Topological heterostructure and sensing detection method

Abstract

This invention relates to a topological heterostructure and a sensing method. The topological heterostructure includes a first photonic crystal region and a second photonic crystal region, which are adjacent to each other to form an interface. The first and / or second photonic crystal regions each include at least one structural unit composed of alternating stacked HMM layers and dielectric layers. The thicknesses of the HMM layer and the dielectric layer satisfy the following condition: the positive phase change provided by the anomalous dispersion of the HMM layer effectively compensates for the negative phase shift of the dielectric layer as the incident angle increases, thereby obtaining a stable omnidirectional dispersion-free bandgap over a wide incident angle range. Furthermore, based on the topological difference between the two photonic crystal regions, local interface states are formed at the interface, and the topological heterostructure is designed such that the local interface states have phase singularities in the reflection spectrum. This avoids dependence on negative permeability, endows the system with the ability to resist structural disturbances, and enables high-sensitivity sensing based on the phase singularities.

Description

Technical Field

[0001] This invention relates to the field of optical technology, specifically to a topological heterostructure and a sensing and detection method. Background Technology

[0002] As an artificial structure with a periodically modulated dielectric constant, photonic crystals can realize photonic bandgap, suppressing light propagation within a specific frequency range. However, in traditional one-dimensional all-dielectric photonic crystals, the bandgap edge exhibits a blue shift, significantly shifting towards higher frequencies as the incident angle increases. In practical applications, this physical characteristic leads to a severe angle dependence in related photonic crystal devices (such as filters, resonant cavities, and sensors), severely limiting their performance in integrated photonic chips, complex sensing environments, and large numerical aperture optical systems.

[0003] To overcome this limitation, researchers have proposed two schemes to achieve angle-independent dispersion-free bandgap: one is a zero-average refractive index mechanism based on phase cancellation of positive and negative refractive index materials; the other is a zero-effective phase mechanism based on evanescent wave compensation in a single negative material. However, both paths require negative permeability materials, and in the near-infrared and visible light bands, it is usually difficult to achieve a negative permeability response, which greatly limits the experimental progress of such dispersion-free bandgap. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a topological heterostructure and a sensing method that utilizes the phase compensation effect between the HMM (hyperbolic metamaterial) layer and the dielectric layer. By precisely matching the thickness and leveraging the anomalous dispersion characteristics of the HMM, the phase shift in the dielectric layer caused by the increase of the incident angle is offset, completely avoiding the dependence on negative permeability.

[0005] The present invention is achieved through the following scheme: a topological heterostructure comprising a first photonic crystal region and a second photonic crystal region, which are adjacent to each other to form an interface; wherein the first photonic crystal region and / or the second photonic crystal region comprises at least one structural unit formed by alternating stacking of HMM layers and dielectric layers, and the thicknesses of the HMM layers and the dielectric layers satisfy the following: the positive phase change provided by the anomalous dispersion of the HMM layers effectively compensates for the negative phase shift of the dielectric layers as the incident angle increases, thereby obtaining a stable omnidirectional dispersion-free bandgap over a wide incident angle range.

[0006] A further improvement of the topological heterostructure of the present invention is that the wide incident angle range is [0~80] degrees.

[0007] A further improvement of the topological heterostructure of the present invention is that the HMM layer is a multilayer structure formed by alternating stacking of metal layers and dielectric layers with subwavelength thickness, so as to achieve hyperbolic dispersion characteristics in the target operating band.

[0008] A further improvement of the topological heterostructure of the present invention is that the first photonic crystal region and the second photonic crystal region are configured such that the topological heterostructure forms a topologically protected local interface state at the interface.

[0009] A further improvement of the topological heterostructure of the present invention is that the first photonic crystal region and the second photonic crystal region have opposite Zak phases, so as to achieve the formation of topologically protected local interface states at the interface.

[0010] A further improvement of the topological heterostructure of the present invention is that the topological heterostructure satisfies the following: the local interface state has a phase singularity in the reflection spectrum, and the spectral position of the phase singularity is configured to drift with the change of the dielectric environment at the interface.

[0011] The present invention also provides a sensing and detection method, comprising the steps of:

[0012] The material to be tested is introduced into the above-mentioned topological heterostructure in which local interface states are formed at the interface and the local interface states have phase singularities in the reflection spectrum, so as to change the dielectric environment at the interface.

[0013] The spectral position change of the phase singularity is detected to achieve the detection of the substance to be tested.

[0014] This invention includes, but is not limited to, the following beneficial effects:

[0015] 1. By leveraging the phase compensation effect between the HMM layer and the dielectric layer and precisely matching the thickness, the anomalous dispersion characteristics of the HMM are used to counteract the phase shift in the dielectric layer that occurs as the incident angle increases. This allows for the realization of an omnidirectional dispersion-free bandgap with a high frequency constant within a wide incident angle range of 0° to 80°, completely avoiding the dependence on negative permeability. This represents a completely new path for achieving a dispersion-free bandgap.

[0016] 2. By combining topological bandgap design, local topological interface states with immune properties to random structural perturbations such as hyperbolic layer fill rate are constructed in the realized dispersionless bandgap, which endows the system with the ability to resist structural perturbations. This makes the resonant frequency and performance of the interface states highly stable even if there are fabrication errors.

[0017] 3. Innovatively utilizes the phase singularity jump mechanism for sensing detection. This mechanism captures the intense phase jump signal at the resonance point, which can significantly improve sensing sensitivity compared to traditional amplitude-type sensing schemes. At the same time, this mechanism maintains extremely high detection accuracy and signal-to-noise ratio even under large-angle oblique incidence. Attached Figure Description

[0018] Figure 1 A schematic diagram illustrating the structure and electromagnetic characteristics of an embodiment of the present invention is shown.

[0019] Figure 2 This diagram illustrates the bandgap verification and topological characteristics of an embodiment of the present invention, independent of the incident angle.

[0020] Figure 3 A schematic diagram illustrating the key characteristics of a local interface state according to an embodiment of the present invention is shown.

[0021] Figure 4 A schematic diagram of the refractive index sensing response under vertical incidence is shown in an embodiment of the present invention.

[0022] Figure 5 A schematic diagram of the refractive index sensing response at different incident angles is shown in an embodiment of the present invention.

[0023] Figure 6 The diagram illustrates the phase sensing response of perturbation samples with different fill rates under vertical incidence, according to an embodiment of the present invention. Detailed Implementation

[0024] To address the severe dispersion problem of the bandgap edge shifting towards higher frequencies with increasing incident angle in traditional one-dimensional all-dielectric photonic crystals, and the fact that existing dispersion-free bandgap solutions often rely on materials with extremely high refractive index or negative magnetic permeability, this invention provides a topological heterostructure and a sensing method. The topological heterostructure includes a first photonic crystal region and a second photonic crystal region, which are adjacent to each other to form an interface. The first photonic crystal region and / or the second photonic crystal region includes at least one structural unit composed of alternating stacked HMM layers and dielectric layers. The thicknesses of the HMM layer and the dielectric layer satisfy the following condition: the positive phase change provided by the anomalous dispersion of the HMM layer effectively compensates for the negative phase shift of the dielectric layer with increasing incident angle, thereby obtaining a stable omnidirectional dispersion-free bandgap over a wide incident angle range.

[0025] This topological heterostructure, by leveraging the phase compensation effect between the HMM layer and the dielectric layer, and through precise thickness matching, utilizes the anomalous dispersion characteristics of the HMM to counteract the phase shift in the dielectric layer that occurs with increasing incident angle. This achieves a highly constant omnidirectional dispersion-free bandgap across a wide incident angle range of 0° to 80°, completely avoiding dependence on negative permeability, representing a novel path to achieving a dispersion-free bandgap. Furthermore, the first and second photonic crystal regions are configured to form topologically protected local interface states at the interface. Specifically, this is achieved by constructing a first and a second photonic crystal region with opposite Zak phases. These local interface states are not only insensitive to changes in incident angle but also maintain frequency stability even when structural parameters such as the HMM layer fill rate are randomly perturbed. Furthermore, by enabling the local interface state to have a phase singularity and utilizing the phase singularity transition mechanism for sensing, the sensing sensitivity can be significantly improved compared to traditional amplitude-type sensing schemes. At the same time, this mechanism maintains extremely high detection accuracy and signal-to-noise ratio even under large-angle oblique incidence.

[0026] The following description, in conjunction with specific embodiments and accompanying drawings, further illustrates the topological heterostructure and sensing method. 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, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of the present invention is for describing specific implementation schemes and not for limiting the scope of protection of the present invention.

[0027] See Figure 1 As shown, Figure 1 Figure (a) illustrates a topological heterostructure comprising a first photonic crystal region PC1 and a second photonic crystal region PC2, which are adjacent to each other to form an interface. Specifically, this topological heterostructure can be represented as follows: .in, PC1 is the first photonic crystal region with four ABA structural units. The second photonic crystal region PC2 has four CDC structural units. The number of periods for the structural units in PC1 and PC2 is not limited to four; it can be determined by considering both bandgap characteristics and interface state formation. Layers A and D are dielectric layers; in this embodiment, they are high-refractive-index dielectric silicon (Si), with a refractive index of... (relative permittivity) Layers B and C are HMMs, which are metamaterials with extreme electromagnetic anisotropy and opposite signs for their dielectric tensor components. In this embodiment, the HMM layer is a multilayer structure formed by alternating stacks of metal and dielectric layers at subwavelength thicknesses.

[0028] Figure 1 The enlarged view in Figure (a) shows the internal structure of the HMM layer. Each HMM layer consists of four symmetrical unit cells (EFE). The number of periods in the unit cell is not limited to four; it can be determined by considering both the theoretical effect and the difficulty of fabricating the actual structure. Here, E is the dielectric layer. To avoid using too many different materials in the structure, in this embodiment, the E layer is made of high-refractive-index dielectric silicon (Si). The F layer is made of indium tin oxide (ITO), which exhibits metal-like properties in the near-infrared band and has a relatively high permittivity. Described by the Drude model:

[0029] ;

[0030] in: It is the high-frequency dielectric constant. ; For plasma frequency, ; It is the frequency of the electromagnetic wave.

[0031] Of course, other materials can also be used for the F layer, such as copper (Au) or silver (Ag), as long as the real part of the dielectric constant is less than zero in a specific wavelength band. The HMM layers are stacked with subwavelength thicknesses, which are much smaller than the operating wavelength. The electromagnetic parameters of the HMM layer can be described by the anisotropic relative permittivity tensor determined by effective dielectric theory, and its component expression is:

[0032] ;

[0033] ;

[0034] in: The tangential component is parallel to the surface of the HMM layer; is the normal component perpendicular to the surface of the HMM layer; is the indium tin oxide (ITO) filling rate in the unit cell (EFE), which is set to 0.5 in this design.

[0035] Figure 1 Figure (b) shows the variation of the effective dielectric tensor components with frequency over a wide frequency range of 150–300 THz. This indicates that the structure exhibits the characteristics of a Type-I hyperbolic metamaterial. Figure 1Figure (c) shows a comparison of the isotropic media Si and HMM at the bandgap center frequency. For transverse magnetic (TM) polarized waves, the normal wave vector in Si... It decreases as the incident angle increases, while in HMM the normal wave vector... The band gap increases with the incident angle, and this anomalous property makes it possible to achieve an angle-independent band gap. Figure 1 Figure (d) illustrates the thickness relationship between the HMM layer and the Si layer, determined based on the phase change compensation effect. According to the first-order Bragg condition, in order to eliminate the dependence of the bandgap on the incident angle, the total propagation phase must be independent of the tangential wave vector. Change, that is, satisfaction:

[0036] ;

[0037] By combining the proportional relationship between the partial derivatives of the HMM and Si normal wave vectors with respect to the tangential wave vectors, the analytical condition for thickness can be derived. As shown in the figure, at the bandgap center frequency of 199.5 THz, the HMM layer thickness that satisfies this condition is... Si layer thickness .

[0038] See Figure 2 As shown, Figure 2 The realization of angle-independent bandgap and the excitation of topological interface states were verified. Figure 2 Figures (a) and (b) show ABA structural units with 10 periods (i.e., The first photonic crystal region PC1 and the CDC structural unit with 10 periods (i.e.) The full-incident-angle reflection spectrum of the second photonic crystal region PC2 under TM polarization was obtained. In both unit cells (ABA and CDC), the thicknesses of the HMM layer and the Si layer strictly adhered to the aforementioned design. The results show that both exhibit highly stable full-angle bandgap near the bandgap center frequency of 199.5 THz. This phenomenon indicates that the positive phase change provided by the anomalous dispersion of the HMM layer effectively compensates for the negative phase shift of the dielectric layer as the angle increases, achieving a phase change compensation effect. Figure 2 Figures (c) and (d) show the band structure and Zak phase distribution at incident angles of 0° and 60°, respectively. The left side of each figure shows the results for the first photonic crystal region PC1, and the right side shows the results for the second photonic crystal region PC2. For a one-dimensional photonic crystal containing an HMM layer, the dispersion relation of its TM waves can be expressed as:

[0039] ;

[0040] Where: K is the Bloch wave vector; This represents the total thickness of the unit cell; and These represent the wave vector components of the wave in the Si layer and the HMM layer along the direction perpendicular to the interface (i.e., the z-axis direction), respectively. and This corresponds to the thickness of the Si layer and the HMM layer; and The impedances of the Si and HMM layers are shown, respectively, and their specific forms depend on the polarization mode. The results in the figure show that the position and width of the bandgap remain almost constant under different incident angles within the frequency band of approximately 175-227 THz. This result further verifies the angular robustness provided by the phase compensation mechanism from an energy band perspective. Calculations of the Zak phase of each isolated energy band reveal that the Zak phase of the bandgap in PC1 is... In the first arrangement, the upper band is 0, while in the second arrangement it is exactly the opposite. According to topological band theory, the reflection phase signs of photonic crystals with the two arrangements are opposite within the same band gap, which is a direct topological criterion for the existence of topological interface states.

[0041] To further reveal the generation mechanism of topological interface states, the theoretical framework of the Dirac equations is introduced. Within the bandgap frequency range, the symmetric unit cell of a one-dimensional photonic crystal can be equivalently represented as a "photonic insulator" with uniform and effective electromagnetic parameters. Assuming that the TM-polarized wave is incident perpendicularly, the Maxwell equations can be used to introduce spinors. The Dirac equations can be reconstructed as follows:

[0042]

[0043] in: It is the vacuum permittivity; The vacuum permeability; The component of the electric field intensity along the y-axis; The component of the magnetic field strength along the x-axis; T is the transpose sign; For effective quality, , For the effective dielectric constant, Where is the effective permeability, and c is the speed of light in vacuum. The frequency of electromagnetic waves; Here, V is the Pauli matrix; V is the effective potential; E is the energy eigenvalue; To find the partial derivative with respect to the z-axis.

[0044] Within this framework, when the bandgap of a photonic crystal exhibits either electrically single-negative or magnetically single-negative characteristics, its effective mass... These can be negative or positive, corresponding to different topological orders. The Dirac equation theory further states that in a heterostructure composed of two photonic insulators with opposite topological orders, if the zero-average effective mass condition is satisfied... If a bound state exists at the interface, and this state is robust to perturbations of the effective mass distribution that satisfy this condition.

[0045] See Figure 3 As shown, Figure 3 The excitation of topological interface states and their key characteristics are demonstrated. Figure 3 Figure (a) in the figure shows the heterostructure. In the full-incident-angle reflection spectrum under TM polarization, an extremely flat reflection line appears in the bandgap frequency range near 200 THz, corresponding to the topologically protected topological interface state. Figure 3 Figure (b) verifies the robustness of the interface states to structural perturbations. While keeping the unit cell thickness constant, a random perturbation of the HMM layer fill rate is introduced in each period of the first photonic crystal region PC1. The HMM layer thickness in each unit cell fluctuates within ±30 nm, and the corresponding fill rate varies randomly within ±0.1 nm. According to the aforementioned Dirac equation theory, since the first photonic crystal region PC1 and the second photonic crystal region PC2 are equivalent to magnetically and electrically mononegative materials, respectively, possessing effective masses of opposite signs, and by design satisfying the zero-average effective mass condition, the interface states exhibit inherent robustness to structural perturbations. Figure 3 (b) The reflection spectra of the heterostructure were compared at incident angles of 0°, 30°, 60°, and 80° with and without the introduction of a perturbation (solid line) and with the introduction of a perturbation of the filling rate (dashed line). Simultaneously, we traced the evolution path of the interface state resonance frequency as the incident angle continuously changed. The results show that at all incident angles, the resonance frequency and reflectivity of the interface state remain stable before and after the perturbation, demonstrating the dual robustness of this state to angle changes and perturbations of the filling rate.

[0046] The topological heterostructure in this embodiment also satisfies the following: the local interface state has a phase singularity in the reflection spectrum, and the spectral position of the phase singularity is configured to drift with changes in the dielectric environment at the interface. Sensing can be performed through the phase singularity's jump mechanism. This mechanism, by capturing the dramatic phase jump signal at the resonance point, can significantly improve sensing sensitivity compared to traditional amplitude-based sensing schemes. Furthermore, this mechanism maintains extremely high detection accuracy and signal-to-noise ratio even under large-angle oblique incidence.

[0047] Figure 3 Figure (c) illustrates the reflection phase singularity characteristics of this interface state under perpendicular incidence. This figure depicts the distribution of the reflection phase as a function of frequency and the refractive index at the incident end under perpendicular incidence. The phase singularity essentially corresponds to the zero point of the complex reflection coefficient, and its topological properties can be characterized by the topological charge. The topological charge C is defined as:

[0048] ;

[0049] in: The gradient of the phase in the parameter space is represented by L; L is the integration path, specifically an arbitrary closed curve around the singularity. Let L be a directed linear element vector in the parameter space along a closed integration path L; this integral calculates the phase. The total change along the closed curve divided by The result is an integer, reflecting the number of entanglements at the phase singularity. Calculating this integral yields the topological charge C = -1. This non-zero topological property ensures the stability of the phase singularity in the parameter space. As shown in the figure, the phase distribution exhibits a distinct vortex characteristic in the frequency-refractive index parameter space, with the central location being the phase singularity. Near the singularity, the reflected phase undergoes abrupt changes, forming a large phase gradient, providing a physical basis for subsequent high-sensitivity sensing applications.

[0050] The method for sensing and detection using the aforementioned topological heterostructure includes the following steps: introducing a analyte into the aforementioned topological heterostructure, where local interface states are formed at the interface and these local interface states have a phase singularity in the reflection spectrum, to change the dielectric environment at the interface; detecting the change in the spectral position of the phase singularity to achieve the detection of the analyte. The following is an explanation using specific experiments and accompanying figures:

[0051] Using electron beam evaporation or magnetron sputtering, Si and ITO materials were alternately deposited on a substrate to construct a four-cycle (EFE) symmetric unit cell structure as an HMM layer, where E is a Si layer and F is an ITO layer. The ITO fill factor in the unit cell was set to 0.5 to ensure Type-I hyperbolic dispersion characteristics in the frequency range of 150–300 THz. Based on this, two one-dimensional photonic crystal regions, PC1 and PC2, were designed. The unit cell structure of PC1 was (ABA), and that of PC2 was (CDC), where A and D were Si layers (95.5 nm thick), and B and C were HMM layers (200 nm thick). Each photonic crystal region was stacked in four cycles. During the fabrication process, PC1 and PC2 were sequentially deposited and grown on the substrate to form a complete structure. Heterogeneous structures. Refractive index sensing experiments are conducted using the reflection phase singularities corresponding to the topological interface states in these heterogeneous structures (these phase singularities are not limited to refractive index sensing; they can also be used to sense other sensitive parameters). A test medium layer is placed at the sample incident end. By introducing test liquids with different refractive indices, a tunable laser combined with a phase detection system is used to measure the change in reflection phase as a function of the incident refractive index.

[0052] Figure 4 The sensing response to the refractive index change under vertical incidence is demonstrated. Figure 4Figure (a) shows the reflectance spectra for different refractive indices. It can be seen that as the refractive index increases, the reflectance spectra shift generally towards lower frequencies. The resonant frequency relative to the reference value is extracted for each case. The offset size, such as Figure 4 As shown in Figure (b), the reflectivity sensing sensitivity is obtained through data fitting. Compared to the frequency response, phase abrupt changes exhibit a more significant trend during sensing. Figure 4 Figure (c) shows the reflection phase spectrum at the corresponding refractive index, with a sharp phase jump near the singular frequency. Figure 4 The inset of figure (d) shows the phase shift spectral lines relative to the reference case under different refractive indices. The maximum phase shift is extracted from these lines and plotted in the main figure. The phase sensing sensitivity is obtained through data fitting. This represents an improvement of several orders of magnitude compared to reflectivity sensing.

[0053] Figure 5 The sensing performance of the structure under oblique incidence conditions was verified. Figure 5 Figures (a), (c), and (e) show the reflection phase spectra corresponding to different refractive indices at incident angles of 5°, 10°, and 15°, respectively. Figure 5 Figures (b), (d), and (f) show the distribution of the maximum phase shift as a function of refractive index and the linear fitting results at the corresponding angles, respectively. The insets in each figure represent the phase shift spectral lines at the corresponding angles. The calculated phase sensing sensitivities at incident angles of 5°, 10°, and 15° are as follows: , and This indicates that the structure maintains high sensitivity under oblique incidence conditions, and this sensitivity increases slightly with increasing angle.

[0054] While maintaining the total unit cell thickness, this invention differentiates the thicknesses of the HMM layer and Si layer in each period of PC1, randomly generating four samples with different fill rate fluctuation distributions. The refractive index sensing response is then calculated under perpendicular incidence conditions, and the results are as follows: Figure 6 As shown. Figure 6 Figures (a) and (b) correspond to sample 1, figures (c) and (d) correspond to sample 2, figures (e) and (f) correspond to sample 3, and figures (g) and (h) correspond to sample 4. The left column of subfigures shows the reflection phase spectra under different refractive index conditions, while the right column of subfigures shows the corresponding phase difference curves and linear fitting results. The specific layer thickness parameters for the four random samples are as follows:

[0055] The HMM layer thicknesses of the four periods in Sample 1 are 215.5 nm, 195.1 nm, 184.9 nm and 204.5 nm, respectively, and the corresponding Si layer thicknesses are 80.1 nm, 100.4 nm, 110.7 nm and 91.1 nm.

[0056] The HMM layer thicknesses of the four periods in Sample 2 are 211.1 nm, 200.1 nm, 183.9 nm and 204.5 nm, respectively, and the corresponding Si layer thicknesses are 84.4 nm, 95.4 nm, 111.7 nm and 91.0 nm.

[0057] The HMM layer thicknesses of the four periods in Sample 3 are 204.5 nm, 212.3 nm, 177.6 nm and 205.1 nm, respectively, and the corresponding Si layer thicknesses are 91.1 nm, 83.2 nm, 118.0 nm and 90.5 nm.

[0058] The HMM layer thicknesses of the four periods in Sample 4 are 197.4 nm, 214.2 nm, 184.7 nm and 203.3 nm, respectively, and the corresponding Si layer thicknesses are 98.1 nm, 81.36 nm, 110.8 nm and 92.27 nm.

[0059] observe Figure 6 As can be seen from the phase spectra in the left column, although there are significant differences in the layer thickness distribution of the four random samples, all samples exhibit clear phase evolution trajectories under different refractive indices. The phase sensing sensitivities of samples 1 to 4, obtained through linear fitting, are as follows: , , and This indicates that the structure can still achieve effective refractive index sensing even when the HMM layer filling rate is randomly perturbed.

[0060] The above results confirm that the heterostructure designed in this invention not only has a wide-angle robustness to changes in incident angle, but also has good stability to random fluctuations in the HMM layer filling rate that are difficult to control precisely during the preparation process, exhibiting dual robustness characteristics in both the angle dimension and the structural parameter dimension.

[0061] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A topological heterostructure, characterized in that: It includes a first photonic crystal region and a second photonic crystal region, which are adjacent to each other to form an interface; wherein the first photonic crystal region and / or the second photonic crystal region includes at least one structural unit formed by alternating stacking of HMM layers and dielectric layers, and the thicknesses of the HMM layers and the dielectric layers satisfy the following: the positive phase change provided by the anomalous dispersion of the HMM layers effectively compensates for the negative phase shift of the dielectric layers as the incident angle increases, thereby obtaining a stable omnidirectional dispersion-free bandgap over a wide incident angle range.

2. The topological heterostructure according to claim 1, characterized in that, The wide incident angle range is [0~80] degrees.

3. The topological heterostructure according to claim 1, characterized in that, The HMM layer is a multilayer structure formed by alternating stacking of metal and dielectric layers with subwavelength thicknesses, in order to achieve hyperbolic dispersion characteristics in the target operating band.

4. The topological heterostructure according to any one of claims 1 to 3, characterized in that, The first photonic crystal region and the second photonic crystal region are configured such that the topological heterostructure forms a topologically protected local interface state at the interface.

5. The topological heterostructure according to claim 4, characterized in that, The first photonic crystal region and the second photonic crystal region have opposite Zak phases to achieve the formation of topologically protected local interface states at the interface.

6. The topological heterostructure according to claim 4, characterized in that, The topological heterostructure satisfies the following: the local interface state has a phase singularity in the reflection spectrum, and the spectral position of the phase singularity is configured to drift with the change of the dielectric environment at the interface.

7. A sensing and detection method, characterized in that, Including the following steps: Introduce the material to be tested into the topological heterostructure as described in claim 6 to change the dielectric environment at the interface; The spectral position change of the phase singularity is detected to achieve the detection of the substance to be tested.

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