A topological beam splitter and its application

Abstract

The present invention provides a topological beam splitter and its preparation method and application, belonging to the field of topological photonic crystal application technology. The present invention designs a topological beam splitter, realizes topological states in two-dimensional photonic crystals, and realizes the light quantum spin Hall effect by utilizing lattice symmetry. By stretching or compressing the lattice, the band flip of p and d orbitals is realized, and robust boundary states with pseudospins are formed in the energy gap of the body band after degeneracy breaking. By controlling the angles between the first boundary and the second boundary, and the first boundary and the third boundary, the two-dimensional photonic crystal structure has a wider band gap and more stable topological boundary states, resulting in a topological beam splitter with low transmission loss, high transmittance, and high stability. It can operate within the operating frequency range of the optical communication C band. By adjusting the lattice size, it can realize functions in a wider frequency range to meet different application requirements. It has broad application prospects in the field of all-optical integrated circuits and is expected to promote the practical application of photonic topological insulators in various optical applications.

Description

Technical Field

[0001] The present invention relates to the technical field of topological photonic crystal applications, and in particular to a topological beam splitter and applications thereof. Background Art

[0002] Photonic crystals provide a convenient platform for the design and study of topological insulators, promising solutions for low-loss transmission in photonic devices. Consequently, research in photonics based on the quantum spin Hall effect has led to rapid development of the theory of topological photonics. When photonic crystals with different topological values ​​are spliced ​​together, topologically protected edge states are achieved. These properties, such as strong unidirectional transmission, suppressed backscattering, and robustness to sharp bends and defects, enhance device stability and interference resistance.

[0003] Topological beam splitters can reduce insertion loss, achieve more uniform optical signal distribution, and be affected by topological protection, thereby reducing the degree of damage to optical signals and improving transmission stability. They are also small in size and easy to integrate.

[0004] Related technologies disclose topological beam splitters with different structures, such as a beam splitter with topological protection properties, in which the two middle dielectric columns of each unit cell are removed to construct a line defect structure, and a tree-type transmission channel is constructed based on the line defect structure. By adjusting the radius of the retained dielectric columns in the input channel and the output channel, the functions of the topological beam splitter and the wavelength divider can be realized; another example is a large-width waveguide wavelength division multiplexing beam splitter based on a triangular lattice topological photonic crystal, in which the middle layer of the non-trivial topological photonic crystal is used as a tunable "finite width". By changing the number of lattice layers in the middle layer, different working energy band distributions are obtained, successfully realizing a beam splitter with a large working bandwidth, a large-width waveguide, and wavelength division multiplexing.

[0005] Existing topological beam splitters lack the ability to achieve low transmission loss in the C-band of optical communications. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a topological beam splitter and its application. The topological beam splitter provided by the present invention has a two-dimensional photonic crystal structure with a wider bandgap and more stable topological boundary states, thereby having low transmission loss in the optical communication C-band.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a topological beam splitter, comprising: a mediocre topological photonic crystal and a non-trivial topological photonic crystal, wherein the region formed by the mediocre topological photonic crystal is a mediocre region, and the region constructed by the non-trivial topological photonic crystal is a non-trivial region, the mediocre region includes a first mediocre region 3 and a second mediocre region 4, and the non-trivial region includes a first non-trivial region 1 and a second non-trivial region 2; the boundary between the first non-trivial region 1 and the first mediocre region 3 is a first boundary, the boundary between the first non-trivial region 1 and the second mediocre region 4 is a second boundary, and the boundary between the second non-trivial region 2 and the first mediocre region 3 is a third boundary, the first boundary, the second boundary and the third boundary form a Y-shaped structure, the angle between the first boundary and the second boundary is 120° or 150°, and the angle between the first boundary and the third boundary is 120° or 150°.

[0009] Preferably, the included angle between the first boundary and the second boundary is 120°, and the included angle between the first boundary and the third boundary is 120°.

[0010] Preferably, the included angle between the first boundary and the second boundary is 150°, and the included angle between the first boundary and the third boundary is 150°.

[0011] Preferably, the included angle between the first boundary and the second boundary is 120°, and the included angle between the first boundary and the third boundary is 150°.

[0012] Preferably, the first boundary is arranged horizontally, and the second non-trivial region 2 and the second trivial region 4 extend toward the boundary respectively.

[0013] Preferably, the dielectric constants of the trivial topological photonic crystal and the non-trivial topological photonic crystal are both 12.

[0014] Preferably, the trivial topological photonic crystal and the non-trivial topological photonic crystal are both composed of a honeycomb lattice containing 6 circular ring columns arranged in a regular hexagon. The separation and mode inversion of the pseudospin photonic band gap are achieved by changing the distance between the circular ring columns and the hexagon center.

[0015] Preferably, the operating frequency domain range of the topological beam splitter is 192~198THz, and the electromagnetic waves within the operating frequency domain are unidirectionally transmitted in the topological beam splitter, with a minimum transmission loss of 0.23dB. When the beam splitter power is equally divided, the minimum transmission loss is 0.29dB.

[0016] Preferably, the photon pseudospin states p and d states of the trivial topological photonic crystal in the first Brillouin zone photon band distribution are opened at the Γ point; the photon pseudospin states p and d states of the non-trivial topological photonic crystal in the first Brillouin zone photon band distribution are flipped at the Γ point.

[0017] The present invention also provides the application of the topological beam splitter described in the above technical solution in the field of optical waveguides.

[0018] The present invention provides a topological beam splitter, comprising: a mediocre topological photonic crystal and a non-trivial topological photonic crystal, wherein the region formed by the mediocre topological photonic crystal is a mediocre region, and the region constructed by the non-trivial topological photonic crystal is a non-trivial region, the mediocre region comprises a first mediocre region 3 and a second mediocre region 4, the non-trivial region comprises a first non-trivial region 1 and a second non-trivial region 2, the first non-trivial region 1 is provided with the second mediocre region 4, and the first mediocre region 3 is provided with the second non-trivial region 2; the boundary between the first non-trivial region 1 and the first mediocre region 3 is a first boundary, the boundary between the first non-trivial region 1 and the second mediocre region 4 is a second boundary, and the boundary between the second non-trivial region 2 and the first mediocre region 3 is a third boundary, the first boundary, the second boundary and the third boundary form a Y-shaped structure, the angle between the first boundary and the second boundary is 120° or 150°, and the angle between the first boundary and the third boundary is 120° or 150°.

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

[0020] The design concept of the topological beam splitter of the present invention is as follows:

[0021] The two-dimensional photonic crystal structure of the topological beam splitter of the present invention is as follows Figure 1 As shown in (a), the hexagon is the lattice unit cell, the blue ring is the dielectric ring cylinder, and the background is air. The relative dielectric constant of the ring cylinder is 12, the radius of the large ring is R1 = 0.1a, the radius of the small ring is R2 = 0.05a, the distance between the ring and the center of the unit cell is D = 0.035a, and the side length of the unit cell is The lattice basis vector is a2=a, the lattice constant is a, and the first Brillouin zone based on which the energy band is calculated, Γ, K and M are the three high symmetry points of the simplified Brillouin zone.

[0022] (1) Pseudo-spin states of honeycomb photonic crystals

[0023] The honeycomb photonic crystal structure designed in the present invention can utilize lattice symmetry to realize the optical quantum spin Hall effect and achieve topological boundary state transmission.

[0024] Consider the TM mode of electromagnetic waves (with E z 、H x and H y The scanning direction is M-Γ-K. Figure 1 The lattice structure shown in (a) has an energy band structure as shown in Figure 1As shown in (d), the frequency band forms a doubly degenerate Dirac cone at the Γ point in the first Brillouin zone. The triangular lattice has point C6 group symmetry, and the characteristic state of the Γ point is represented by two irreducible representations: E1 and E2, which are analogous to the p orbital and d orbital of the electronic system respectively. The irreducible representation E1 corresponds to a doubly degenerate dipole state, that is, two p orbitals: p x and p y , with odd parity; the irreducible representation E2 corresponds to a doubly degenerate quadrupole state, i.e., two d orbitals: and d 2xy , with even parity. To understand the evolution of the topological phase, the frequency of the p orbital and the d orbital is calculated as a function of the parameter D. Figure 1 As shown in (b), the parameter D is scanned from 0.25a to 0.4a, with green and blue lines representing d orbitals and p orbitals, respectively, and the band gap is shown in the colored area in the figure. When D < 0.335a, the frequency of the d orbital is higher than that of the p orbital, and the corresponding band gap is topologically trivial; when D > 0.355a, the frequency of the p orbital is higher than that of the d orbital, the band orbitals are inverted, and the corresponding band gap is topologically extraordinary. The band structures of D = 0.25a and D = 0.4a are shown in Figure 1 As shown in (c) and (e), the two lattices have a large common band gap ranging from 0.53(2πc / a) to 0.63(2πc / a), with a relative bandwidth of Δω / ω c =17%(ω c is the band gap middle frequency). In the prior art, the relative band gap width is Δω / ω c = 12.7%, or Δω / ω c =15%. A larger common band gap can produce a strong topological edge state effect and improve the transmission performance of the edge state.

[0025] (2) Constructing topological boundary states

[0026] A supercell constructed with 30 primitive cells Figure 2 As shown in (a), the blue one is the topological trivial lattice (D = 0.25a), and the green one is the topological non-trivial lattice (D = 0.4a). Figure 2 As shown in (b), in k x = ±0.2(π / a), take two points A and B on the boundary state dispersion curve. Figure 2 In (c), the mode field E corresponding to points A and B is drawn. zThe distribution of energy flux density vector at the interface. The top is the left and right boundaries of the supercell at point A, and the bottom is the left and right boundaries of point B. It can be seen that the boundary states corresponding to A and B are indeed completely localized at the interface between the two lattice structures. The energy flux rotation directions of points A and B at the same interface are opposite, and the energy flux vector vortex is not at the boundary, but on the side of the non-trivial structure. The rotation direction is related to the direction of energy flow, which means that pseudospin locks unidirectional propagation. Figure 3 As shown in (a), the electromagnetic wave E is drawn z The red five-pointed star represents the position of the pseudospin light source. c Robust unidirectional transmission is achieved on trivial and topological interfaces with a wavelength of πc / a = 0.549(2πc / a). Figure 3 (b) The energy flux vector of the electric field excited by the pseudospin light source, the direction of the energy flux vector is consistent with the propagation direction.

[0027] Based on the quantum spin Hall effect, the present invention designs a topological beam splitter that realizes topological states in a two-dimensional photonic crystal, leveraging lattice symmetry to achieve the optical quantum spin Hall effect. By stretching or compressing the lattice, the energy bands of p and d orbitals are flipped, resulting in robust boundary states with pseudospins in the energy gap of the bulk band after degeneracy breaking. By controlling the angles between the first boundary and the second boundary, and between the first boundary and the third boundary, the two-dimensional photonic crystal structure has a wider band gap and more stable topological boundary states. The resulting topological beam splitter has low transmission loss, high transmittance, and high stability, capable of operating within the operating frequency range of the optical communication C-band. By adjusting the lattice size, it can function over a wider frequency range, meeting different application requirements. This has broad application prospects in the field of all-optical integrated circuits and is expected to promote the practical application of photonic topological insulators in various optical applications.

[0028] The embodiments show that in an optical communication system, the different splitting angle channels of the present invention can be used to achieve angle diversity and spatial multiplexing, thereby improving the transmission capacity and efficiency of the system, meeting different application requirements, and having high flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Figure 2 is a photonic crystal and its energy band diagram, where (a) is the lattice structure, with the inset being the eigenstate of the Γ-point degenerate point; (b) is the frequency variation of the p-orbital (green curve) and the d-orbital (blue curve) with the parameter D; (c) is the lattice energy band diagram for D = 0.25a; (d) is the lattice energy band diagram for D = 0.335a; (e) is the lattice energy band diagram for D = 0.4a;

[0030] Figure 2The construction of a topological boundary state, where (a) is a supercell consisting of 15 topologically trivial lattices (green) and 15 topologically nontrivial lattices (blue); (b) is the band structure of the supercell; (c) is the electric field distribution on the left and right sides of points A and B in the boundary state, as well as the energy flow vector diagram at the boundary. The arrow indicates the rotation direction of the pseudospin.

[0031] Figure 3 It is a spin-locked unidirectional transmission, where (a) is the clockwise transmission path of the pseudospin light source; (b) is the counterclockwise transmission path of the pseudospin light source;

[0032] Figure 4 The structure and performance test results of a topological beam splitter with a splitting channel angle of 60°+60°, where (a) is the topological beam splitter structure; (b) is the electric field distribution at a frequency of 192.6 THz; (c) is the normalized energy value of the electromagnetic wave detected in each channel within the operating frequency range of 192 to 198 THz; and (d) is the transmission loss curve of the system.

[0033] Figure 5 The structure and performance test results of a topological beam splitter with a splitting channel angle of 30°+30°, where (a) is the topological beam splitter structure; (b) is the electric field distribution at a frequency of 194.9 THz; (c) is the normalized energy value of the electromagnetic wave detected in each channel within the operating frequency range of 192 to 198 THz; and (d) is the transmission loss curve of the system.

[0034] Figure 6 The structure and performance test results of a topological beam splitter with a splitting channel angle of 60°+30°, where (a) is the topological beam splitter structure; (b) is the electric field distribution at a frequency of 197.3 THz; (c) is the normalized energy value of the electromagnetic wave detected in each channel within the operating frequency range of 192 to 198 THz; (d) is a comparison of the transmission loss curves of different systems;

[0035] Figure 7 is the splitting ratio and insertion loss, where (a) is the power ratio X of the two output ports; (b) is the insertion loss of the two ports;

[0036] Figure 8 The robustness verification of the topological beam splitter, where (a) is a schematic diagram of the structure with defects and disorder; (b) is the transmission characteristics of the topological beam splitter with defects and disorder; (c) is the transmission spectrum of the system;

[0037] Figure 9 This is a schematic structural diagram of the topological beam splitter of the present invention, in which 1 is the first non-trivial region 1, 2 is the second non-trivial region, 3 is the first trivial region, and 4 is the second trivial region. DETAILED DESCRIPTION

[0038] The present invention provides a topological beam splitter, comprising: a trivial topological photonic crystal (Trivial PC) and a nontrivial topological photonic crystal (Nontrivial PC), wherein the region formed by the trivial topological photonic crystal is a trivial region, and the region constructed by the nontrivial topological photonic crystal is a nontrivial region, the trivial region comprises a first trivial region 3 and a second trivial region 4, and the nontrivial region comprises a first nontrivial region 1 and a second nontrivial region 2; the boundary between the first nontrivial region 1 and the first trivial region 3 is a first boundary, the boundary between the first nontrivial region 1 and the second trivial region 4 is a second boundary, and the boundary between the second nontrivial region 2 and the first trivial region 3 is a third boundary, the first boundary, the second boundary and the third boundary form a Y-shaped structure, the angle between the first boundary and the second boundary is 120° or 150°, and the angle between the first boundary and the third boundary is 120° or 150°.

[0039] Figure 9 This is a schematic structural diagram of the topological beam splitter of the present invention, in which 1 is the first non-trivial region 1, 2 is the second non-trivial region, 3 is the first trivial region, and 4 is the second trivial region.

[0040] In the present invention, the first mediocre area 3, the second mediocre area 4, the first non-mediocre area 1 and the second non-mediocre area 2 are all arranged in a single layer, and the non-mediocre area does not overlap with the mediocre area.

[0041] In the present invention, the angle between the first boundary and the second boundary is preferably 120°, and the angle between the first boundary and the third boundary is 120°. The structure of the topological beam splitter formed at this time is as follows: Figure 4 As shown in (a), it is also recorded as a topological beam splitter with a splitting channel angle of 60°+60°.

[0042] In the present invention, the angle between the first boundary and the second boundary is preferably 150°, and the angle between the first boundary and the third boundary is preferably 150°. The structure of the topological beam splitter formed at this time is as follows: Figure 5 As shown in (a), it is also recorded as a topological beam splitter with a splitting channel angle of 30°+30°.

[0043] In the present invention, the angle between the first boundary and the second boundary is preferably 120°, and the angle between the first boundary and the third boundary is preferably 150°. The structure of the topological beam splitter formed at this time is as follows: Figure 6 As shown in (a), it is also recorded as a topological beam splitter with a splitting channel angle of 60°+30°.

[0044] In the present invention, the topological beam splitter is robust when encountering defects and disturbances, and can stabilize unidirectional transmission.

[0045] In the present invention, the first boundary is preferably arranged horizontally, and the second non-trivial region 2 and the second trivial region 4 are preferably extended toward the boundary respectively.

[0046] In the present invention, the dielectric constants of the trivial topological photonic crystal and the non-trivial topological photonic crystal are preferably 12.

[0047] In the present invention, the trivial topological photonic crystal and the non-trivial topological photonic crystal are preferably composed of a honeycomb lattice, which preferably contains 6 circular ring columns arranged in a regular hexagon. The separation and mode inversion of the pseudospin photonic band gap are achieved by changing the distance between the circular ring columns and the hexagon center.

[0048] In the present invention, the operating frequency domain range of the topological beam splitter is preferably 192~198THz, and the electromagnetic waves within the operating frequency domain preferably exhibit unidirectional transmission in the topological beam splitter, and the minimum transmission loss is preferably 0.23dB. When the beam splitter power is equally divided, the minimum transmission loss is preferably 0.29dB.

[0049] In the present invention, the photon pseudospin states p and d states of the trivial topological photonic crystal are preferably opened at the Γ point in the first Brillouin zone photon band distribution; the photon pseudospin states p and d states of the non-trivial topological photonic crystal are preferably flipped at the Γ point in the first Brillouin zone photon band distribution.

[0050] The present invention has no special limitation on the preparation method of the topological beam splitter described in the above technical solution, and a method well known to those skilled in the art can be used.

[0051] In a specific embodiment of the present invention, electron beam lithography (EBL) is preferably used to prepare the topological beam splitter, including the following steps: first, a high-quality silicon wafer is selected, cleaned and dried to remove surface contaminants, and then a high-resolution silicon hydroxide (HSQ) photoresist is evenly coated on the surface of the silicon wafer using a spin coater. Before actual exposure, a low-dose pre-exposure is performed to help reduce the influence of the proximity effect. After electron beam exposure, the exposed sample is developed using a developer (ZED-N50). After post-baking, the obtained sample is placed in a dry etching device and etched using SF6 gas. Finally, oxygen plasma is used to remove the photoresist and clean the silicon surface to obtain the topological beam splitter.

[0052] The present invention also provides the application of the topological beam splitter described in the above technical solution in the field of optical waveguides.

[0053] The present invention has no particular limitation on the specific manner of the application, and any manner familiar to those skilled in the art may be used.

[0054] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] Example 1

[0056] Prepare a topological beam splitter structure with splitting channel angles of 60°+60° and 30°+30°, such as Figure 4 (a) and Figure 5 As shown in (a), the blue region represents a non-trivial structure with D = 0.4a, and the green region represents a trivial structure with D = 0.27a. The red five-pointed star represents the location of the pseudospin source, the yellow dashed line represents the propagation path of the system, and the black dashed line also represents a boundary interface, but the direction of the pseudospin state in this path is opposite to the output path of the yellow dashed line. Two-dimensional topological PCs (photonic crystals) are fabricated using electron beam etching. First, a high-quality silicon wafer is selected, cleaned, and dried to remove surface contaminants. Then, a high-resolution hydroxysilane (HSQ) photoresist is evenly coated on the silicon wafer surface using a spin coater. Before actual exposure, a low-dose pre-exposure is performed to help reduce the influence of proximity effects. After electron beam exposure, the exposed sample is developed using a developer (ZED-N50). After post-baking, the resulting sample is placed in a dry etching apparatus and etched using SF6 gas. Finally, oxygen plasma is used to remove the photoresist and clean the silicon surface to obtain the topological beam splitter.

[0057] The performance of these two topological beam splitters is analyzed. Figure 4 As shown in (b), the electric field distribution of the 60°+60° beam splitting channel of the topological beam splitter at a frequency of 192.6THz is simulated. The transmission light of the light source and the two output ports is checked, and the normalized energy field value at the operating frequency is as follows Figure 4 As shown in (c), the transmission spectrum is as follows Figure 4 The transmission loss indicates the quality of signal transmission. The following formula is used to calculate the transmission loss:

[0058]

[0059] Among them, P in Indicates input power, P out Indicates the output power. The light energy can be at 192.6THz and 196.2THz ( Figure 4 (c) is marked as A1 and B1) and is evenly distributed. Figure 4(d) is the transmission loss curve. It can be seen that the transmission losses are 1.36dB and 2.62dB respectively.

[0060] Figure 5 (b) shows the electric field distribution of the topological beam splitter structure at a frequency of 194.9 THz, with a beam splitter channel angle of 30° + 30°. Light propagates unidirectionally to the left, with no backscattering, and two equal output waves are separated. The energy is concentrated near the interface, and no energy is dissipated into the structure. The normalized energy field value at its operating frequency is as follows: Figure 5 As shown in (c), the transmission loss curve is as follows Figure 5 As shown in (d). At 193.2THz, 194.9THz, 196.5THz and 197.5THz ( Figure 5 At the frequencies marked with A2, B2, C2, and D2 in (c), the energies of the two output ports are equal, and equivalent splitting is achieved at these frequencies. The transmission losses are 3.08dB, 0.48dB, 1.16dB, and 1.71dB, respectively, and the minimum transmission loss is 0.47dB.

[0061] Example 2

[0062] The conventional equal splitting angles are changed to construct a topological beam splitter structure with a splitting channel angle of 60°+30°. The preparation method is similar to that of Example 1.

[0063] Structure such as Figure 6 As shown in (a). The electric field distribution at 197.3THz frequency is as follows Figure 6 As shown in (b) in the figure, it can be seen that the light source propagates unidirectionally to the left without backward scattering, and separates two equal output waves. By detecting the transmitted light of the light source and the two output ports, the normalized energy field value at the operating frequency is as follows Figure 6 As shown in (c), it can be seen that the energy of the two output ports at 195.7THz and 197.3THz is equal ( Figure 6 (c) is marked with A3 and B3, and equal beam splitters are realized at these frequencies. The transmission loss curve of this system is shown in Figure 8 As shown in (d), the structure is compared with 60°+60° and 30°+30° topological beam splitters. Between 194.1 THz and 198 THz, the transmission loss of the 60°+30° topological beam splitter is less than 1 dB, making it more stable than topological beam splitters with beam channel angles of 60°+60° and 30°+30°. An equal beam splitter can be realized at 195.7 THz and 197.3 THz, with transmission losses of 0.74 dB and 0.29 dB, respectively. The transmission loss is minimized at 0.23 dB at 197.6 THz and is less than 3 dB within the 192-198 THz range. Therefore, the bandwidth of this structure is 192-198 THz.

[0064] Performance analysis of beam splitters with different splitting channel topologies

[0065] Two important factors in evaluating the performance of the topological splitter designed in this invention are the splitting ratio and the insertion loss IL (Isertion Lss). The splitting ratio refers to the ratio of the power applied to the input optical signal between the different output ports of the splitter. In this invention, the following formula is used to calculate it:

[0066]

[0067] Among them, P in Indicates input power, P out Represents the output power of the output port, and X represents the power ratio of the two output ports. Figure 7 As shown in (a), it fluctuates between [0.5, 4.72] in the operating frequency range of 192 to 198 THz. This shows that the 60°+30° topological beam splitter has better flexibility and adaptability in optical transmission applications.

[0068] IL is an important indicator for evaluating energy transfer efficiency and signal attenuation. IL is calculated using the following formula:

[0069]

[0070] Among them, P in Indicates input power, P out1 and P out2 The insertion loss of the two ports is as follows: Figure 7 As shown in (b), the IL1 measurement ranges from 1.6dB to 5.2dB. The IL2 measurement is slightly higher, ranging from 2.5dB to 8.4dB. These results show that the topological splitter with splitter channel angle has a wide operating bandwidth and excellent and stable transmission performance.

[0071] In order to further analyze the performance of the topological beam splitter and verify the robustness of the 60°+30° topological beam splitter, as shown in Figure 8 As shown in (a), dielectric pillars are randomly removed and their positions are changed to construct defects and disorder, and the red stars represent the positions of pseudo-spin sources. Figure 8 As shown in (b), in the electric field diagram at a frequency of 197.2 THz, the light propagates to the left all the time, propagates smoothly in the cavity and disorder, has no backscattering, and suppresses the inward scattering into the bulk state. Figure 8As shown in (c). The data shows that after the defect is introduced, the transmission loss at 194.8 THz is as low as 2.5 dB. Between 194 and 195.2 THz, the transmission loss differs by more than 1 dB compared to before the defect is introduced. However, between 195.3 and 198 THz, the difference in transmission loss is 0.6 dB, and the transmission loss at each frequency is less than 1 dB. The results show that within a certain frequency band, the introduction of defects has little effect on the beam splitter, which proves that the topological beam splitter of this structure has good robustness. Therefore, the system has excellent unidirectional transmission performance and good backscattering suppression capability, which can improve the anti-interference performance of the device. In addition, the structure is simple and suitable for miniaturization. It has great application potential in the field of optical communications. By further adjusting the lattice size, functions can be realized in a wider frequency range to meet different application requirements. It has broad application prospects in the field of all-optical integrated circuits and is expected to promote the practical application of photonic topological insulators in various optical applications.

[0072] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A topological beam splitter, characterized in that: include: A trivial topological photonic crystal and a non-trivial topological photonic crystal, wherein the region formed by the trivial topological photonic crystal is a trivial region, and the region constructed by the non-trivial topological photonic crystal is a non-trivial region, the trivial region includes a first trivial region (3) and a second trivial region (4), and the non-trivial region includes a first non-trivial region (1) and a second non-trivial region (2); the boundary between the first non-trivial region (1) and the first trivial region (3) is a first boundary, the boundary between the first non-trivial region (1) and the second trivial region (4) is a second boundary, and the boundary between the second non-trivial region (2) and the first trivial region (3) is a third boundary, the first boundary, the second boundary and the third boundary form a Y-shaped structure, the angle between the first boundary and the second boundary is 120° or 150°, and the angle between the first boundary and the third boundary is 120° or 150°.

2. The topological beam splitter according to claim 1, characterized in that The included angle between the first boundary and the second boundary is 120°, and the included angle between the first boundary and the third boundary is 120°.

3. The topological beam splitter according to claim 1, characterized in that The included angle between the first boundary and the second boundary is 150°, and the included angle between the first boundary and the third boundary is 150°.

4. The topological beam splitter according to claim 1, characterized in that The included angle between the first boundary and the second boundary is 120°, and the included angle between the first boundary and the third boundary is 150°.

5. The topological beam splitter according to claim 1, characterized in that The first boundary is set horizontally, and the second non-mediocre area (2) and the second mediocre area (4) extend towards the boundary respectively.

6. The topological beam splitter according to claim 1, characterized in that The dielectric constants of the trivial topological photonic crystal and the non-trivial topological photonic crystal are both 12.

7. The topological beam splitter according to claim 1, characterized in that: The trivial topological photonic crystal and the non-trivial topological photonic crystal are both composed of a honeycomb lattice containing six circular ring columns arranged in a regular hexagon. The separation of the pseudospin photonic band gap and the mode inversion are achieved by changing the distance between the circular ring columns and the hexagon center.

8. The topological beam splitter according to claim 1, characterized in that: The operating frequency domain range of the topological beam splitter is 192~198THz. The electromagnetic waves within the operating frequency domain are unidirectionally transmitted in the topological beam splitter, with a minimum transmission loss of 0.23dB. When the beam splitter power is equally divided, the minimum transmission loss is 0.29dB.

9. The topological beam splitter according to claim 1, characterized in that: Photonic pseudospin states in the first Brillouin zone photonic band distribution of the trivial topological photonic crystal p 、 d The state is opened at the Γ point; the non-trivial topological photonic crystal has a photon pseudospin state in the first Brillouin zone photon band distribution p 、 d The state flips at point Γ.

10. Application of the topological beam splitter according to any one of claims 1 to 9 in the field of optical waveguides.

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