A substrate integrated topological waveguide based on chiral boundary states

Abstract

This invention provides a substrate-integrated topological waveguide based on chiral boundary states, comprising an upper metal thin film layer, a dielectric substrate F4B, a lower metal layer, and a microstrip transmission line. The two side interfaces of the substrate-integrated topological waveguide are respectively configured as type A and type B interfaces, with serrated boundaries. Waveguide channels 1 and 2 are respectively located at the junctions of the two side boundaries and the air, supporting the transmission of chiral boundary states. The chiral boundary states transmitted by waveguide channels 1 and 2 propagate in opposite directions at the same frequency. Several combined air holes are provided in the upper metal thin film layer, each consisting of three interconnected Y-shaped air holes. By introducing a microstrip transmission line with a tapered gradient and employing a triangular transition structure at the beginning of the waveguide channels, efficient coupling and conversion between traditional guided waves and chiral boundary waves are achieved, enabling low-loss and high-efficiency transmission of electromagnetic signals along the topological waveguide.

Description

Technical Field

[0001] This invention relates to the field of topological photonic crystal technology, and more particularly to a substrate-integrated topological waveguide based on chiral boundary states. Background Technology

[0002] Photonic topological insulators, a branch of photonic topological physics, have become a cutting-edge field in photonics and have recently attracted widespread attention. Due to the presence of various topologically protected boundary or surface states in photonic topological systems, these states exhibit immunity to backscattering and robustness to transmission from perturbations (e.g., defects and bends) at the interface. Therefore, research in topological photonics has revealed various promising applications, such as backscatter-immune waveguides, topological frequency division multiplexing, topological cross-channels, and large-area waveguide states.

[0003] In recent years, many topological phenomena have been extended from electronic systems to classical wave systems and realized in a controllable manner in photonic crystal (PhC) systems. Typically, in graphene-like PhCs, a nontrivial bandgap is formed by breaking the spatial inversion symmetry of the lattice, opening a pair of degenerate Dirac points. Boundary states in the bandgap appear at the interface (domain wall) between topological structures with opposite valley Chern numbers, exhibiting valley-locked and perturbation-resistant transport characteristics, and are called valley-knotted states (valley boundary states). Due to their topological protection, they can suppress inter-valley scattering, making valley photonic crystals promising for applications in on-chip communications, topological energy concentrators, and topological lasers. However, recent research has revealed a new class of topological chiral boundary states at the outer boundary of PhCs. By manipulating the boundary potential, the existence of topological chiral boundary states in PhCs has been demonstrated. Furthermore, the chiral boundary states are self-guided and do not depend on the cladding to prevent electromagnetic energy radiative leakage. Compared to valley knot states that depend on domain walls or internal boundaries, chiral boundary states appear at the outer boundaries of PhC, making it easier to realize robust and miniaturized topological electromagnetic devices.

[0004] Compared to previous topological valley photonic crystal (PhC) waveguides, substrate-integrated topological waveguides exhibit the advantage of compatibility with standard substrate-integrated waveguide circuits. Therefore, the proposal of substrate-integrated topological waveguides opens a new avenue for freely manipulating topological boundary states in substrate-integrated photonic circuits. However, current research on substrate-integrated topological waveguides requires the design of metal vias or metal pillar structures; during fabrication, when the dimensions are small, it is difficult to guarantee precision, leading to increased machining difficulty and manufacturing costs, which significantly limits the aforementioned applications. Furthermore, when studying the propagation of chiral boundary states, point sources are typically used as excitation sources, resulting in extremely low coupling efficiency and high losses from the source to the topological boundary states, leading to low overall transmission efficiency in topological PhC systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a substrate-integrated topological waveguide based on chiral boundary states, which has the advantages of high coupling efficiency, low loss, miniaturization, and ease of manufacturing.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] A substrate-integrated topological waveguide based on chiral boundary states includes an upper metal thin film layer, a dielectric substrate F4B, a lower metal layer, and a microstrip transmission line;

[0008] The substrate-integrated topological waveguide has two side interfaces configured as type A and type B interfaces, respectively. The boundaries of both type A and type B interfaces are serrated. Waveguide channels 1 and 2 are respectively located at the junctions of these boundaries and the air. Waveguide channels 1 and 2 support the propagation of chiral boundary states, and the chiral boundary states propagated by waveguide channels 1 and 2 have opposite propagation directions at the same frequency. A plurality of combined pores are provided on the upper metal thin film layer, each composed of three interconnected Y-shaped pores.

[0009] The present invention is further configured such that the three Y-shaped pores of the combined pores in the body domain are of the same size and adjacent Y-shaped pores are connected by air slits, and the Y-shaped pores in the combined pores near the boundary are of different sizes than the Y-shaped pores in the body domain.

[0010] The present invention is further configured such that: the length of the Y-shaped pores in the bulk domain is l = 1.5 mm and the width is w = 0.5 mm; the length of the Y-shaped pores of the A-type interface unit cell near waveguide channel 1 is l1 = 0.7 mm and the width is w1 = 0.9 mm; and the length of the Y-shaped pores of the B-type interface unit cell near waveguide channel 2 is l2 = 0.6 mm and the width is w2 = 0.9 mm.

[0011] The present invention is further configured such that the thickness of the dielectric substrate F4B is t = 1 mm and the dielectric constant is 2.65.

[0012] The present invention is further configured such that: the microstrip transmission line includes a tapered gradient section, the impedance of the microstrip transmission line is set to 50Ω, and a triangular transition structure is adopted at the beginning of waveguide channel 1 and waveguide channel 2.

[0013] The present invention is further configured such that the material of the upper metal thin film layer is copper.

[0014] The invention is further configured such that the Y-shaped pore has C3 symmetry, which disrupts the C3 symmetry in momentum space. 3v Symmetry opens up a pair of degenerate Dirac points that were originally located at the K and K' valleys, resulting in a photonic band gap in the band structure of the photonic crystal.

[0015] By analyzing the distribution characteristics of electromagnetic modes and energy flow in the topological waveguide structure, a tapered microstrip transmission line with an impedance of 50Ω was designed to match the impedance at the interface between the transmission line and the waveguide channel, smoothly transitioning the traditional guided wave mode to the chiral boundary state; achieving efficient conversion from the traditional guided wave mode to the topological mode. Furthermore, when there is a bend in the topological waveguide interface, the chiral boundary state can smoothly continue propagating forward through the bend, enabling smooth transitions between boundary states. That is, when an electromagnetic signal is input from port1 of the waveguide channel, the electromagnetic signal can be robustly transmitted to port2. Therefore, it exhibits low-loss and high-efficiency transmission characteristics in the face of both disturbed (different types of bend interfaces) and undisturbed (straight-through) topological waveguide interfaces.

[0016] The present invention has the following advantages:

[0017] 1. The novel structural design is compatible with standard printed circuit board (PCB) technology, allowing for easy integration with power supply networks and planar circuits. It is easy to manufacture, miniaturized, lightweight, and low-cost. This ensures the substrate-integrated waveguide structure possesses high efficiency, low loss, and reliable mechanical and electromagnetic performance.

[0018] 2. Since electromagnetic signals propagate at two different types of interfaces, they can be well confined at the interface of the topological waveguide. This topology reduces electromagnetic signal scattering into the photonic crystal, reduces electromagnetic mutual coupling and crosstalk during dual-channel transmission, and improves the transmission efficiency of the waveguide. There is no valley scattering, and efficient and robust transmission can be achieved for different types of bent interfaces.

[0019] 3. In communication systems, this substrate-integrated topological waveguide can be integrated with a variety of passive and active devices onto a single platform, enabling the self-guided transmission of electromagnetic signals along the PhC-air interface. It also has great application potential for exploring novel physical phenomena of topological chiral boundary states. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a substrate integrated topological waveguide based on chiral boundary states and its structural dimensions in an embodiment of the present invention;

[0021] Figure 2 This invention illustrates two types of boundaries composed of PhC and air, along with their projected energy bands. The shaded areas in the band structure represent bulk states, and the circular and square dotted lines within the band gap represent chiral boundary states generated by the upper boundary (Type A interface) and lower boundary (Type B interface) of PhC. The left and right panels respectively display structural schematics and energy flows (arrows indicate directions) of the Type B and Type A interfaces.

[0022] Figure 3This is a schematic diagram of the electric field intensity distribution and S-parameters in a topological electromagnetic waveguide at a frequency of 13 GHz in an embodiment of the present invention; Figure 3 (a) and 3(c) show the electric field E when an electromagnetic signal is input from port 1 along the type A interface of the topological electromagnetic waveguide. z Distribution and S-parameters. Figure 3 (b) and 3(d) show the electric field E when an electromagnetic signal is input from port 3 along the type B interface of the topological electromagnetic waveguide. z Distribution and S-parameters;

[0023] Figure 4 This describes the transmission characteristics of chiral boundary states in a bent interface containing type A and type B interfaces in an embodiment of the present invention. Figure 4 (a) shows a schematic diagram of a bent interface consisting of two types of boundaries, where the two types of transmission channels are represented by waveguide channel 1 and waveguide channel 2, respectively; Figure 4 (b) and 4(c) show the electric field intensity E during the smooth transition from waveguide channel 1 to waveguide channel 2 when an electromagnetic signal is input from port 1. z Distribution and S-parameters.

[0024] Figure 5 The transmission characteristics of the zigzag topological waveguide channel from the chiral boundary state to the valley knot state in this embodiment of the invention; Figure 5 (a) shows a schematic diagram of the Z-shaped topological waveguide channel, where the dashed line represents waveguide channel 2 that supports chiral boundary state transmission and the solid dotted line represents waveguide channel 3 that supports valley knot state transmission. Figure 5 (c) shows the dispersion curves for the corresponding Type A and Type B interfaces. Figure 5 (b) and 5(d) show the electric field intensity E of the chiral boundary state propagating from waveguide channel 2 to the valley knot state propagating in waveguide channel 3 when an electromagnetic signal is input from port 1. z Distribution and S-parameters.

[0025] Figure 6 This describes the transmission characteristics of the Z-shaped topological waveguide channel from the valley knot state to the chiral boundary state in an embodiment of the present invention. Figure 6 (a) shows a schematic diagram of the Z-shaped topological waveguide channel, where the solid line represents waveguide channel 1 that supports chiral boundary state propagation and the dotted line represents waveguide channel 3 that supports valley knot state propagation. Figure 6 (c) shows the dispersion curves for the corresponding Type A and Type B interfaces. Figure 6 (b) and 6(d) show the smooth transition of the valley knot state propagating from waveguide channel 3 to the electric field intensity E of the chiral boundary state propagating in waveguide channel 1 when an electromagnetic signal is input from port 1. z Distribution and S-parameters. Detailed Implementation

[0026] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] A substrate-integrated topological waveguide based on chiral boundary states, such as Figure 1 As shown, the structure includes a patterned copper overlay metal film (35 μm thick), a dielectric substrate F4B, a lower metal layer, and microstrip transmission lines. The F4B dielectric substrate has a thickness of t = 1 mm and a dielectric constant of 2.65. The pattern here consists of combined pores within the unit cells of the bulk domain. Specifically, the combined pores are three interconnected Y-shaped pores, with adjacent pores connected by air slits. The length of each Y-shaped pore is l = 1.5 mm, and the width is w = 0.5 mm. The Y-shaped pore pattern exhibits C3 symmetry, which disrupts the C3 symmetry in momentum space. 3v Symmetry causes the pair of degenerate Dirac points at the K and K' valleys to be opened, resulting in a photonic bandgap in the band structure of the photonic crystal. Chiral boundary states are propagated by altering the boundary potential in the substrate-integrated topological waveguide. This boundary potential can be controlled by changing the structural dimensions of the boundary unit cells. The chiral boundary states are primarily located at the PhC-air interface, and their field decays rapidly in the bulk domain. Four unit cells in the bulk domain are sufficient to represent the photonic bandgap characteristics.

[0028] The substrate-integrated topological waveguide has two interfaces, designated as type A and type B, respectively. Both interfaces have serrated boundaries. Waveguide channels 1 and 2 are located at the junctions of these interfaces and the air, supporting the propagation of chiral boundary states. The chiral boundary states propagated in opposite directions at the same frequency. Feed and transition structures connect to both sides of waveguide channels 1 and 2, located at the beginning of the topological waveguide structure. The input source is fed by a microstrip line with a characteristic impedance of 50Ω, and a tapered transition structure is used to connect and convert between the microstrip mode and the chiral boundary state. The dimensions of the microstrip transmission line are W0 = 2.7 mm, w3 = 0.775 mm, W4 = 6.2 mm, and L3 = 13.8 mm. The length of the Y-shaped vent near waveguide channel 1 in the type A interface unit cell is l1 = 0.7 mm, and the width is w1 = 0.9 mm. The length of the Y-shaped vent near waveguide channel 2 in the type B interface unit cell is l2 = 0.6 mm, and the width is w2 = 0.9 mm. The unit cells are arranged in a triangular lattice to form a substrate-integrated topological waveguide without metal vias in the dielectric, with a lattice constant a = 13 mm. The coupling effect between the traditional guided wave modes and chiral boundary states is utilized to achieve low-loss and high-efficiency chiral boundary states. The entire waveguide structure is fabricated using PCB printing and laser cutting technologies, making the manufacturing process convenient and easy. It meets impedance matching requirements and features low loss, miniaturization, and easy integration.

[0029] By analyzing the properties of chiral boundary states at type A and type B interfaces within the band gap, it was found that the frequency range of these boundary states can be tuned by controlling the structural dimensions of the unit cells on either side. Therefore, by controlling the frequency range of the boundary states at either type A or type B interfaces, the propagation path and frequency range of these boundary states can be controlled. Figure 5 In this study, the propagation of the B-type boundary state is achieved by reducing the frequency range of the A-type interface boundary states. The dimensions of the unit cells for both the A-type and B-type interfaces are l1 = 1.25 mm and l2 = 0.6 mm, respectively. Figure 6 In this study, the propagation of type A boundary states is achieved by reducing the frequency range of type B interface boundary states. At this time, the unit cell sizes of type A and type B interfaces are l1 = 0.7 mm and l2 = 1.2 mm. By analyzing the energy flow of type A and type B interfaces, it is found that topological modes at the same frequency have opposite propagation characteristics, and chiral boundary states propagate robustly in serrated interfaces. By changing the upper and lower positions of type A and type B interfaces and creating internal domain walls in the bulk domain, a smooth transition between chiral boundary states and valley knot states can be achieved.

[0030] Figure 2 This diagram illustrates the chiral boundary states at the A-type and B-type interfaces. Using y=0 as the boundary reference, two unit cells are taken along the ±y (upper and lower) directions. The A-type and B-type interface unit cells are placed together, and the projection energy bands along the x-direction of the zigzag interface formed by the A-type and B-type interface unit cells and air are calculated using supercell methods to determine the chiral boundary states. The shaded areas represent volume bands, and the dotted circular and directional lines represent the band structures for transmitting chiral boundary states at the A-type and B-type interfaces, respectively. To more vividly characterize the chiral boundary states at the A-type and B-type interfaces, the left and right panels show schematic diagrams of the supercells for both interfaces and the energy flux distribution at corresponding frequencies (upright and inverted triangles), respectively. The arrows indicate the Poynting power flux direction, with the field mainly concentrated in the zigzag interface in contact with air and attenuating into the volume domain. In the boundary state dispersion relation, it can be seen that the group velocities of the chiral boundary states at the same frequency within the band gap at the A-type and B-type interfaces exhibit opposite chiral characteristics.

[0031] To visually illustrate the transmission characteristics of electromagnetic signals, the S-parameter curves of the proposed substrate-integrated topological waveguide and the electric field strength E when the electromagnetic signal is input along different ports were numerically simulated using the commercial software CST Microwave Studio. z distributed, Figures 3 to 6The working principle and transmission characteristics are illustrated more clearly, with arrows indicating the directions of electromagnetic signal input and output. The two terminals of the microstrip structure with tapered transition sections constitute two ports, port1 and port2. This section focuses on the propagation of chiral boundary states at type A and type B interfaces.

[0032] Figure 3 The electric field intensity E of the entire waveguide is shown when electromagnetic waves are input from port1 and port3, respectively. z The distribution and S-parameter variations were analyzed. By examining the electromagnetic field distribution and polarization characteristics within the waveguide channel, and combining this with the field distribution of the tapered transmission line, the location of the boundary feed point was determined. A triangular transition structure was adopted at the beginning of the waveguide channel (gradually filling some Y-shaped vents, such as...). Figure 1 As shown, a smooth transition of electromagnetic modes is achieved. Figure 3 (a) and 3(b) show the electric field intensity E throughout the waveguide. z The electromagnetic energy is tightly confined to the sawtooth boundaries of the type A and type B interfaces in contact with air. Electromagnetic signals input from ports 1 and 3, after a tapered transition, effectively transition the guided wave mode to the chiral boundary state, and most of the electromagnetic signal propagates well along the interfaces to ports 2 and 4; Figure 3 As can be seen from the S-parameter curves in (c) and 3(d), the propagation of chiral boundary states and the analysis of dispersion curves in the bandgap are in good agreement within the frequency range corresponding to each boundary state in the bandgap. Figure 3 Transmission coefficient S in (c) 21 Slightly lower Figure 3 Transmission coefficient S in (d) 34 This is mainly due to the differences in mode profiles and wave vectors between the transmission line modes and the chiral boundary states of the type A interface. However, the entire substrate-integrated topological waveguide still exhibits excellent characteristics of low insertion loss and high-efficiency transmission.

[0033] The most significant characteristic of topological waveguides is their immunity to defects and insensitivity to disturbances. To verify the immunity of the proposed substrate-integrated topological waveguide to structural disturbances, in... Figure 4-6 We introduce three different types of bent interfaces. The first involves introducing waveguide channels of two structural types, A and B, into the topological waveguide interface to achieve the conversion between two types of chiral boundary states. The second involves a bent channel with a 120° turn in the topological waveguide interface to achieve a smooth transition between chiral boundary states and valley knot states. The third involves transforming the topological waveguide interface into a Z-shaped channel with a 60° turn to achieve a smooth transition between valley knot states and chiral boundary states. As can be seen from the figure, the chiral boundary states propagating in the topological waveguide can smoothly continue to propagate forward through different types of bent interfaces.

[0034] Figure 4 (a) shows the first waveguide channel consisting of a type A interface and a type B interface, which consists of three boundary surfaces and bends of 120° and 60°. Figure 4 (b) and 4(c) show the electric field intensity E propagating along the bent interface in the chiral boundary state waveguide channel. z Distribution and S-parameters. It can be seen that the electromagnetic signal input from port1, under the condition of uniform distribution at the external boundary, can smoothly pass through the bend, achieving effective conversion between the two types of chiral boundary states; the transmission curve is similar to that previously... Figure 3 The transmission curves in (c) when inputting from port1 are almost identical, revealing a key feature of the topological chiral boundary state.

[0035] Figure 5 (a) shows a second type of waveguide channel 2 and waveguide channel 3, which are composed of a type B interface and a domain wall between two domains with topological non-trivial properties. The two channels have a 120° bend, and the upper and lower boundary surfaces of the waveguide are composed of type A (solid box) and type B (dashed box) interfaces. Figure 5 (c) shows the dispersion curves of the type A and type B interfaces. For the type A interface, the dispersion curve corresponds to a very narrow frequency range that is close to the bulk band. However, for the type B interface, the dispersion curve spans the entire band gap. Therefore, the chiral boundary states propagating along the type B interface exhibit forbidden behavior at the type A interface. Figure 5 (b) Shows the electric field strength E at 14 GHz (inverted triangle) when the electromagnetic signal is input from port1. z Distribution. It can be seen that almost no energy is coupled to the type A interface, but is transmitted to port 2 along waveguide channel 3 and waveguide channel 2. No scattering occurs at the interface bend, achieving a smooth transition between the chiral boundary state and the valley knot state. Figure 5 (d) shows the S-parameter transmission curve, whose transmission range is... Figure 5 The dispersion characteristics are consistent with those in (b).

[0036] Figure 6 (a) illustrates a third type of waveguide channel 3 and waveguide channel 1, consisting of an internal boundary (domain wall) between two domains with topological nontrivial properties and an A-type interface. Both channels have a 60° bend, and the lower boundary surface of the waveguide is composed of A (solid box) and B (dashed box) type interfaces. A smooth transition between valley knot states and chiral boundary states is achieved. Figure 6(c) Dispersion curves for the type A and type B interfaces are shown. For the type B interface, the dispersion curve is divided into upper and lower portions. The lower portion is located in a narrow frequency range close to the bulk band; the upper portion is located between 13.6 and 14.5 GHz. However, for the type A interface, the dispersion curve is located between 12.8 and 14.1 GHz. Therefore, for the frequency range of 12.8–13.6 GHz, the chiral boundary states propagating along the type A interface exhibit forbidden behavior at the type B interface. Figure 6 (b) shows the electric field strength E at 13.5 GHz (equilateral triangle) when the electromagnetic signal is input from port1. z Distribution. It can be seen that almost no energy is coupled to the B-type interface, but is transmitted to port 2 along waveguide channel 3 and waveguide channel 1, realizing a smooth transition from valley knot state to chiral boundary state. Figure 6 (d) shows the S-parameter transmission curves, whose transmission frequency range is... Figure 6 The dispersion characteristics are consistent with those in (b).

[0037] It can be seen that the transmission characteristics under the three different conditions are... Figure 1 Compared to the unperturbed (straight-through) state, there was no significant change, revealing the inherent robustness of topological chiral boundary states to bent interfaces. Therefore, electromagnetic signals input from the port can be designed to achieve different types of chiral boundary states and the conversion and transition between chiral boundary states and valley knot states, enabling most electromagnetic signals to be output from the designated port; even with perturbed electromagnetic signals, low-loss and high-efficiency transmission can be achieved in the topological waveguide.

[0038] This invention proposes a substrate-integrated topological waveguide based on chiral boundary states. Through precise control of the boundary potential, robust chiral boundary states with external sawtooth boundaries are achieved in a substrate-integrated PhC. By adjusting the boundary structure, the group velocity and frequency range of the chiral boundary states can be flexibly controlled. A microstrip transmission line with a tapered gradient structure is used as the initial feed line to reduce the return loss of the chiral boundary states in the waveguide channel, improving transmission efficiency and making it closer to the integration characteristics in practical applications. Simulated electric fields and S-parameters demonstrate the transmission characteristics of the chiral boundary states, robust transmission through bent interfaces, and a smooth transition between the chiral boundary states and valley knot states. This self-guided chiral boundary state does not rely on internal boundaries or cladding to prevent energy radiation and is more compact than electromagnetic devices based on valley knot states. The proposed substrate-integrated topological waveguide based on chiral boundary states has significant application prospects in millimeter-wave, terahertz, and optical bands, including passive, active, or other planar devices such as robust delay lines, on-chip communication, and topological lasers. Through practical examples, the proposed substrate-integrated topological waveguide exhibits excellent transmission characteristics under different perturbations (bending) when electromagnetic signals are input from different ports. This demonstrates that the proposed structure possesses features such as no backscattering, robustness to perturbations, high transmission efficiency, and low loss. Furthermore, compared to previous valley topological waveguides, the proposed chiral boundary state-based topological waveguide not only demonstrates higher transmission efficiency but also exhibits subwavelength thickness, ease of design, and excellent self-consistent electrical shielding, perfectly compatible with traditional substrate-integrated waveguide circuits. This design provides the possibility of fabricating and integrating complete topological waveguide circuits on the same substrate using standard printed circuit board technology. It also offers a cost-effective, miniaturized, lightweight, and easily integrated design option.

[0039] 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 technical solutions 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 substrate-integrated topological waveguide based on chiral boundary states, characterized in that: It includes an upper metal thin film layer, a dielectric substrate F4B, a lower metal layer, and a microstrip transmission line; The two sides of the substrate integrated topological waveguide are respectively set as type A interface and type B interface, and the boundaries of the type A interface and type B interface are both set as sawtooth. The junctions between the two boundaries and the air are respectively set as waveguide channel 1 and waveguide channel 2. Waveguide channel 1 and waveguide channel 2 are used to support the transmission of chiral boundary states. The chiral boundary states transmitted by waveguide channel 1 and waveguide channel 2 have opposite propagation directions at the same frequency. A number of combined air holes are provided on the upper metal thin film layer. The combined air holes are formed by three Y-shaped air holes connected to each other.

2. The substrate integrated topological waveguide based on chiral boundary states as described in claim 1, characterized in that: The three Y-shaped pores in the combined pores in the body are the same size and adjacent Y-shaped pores are connected by air slits. The Y-shaped pores in the combined pores near the boundary are different in size from the Y-shaped pores in the body.

3. A substrate integrated topological waveguide based on chiral boundary states as described in claim 2, characterized in that: The length of the Y-shaped pores in the bulk domain unit cell is l=1.5mm and the width is w=0.5mm; the length of the Y-shaped pores near waveguide channel 1 in the A-type interface unit cell is l1=0.7mm and the width is w1=0.9mm, and the length of the Y-shaped pores near waveguide channel 2 in the B-type interface unit cell is l2=0.6mm and the width is w2=0.9mm.

4. A substrate integrated topological waveguide based on chiral boundary states as described in claim 3, characterized in that: The dielectric substrate F4B has a thickness of t=1mm and a dielectric constant of 2.

65.

5. A substrate integrated topological waveguide based on chiral boundary states as described in claim 4, characterized in that: The microstrip transmission line includes a tapered transition section, and the impedance of the microstrip transmission line is set to 50Ω. A triangular transition structure is adopted at the beginning of waveguide channel 1 and waveguide channel 2.

6. A substrate integrated topological waveguide based on chiral boundary states as described in claim 5, characterized in that: The material of the upper metal thin film layer is copper.

7. A substrate integrated topological waveguide based on chiral boundary states as described in claim 6, characterized in that: The Y-shaped pores exhibit C3 symmetry, which disrupts the C3 symmetry in momentum space. 3v Symmetry opens up a pair of degenerate Dirac points that were originally located at the K and K' valleys, resulting in a photonic band gap in the band structure of the photonic crystal.

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