Topological valley photonic crystal, broadband topological slow light waveguide and topological beam splitter

Abstract

The present invention relates to the technical field of topological photonic crystals, and particularly relates to a topological valley photonic crystal, a broadband topological slow optical waveguide, and a topological beam splitter. The crystal includes a substrate and a nano-pillar array disposed on the substrate; the nano-pillar array is composed of a plurality of honeycomb-structured unit cells arranged, and the two-dimensional cross-section of each unit cell is a regular hexagon; the unit cell is composed of two types of nano-pillars with different cross-sectional diameters arranged at intervals; two adjacent unit cells share a common edge; the two types of nano-pillars with different cross-sectional diameters are respectively a first nano-pillar and a second nano-pillar, and the diameter of the first nano-pillar is twice that of the second nano-pillar; the lattice constant a has a value range of 480 to 520 nm. The advantages are as follows: solving the problem of broadband slow light regulation in topological optical waveguides; realizing the Brillouin zone winding of the valley boundary state mode, reducing the group velocity of the optical mode; improving the robustness of optical transmission; reducing the backscattering loss caused by manufacturing defects and disorder; and broadening the applicable frequency range of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of topological photonic crystals, and in particular to a topological valley photonic crystal, a broadband topological slow light waveguide, and a topological beam splitter. Background Art

[0002] Slow light technology enhances the interaction between light and matter by reducing the propagation speed of light. In recent years, on-chip devices based on slow light waveguides have been widely used in the fields of biochemical sensing, optical modulation, optical storage, optical communication, nonlinear optics, etc. Periodic optical resonator arrays and photonic crystal waveguides are two of the most commonly used integrated slow light waveguide structures, which have the advantages of flexible design, high group refractive index, and compatibility with silicon-based integration processes. However, due to the limitations of micro-nano optical fabrication processes, when the group refractive index of slow light devices exceeds 30, the transmission loss is as high as 100 dB / cm, resulting in the inability of slow light devices to be practically applied.

[0003] Slow light devices increase the interaction time between light and matter by reducing the group velocity of light, thereby significantly enhancing the intensity of nonlinear effects and other optical phenomena. This is particularly crucial for applications such as optical amplifiers, sensors, and quantum optics. However, traditional slow light technology still has the following disadvantages: (1) Sensitivity to manufacturing defects and disorder. Traditional slow light devices are easily affected by inevitable defects during the manufacturing process, prone to unexpected backscattering effects, and even lead to Anderson localization. This phenomenon greatly reduces the light propagation efficiency and device performance. (2) The trade-off between bandwidth and group velocity. Traditional slow light devices usually accompany a significant reduction in bandwidth while achieving a low group velocity, which limits their broadband performance in practical applications. (3) Limitations in materials and frequency ranges: Some broadband topological slow light schemes rely on strategies that break time-reversal symmetry, but this requires the use of magneto-optical materials, and the performance of magneto-optical materials is extremely poor in the visible and near-infrared frequency bands, making it difficult to meet the application requirements of integrated photonics. In summary, traditional slow light devices still suffer from problems of sensitivity to manufacturing defects and limited bandwidth.

[0004] With the development of on-chip micro-nano fabrication technology, photonic devices based on photonic crystals are getting smaller and smaller. Uncontrollable factors such as misalignment and defects during the fabrication process can cause significant scattering losses, which greatly reduce the light propagation efficiency and device performance. Topological photonics is a new method to solve the above scattering loss problem and can achieve robust light transmission. Different from traditional slow light devices, topological slow light devices utilize topologically non-trivial edge states, enabling light to have strong robustness against structural defects, scattering, and fabrication errors during waveguide propagation. Therefore, topological photonic crystal waveguides can break through the bottleneck of the transmission length of slow light integrated devices. Topological photonic crystal waveguides are mainly realized by breaking time and space inversion symmetries. Magneto-optical photonic crystals break time inversion symmetry and achieve slow light properties through one-way transmission edge states in non-trivial topological bandgaps. However, the lack of magnetic materials in the optical band restricts the application of this structure in the field of broadband slow light. To overcome these problems, researchers propose to achieve broadband topological slow light under the condition of breaking space inversion symmetry and realize topologically protected one-way light transmission. At the same time, through the Brillouin zone winding mechanism of the energy band structure, effective bandwidth expansion and slow light transmission can be achieved based on topological photonic crystal waveguides. In addition, the above topological slow light mechanism also has extremely small group velocity dispersion properties, which can effectively suppress pulse broadening. In summary, combining topological photonic crystals with broken space inversion symmetry and dispersion engineering of the Brillouin zone winding is the most promising broadband slow light solution at present.

[0005] At present, although the Brillouin zone winding strategy based on topological valley photonic crystals can reduce the group velocity, due to the breaking of the bulk symmetry at the topological boundary, it leads to the discontinuity of the dispersion curve of the mode and the generation of a small bandgap, and true broadband continuous slow light transmission cannot be achieved. Therefore, introducing topological photonics into slow light applications and simultaneously breaking space inversion symmetry, through the dispersion engineering of the Brillouin zone winding, can not only achieve robust light transmission but also achieve the purpose of reducing the group velocity and expanding the bandwidth. Summary of the Invention

[0006] To solve the above problems, the present invention provides a topological valley photonic crystal, a broadband topological slow light waveguide, and a topological beam splitter.

[0007] The first object of the present invention is to provide a topological valley photonic crystal, comprising: a substrate, and a nano-column array disposed on the substrate; the nano-column array is composed of a plurality of unit cells arranged in a honeycomb structure, and the two-dimensional cross-section of each unit cell is a regular hexagon; the unit cell is composed of two types of nano-columns with different cross-sectional diameters arranged at intervals; two adjacent unit cells share a common edge;

[0008] The two types of nano-columns with different cross-sectional diameters are respectively a first nano-column and a second nano-column, and the diameter of the first nano-column is twice that of the second nano-column;

[0009] Lattice constant a has a value range of 480 - 520 nm.

[0010] Preferably, the lattice constant a = 500 nm.

[0011] Preferably, the material of the nanocolumns is dielectric material silicon, and the relative dielectric constant is 12; the diameter of the first nanocolumn is 0.4 a , and the diameter of the second nanocolumn is 0.2 a .

[0012] The second object of the present invention is to provide a broadband topological slow light waveguide, including: an original waveguide region, and topological valley photonic crystals arranged on both sides of the original waveguide region;

[0013] The original waveguide region includes two rows of silicon column groups with the same structure. Each silicon column group is composed of five silicon columns with gradually decreasing cross-sectional diameters. The silicon column with the largest cross-sectional diameter is the same as the diameter of the first nanocolumn.

[0014] Preferably, the diameter sizes of the five silicon columns with gradually decreasing cross-sectional diameters are d1 = 0.4 a , d2 = 0.39 a , d3 = 0.38 a , d4 = 0.37 a , d5 = 0.36 a .

[0015] Preferably, the broadband topological slow light waveguide is a straight waveguide, a defect waveguide or a Z-shaped bent waveguide.

[0016] The third object of the present invention is to provide a topological beam splitter, including: N groups of periodically arranged broadband topological slow light waveguides and M groups of periodically arranged complementary structure waveguides. The last complementary structure waveguide is connected to the first broadband topological slow light waveguide;

[0017] The complementary structure waveguide includes a complementary waveguide region and topological valley photonic crystals arranged on both sides of the complementary waveguide region;

[0018] Both M and N are natural numbers greater than or equal to 6.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] The present invention provides a two-dimensional topological valley photonic crystal, a broadband topological slow light waveguide structure and a topological beam splitter based on the topological valley photonic crystal, which solve the problem of regulating broadband slow light in topological optical waveguides. By optimizing the unit structure size at the domain wall position, the Brillouin zone winding of the valley boundary state mode is realized, thereby greatly reducing the group velocity of the optical mode. In order to solve the problems of limited frequency range of magneto-optical topological photonic crystals, discontinuous frequency bands in topological valley photonic crystals, and slow light modes restricted by small bandgaps in the prior art, the present invention proposes a novel topological broadband slow light waveguide structure based on two frequency-complementary topological valley photonic crystal waveguides. Further, by combining two frequency-complementary waveguide structures, the limitation of the small bandgap on continuous slow light transmission is eliminated, and a continuous broadband slow light waveguide structure is formed. In addition, the present invention also designs a frequency-selective beam splitter based on valley-contrast unidirectional slow light propagation. By adjusting the phase difference of the electric dipole excitation source, the controllable selective output of optical signals at different ports is realized, thereby realizing highly directional frequency-selective beam splitting. Description of the Drawings

[0021] Figure 1 It is a schematic cross-sectional view of a topological valley photonic crystal provided according to an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the structure of a topological valley photonic crystal and the energy band structure of the boundary mode provided according to an embodiment of the present invention; in the figure, (a) is a schematic diagram of the topological valley photonic crystal structure design; (b) is the energy band structure of the topological valley photonic crystal; (c) is a schematic diagram of the zigzag boundary structure formed by the topological valley photonic crystal; (d) is the energy band structure of the topological valley photonic crystal boundary mode; (e) is the group refractive index distribution of the topological valley photonic crystal boundary mode.

[0023] Figure 3 It is a schematic cross-sectional view of a broadband topological slow light waveguide provided according to an embodiment of the present invention.

[0024] Figure 4 It is the projected energy band structure, group refractive index distribution of the broadband topological slow light waveguide provided according to an embodiment of the present invention and the electric field distribution diagram of the eigenmode at ; in the figure, (a) is the projected energy band structure; (b) is the group refractive index distribution diagram; (c) is the electric field distribution of the eigenmode at.

[0025] Figure 5It is the robustness analysis result of the broadband topological slow light waveguide provided by the embodiments of the present invention; in the figure, (a) is the transmission spectra of three different types of waveguides (linear, defect, and Z-shaped bend). (b) is the electric field distribution of the transmission mode of the linear waveguide; (c) is the schematic structural diagram of the defect waveguide and the electric field distribution of the transmission mode; (d) is the electric field distribution of the transmission mode of the Z-shaped bend waveguide.

[0026] Figure 6 It is a schematic cross-sectional view of the overall structure of a topological beam splitter provided by the embodiments of the present invention.

[0027] Figure 7 It is the structural diagram, energy band structure, directivity distribution under a point dipole excitation source, and electric field distribution diagram of the topological beam splitter provided by the embodiments of the present invention; in the figure, (a) is the schematic design diagram of the topological beam splitter structure; (b) is the energy band structures of the broadband topological slow light waveguide and the complementary structure waveguide in the topological beam splitter; (c) is the directivity distribution diagram under magnetic dipole excitation sources with different phase differences; (d) is the electric field distribution diagram of the waveguide mode with the phase difference of the switched point dipole.

[0028] Reference numerals:

[0029] 1. Topological valley photonic crystal;

[0030] 11. First nanorod;

[0031] 12. Second nanorod;

[0032] 2. Original waveguide region;

[0033] 3. Complementary waveguide region. Detailed implementation manners

[0034] In the following, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0036] The present invention provides a topological valley photonic crystal, including: a substrate, and a nanorod array disposed on the substrate; the nanorod array is composed of the arrangement of multiple unit cells with a honeycomb structure, the two-dimensional cross-section of each unit cell is a regular hexagon, and is composed of two types of nanorods with different cross-sectional diameters arranged at intervals; two adjacent unit cells share a common edge;

[0037] Lattice constanta The value range of a is 480 - 520 nm; in a specific embodiment, the lattice constant

[0038] The nanocolumn material is dielectric material silicon with a relative dielectric constant of 12; the substrate material is silicon;

[0039] The silicon nanocolumn array is formed by deposition or etching.

[0040] See Figure 1 , the two nanocolumns with different cross-sectional diameters are the first nanocolumn 11 and the second nanocolumn 12 respectively, and the diameter of the first nanocolumn 11 is twice that of the second nanocolumn 12; in a specific embodiment, the diameter of the first nanocolumn 11 is 0.4 a , and the diameter of the second nanocolumn 12 is 0.2 a ; The spatial inversion symmetry is broken by two silicon nanocolumns with different diameters, thereby opening the topological band gap.

[0041] See Figure 2 , Figure 2 In (a) of

[0042] The transverse magnetic mode (TM, that is, the magnetic field is distributed in the plane and the electric field is distributed outside the plane) energy band structure of the topological valley photonic crystal is shown in (b) of the appendix Figure 2 . The shaded area is the topological band gap, located between the first and second energy bands, and the topological Chern number of the band gap is 0. The solid line and the dashed line are the situations before and after breaking the spatial inversion symmetry respectively. Among them, the phase distribution diagram shows that there are singular points of phase vortices at the K and K' valleys, with topological charges of ±1. The topological photonic crystal is composed of two valley photonic crystals with ∆d = 0.2 a and ∆d = -0.2 a stitched together to form a zigzag boundary, and the projected energy band structure can obtain the topological boundary mode. The wavelength range of the valley boundary mode is from 1690.88 nm to 1823.56 nm, and the relative bandwidth of the band gap is 21.75%. To illustrate the slow light characteristics of the valley boundary mode, the group refractive index n g is calculated. At positions such as k = 0, π / a , 2π / a , the maximum group refractive index of 3000 can be achieved, as shown in (d) of the appendix Figure 2 .

[0043] Brief principle: The topological valley photonic crystal consists of periodically arranged silicon nanocolumns with a honeycomb structure. By breaking the spatial inversion symmetry, a valley photonic crystal with a complete topological bandgap is realized. According to the bulk-edge correspondence in topological theory, the boundary formed by two photonic crystals with opposite topological valley Chern numbers supports topological boundary states, which can turn at large angles and maintain anti-scattering transmission.

[0044] Based on the above topological valley photonic crystal, the present invention provides a broadband topological slow light waveguide, comprising: an original waveguide region, and topological valley photonic crystals arranged on both sides of the original waveguide region;

[0045] The original waveguide region includes two rows of silicon column groups with the same structure. Each silicon column group consists of five silicon columns with gradually decreasing cross-sectional diameters. The silicon column with the largest cross-sectional diameter is the same as the diameter of the first nanocolumn;

[0046] In a specific embodiment, the diameter sizes of the five silicon columns with gradually decreasing cross-sectional diameters are d1 = 0.4 a 、d2 = 0.39 a 、d3 = 0.38 a 、d4 = 0.37 a 、d5 = 0.36 a .

[0047] See Figure 3 , the broadband topological slow light waveguide of the present invention includes: an original waveguide region 2, and topological valley photonic crystals 1 arranged on both sides of the original waveguide region 2; the slow light bandwidth of the mode is expanded by realizing the periodic continuous change of the silicon column diameter at the domain wall. The diameters (decreasing in sequence) of the silicon columns at the boundary are d1, d2, d3, d4, d5, and the sizes are d1 = 0.4 a 、d2 = 0.39 a 、d3 = 0.38 a 、d4 = 0.37 a 、d5 = 0.36 a , repeating periodically in groups of five, and the new Brillouin zone formed is 1 / 5 of the original, that is, 2π / 5 a . Adjust the size of the diameter change at the boundary so that the bandwidth of the topological boundary mode matches the topological bandgap, realizing the winding of the topological boundary mode in the folded Brillouin zone. The winding times are equal to the number of silicon columns with different diameters. The group refractive index of the slow light mode is increased by 2 - 3 orders of magnitude, and at the same time, the bandwidth is expanded to 31.7% relative to the bandgap, as shown in the appendix Figure 4As shown in Figs. (a) - (b). However, when \(k = 0,\frac{\pi}{\Lambda},\frac{2\pi}{\Lambda}\), four tiny bandgaps will be generated due to the coupling between modes. It should be noted that the number of resonators within a period can continue to increase so that the slow - light bandwidth covers the entire topological bandgap. Although the discontinuous band structure will limit some slow - light applications, introducing nanocolumns with a size gradient change can further reduce the group velocity. To understand the relationship between the nanocolumn size and the near - flat - band frequency, by analyzing the distribution of the eigenmodes corresponding to each frequency band, it is observed that the enhanced electric field occurs at the position with a large nanodiameter in the low - frequency case, and the enhanced electric field occurs at the position with a small nanodiameter in the high - frequency case, as shown in Fig. (c). Figure 4 in Fig. (c).

[0048] Construct three different types of waveguides (linear, defect, and Z - shaped bend), and simulate their transmission spectra. The numerical simulation results are as shown in Fig. Figure 5 . The results show that the broadband topological slow - light waveguide has the property of anti - scattering transmission and is robust to linear waveguides, defect waveguides, and Z - shaped bend waveguides.

[0049] Principle summary: The broadband topological slow - light waveguide mode is realized through the dispersion engineering of Brillouin zone winding, that is, an array with a uniform change in the diameter of silicon nanocolumns with topological domain walls is used to effectively reduce the group velocity of the waveguide mode. The extended frequency range expands with the increase in the number of silicon column arrays with different diameters at the topological boundary, thus realizing a broadband topological slow - light waveguide. However, this broadband expansion method will open tiny bandgaps at the Brillouin zone boundary positions. To solve the problem of tiny bandgaps, the lattice constant is kept unchanged, and the diameter of the silicon nanocolumns at the topological boundary is optimized to match the band structure of the complementary structure with the tiny bandgaps, thereby realizing a continuous broadband slow - light waveguide.

[0050] The present invention also provides a frequency - selective topological beam splitter, including: N groups of periodically arranged broadband topological slow - light waveguides and M groups of periodically arranged complementary - structure waveguides, with the last complementary - structure waveguide connected to the first broadband topological slow - light waveguide; both M and N are natural numbers greater than or equal to 6; the complementary - structure waveguide includes a complementary waveguide region and topological valley photonic crystals arranged on both sides of the complementary waveguide region;

[0051] See Figure 6 , the complementary waveguide region 3 includes two rows of silicon column groups with the same structure. Each silicon column group consists of four silicon columns with a perturbed cross - sectional diameter. The diameter sizes of the four silicon columns with a perturbed cross - sectional diameter are \(d1 = 0.373\) a , \(d2 = 0.374\) a , \(d3 = 0.38\) a , \(d4 = 0.383\) a .

[0052] To solve the problem of the tiny bandgap, a complementary structure waveguide is introduced, whose energy band structure matches the tiny bandgap, thus realizing continuous broadband topological slow light. The design of the overall structure is shown in the appendix Figure 6 As shown, the dotted line divides the structure into two parts, 3 groups of broadband topological slow light waveguides and 3 groups of complementary structure waveguides. The design idea of the complementary structure waveguide is to fix the lattice constant of the topological photonic lattice. The number of silicon pillars with size perturbation in the complementary waveguide region is the same as the number of bandgaps in the original waveguide region of the broadband topological slow light waveguide. Only by adjusting the diameter of the nanocolumns at the domain walls can the complementarity of the energy band structure frequencies be achieved. The diameters of the silicon pillars in the complementary structure are 0.373 a , 0.374 a , 0.38 a and 0.383 a .

[0053] To realize the function of a frequency-selective topological beam splitter, a pair of point dipole excitation sources with a phase difference of ±π / 2 and a distance of a are used. When switching the phase difference between π / 2 or -π / 2, directional output at the left and right ports can be achieved. When the directionality parameter = -1, the light corresponding to the frequency of the tiny bandgap of the initial structure is reflected into the complementary structure waveguide; in the above formula, P L represents the total energy output at port 2, P R represents the total energy output at port 1. For the overlapping frequency range of the two structures, by adjusting the phase difference of the point dipole excitation source, selective output at the left and right ports can be achieved, as shown in (a) - (d) of the appendix Figure 7 . Figure 7 In (b), the solid line is the energy band structure of the broadband topological slow light waveguide, and the dotted line is the energy band structure of the complementary structure waveguide; Figure 7 In (c), it is the directional distribution under point dipole excitation sources with different phase differences; Figure 7 In (d), it is the electric field distribution diagram of the waveguide mode when switching the phase difference of the point dipole ( ).

[0054] Principle brief: To realize a frequency-selective beam splitter, mainly by splicing two broadband topological slow light waveguides with complementary energy band structures and complementary structure waveguides, continuous broadband slow light can be realized. At the same time, at the position where the difference in the splicing boundary is a distance of a , two point dipoles with phase differences of -π / 2 and π / 2 are placed respectively. By switching the phase difference of the point dipoles, selective output at the frequency ports can be achieved, thus realizing the function of a frequency-selective beam splitter.

[0055] The present invention aims at the drawbacks of the prior art and provides a two-dimensional topological valley photonic crystal, a broadband topological slow light waveguide structure and a topological beam splitter based on the topological valley photonic crystal, and a method for their applications. First, broadband continuous topological slow light transmission is achieved. Through dispersion engineering of Brillouin zone winding, a broadband topological slow light waveguide mode is realized, that is, an array with a uniform change in the diameter of silicon nanocolumns at the topological boundary is used to effectively reduce the group velocity of the waveguide mode. The extended frequency range expands with the increase in the number of silicon column arrays with different diameters at the topological boundary, thereby realizing a broadband topological slow light waveguide. However, due to the broken symmetry at the topological boundary, discontinuity of mode dispersion and the generation of a small bandgap are caused. To solve the problem of the tiny bandgap, a topological waveguide structure with complementary frequencies is proposed at the same time, and the energy band frequency matches the tiny bandgap frequency to achieve truly continuous broadband slow light mode transmission. Second, the robustness of light transmission is improved. By utilizing the valley degree of freedom and topological protection characteristics, the backscattering loss caused by manufacturing defects and disorder is effectively reduced, ensuring the high-efficiency light transmission performance of slow light devices in complex environments. Without relying on magneto-optical materials, the present invention realizes efficient broadband slow light transmission through topological design, broadens the applicable frequency range of the device, especially for on-chip applications in the visible light and near-infrared bands. Finally, to enhance the functionality of the application, the function of a frequency-selective beam splitter is further realized. Combining the broadband slow light characteristics, it provides an efficient solution for optical communication integrated photonics systems.

[0056] It should be understood that the various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps recited in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved. No limitation is made herein.

[0057] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A broadband topological slow light waveguide, characterized in that: It includes an original waveguide region, and topological valley photonic crystals arranged on both sides of the original waveguide region; The original waveguide region includes two rows of silicon pillar groups with the same structure, each silicon pillar group is composed of five silicon pillars with decreasing cross-sectional diameters, and the silicon pillar with the largest cross-sectional diameter is the same as the diameter of the first nano-pillar; The topological valley photonic crystal comprises a substrate and a nanocolumn array arranged on the substrate; the nanocolumn array is composed of a plurality of honeycomb structured unit cells, each unit cell having a two-dimensional cross-section of a regular hexagon; the unit cell is composed of two types of nanocolumns with different cross-sectional diameters arranged in an interval manner; two adjacent unit cells share a side; The two nanorods with different cross-sectional diameters are respectively a first nanorod and a second nanorod, and the diameter of the first nanorod is twice the diameter of the second nanorod; Lattice constant a The value range is 480~520nm.

2. A broadband topological slow light waveguide according to claim 1, characterized in that: The lattice constant a =500nm.

3. The broadband topological slow light waveguide according to claim 1, characterized in that: The material of the nanorod is dielectric silicon, with a relative dielectric constant of 12; the diameter of the first nanorod is 0.4 a , the diameter of the second nanorod is 0.2 a .

4. The broadband topological slow light waveguide according to claim 1, characterized in that: The diameters of the five silicon pillars with decreasing cross-sectional diameters are d1=0.4 a d2=0.39 a d3=0.38 a d4=0.37 a d5=0.36 a .

5. The broadband topological slow light waveguide according to claim 1, characterized in that: The broadband topological slow light waveguide is a straight waveguide, a defect waveguide or a Z-shaped bending waveguide.

6. A topological beam splitter, characterized in that: Comprising N groups of periodically arranged broadband topological slow light waveguides as claimed in claim 1 and M groups of periodically arranged complementary structure waveguides, wherein the last complementary structure waveguide is connected to the first broadband topological slow light waveguide; The complementary structure waveguide includes a complementary waveguide region and topological valley photonic crystals arranged on both sides of the complementary waveguide region; Both M and N are natural numbers greater than or equal to 6.

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