spectrum at periods P of 121 μm and 150 μm, respectively.

[0055] Figure 7(a) is a schematic diagram of the preparation process of the corresponding metasurface sample in Implementation Case 2;

[0056] Figure 7(b) is an optical microscope image of the metasurface sample prepared by the corresponding process in Example 2;

[0057] Figure 7(c) shows the relationship between the conductivity of vanadium dioxide and temperature in Implementation Case 2. The rectangle represents the heating curve and the circle represents the cooling curve.

[0058] Figure 7(d) shows the experimental reflectance spectrum of BIC to QBIC evolution in a sample with a period P of 121 micrometers in Implementation Case 2, achieved by adjusting the temperature from 30℃ to 88℃.

[0059] Figure 7(e) shows the experimental absorption spectrum of BIC to QBIC evolution in a sample with a period P of 139 micrometers in Implementation Case 2, achieved by adjusting the temperature from 30℃ to 96℃. Detailed Implementation

[0060] The technical solution of the present invention will be more clearly and completely explained below with reference to the accompanying drawings and through the description of preferred embodiments of the present invention.

[0061] like Figure 1 As shown, it includes:

[0062] Metal backplate 1;

[0063] The dielectric substrate 2 is disposed on one side of the metal backplate 1;

[0064] Metal resonant unit cell 3 is disposed on the other side of the dielectric substrate 2. Each metal resonant unit cell 3 consists of a pair of metal resonant ring units 5 arranged in a mirror-symmetrical manner along the x-axis direction. The metal resonant unit cells are spaced apart along the x-axis direction.

[0065] A phase change material bridging module 4 is disposed on the dielectric substrate 2 and bridges the metal resonant unit cell 3. The conductivity of the phase change material bridging module 4 can be continuously adjusted between the insulating state and the metallic state by external excitation.

[0066] The period of the metasurface unit in the y direction is P, and the effective period in the x direction switches between P and 2P according to the state of the phase change material bridging module 4.

[0067] When the phase change material bridging module 4 is in an insulating state, adjacent metasurface units maintain electromagnetic decoupling in the x-direction, and the effective period in the x-direction is P.

[0068] When the phase change material bridging module 4 is in a metallic state, adjacent metasurface units form electromagnetic coupling in the x-direction through the phase change material bridging module, and the effective period in the x-direction becomes 2P.

[0069] In one specific implementation, at low temperatures, the vanadium dioxide material is in a monoclinic insulator state, and the metasurface reflects y-polarized terahertz normal incident waves; at high temperatures, the vanadium dioxide material transforms into a rutile metallic phase, and the metasurface can achieve perfect absorption at a specific frequency (0.41 THz) under the condition of normal terahertz wave incidence and y-polarization.

[0070] Figures 2(a) and 2(b) show a schematic diagram and a top view of the unit structure of the dynamically perfect absorbing metasurface achieved by the reconfigurable coupling of the self-folding BIC of the present invention, respectively. The metasurface schematic diagram of the present invention includes: a metal resonant unit cell 3, a phase change material bridging module 4, a dielectric substrate 2, and a metal backplate 1. The metal backplate 1 is on one side of the dielectric substrate 2, and the metal resonant unit cell 3 and the phase change material bridging module 4 are on the other side of the dielectric substrate 2, both in direct contact with the dielectric substrate 2. The metal resonant unit cell 3 consists of a pair of short-arm U-shaped metal resonant ring units with a period of P. The pair of metal resonant unit cells 3 are connected by the phase change material bridging module 4, with a period of 2P. The metasurface array is arranged in the XY plane, and the incident electromagnetic field is a y-polarized terahertz beam, which is perpendicularly incident on the metasurface along the -Z direction.

[0071] Figure 3(a) shows a schematic diagram of the principle of band self-folding to form a BIC, with the dashed line representing the light cone boundary. The upper inset shows the schematic process of the metasurface periodicity abruptly caused by the structural perturbation introduced by the vanadium dioxide phase change material. The dashed line in the inset marks the irreducible representation region in the first Brillouin zone. Γ represents the center of the structure, and X1 and X represent the structural boundaries with periods of 2P and P, respectively. This figure illustrates how the Brillouin zone folding is induced by adjusting the vanadium dioxide module to change the structural period and symmetry, folding the guided mode originally located at point X to point Γ, and forming a lossless folded BIC mode in the radiation continuum. This BIC mode coexists with the inherent loss mode at point Γ, creating conditions for coupling between the two. Figure 3(b) is a schematic diagram of the process of dynamically controlling the folded BIC to form a QBIC and finally achieving perfect absorption, where the dotted symbol represents the loss mode with a corresponding characteristic frequency of ω1, and the star symbol represents the folded BIC mode with a corresponding characteristic frequency of ω2. The figure shows that by externally exciting and controlling the conductivity of vanadium dioxide, the structural symmetry can be actively broken, causing the BIC to degenerate into a QBIC mode with radiation loss, and then coupling with the loss mode. By continuously adjusting the conductivity, the system loss can be matched, and when the critical coupling condition is met, efficient and perfect absorption can be achieved in the terahertz band.

[0072] Figure 4(a) shows the electric field distribution of the metasurface unit of the present invention with a period P of 121 micrometers. The left figure clearly shows that the electric field in the folded BIC mode is highly localized inside the metal resonant structure, with almost no energy radiating to free space, confirming that this mode has typical continuous domain bound state characteristics. The right figure shows the electric field distribution in the loss mode, whose energy localization is relatively weak. Figure 4(b) reflects the evolution of the continuous reflection spectrum obtained by adjusting the conductivity of the vanadium dioxide phase change material under normal terahertz wave incidence. It can be seen that as the conductivity increases, the originally non-radiative BIC mode gradually degenerates into a QBIC mode with certain radiation loss, and its resonance peak appears from nothing and gradually broadens. Figure 4(c) further shows different conductivity from 10 S / m to 2 × 10 5 The discrete reflection spectrum under different S / m values ​​more clearly shows the changes in resonance depth and line shape during the evolution from BIC to QBIC, indicating that the continuous reconfigurable function of resonance state and quality factor can be achieved by adjusting conductivity.

[0073] Combination Figures 5(a) to 5(d) Description of Implementation Case 1

[0074] In the first example, this embodiment verifies the technical effect of dynamically reconstructing the quality factor Q of the folded BIC mode by adjusting the conductivity of the vanadium dioxide bridging module through simulation calculations, and proves the universality of this adjustment law under different structural periods. Specifically, the metasurface unit structure described in this invention is used, with the period parameter P set to 121 μm and 150 μm respectively. Under the condition of normal incidence of y-polarized terahertz waves, the quality factor Q is calculated by changing the conductivity of vanadium dioxide and extracting the characteristic frequencies and half-width at half-maximum (FWHM) from the reflection spectrum. The results show that, as shown in Figures 5(a) and (b), the quality factor Q exhibits a clear and regular turning point with increasing conductivity under different periods, i.e., there is a critical inflection point: when the conductivity is below the inflection point, the quality factor Q decreases with increasing conductivity in an inverse square relationship; when the conductivity is above the inflection point, the quality factor Q increases in an inverse first power relationship. This phenomenon indicates that this invention achieves flexible bidirectional control of the resonant quality, and can actively select high or low Q values ​​according to application requirements.

[0075] In Figures 5(a) and 5(b), the curve pointing to the right represents the relationship between the intrinsic frequency and conductivity, while the curve pointing to the left represents the relationship between the quality factor Q and conductivity.

[0076] Furthermore, Figure 5(c) shows that the critical conductivity values ​​corresponding to the inflection point (marked with an asterisk in the figure) when the period changes from 121 micrometers to 155 micrometers are different. Figure 5(d) shows the distribution trend of the inflection point relative to the period, proving that the resonant characteristics can be precisely controlled by jointly designing geometric parameters and conductivity, thereby meeting the requirements of different terahertz application scenarios for operating frequency and bandwidth. This embodiment confirms that the present invention has the ability to continuously and reversibly control the BIC mode quality factor Q through conductivity, and has clear regularity and good designability, providing an effective implementation basis for realizing high-performance terahertz reconfigurable functional devices.

[0077] Combination Figures 6(a) to 6(c) Description of Implementation Case 2

[0078] In the second example, we achieved dynamic coupling between the self-folding QBIC mode and the loss mode by adjusting the structural period and the conductivity of vanadium dioxide, ultimately achieving reconfigurable perfect absorption in the terahertz band. Specifically, the conductivity of vanadium dioxide was fixed at 9.2 × 10⁻⁶. 4 The characteristic frequency changes of the two modes under different periods were obtained through simulation calculations, as shown in Figure 6(a): As the period increases, the eigenfrequency of the self-folding BIC mode redshifts, while the eigenfrequency of the loss mode only slightly blueshifts. The two eigenfrequency points intersect near P=148 μm, indicating the entry into a strong coupling region. Further, the conductivity of vanadium dioxide was further adjusted at a selected period of P=139 μm, and its reflection spectrum evolution is shown in Figure 6(b): With the continuous increase of conductivity, the system gradually evolved from a single resonance peak to two distinct resonance modes, and the resonance mode reached a peak at conductivity of 9.2 × 10⁻⁶. 4 Near-perfect absorption (absorption rate greater than 99%) is achieved at 0.413 THz when the conductivity is S / m, indicating that the system's radiation loss and dissipation loss are balanced at this point, satisfying the critical coupling condition. Furthermore, Figure 6(c) shows the absorption at a fixed conductivity of 9.2 × 10⁻⁶ THz. 4 The reflection spectrum, obtained by adjusting the period at a frequency of S / m, demonstrates that absorption peaks at multiple frequencies can be achieved by adjusting the period under a fixed conductivity. The insets from bottom to top show the reflection spectra at periods P of 121 μm and 150 μm, respectively, indicated by white and black lines. This further proves that the coupling mechanism has good reconfigurability and design flexibility. The results show that the metasurface described in this invention can achieve dynamic and efficient terahertz wave absorption through the synergistic control of conductivity and geometric parameters, providing an effective approach for the design of intelligent terahertz devices.

[0079] Combination Figures 7(a) to 7(e) Description of Implementation Case 3

[0080] In the third example, we experimentally prepared and tested the dynamically reconfigurable absorption function of the metasurface described in this invention in the terahertz band. First, following the process flow shown in Figure 7(a), a metasurface sample with a periodic metal resonant ring structure and a vanadium dioxide bridging module was prepared on a sapphire substrate using physical vapor deposition (PVD), photolithography, reactive ion etching (RIE), and lift-off processes. Its optical microscope image is shown in Figure 7(b), demonstrating a clear structure and complete outline, meeting the design requirements. In performance characterization, the sample was heated using a temperature-controlled platform, and the reflectance spectrum was measured using a terahertz time-domain spectroscopy system. Figure 7(c) shows the relationship between the conductivity of vanadium dioxide and temperature obtained by fitting the Drude model, indicating that its conductivity can continuously and reversibly switch between the insulating and metallic states, providing a physical basis for dynamic control. Figure 7(d) shows the experimental reflectance spectrum of the dynamic evolution from BIC to QBIC in a sample with a period P of 121 μm, achieved by adjusting the temperature: as the temperature increases (from 30 °C to 88 °C), the conductivity of vanadium dioxide continuously increases, and the originally non-resonant spectrum gradually appears and broadens, confirming the active tuning capability of BIC to QBIC. Furthermore, the sample was replaced with a structure with a period P of 139 μm and temperature-varying tests were performed, the results of which are shown in Figure 7(e): at 88 °C (corresponding to a conductivity of approximately 9.2 × 10⁻⁶), the temperature was... 4 At a temperature of 0.41 THz (S / m), a maximum absorption rate of approximately 87% was achieved. Further heating resulted in a decrease in absorption rate, a trend that closely matched simulation predictions, indicating that dynamic matching of the coupling state and absorption switching functions can be achieved through temperature control. Ultimately, a modulation depth of 78% was obtained in the experiment, confirming the good practical value of this invention in terahertz dynamic modulation and sensing applications. In summary, this embodiment successfully realized the preparation and dynamic control of a reconfigurable metasurface based on vanadium dioxide phase change material through experimental methods, verifying its technical feasibility for achieving efficient absorption and rapid modulation in the terahertz band.

[0081] As demonstrated by the above embodiments, this invention dynamically achieves the breaking and reconstruction of the symmetry of metasurface units by electrically or thermally controlling the conductivity of vanadium dioxide phase change materials. This enables reversible conversion from BIC to QBIC, dual-mode dynamic coupling, and efficient and perfect absorption in the terahertz band. Compared to traditional devices that rely on fixed-structure perturbations to achieve BIC, this invention achieves active and continuous control of the resonant state, quality factor, and absorption performance, possessing advantages such as dynamic reconfigurability, high absorption efficiency, and fast response speed. The proposed metasurface structure unit is simple to design and easy to fabricate, and can be scaled up to microwave, infrared, and visible light bands, showing broad application prospects in intelligent spectrum management, real-time sensing, and programmable quantum control.

[0082] The above-described specific embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications, substitutions, and improvements made by those skilled in the art to the technical solutions of the present invention based on the provided textual description and drawings, without departing from the design concept and spirit of the present invention, should all fall within the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

Claims

1. A reconfigurable coupled dynamic perfect absorbing metasurface unit based on self-folding BICs, characterized in that, include: Metal backplate (1); A dielectric substrate (2) is disposed on one side of the metal backplate (1); Metal resonant unit cell (3) is disposed on the other side of the dielectric substrate (2). Each metal resonant unit cell (3) consists of a pair of metal resonant ring units (5) arranged in a mirror-symmetrical manner along the x-axis direction. The metal resonant unit cells are spaced apart along the x-axis direction. A phase change material bridging module (4) is disposed on the dielectric substrate (2) and bridges the metal resonant unit cell (3). The conductivity of the phase change material bridging module (4) can be continuously adjusted between the insulating state and the metallic state by external excitation. The period of the metasurface unit in the y direction is P, and the effective period in the x direction switches between P and 2P depending on the state of the phase change material bridging module (4). When the phase change material bridging module (4) is in an insulating state, adjacent metasurface units maintain electromagnetic decoupling in the x direction, and the effective period in the x direction is P; When the phase change material bridging module (4) is in a metallic state, adjacent metasurface units form electromagnetic coupling in the x direction through the phase change material bridging module, and the effective period in the x direction becomes 2P.

2. The dynamically perfectly absorbing metasurface unit based on reconfigurable coupling of self-folding BICs according to claim 1, characterized in that: The metal backplate (1) is a metal layer; The dielectric substrate (2) is made of sapphire, quartz or alumina, with a relative permittivity of 4-12; The metal resonant ring unit is a U-shaped, C-shaped or open ring structure with a linewidth of 10-30 micrometers, and the spacing between the pair of metal resonant ring units (5) is 10-40 micrometers; The period P is 100-200 micrometers.

3. The dynamically perfectly absorbing metasurface unit based on reconfigurable coupling of self-folding BICs according to claim 1, characterized in that: The phase change material bridging module (4) uses vanadium dioxide, tungsten dioxide or GST phase change material, with a width of 10-30 micrometers; The conductivity of the insulating state is less than 10. 2 S / m, the conductivity of the metallic state is greater than S / m; The external excitation is either thermal or electrical. The temperature range of the thermal excitation is 20-100℃, and the voltage range of the electrical excitation is 1-10V.

4. The dynamically perfectly absorbing metasurface unit based on reconfigurable coupling of self-folding BICs according to claim 1, characterized in that: The metal resonant ring unit (5) is a short-arm U-shaped structure, including two long arms and one short arm. The long arms are parallel to the x-axis, the short arms are parallel to the y-axis, and the opening faces the y-axis direction. The openings of the pair of metal resonant ring units (5) are arranged facing each other.

5. A dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BICs, used to implement the dynamically perfect absorbing metasurface unit based on reconfigurable coupling of self-folding BICs as described in any one of claims 1-4, characterized in that: The reconfigurable coupled dynamic perfect absorbing metasurface units based on self-folding BIC are arranged in an array on a two-dimensional plane; The reconfigurable coupled dynamic perfect absorbing metasurface unit based on self-folding BIC has an arrangement period of P in the y direction and an arrangement period of 2P in the x direction. The phase change material bridging module (4) of two adjacent reconfigurable coupled dynamic perfect absorbing metasurface units based on self-folding BIC is connected to their respective metal resonant unit cells (3).

6. The dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BIC according to claim 5, characterized in that: When the conductivity of the phase change material bridging module (4) is less than 10 3 At S / m, the structure of the metasurface maintains mirror symmetry and supports a lossless folded BIC mode at the Γ point in the Brillouin zone. When the conductivity of the phase change material bridging module (4) is greater than At S / m, the phase change material bridging module introduces C2 rotational symmetry breaking, transforming the folded BIC mode into a folded quasi-BIC mode with radiation loss.

7. The dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BIC as described in claim 6, characterized in that: By adjusting the conductivity of the phase change material bridging module (4) at... The coupling strength between the folded quasi-BIC mode and the loss mode can be continuously adjusted within the range of S / m.

8. The dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BIC according to claim 7, characterized in that: Under the condition of normal incidence of terahertz waves and electric field polarization along the y-direction, when the conductivity of the phase change material bridging module (4) is at... Within the S / m range, the folded quasi-BIC mode and the loss mode reach a critical coupling state, achieving perfect absorption with an absorption rate greater than 85% in the 0.3-0.5THz frequency range.

9. The dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BIC according to claim 8, characterized in that: The absorption peak frequency of the perfect absorption is inversely proportional to the period P. By adjusting the period P within the range of 100-200 micrometers, the absorption peak frequency can be tuned within the range of 0.3-0.6 THz. Under a fixed period, by adjusting the conductivity of the phase change material bridging module (4), the absorption rate can be continuously controlled within the range of 10% to 99%, and the modulation depth is greater than 70%.

10. The application of the dynamically perfect absorbing metasurface based on reconfigurable coupling of self-folding BIC in terahertz intelligent control according to any one of claims 5 to 9, characterized in that: The conductivity of the phase change material bridging module (4) is dynamically adjusted by external excitation to achieve real-time switching of the terahertz wave absorption state, which can be applied to at least one of the following scenarios: Dynamic spectrum management and absorption modulation in the terahertz band; Terahertz biosensing and chemical sensing based on absorption peak shift; Programmable absorption control in terahertz quantum information processing.

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