A topology-protected electromagnetic energy combiner

Abstract

This invention provides a topology-protected electromagnetic energy combiner, comprising a first copper-clad substrate, a photonic crystal cluster, and a second copper-clad substrate connected sequentially from top to bottom. The photonic crystal cluster is composed of multiple photonic crystals, which are rectangular arrays of square YIG lattice pillars. Each photonic crystal has different topological indices. Adjacent photonic crystals generate unidirectional, non-scattering topological boundary states in a first, second, or third direction at their boundaries. Based on the topology-protected mode orthogonal excitation theory, this invention introduces unidirectional, non-scattering topological boundary states into electromagnetic energy combining, breaking through the constraints of phase correlation and polarization degrees of freedom of the input electromagnetic energy source in traditional electromagnetic energy combining theory. This enables the design of an electromagnetic energy combiner structure with arbitrary phase, high efficiency, wide bandwidth, and scalability.

Description

Technical Field

[0001] This invention belongs to the field of photonic crystal and energy transmission technology, specifically relating to a novel structure for topologically protected electromagnetic energy combining. By controlling and splicing the topological parameters of various YIG photonic crystals, multiple single-boundary state input channels and one multi-boundary state output channel are constructed to achieve multi-channel electromagnetic energy combining with arbitrary phase, high efficiency, wide bandwidth, and scalability. Background Technology

[0002] High-energy-density electromagnetic beams have broad application prospects in numerous fields, including laser weapons, laser particle accelerators, advanced materials manufacturing, and surgical applications. In the microwave band, high-energy electromagnetic beam systems have demonstrated enormous potential in applications such as directional energy radiation, Earth-Moon energy transfer, and high-energy radar. However, there are inherent physical limitations to the power amplification of a single laser, including nonlinear effects, thermal problems, optical damage, and pump power limitations. Therefore, combining the output power of multiple lasers is an important technique for obtaining high-energy electromagnetic beams.

[0003] Electromagnetic energy combining of continuous waves can be categorized into coherent and incoherent methods. Coherent beam combining technology controls parameters such as frequency, phase difference, amplitude, and polarization between electromagnetic waves, enabling constructive interference between multiple waves to obtain a high-energy electromagnetic beam. It strongly relies on precise modulation of parameters such as the phase of the input channel electromagnetic waves to maintain their temporal and spatial coherence. While coherent beam combining technology has made significant progress over the past few decades, its current limitations remain due to complex phase feedback and control systems.

[0004] Incoherent beam combining technology refers to combining multiple electromagnetic waves into a single high-energy electromagnetic beam using methods such as spectral beam combining, polarization beam combining, and spatial beam combining. Compared to coherent beam combining, incoherent beam combining has no phase or amplitude requirements and is easier to adjust; however, it is limited by the beam combining mechanism and the required devices. For example, the number of input channels in passive beam combiners such as polarization beam combiners is limited by the number of polarizations required for power orthogonality. Summary of the Invention

[0005] In view of the aforementioned shortcomings in existing electromagnetic energy combining technologies, this invention provides a topology-protected yttrium iron garnet (YIG) photonic crystal electromagnetic energy combiner to address these technical problems. This invention's electromagnetic energy combiner supports electromagnetic waves propagating at the photonic crystal boundary in the form of boundary states. Due to the non-scattering unidirectional transmission characteristics and power orthogonality of the boundary states, a high-power broadband electromagnetic energy combiner independent of the phase of the input electromagnetic wave can be realized.

[0006] To achieve the aforementioned objectives of the invention, the concept of this invention is as follows:

[0007] This invention discloses a topology-protected electromagnetic energy combiner that employs a topology protection mechanism. Orthogonal mode excitation achieves scatter-free unidirectional transmission of topological boundary states. This orthogonal excitation ensures that the boundary states in different input channels are mutually orthogonal, preventing interference and destructive forces. The performance of the electromagnetic energy combiner is independent of the phase of the electromagnetic waves in the input channels. The orthogonality of the boundary states is characterized by power orthogonality, meaning their inner product in an energy sense is zero. The combiner structurally comprises a photonic crystal composed of a YIG column array and upper and lower copper-clad substrates surrounding the photonic crystal. Preferably, the combiner further includes a NdFeB magnet for controlling the relative permeability tensor of the YIG material. By splicing together YIG photonic crystals with different topological indices, topological boundary states are generated at their boundaries, with the number equal to the difference in their topological indices. Electromagnetic energy combining can be achieved by controlling and splicing the topological indices of various photonic crystals. Furthermore, boundary states possess scatter-free unidirectional propagation characteristics and energy orthogonality, and are insensitive to structural defects and impurities. Therefore, through structural optimization, topology-protected multi-channel electromagnetic energy combiners with arbitrary phase, high efficiency, wide bandwidth, and scalability can be realized. The topological boundary states are an important property of topologically nontrivial photonic crystals, propagating along the photonic crystal boundary, exhibiting unidirectional and scatter-free characteristics, and the number of topological boundary states is equal to the difference in topological indices of the photonic crystals on both sides of the boundary.

[0008] The photonic crystal is formed by arranging YIG pillars in a cubic lattice. By adjusting the diameter of the YIG pillars, the corresponding photonic crystal can have different topological indices, that is, photonic crystals with different topological properties can be constructed. The topological indices are the sum of the topological numbers of all energy bands below the band gap of the photonic crystal, and the topological numbers are Chern numbers, which are one of the topological invariants.

[0009] The upper and lower copper-clad substrates surround the YIG photonic crystal in the middle, thereby localizing the electromagnetic energy between the two copper-clad substrates and allowing it to propagate only in the photonic crystal.

[0010] The YIG material exhibits magnetic anisotropy and ferromagnetic resonance under an applied magnetic field. It also possesses excellent properties such as high dielectric constant, low dielectric loss, high saturation magnetization, and narrow ferromagnetic resonance linewidth. An external magnetic field can be applied to the YIG using neodymium iron boron magnets to optimize the photonic crystal parameters.

[0011] Based on the above inventive concept, the present invention adopts the following technical solution:

[0012] A topology-protected electromagnetic energy combiner comprises a first copper-clad substrate, a photonic crystal group, and a second copper-clad substrate connected sequentially from top to bottom. The photonic crystal group is composed of multiple photonic crystals spliced ​​together. The photonic crystals are rectangular arrays of square YIG prisms, and each array of YIG prisms has a different diameter so that each photonic crystal has a different topological index. The topological index is the sum of the topological numbers of all energy bands below the band gap of the photonic crystal.

[0013] Adjacent photonic crystals generate unidirectional transmission topological boundary states with no scattering in a first direction, a second direction, or a third direction at the boundary, and the number of topological boundary states is equal to the difference in topological indices of the photonic crystals on both sides of the boundary. The first direction and the third direction are parallel, and the first direction, the third direction, and the second direction are perpendicular to each other.

[0014] The input channel is formed by a unidirectional transmission topological boundary state with a topological boundary state number of 1. The boundary states in different input channels are orthogonal to each other and do not interfere with each other. The performance of the electromagnetic energy combiner is independent of the phase of the electromagnetic wave in the input channel.

[0015] Topological boundary states with a number greater than 1 constitute the output channels, and all output channels are on the same straight line.

[0016] Optionally, the photonic crystal group is formed by splicing photonic crystals with topological indices of 0, 1, and -1 adjacent to each other.

[0017] According to a specific embodiment of the present invention, the photonic crystals with topological indices of 0, 1, and -1 are spliced ​​together in the following order:

[0018] Place a photonic crystal with a topological index of 0, and arrange the other two types of photonic crystals adjacent to it as a reference.

[0019] A photonic crystal with a topological index of 1 is placed to the upper right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 1.

[0020] A photonic crystal with a topological index of -1 is placed to the lower right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as an electromagnetic energy input channel 2.

[0021] The photonic crystal with a topological index of -1 is also located below the photonic crystal with a topological index of 1. The boundary between these two crystals can generate two topological boundary states, which serve as the output channel after the electromagnetic energy is combined.

[0022] Optionally, three photonic crystals with different topological indices can be constructed by adjusting the diameter of the YIG pillars. Further, the YIG pillar radii of the photonic crystals with topological indices of -1, 1, and 0 are 0.152*L, 0.202*L, and 0.360*L, respectively, where L refers to the lattice constant, which is equal to 2 cm.

[0023] Optionally, the photonic crystal group is formed by splicing photonic crystals with topological indices of -1, 0, 1, and 2 in a clockwise manner, wherein the photonic crystal with topological index 0 is adjacent to the photonic crystals with topological indices of 1 and -1, and the photonic crystal with topological index 2 is adjacent to the photonic crystals with topological indices of 1 and -1.

[0024] Preferably, the photonic crystals with topological indices of -1, 0, 1, and 2 are spliced ​​together in the following order:

[0025] S1: Place a photonic crystal with a topological index of 0. The other three types of photonic crystals are arranged adjacent to it as a reference.

[0026] S2: Place a photonic crystal with a topological index of 1 to the right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 1.

[0027] S3: Place a photonic crystal with a topological index of 2 below a photonic crystal with a topological index of 1. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 2.

[0028] S4: Place a photonic crystal with a topological index of -1 below the photonic crystal with a topological index of 0. The photonic crystal with a topological index of -1 is also placed to the left of the photonic crystal with a topological index of 2. The boundary between the photonic crystals with topological indices of 0 and 1 can generate 1 boundary state, which serves as the electromagnetic energy input channel 3. The boundary between the photonic crystals with topological indices of -1 and 2 can generate 3 boundary states, which serve as the output channel after the electromagnetic energy is combined.

[0029] Optionally, four photonic crystals with different topological indices can be constructed by adjusting the diameter of the YIG pillars. Further, the YIG pillar radii of the photonic crystals with topological indices of -1, 0, 1, and 2 are 1.13, 1.36, 1.54, and 1.66 mm, respectively, corresponding to lattice constants of 7.14, 6.55, 7.87, and 10.26 mm.

[0030] Furthermore, the beam combiner also includes a neodymium iron boron magnet located below the second copper-clad substrate. The neodymium iron boron magnet optimizes the parameters of the YIG photonic crystal with magnetic anisotropy through a magnetic field, so that the system is in a ferromagnetic resonance state.

[0031] Furthermore, the neodymium iron boron magnets are arranged in an array, corresponding one-to-one with the YIG pillar array of the photonic crystal. That is, each neodymium iron boron magnet in the array is directly below its corresponding YIG pillar, in order to adjust the parameters of the photonic crystal and put the system in a ferromagnetic resonance state, in which the absorption of electromagnetic waves by the YIG pillars reaches its maximum value.

[0032] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0033] 1. This invention is based on the fact that the topological boundary states existing on the boundary of YIG photonic crystal have the characteristics of non-scattering unidirectional transmission, thus the electromagnetic energy combining efficiency is high, and the energy between the boundary states is orthogonal. Therefore, the performance of the topology-protected electromagnetic energy combiner is independent of the phase of the input electromagnetic wave, which greatly enhances the stability of the combiner.

[0034] 2. This invention can significantly improve the operating bandwidth of the electromagnetic energy combiner by optimizing the topological nontrivial band gap of the YIG photonic crystal;

[0035] 3. This invention has the advantages of miniaturization, integration, and modularity, and is also scalable, providing a new design platform for electromagnetic energy combiners. Attached Figure Description

[0036] To more clearly understand and illustrate the implementation methods and features of the embodiments of the present invention, a brief description will be given in conjunction with the accompanying drawings of the embodiments of the present invention.

[0037] Figure 1 This is a schematic diagram of the unit cell structure of a topologically protected electromagnetic energy combiner according to the present invention.

[0038] Figure 2 These are the topologically nontrivial photonic crystal bands of the three YIG photonic crystals in Example 1.

[0039] Figure 3 These are the projected energy bands of the topological boundary states of the three YIG photonic crystals in Example 1.

[0040] Figure 4 This is the mode field distribution simulated in the full-wave simulation of the Y-type electromagnetic energy combiner in Example 1.

[0041] Figure 5 This is a full-wave simulation diagram of the boundary states and electromagnetic energy beams in Example 1.

[0042] Figure 6 It is the inner product between the topological boundary states in the two input channels in Example 1.

[0043] Figure 7 This is a full-wave simulation diagram of the electromagnetic energy combiner with the topological protection 3-channel spiral staircase configuration in Example 2.

[0044] Figure 8 This is a simulation diagram of the beam combining efficiency of the electromagnetic energy combiner in the topology protection 3-channel spiral staircase configuration of Example 2. Detailed Implementation

[0045] The above solution will be further described below with reference to specific embodiments. Preferred examples of the present invention are as follows:

[0046] Example 1

[0047] See Figure 1-6 This embodiment uses the most basic Y-type electromagnetic energy combiner to conveniently and clearly illustrate the structural design process of the topology-protected electromagnetic energy combiner.

[0048] In this embodiment, the Y-type electromagnetic energy combiner includes three types of YIG photonic crystals, the arrangement of which is shown in [reference needed]. Figure 4 The upper and lower channels are input channels, while the right channel is the output channel. In the photonic crystal group (1), the YIG pillars are surrounded by a first copper-clad substrate (2) and a second copper-clad substrate (3) to form a three-dimensional structure, and a corresponding neodymium iron boron magnet (4) is mounted below the second copper-clad substrate (3), such as Figure 1 As shown. The photonic crystal group (1) is composed of three types of photonic crystals. The only structural difference between the three types of photonic crystals is the radius of the YIG pillars, such as... Figure 4 As shown.

[0049] based on Figure 4 In this embodiment, to meet the corresponding input / output channel functions, the topology index of the lower right photonic crystal is set to -1, the top right photonic crystal is set to 1, and the topology index of the left photonic crystal is set to 0.

[0050] In this embodiment, the YIG cylinder radii of the three photonic crystals with topological indices of -1, 1, and 0 are 0.152*L, 0.202*L, and 0.360*L, respectively, where L refers to the lattice constant, equal to 2 cm. The topologically nontrivial photonic crystal band structures of these three YIG photonic crystals are as follows: Figure 2 As shown, the horizontal solid lines represent energy bands, the shaded areas represent topologically nontrivial band gaps, the Chern numbers corresponding to the energy bands are represented by black numbers, and the topological index of the band gap is the sum of the Chern numbers of all energy bands below the band gap. Figure 2 It can be seen that the band gaps represented by the shaded areas in the three sub-figures have overlapping frequencies, and therefore can be used in the same photonic system. Their topological indices are -1, 1 and 0, respectively, which meet the above requirements.

[0051] In this embodiment, the projected energy bands of the unidirectional transmission topological boundary states generated by pairwise splicing of the three types of photonic crystals are as follows: Figure 3As shown in the diagram, the thick vertical lines indicate the existence of topological boundary states and their unidirectional propagation properties: the number of thick vertical lines equals the number of topological boundary states present at the interfaces of the two corresponding photonic crystals, and the sign of the slope of the thick lines indicates the propagation direction of the boundary states. Therefore, the propagation direction of the topological boundary states in the second and third sub-figures is the same, but opposite to that in the first sub-figure; furthermore, there are two topological boundary states in the second sub-figure, while only one topological boundary state exists in the other two sub-figures.

[0052] In this embodiment, the full-wave simulation of the Y-type electromagnetic energy combiner is as follows: Figure 4 As shown, two electromagnetic energy streams are input from the upper and lower boundaries, then combined and output from the right boundary. Figure 5 The three sub-figures respectively illustrate the simulation of the two input boundary states of the Y-type electromagnetic energy combiner and its beam combining.

[0053] In this embodiment, Figure 6 The inner product of the two input boundary states is shown, and its value remains basically 0, indicating that the two input boundary states have energy orthogonality, that is, the performance of the combiner is independent of the phase.

[0054] Example 2

[0055] See Figure 7-8 The structural design process of this embodiment is basically the same as that of Embodiment 1, with the following differences:

[0056] This embodiment uses four YIG photonic crystals with different topological indices to construct a topology-protected 3-channel electromagnetic energy combiner. Their topological indices are -1, 0, 1, and 2, respectively, and they are arranged in a spiral staircase configuration in a clockwise direction, as shown below. Figure 7 As shown. The specific splicing order is as follows:

[0057] S1: Place a photonic crystal with a topological index of 0. The other three types of photonic crystals are arranged adjacent to it as a reference.

[0058] S2: Place a photonic crystal with a topological index of 1 to the right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 1.

[0059] S3: Place a photonic crystal with a topological index of 2 below a photonic crystal with a topological index of 1. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 2.

[0060] S4: A photonic crystal with a topological index of -1 is placed below the photonic crystal with a topological index of 0. The photonic crystal with a topological index of -1 is also placed to the left of the photonic crystal with a topological index of 2. The boundary between the photonic crystals with topological indices of 0 and 1 generates one boundary state, serving as the electromagnetic energy input channel 3. The boundary between the photonic crystals with topological indices of -1 and 2 generates three boundary states, serving as the output channel after electromagnetic energy beam combining. In this embodiment, the YIG cylinder radii of the four photonic crystals are 1.13, 1.36, 1.54, and 1.66 mm, respectively, with corresponding lattice constants of 7.14, 6.55, 7.87, and 10.26 mm.

[0061] In this embodiment, the full-wave simulation of the topology-protected 3-channel electromagnetic energy combiner is as follows: Figure 7 As shown, three electromagnetic energy streams are input from the left, top, and right boundaries, then combined and output from the bottom boundary.

[0062] In this embodiment, Figure 8 The simulation results of the beam combining efficiency of the topology-protected 3-channel electromagnetic energy beam combiner are shown, with a beam combining efficiency of up to 96.2% and a corresponding bandwidth of 1.47 GHz.

[0063] In summary, the above embodiments demonstrate the structural design process of an electromagnetic energy combiner and design an arbitrary phase, high-efficiency, wide-bandwidth topology-protected 3-channel electromagnetic energy combiner.

[0064] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A topology-protected electromagnetic energy combiner, characterized in that, The components include a first copper-clad substrate, a photonic crystal group, and a second copper-clad substrate connected from top to bottom. The photonic crystal group is composed of 3 or 4 types of photonic crystals. The photonic crystals are rectangular arrays of square YIG pillars. Each array of YIG pillars has a different diameter so that each type of photonic crystal has a different topological index. The topological index is the sum of the topological numbers of all bands below the band gap of the photonic crystal. Adjacent photonic crystals generate unidirectional transmission topological boundary states with no scattering in a first direction, a second direction, or a third direction at the boundary, and the number of topological boundary states is equal to the difference in topological indices of the photonic crystals on both sides of the boundary. The first direction and the third direction are parallel, and the first direction, the third direction, and the second direction are perpendicular to each other. The input channel is formed by a unidirectional transmission topological boundary state with a topological boundary state number of 1. The boundary states in different input channels are orthogonal to each other and do not interfere with each other. The performance of the electromagnetic energy combiner is independent of the phase of the electromagnetic wave in the input channel. Topological boundary states with a number greater than 1 constitute the output channels, and all output channels are on the same straight line.

2. The bundle combiner according to claim 1, characterized in that, The photonic crystal group is composed of photonic crystals with topological indices of 0, 1, and -1 connected in an adjacent manner.

3. The bundle combiner according to claim 2, characterized in that, The photonic crystals with topological indices of 0, 1, and -1 are spliced ​​together in the following order: Place a photonic crystal with a topological index of 0, and arrange the other two types of photonic crystals adjacent to it as a reference. A photonic crystal with a topological index of 1 is placed to the upper right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 1. A photonic crystal with a topological index of -1 is placed to the lower right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as an electromagnetic energy input channel 2. The photonic crystal with a topological index of -1 is also located below the photonic crystal with a topological index of 1. The boundary between these two crystals can generate two topological boundary states, which serve as the output channel after the electromagnetic energy is combined.

4. The bundle combiner according to claim 3, characterized in that, The YIG cylinder radii of the photonic crystals with topological indices of -1, 1, and 0 are 0.152*L, 0.202*L, and 0.360*L, respectively, where L refers to the lattice constant, which is equal to 2 cm.

5. The bundle combiner according to claim 1, characterized in that, The photonic crystal group is composed of photonic crystals with topological indices of -1, 0, 1, and 2 arranged in a clockwise direction. The photonic crystal with topological index 0 is adjacent to the photonic crystals with topological indices of 1 and -1, respectively, and the photonic crystal with topological index 2 is adjacent to the photonic crystals with topological indices of 1 and -1, respectively.

6. The bundle combiner according to claim 5, characterized in that, The photonic crystals with topological indices of -1, 0, 1, and 2 are spliced ​​together in the following order: S1: Place a photonic crystal with a topological index of 0. The other three types of photonic crystals are arranged adjacent to it as a reference. S2: Place a photonic crystal with a topological index of 1 to the right of a photonic crystal with a topological index of 0. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 1. S3: Place a photonic crystal with a topological index of 2 below a photonic crystal with a topological index of 1. The boundary between the two can generate a topological boundary state, which serves as electromagnetic energy input channel 2. S4: Place a photonic crystal with a topological index of -1 below the photonic crystal with a topological index of 0. The photonic crystal with a topological index of -1 is also placed to the left of the photonic crystal with a topological index of 2. The boundary between the photonic crystals with topological indices of 0 and 1 can generate one topological boundary state, which serves as the electromagnetic energy input channel 3. The boundary between the photonic crystals with topological indices of -1 and 2 can generate three topological boundary states, which serve as the output channels after the electromagnetic energy is combined.

7. The bundle combiner according to claim 6, characterized in that, The YIG cylinder radii of the photonic crystals with topological indices of -1, 0, 1, and 2 are 1.13, 1.36, 1.54, and 1.66 mm, respectively, and the corresponding lattice constants are 7.14, 6.55, 7.87, and 10.26 mm, respectively.

8. The bundle combiner according to any one of claims 1-7, characterized in that, The beam combiner also includes a neodymium iron boron magnet located below the second copper-clad substrate. The neodymium iron boron magnet optimizes the parameters of the YIG photonic crystal with magnetic anisotropy through a magnetic field, so that the system is in a ferromagnetic resonance state.

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