A design method and system for wavelength division multiplexers based on topological photonic crystals

Abstract

This invention relates to a design method and system for wavelength division multiplexers (WDM) based on topological photonic crystals. The method includes: obtaining three photonic crystal units (PC1, PC3, and PC4) after topological optimization; combining the three photonic crystal units in pairs to obtain different supercells; determining the boundary states and transmission efficiency of each supercell; designing four directional point sources at the junction of PC3 and PC4 units to verify whether the structure composed of the three photonic crystal units can produce a combined effect of unidirectional propagation, boundary states, and wavelength division multiplexing, thus obtaining a wavelength division multiplexer; and destroying the structure of each supercell to ensure that the overall effect of the wavelength division multiplexer is not affected. This invention enables the design of a wavelength division multiplexer that effectively produces a combined effect of unidirectional propagation, boundary states, and wavelength division multiplexing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wavelength division multiplexer design, in particular to a wavelength division multiplexer design method and system based on topological photonic crystals. BACKGROUND

[0002] Recent exploration of valley degrees of freedom in photonic systems has enriched the topological phase of light and brought about robust transport of edge states around sharp bends. The two bandgaps in the valley Hall system have attracted the attention of researchers due to the simultaneous expansion of the working bandwidth. The wider the bandgap, the better the stability of the system. A good performance wavelength division multiplexer can be applied in many fields. The wavelength division multiplexer is a key component for realizing the parallel transmission of multiple signals in an optical communication system, and it is essential for realizing high-capacity communication and sensing systems. As an important component in optical communication systems, the wavelength division multiplexer has the function of realizing the simultaneous transmission of multiple signals, and is widely used in high-speed optical fiber communication systems. In the use of electromagnetic wave transmission, by adjusting the frequency of the transmitted electromagnetic wave, the transmission path of the electromagnetic wave can be artificially controlled. However, in previous studies, the one-way transmission capability of traditional photonic crystal waveguides is poor. When the traditional waveguide structure is damaged, the electromagnetic wave transmission efficiency is very low, and even the propagation is blocked. When electromagnetic waves encounter corners or small obstacles, they will suffer serious loss, resulting in low propagation efficiency. In topological photonics, adjusting the structure of the device through topological optimization to widen the bandgap or realize some novel properties has always been a field where topological optimization is more commonly applied. Topological optimization can be applied in a single unit cell of a photonic crystal. The new topological photonic crystal has many novel properties compared to traditional photonic crystals, such as one-way transmission of topological edge states, robustness to structural defects, high-quality factor angular states, and other novel properties. The present application designs a wavelength division multiplexer based on topological photonic crystals, which solves the problems of poor one-way transmission capability of traditional waveguides and poor electromagnetic wave propagation when the waveguide structure is damaged. The research results of the present application provide guidance for designing topological structure wavelength division multiplexers and provide a new idea for designing integrated photonic waveguide wavelength division multiplexers in the future. SUMMARY

[0003] The purpose of the present application is to provide a wavelength division multiplexer design method and system based on topological photonic crystals, which can realize effective one-way transmission of electromagnetic waves in the boundary state and design a wavelength division multiplexer with robustness and wave division multiplexing.

[0004] To achieve the above purpose, the present application provides the following scheme:

[0005] A wavelength division multiplexer design method based on topological photonic crystals comprises:

[0006] Three types of photonic crystal units were obtained after topology optimization, including PC1 unit cell, PC3 unit cell and PC4 unit cell;

[0007] By combining the three types of photonic crystal unit cells in pairs, different supercells are obtained;

[0008] Determine the boundary states and transmission efficiency of each supercell;

[0009] Four directional point sources were designed at the junction of the PC3 and PC4 units to verify whether the structure composed of three photonic crystal units could produce a composite effect of unidirectional propagation, boundary states and wavelength division multiplexing, thus obtaining a wavelength division multiplexer.

[0010] By disrupting the structure of each supercell, it is determined that the overall performance of the wavelength division multiplexer remains unaffected.

[0011] Optionally, the PC3 unit cell and the PC4 unit cell have opposite topological phases near the high-frequency and low-frequency band gaps; the PC1 unit cell and the PC3 unit cell have opposite topological phases near the low-frequency band gap and the same topological phase near the high-frequency band gap; the PC1 unit cell and the PC4 unit cell have the same topological phase near the low-frequency band gap and opposite topological phases near the high-frequency band gap.

[0012] Optionally, the supercell is a combination of primitive cells in one direction, with periodic boundary conditions added to the two sides of each primitive cell to form a new periodic structure.

[0013] Optionally, determining the boundary states and transmission efficiency of each supercell specifically includes:

[0014] By combining the PC3 unit cell and the PC4 unit cell, clear boundary states were observed in both the low-frequency and high-frequency ranges. A point source was placed at the interface between the PC3 unit cell and the PC4 unit cell, with the point source frequency covering the required high-frequency and low-frequency ranges. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the respective frequencies.

[0015] By combining the PC1 unit cell and the PC3 unit cell, a clear boundary state was observed in the low-frequency range. A point source was placed at the interface between the PC1 unit cell and the PC3 unit cell, with the point source frequency covering the required low-frequency range. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the frequency.

[0016] By combining the PC1 unit cell and the PC4 unit cell, a clear boundary state was observed in the high-frequency range. A point source was placed at the interface between the PC1 unit cell and the PC4 unit cell, with the point source frequency covering the required high-frequency range. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the frequency.

[0017] Optionally, the disruption of the structure of each supercell to ensure that the overall performance of the wavelength division multiplexer is not affected specifically includes:

[0018] Several dielectric units in the transmission path were removed, and the supercell structure was destroyed. It was observed that the boundary states of the supercell still existed, and the energy transmission remained intact, confirming that the overall effect of the wavelength division multiplexer was not affected.

[0019] A wavelength division multiplexer design system based on topological photonic crystals includes:

[0020] A photonic crystal unit cell acquisition module is used to acquire three types of photonic crystal unit cells after topology optimization, wherein the photonic crystal unit cells include PC1 unit cell, PC3 unit cell and PC4 unit cell;

[0021] The supercell determination module is used to combine the three types of photonic crystal unit cells in pairs to obtain different supercells;

[0022] A boundary state and transmission efficiency determination module is used to determine the boundary state and transmission efficiency of each supercell.

[0023] The wavelength division multiplexer generation module is used to design four directional point sources at the junction of the PC3 unit cell and the PC4 unit cell to verify whether the structure composed of three photonic crystal unit cells can produce a composite effect of unidirectional propagation, boundary state and wavelength division multiplexing, and obtain a wavelength division multiplexer.

[0024] The wavelength division multiplexer overall effect verification module is used to destroy the structure of each supercell to determine that the overall effect of the wavelength division multiplexer is not affected.

[0025] Optionally, the photonic crystal unit cell includes PC1 unit cell, PC3 unit cell, and PC4 unit cell. The PC3 unit cell and PC4 unit cell have opposite topological phases near the high-frequency and low-frequency band gaps. The PC1 unit cell and PC3 unit cell have opposite topological phases near the low-frequency band gap and the same topological phase near the high-frequency band gap. The PC1 unit cell and PC4 unit cell have the same topological phase near the low-frequency band gap and opposite topological phases near the high-frequency band gap.

[0026] Optionally, the supercell is a combination of primitive cells in one direction, with periodic boundary conditions added to the two sides of each primitive cell to form a new periodic structure.

[0027] Optionally, the boundary state and transmission efficiency determination module specifically includes:

[0028] The first boundary state and transmission efficiency determination unit is used to combine the PC3 unit cell and the PC4 unit cell to observe clear boundary states in the low-frequency range and the high-frequency range; a point source is placed at the interface between the PC3 unit cell and the PC4 unit cell, and the point source frequency covers the required high-frequency range and low-frequency range, and simulation is performed to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0029] The second boundary state and transmission efficiency determination unit is used to combine the PC1 unit cell and the PC3 unit cell to observe a clear boundary state in the low frequency range; place a point source at the interface between the PC1 unit cell and the PC3 unit cell, with the point source frequency covering the required low frequency range, and perform simulation to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0030] The third boundary state and transmission efficiency determination unit is used to combine the PC1 unit cell and the PC4 unit cell to observe a clear boundary state in the high frequency range; a point source is placed at the interface between the PC1 unit cell and the PC4 unit cell, and the point source frequency covers the required high frequency range. Simulation is performed to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0031] Optionally, the wavelength division multiplexer overall performance verification module specifically includes:

[0032] The wavelength division multiplexer overall performance verification unit is used to remove several dielectric units in the transmission path, destroy the supercell structure, observe that the boundary states of the supercell still exist, the energy transmission is still complete, and determine that the overall performance of the wavelength division multiplexer is not affected.

[0033] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0034] This invention provides a wavelength division multiplexer (WDM) design method based on topological photonic crystals. The method includes: obtaining three photonic crystal units (PC1, PC3, and PC4) after topological optimization; combining the three photonic crystal units in pairs to obtain different supercells; determining the boundary states and transmission efficiency of each supercell; designing four directional point sources at the junction of PC3 and PC4 units to verify whether the structure composed of the three photonic crystal units can produce a combined effect of unidirectional propagation, boundary states, and wavelength division multiplexing, thus obtaining a WDM; and destroying the structure of each supercell to ensure that the overall effect of the WDM is not affected. This invention enables efficient unidirectional transmission of electromagnetic waves in boundary states and designs a WDM with robustness and a combined effect of wavelength division multiplexing. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart of the wavelength division multiplexer design method based on topological photonic crystals according to the present invention;

[0037] Figure 2 A schematic diagram showing the size and three-dimensional structure of a single crystal unit cell;

[0038] Figure 3 To verify the boundary state diagram of the optimized structure;

[0039] Figure 4 A schematic diagram, energy transfer diagram, and transfer efficiency diagram of the PC3 and PC4 unit cell combination;

[0040] Figure 5 A schematic diagram, energy transfer diagram, and transfer efficiency diagram of the PC1 and PC3 unit cell combination;

[0041] Figure 6 A schematic diagram, energy transfer diagram, and transfer efficiency diagram of the PC1 and PC4 unit cell combination;

[0042] Figure 7 The diagram shows the structure, energy transmission, transmission efficiency, and three-dimensional structure of a wavelength division multiplexer.

[0043] Figure 8 This is a schematic diagram showing the damage to the structure of a wavelength division multiplexer.

[0044] Figure 9 This is a structural diagram of the wavelength division multiplexer design system based on topological photonic crystals according to the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] The purpose of this invention is to provide a wavelength division multiplexer design method and system based on topological photonic crystals, which can realize the effective unidirectional transmission of electromagnetic waves in boundary states and design a wavelength division multiplexer with robustness and wavelength division multiplexing combined effect.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Figure 1 This is a flowchart illustrating the wavelength division multiplexer design method based on topological photonic crystals according to the present invention. Figure 1 As shown, a wavelength division multiplexer design method based on topological photonic crystals includes:

[0049] Step 101: Obtain the three photonic crystal units after topology optimization.

[0050] The photonic crystal unit cells include PC1 unit cells, PC3 unit cells, and PC4 unit cells. PC3 unit cells and PC4 unit cells have opposite topological phases near the high-frequency and low-frequency band gaps. PC1 unit cells and PC3 unit cells have opposite topological phases near the low-frequency band gap and the same topological phase near the high-frequency band gap. PC1 unit cells and PC4 unit cells have the same topological phase near the low-frequency band gap and opposite topological phases near the high-frequency band gap.

[0051] To verify that boundary state effects occur in frequency bands with opposite topologies, several sets of primitive cells with two degenerate points opened were selected to verify whether boundary states exist in the band structure of the supercell composed of pairs of primitive cells. Figure 1 For the three photonic crystal unit cells after topology optimization, Figure 2 The unit cells corresponding to (a), (b), and (c) are named PC1, PC3, and PC4, respectively, because the designed unit cell shapes exhibit a C-shape. 3v The symmetry, therefore in Figure 2 The dimensions of the photonic crystal are only shown in a portion of the original image. Figure 2 Each photonic crystal in the array is 20 mm thick. (Note:) Figure 2 All numbers appearing in the text are in mm.

[0052] Step 102: Combine the three types of photonic crystal units in pairs to obtain different supercells.

[0053] The supercell is formed by combining primitive cells in one direction and adding periodic boundary conditions to the two sides of each primitive cell to create a new periodic structure. Observing the simulation characteristics of the supercell can reveal whether the primitive cells that make up the supercell have boundary states and the frequency range in which these boundary states exist, which helps to reduce the simulation time for the overall device in the later stages.

[0054] Step 103: Determine the boundary states and transmission efficiency of each supercell, specifically including:

[0055] By combining the PC3 unit cell and the PC4 unit cell, clear boundary states were observed in both the low-frequency and high-frequency ranges. A point source was placed at the interface between the PC3 unit cell and the PC4 unit cell, with the point source frequency covering the required high-frequency and low-frequency ranges. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the respective frequencies.

[0056] By combining the PC1 unit cell and the PC3 unit cell, a clear boundary state was observed in the low-frequency range. A point source was placed at the interface between the PC1 unit cell and the PC3 unit cell, with the point source frequency covering the required low-frequency range. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the frequency.

[0057] By combining the PC1 unit cell and the PC4 unit cell, a clear boundary state was observed in the high-frequency range. A point source was placed at the interface between the PC1 unit cell and the PC4 unit cell, with the point source frequency covering the required high-frequency range. Simulation was performed to obtain the energy distribution and transmission efficiency corresponding to the frequency.

[0058] like Figure 3 As shown, several groups of four types of primitive cells were selected and combined to form a supercell. Figure 3 (a) combines PC3 and PC4. Since PC3 and PC4 have opposite valley numbers at low and high frequencies and opposite topological phases, the existence of boundary states can be observed at both low and high frequencies. Figure 3 (b) combines PC1 and PC3. Since PC1 and PC3 have opposite valley numbers in the low-frequency part and the same valley number in the high-frequency part, the boundary state is not visible in the high-frequency part, but the boundary state is visible in the low-frequency part. Figure 3 (c) combines PC1 and PC4. Since PC1 and PC4 have the same valley-Cell number in the low-frequency part and opposite valley-Cell number in the high-frequency part, the existence of boundary states can be seen in the high-frequency part, but not in the low-frequency part.

[0059] Based on the four different unit cells generated, theoretically, different unit cells have different properties, and pairwise combinations will result in boundary states. Next, we will test the pairwise combination of several unit cells and observe their boundary states and transmission efficiency.

[0060] The PC3 primitive cells and PC4 primitive cells were arranged according to... Figure 4The arrangement shown in (a) allows for the observation of distinct boundary states in both the low-frequency and high-frequency ranges because the PC3 and PC4 units have opposite topological phases near both band gaps. A point source is placed at the interface between PC3 and PC4, with its frequency covering the required high-frequency and low-frequency ranges, for simulation. The corresponding energy distribution diagrams for each frequency are shown below. Figure 4 As shown in (b), distinct boundary states can be observed at both low and high frequencies. Its transmission efficiency diagram is as follows: Figure 4 As shown in (c).

[0061] PC1 primitive cells and PC3 primitive cells were arranged according to Figure 5 As shown in (a), the arrangement of PC1 and PC3 unit cells exhibits opposite topological phases near the low-frequency bandgap and identical topological phases near the high-frequency bandgap, thus allowing for the observation of distinct boundary states in the low-frequency range. A point source is placed at the interface between PC1 and PC3, with its frequency covering the required low-frequency range, for simulation. The corresponding energy distribution diagrams for each frequency are shown below. Figure 5 As shown in (b), a distinct boundary state can be observed at low frequencies. Its transmission efficiency diagram is as follows. Figure 5 As shown in (c).

[0062] PC1 primitive cells and PC4 primitive cells were arranged according to Figure 6 As shown in (a), the arrangement of PC1 and PC4 unit cells exhibits the same topological phase near the low-frequency bandgap and opposite topological phases near the high-frequency bandgap, thus allowing for the observation of distinct boundary states in the high-frequency range. A point source is placed at the interface between PC1 and PC4, with its frequency covering the required high-frequency range, for simulation. The corresponding energy distribution diagrams for the relevant frequencies are shown below. Figure 6 As shown in (b), distinct boundary states can be observed at both low and high frequencies. Its transmission efficiency diagram is as follows: Figure 6 As shown in (c), note: only the band passing through the boundary has frequencies between 11.62-11.72 GHz.

[0063] The above test examined the boundary states by combining pairs of unit cells. The existence of these boundary states confirms that if two unit cells have opposite topological phases within the same frequency range, combining them will generate boundary states. These boundary states allow topological photonic crystals to respond appropriately to external environments without altering their fundamental physical properties. This ensures the stability of topological photonic crystals when processing complex environmental information, providing a basis for the subsequent construction of wavelength division multiplexers.

[0064] Step 104: Design four directional point sources at the junction of the PC3 and PC4 units to verify whether the structure composed of the three photonic crystal units can produce a composite effect of unidirectional propagation, boundary states and wavelength division multiplexing, and obtain a wavelength division multiplexer.

[0065] The unidirectional propagation characteristic of topological photonic crystals refers to the propagation process of a topological photonic crystal, under a specific structural configuration, that only allows propagation from a specific incident end to a specific output end. It possesses the property of being able to pass through in a specific direction while being prohibited from passing through in the opposite direction. This characteristic is due to the boundary states of the topological photonic crystal and arises from its unique structural properties. Therefore, the unidirectional propagation characteristic of topological photonic crystals exhibits high robustness. Four directional point sources are placed at the boundary between PC3 and PC4, with a phase difference of π / 2 between the four point sources. The approximate placement and relative positions of the point sources are determined by… Figure 7 As shown in (a), when two structures have different topological phases, boundary states can appear at the boundary between the two structures. With PC3 placed above the overall structure and PC4 below, PC3 and PC4 have completely opposite topological phases at high and low frequencies, so high-frequency and low-frequency electromagnetic wave energy can be observed at their boundary. With PC1 placed on the right side of the structure, since PC1 and PC3 have opposite topological phases at low frequencies, low-frequency boundary states can appear at this boundary. Furthermore, since PC1 and PC4 have opposite topological phases at high frequencies, high-frequency boundary states can appear at the lower boundary, thus realizing the function of a wavelength division multiplexer. The power distribution generated by the low-frequency point source is shown below. Figure 7 As shown in (b), since the source used is a directional point source, the generated electric field propagates in one direction, greatly reducing energy dissipation. The energy propagation direction is also as analyzed above: it propagates forward along the boundary between PC3 and PC4, and at the boundary of the three photonic crystals, it propagates along the direction of the boundary between PC1 and PC3. Simultaneously, at high frequencies, energy propagates forward along the boundary between PC1 and PC4, as... Figure 7 As shown in (c), its energy transfer efficiency curve is derived from... Figure 7 As shown in (d). The three-dimensional structure diagram is shown in 7(e) (Note: The line current source is not shown in this figure for better observation of the three-dimensional structure).

[0066] Step 105: Destroy the structure of each supercell to ensure that the overall performance of the wavelength division multiplexer is not affected, specifically including:

[0067] Several dielectric units in the transmission path were removed, and the supercell structure was destroyed. It was observed that the boundary states of the supercell still existed, and the energy transmission remained intact, confirming that the overall effect of the wavelength division multiplexer was not affected.

[0068] A schematic diagram of removing several media structures is shown below. Figure 8 As shown in (a), the entire unit cell was removed from the transmission channel to simulate structural damage caused by accidents such as collisions during use. If the boundary states still exist and the energy transfer remains intact, it can be proven that crystal combinations with different topological phases (opposite valley Chern numbers in a specific frequency band) have good robustness.

[0069] Simulation results showed that even with minor structural damage, the overall performance of the device was not significantly affected. The complete boundary state effect still existed, and a clear energy wavelength division multiplexing effect could be observed. Its transmission efficiency was not much different from that of the complete structure. Figure 8 (b) is the energy transfer diagram at low frequencies when there is a structural defect. Figure 8 (c) is the energy transfer diagram at high frequencies when there are structural defects. Figure 8 (d) is a graph showing the transmission efficiency curves at high and low frequencies when there are structural defects. Figure 8 (e) is a 3D model of the structural defects. This demonstrates that the designed topological photonic crystal exhibits excellent structural robustness and can function normally even when its structure is slightly damaged.

[0070] This invention introduces a frequency range degree of freedom for valley-type photonic crystals with dual bandgap. Based on the theory that combining two photonic crystals with different topological phases forms boundary states, three structures of the designed valley-type photonic crystal with dual bandgap are arranged in an orderly manner on a 2D plane. Four directional point sources are designed between PC3 and PC4. The results demonstrate that the designed structure can effectively generate a composite effect of unidirectional propagation, boundary states, and wavelength division multiplexing, and exhibits good robustness. The research results provide guidance for designing the frequency range correlation characteristics of topological structures and offer a new approach for the design of wavelength division multiplexers integrating photonic waveguides in the future.

[0071] Figure 9 This is a system structure diagram of the wavelength division multiplexer design based on topological photonic crystals according to the present invention. Figure 9 As shown, a wavelength division multiplexer design system based on topological photonic crystals includes:

[0072] The photonic crystal unit cell acquisition module 201 is used to acquire three types of photonic crystal units after topology optimization, including PC1 unit cell, PC3 unit cell and PC4 unit cell;

[0073] The supercell determination module 202 is used to combine the three types of photonic crystal unit cells in pairs to obtain different supercells;

[0074] Boundary state and transmission efficiency determination module 203 is used to determine the boundary state and transmission efficiency of each supercell;

[0075] The wavelength division multiplexer generation module 204 is used to design four directional point sources at the junction of the PC3 unit cell and the PC4 unit cell to verify whether the structure composed of three photonic crystal unit cells can produce a composite effect of unidirectional propagation, boundary state and wavelength division multiplexing, and obtain a wavelength division multiplexer.

[0076] The wavelength division multiplexer overall effect verification module 205 is used to destroy the structure of each supercell to determine that the overall effect of the wavelength division multiplexer is not affected.

[0077] The PC3 and PC4 units have opposite topological phases near the high-frequency and low-frequency band gaps; the PC1 and PC3 units have opposite topological phases near the low-frequency band gap and the same topological phase near the high-frequency band gap; the PC1 and PC4 units have the same topological phase near the low-frequency band gap and opposite topological phases near the high-frequency band gap.

[0078] The supercell is formed by combining primitive cells in one direction and adding periodic boundary conditions to the two sides of each primitive cell to form a new periodic structure.

[0079] The boundary state and transmission efficiency determination module 203 specifically includes:

[0080] The first boundary state and transmission efficiency determination unit is used to combine the PC3 unit cell and the PC4 unit cell to observe clear boundary states in the low-frequency range and the high-frequency range; a point source is placed at the interface between the PC3 unit cell and the PC4 unit cell, and the point source frequency covers the required high-frequency range and low-frequency range, and simulation is performed to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0081] The second boundary state and transmission efficiency determination unit is used to combine the PC1 unit cell and the PC3 unit cell to observe a clear boundary state in the low frequency range; place a point source at the interface between the PC1 unit cell and the PC3 unit cell, with the point source frequency covering the required low frequency range, and perform simulation to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0082] The third boundary state and transmission efficiency determination unit is used to combine the PC1 unit cell and the PC4 unit cell to observe a clear boundary state in the high frequency range; a point source is placed at the interface between the PC1 unit cell and the PC4 unit cell, and the point source frequency covers the required high frequency range. Simulation is performed to obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

[0083] The wavelength division multiplexer overall performance verification module 205 specifically includes:

[0084] The wavelength division multiplexer overall performance verification unit is used to remove several dielectric units in the transmission path, destroy the supercell structure, observe that the boundary states of the supercell still exist, the energy transmission is still complete, and determine that the overall performance of the wavelength division multiplexer is not affected.

[0085] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0086] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A design method of a topological photonic crystal-based wavelength division multiplexer, characterized by, The application relates to a photonic crystal waveguide and a preparation method thereof. Three kinds of photonic crystal unit cells after topological optimization are acquired, wherein the photonic crystal unit cells include a PC1 unit cell, a PC3 unit cell and a PC4 unit cell; The three kinds of photonic crystal unit cells are combined in pairs to obtain different supercells; Boundary states and transmission efficiency of each supercell are determined; Four directional point sources are designed at the junction of the PC3 unit cell and the PC4 unit cell, whether the structure composed of the three kinds of photonic crystal unit cells can produce the composite effects of unidirectional propagation, boundary state and wavelength division multiplexing is verified, and a wavelength division multiplexer is obtained; The structure of each supercell is destroyed, and it is determined that the overall effect of the wavelength division multiplexer is not affected; The PC3 unit cell and the PC4 unit cell have opposite topological phases near high-frequency and low-frequency band gaps; the PC1 unit cell and the PC3 unit cell have opposite topological phases near a low-frequency band gap and have the same topological phase near a high-frequency band gap; and the PC1 unit cell and the PC4 unit cell have the same topological phase near a low-frequency band gap and have opposite topological phases near a high-frequency band gap; The supercell is a new periodic structure formed by combining the unit cells in one direction and adding periodic boundary conditions to the two sides of each unit cell; The determination of the boundary states and the transmission efficiency of each supercell specifically includes the following steps: The PC3 unit cell and the PC4 unit cell are combined, and clear boundary states are observed in a low-frequency range and a high-frequency range; a point source is placed at the junction of the PC3 unit cell and the PC4 unit cell, the frequency of the point source covers the required high-frequency range and the low-frequency range, simulation is performed, and the energy distribution and the transmission efficiency corresponding to the corresponding frequency are obtained; The PC1 unit cell and the PC3 unit cell are combined, and clear boundary states are observed in a low-frequency range; a point source is placed at the junction of the PC1 unit cell and the PC3 unit cell, the frequency of the point source covers the required low-frequency range, simulation is performed, and the energy distribution and the transmission efficiency corresponding to the corresponding frequency are obtained; The PC1 unit cell and the PC4 unit cell are combined, and clear boundary states are observed in a high-frequency range; a point source is placed at the junction of the PC1 unit cell and the PC4 unit cell, the frequency of the point source covers the required high-frequency range, simulation is performed, and the energy distribution and the transmission efficiency corresponding to the corresponding frequency are obtained.

2. The design method of a topological photonic crystal based wavelength division multiplexer as claimed in claim 1, wherein, The destruction of the structure of each supercell to determine that the overall effect of the wavelength division multiplexer is not affected specifically includes the following steps: Some medium units on a transmission path are dug out, the supercell structure is destroyed, the boundary state of the supercell is observed, energy transmission is still complete, and it is determined that the overall effect of the wavelength division multiplexer is not affected.

3. A design system for a topological photonic crystal based wavelength division multiplexer, characterized by, The application relates to a photonic crystal waveguide and a preparation method thereof. A photonic crystal unit cell acquisition module is used for acquiring three kinds of photonic crystal unit cells after topological optimization, wherein the photonic crystal unit cells include a PC1 unit cell, a PC3 unit cell and a PC4 unit cell; A supercell determination module is used for combining the three kinds of photonic crystal unit cells in pairs to obtain different supercells; A boundary state and transmission efficiency determination module is used for determining the boundary states and the transmission efficiency of each supercell. The wave division multiplexer generation module is configured to design four directional point sources at the junction of the PC3 primitive cell and the PC4 primitive cell, verify whether the structure composed of the three photonic crystal primitive cells can produce the combined effect of unidirectional propagation, boundary state and wave division multiplexing, and obtain a wave division multiplexer. The wave division multiplexer overall effect verification module is configured to destroy the structure of each super cell and determine that the overall effect of the wave division multiplexer is not affected. The PC3 primitive cell and the PC4 primitive cell have opposite topological phases near the high-frequency and low-frequency band gaps; the PC1 primitive cell and the PC3 primitive cell have opposite topological phases near the low-frequency band gap and have the same topological phase near the high-frequency band gap; and the PC1 primitive cell and the PC4 primitive cell have the same topological phase near the low-frequency band gap and have opposite topological phases near the high-frequency band gap. The super cell is a combination of the primitive cells in one direction, and a periodic boundary condition is added to the two sides of the boundary of each primitive cell to form a new periodic structure. The boundary state and transmission efficiency determination module specifically includes: The first boundary state and transmission efficiency determination unit is configured to combine the PC3 primitive cell and the PC4 primitive cell, observe clear boundary states in the low-frequency range and the high-frequency range, place a point source at the junction of the interface of the PC3 primitive cell and the PC4 primitive cell, cover the required high-frequency range and low-frequency range with the frequency of the point source, perform simulation, and obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency. The second boundary state and transmission efficiency determination unit is configured to combine the PC1 primitive cell and the PC3 primitive cell, observe clear boundary states in the low-frequency range, place a point source at the junction of the interface of the PC1 primitive cell and the PC3 primitive cell, cover the required low-frequency range with the frequency of the point source, perform simulation, and obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency. The third boundary state and transmission efficiency determination unit is configured to combine the PC1 primitive cell and the PC4 primitive cell, observe clear boundary states in the high-frequency range, place a point source at the junction of the interface of the PC1 primitive cell and the PC4 primitive cell, cover the required high-frequency range with the frequency of the point source, perform simulation, and obtain the energy distribution and transmission efficiency corresponding to the corresponding frequency.

4. The topology photonic crystal based wavelength division multiplexer design system of claim 3, wherein, The wave division multiplexer overall effect verification module specifically includes: The wave division multiplexer overall effect verification unit is configured to remove a plurality of medium units on the transmission path, destroy the super cell structure, observe that the boundary state of the super cell still exists and the energy transmission is still complete, and determine that the overall effect of the wave division multiplexer is not affected.

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