Topological photonic switch with adjustable band gap range

Abstract

The invention discloses a topological photonic switch with an adjustable band gap range. According to the device, air is in direct contact with a chiral medium to form a topological photonic switch structure which does not need a coating layer and is adjustable in band gap range. The non-trivialness topological characteristic of the chiral medium is induced by a non-zero magnetoelectric coupling effect, and a boundary state of wave vector direction locking transmission exists between the chiral medium and an air boundary. A scatterer is introduced into the photonic switch, so that the robust transmission with controllable port emergent light of boundary waves can be tested. According to the invention, by changing the operation parameter omega in the topological photonic switch, the topological photonic switch device with adjustable band gap range and controllable port light emission can be realized. The method is suitable for topological functional devices such as a topological photonic switch, a topological photonic router, a topological photonic isolator and a topological wavelength splitter with the adjustable band gap range, and higher flexibility is provided for designing and achieving a multiplexing topological device with the adjustable band gap range and controllable port light emitting.

Description

Technical Field

[0001] This invention belongs to the field of topological photonics and basic optical element technology, and relates to a topological photonic switch with adjustable bandgap range. Background Technology

[0002] Topological photonics, originating from the topological concept in condensed matter physics, has become a rapidly emerging key research area in photonics. Since its inception, this research direction has achieved a series of groundbreaking advancements: from the initial theoretical conception and experimental verification of two-dimensional photonic topological insulators to the exploration of three-dimensional topological insulators and three-dimensional Weyl half-metals, each representing a significant milestone. In particular, the study of Weyl half-metals has sparked a widespread research boom in physics and photonics, leading to the emergence of many novel physical phenomena, such as negative magnetoresistance, topological negative refraction, and three-dimensional topological photonic routing.

[0003] Recently, topological switching based on topological boundary modes in photonic and phononic crystals has been extensively studied. Based on the topological switching effect, several interesting applications can be realized in topological systems, such as dynamically controllable topological waveguides, dynamically on / off topological lasers, optical communication, and quantum information processing. However, photonic and phononic crystals typically require complex cell structures and strict periodicity conditions. Therefore, topological functional devices designed and implemented on photonic and phononic crystal platforms lack relatively flexible tunability.

[0004] Conversely, under the long-wavelength approximation, chiral media can be considered as continuous photonic materials, and their optical response is described by an equivalent electromagnetic tensor. Chiral media lack spatial inversion symmetry due to the inherent magnetoelectric coupling between their magnetic and electric field components. In recent years, chiral media have been extensively studied in the application of topological photonic devices, such as topological photonic routing, topological negative refraction, and topological beam splitters. However, current research on chiral-based topological photonic switches relies on limited methods, with most studies focusing on single-frequency, single-channel topological photonic switch systems. Research on functional devices such as multiplexed, bandgap-adjustable topological photonic switches is rarely reported. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a topological photonic switch that enables adjustable bandgap range and multiplexing, thereby providing a multi-channel topological photonic functional device with controllable bandgap range for application in optoelectronic device manufacturing.

[0006] A topological photonic switch with tunable bandgap range comprises a heterostructure consisting of at least one chiral medium and an air layer containing a scatterer; the chiral medium is independent of an externally applied magnetic field; wherein, there is an interface state with tunable bandgap range between the chiral medium and the air layer, and the bandgap range of the chiral medium and the air layer is different due to different frequencies, and light waves within the bandgap range achieve a topological switching effect through the scatterer in the air layer.

[0007] As a preferred method, the controllable emission of light from the interface state can be achieved by adjusting the relative spatial positions of the air layer and the chiral medium in the photonic switching device.

[0008] Preferably, if there are two or more chiral media, an air layer exists between adjacent chiral media.

[0009] Preferably, if there are two or more chiral media, the topological properties of adjacent chiral media may be the same or different.

[0010] Preferably, since the topological photonic switch of the present invention is composed of air and a chiral medium in direct contact, the interface state of the topological photonic switch can achieve wave vector direction locking output.

[0011] Preferably, the chiral medium is a bulk material that can be described by an equivalent electromagnetic tensor, and its nontrivial topological response is induced by non-zero magnetoelectric coupling parameters; the non-zero topological invariants in the chiral medium are caused by Berry curvature. When the operating parameter ω of the chiral medium changes, the Berry flux distribution and topological invariants of the chiral medium also exhibit corresponding changes.

[0012] Preferably, at least one type of structural defect is introduced at the interface between the chiral medium and the air layer to test the scattering suppression characteristics of the topological boundary wave during transmission.

[0013] Preferably, the interface states in the topological photonic switch are excited by an excitation source at the interface.

[0014] Compared with existing topological functional devices that typically require complex cell structures and strict periodic conditions, the present invention has at least the following advantages: This invention provides a bandgap-range tunable topological photonic switch that eliminates the dependence on cladding structures, achieving a multiplexed topological photonic switch through direct contact between air and a chiral medium. While suppressing propagation by topological boundary wave scattering, the propagation direction of the boundary wave corresponds one-to-one with its wave vector. Furthermore, by changing the positions of the air and chiral medium in space, a bandgap-range tunable topological photonic switch with controllable output ports can be achieved. Attached Figure Description

[0015] Figure 1This is one example of a topological photonic switch with adjustable bandgap range provided in an embodiment of the present invention. The figures are marked as follows: 1, chiral medium; 1-1, first chiral medium; 1-2, second chiral medium; 2, air layer; 3, scatterer; 4, insulating shell.

[0016] Figure 2 This is a second example of a topological photonic switch with adjustable bandgap provided in an embodiment of the present invention. The following are the markings in the figure: 1, chiral medium; 1-1, first chiral medium; 1-2, second chiral medium; 1-3, third chiral medium; 1-4, fourth chiral medium; 2, air layer; 3, scatterer; 4, insulating shell.

[0017] Figure 3 This is the third example of a topological photonic switch with adjustable bandgap provided in the embodiments of the present invention. The markings in the figure are: 1, chiral medium; 1-1, first chiral medium; 1-2, second chiral medium; 2, air layer; 3, scatterer; 4, insulating shell.

[0018] Figure 4 The fourth example of a topological photonic switch with adjustable bandgap range provided in this embodiment of the invention is shown in the figure. The markings in the figure are: 1, chiral medium; 1-1, first chiral medium; 1-2, second chiral medium; 2, air layer; 3, scatterer; 4, insulating shell.

[0019] Figure 5 This is the fifth example of a topological photonic switch with adjustable bandgap provided in the embodiments of the present invention. In the figure, the following are marked: 1. Chiral medium; 2. Air layer; 3. Scatterer; 4. Insulating shell.

[0020] Figure 6 This is the sixth example of a topological photonic switch with adjustable bandgap range provided in the embodiments of the present invention. The markings in the figure are: 1, chiral medium; 1-1, first chiral medium; 1-2, second chiral medium; 2, air layer; 3, scatterer; 4, insulating shell.

[0021] Figure 7 This is the seventh example of a topological photonic switch with adjustable bandgap provided in the embodiments of the present invention. In the figure, the following are marked: 1. Chiral medium; 2. Air layer; 3. Scatterer; 4. Insulating shell.

[0022] Figure 8 The topological bandgap variation and boundary state distribution of the topological photonic switch of the present invention under different operating parameters ω are shown in (a) as a phase diagram of the evolution of the topological bandgap with operating parameter ω, and (b) as the distribution of the topological boundary state under different operating parameters ω, where ω is 0.5, 0.6, 0.7, 0.8 and 0.9 from left to right. kz and ky express z shaft and y The wave vector component in the axial direction.

[0023] Figure 9 To address the change in the relative spatial positions of air, scatterer, and chiral medium in this invention, a topological photonic switch with an adjustable bandgap range is designed and implemented; where (a) is the specific simulation result corresponding to Case 1, (b) is the specific simulation result corresponding to Case 2, (c) is the specific simulation result corresponding to Case 3, (d) is the specific simulation result corresponding to Case 4, (e) is the specific simulation result corresponding to Case 6, and (f) is the specific simulation result corresponding to Case 7.

[0024] Figure 10 This is a specific one-dimensional normalized electric field intensity distribution of a topological photonic switch composed of air, a scatterer, and a chiral medium, as described in Example 2 of this invention, where (a) is... Figure 9 The one-dimensional normalized electric field intensity distribution corresponding to the interface cutoff line 1 in (b) is shown in (b). Figure 9 (b) shows the one-dimensional normalized electric field intensity distribution corresponding to the interface cutoff line 2, and (c) shows the distribution of the electric field intensity. Figure 9 The one-dimensional normalized electric field intensity distribution corresponding to the interface cutoff line 3 in (b). Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of this application implemented as described and embodied in the accompanying drawings can typically be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "vertical" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first," "second," "third," and "fourth" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] This invention provides a topological photonic switch with an tunable bandgap range. The device is constructed by direct contact between air and a chiral medium, forming a tunable bandgap topological photonic switch structure without a cladding layer. The nontrivial topological properties of the chiral medium are induced by non-zero magnetoelectric coupling effects, and a boundary state with wave vector direction-locked propagation exists at its boundary with air. By introducing sharp structural defects into the photonic switch, the scattering suppression and unidirectional robust propagation of the boundary wave can be tested. This invention enables the realization of a topological photonic switch device with an tunable bandgap range and controllable port output by changing the operating parameter ω in the topological photonic switch. This invention is applicable to topological functional devices such as topological photonic switches, topological photonic routes, topological photonic isolators, and topological wavelength division multiplexers with tunable bandgap ranges, providing greater flexibility for designing and implementing multiplexed topological devices with tunable bandgap ranges and controllable port output.

[0031] One implementation method Figure 1 This provides one example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field, and there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges, and light waves within the bandgap range achieve a topological switching effect through the scatterer within the air layer.

[0032] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0033] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1 and a second chiral medium 1-2. The first chiral medium 1-1 and the second chiral medium 1-2 are cubic blocks of equal size. The first chiral medium 1-1 and the second chiral medium 1-2 are respectively attached to the lower sides of the inner cavity of the insulating shell 4. A first air gap exists between the first chiral medium 1-1 and the second chiral medium 1-2, and a second air gap exists between their tops and the top of the inner cavity of the insulating shell 4, forming a connected air layer 2 with a T-shaped cross-section. The first chiral medium 1-1 and the air layer 2 are in direct contact and form a heterogeneous structure; the second chiral medium 1-2 and the air layer 2 are also in direct contact and form a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1 and the second chiral medium 1-2 can be the same or different, and they can each be independently selected from magnetoelectric coupling parameters of different symbols, such as metals like copper and gold, silicon dioxide, and silicon.

[0034] Within this T-shaped air layer 2, a scatterer 3 is disposed within the first air gap, and does not contact the first chiral medium 1-1 or the second chiral medium 1-2. The scatterer 3 can be made of an isotropic dielectric material, such as aluminum oxide.

[0035] One implementation method Figure 2 This is the second example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field, and there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0036] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0037] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1, a second chiral medium 1-2, a third chiral medium 1-3, and a fourth chiral medium 1-4. The first chiral medium 1-1, the second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 can be cubic blocks of equal size. The first chiral medium 1-1, the second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 are respectively disposed close to the four corners of the inner cavity of the insulating shell 4. An air gap exists between the first chiral medium 1-1 and the second chiral medium 1-2; a second air gap exists between the second chiral medium 1-2 and the fourth chiral medium 1-4; a third air gap exists between the third chiral medium 1-3 and the fourth chiral medium 1-4; a fourth air gap exists between the third chiral medium 1-3 and the first chiral medium 1-1; and a fifth air gap exists at the center of the four chiral media. These air gaps form a connected air layer 2 with a cross-shaped cross-section. The first chiral medium 1-1 and air layer 2 are in direct contact and form a heterogeneous structure; the second chiral medium 1-2 and air layer 2 are in direct contact and form a heterogeneous structure; the third chiral medium 1-3 and air layer 2 are in direct contact and form a heterogeneous structure; and the fourth chiral medium 1-4 and air layer 2 are in direct contact and form a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1, the second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 may be the same or different, and they may be independently selected from magnetoelectric coupling parameters of different symbols, such as metals like copper and gold, silicon dioxide, and silicon.

[0038] Within this cross-shaped air layer 2, three scatterers 3 are positioned within the second, third, and fourth air gaps, respectively, and do not contact the first chiral medium 1-1, the second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4. The three scatterers 3 can be made of the same material or different materials, such as ceramic particles with high dielectric constants (e.g., BST, TiO2) or metal particles.

[0039] One implementation method Figure 3 This is the third example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field, and there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0040] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0041] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1 and a second chiral medium 1-2. The first chiral medium 1-1 has an L-shaped cross-section rotated 90° clockwise, including horizontal and vertical arms arranged perpendicularly to each other; the length of the horizontal arm is the same as the length of the insulating shell 4, and the width is less than the height of the insulating shell 4; the length of the vertical arm is less than the length of the insulating shell 4, and the width is equal to the height of the insulating shell 4. The second chiral medium 1-2 is a cubic block, which is set in close contact with the insulating shell 4, and forms an air layer 2 with a cross-section rotated 90° clockwise between it and the first chiral medium 1-1. The first chiral medium 1-1 and the air layer 2 are in direct contact and constitute a heterogeneous structure; the second chiral medium 1-2 and the air layer 2 are in direct contact and constitute a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1 and the second chiral medium 1-2 can be the same or different, and can be independently selected from magnetoelectric coupling parameters of different symbols, such as metals such as copper and gold, silicon dioxide, and silicon.

[0042] Within this T-shaped air layer 2, a scatterer 3 is disposed within the first air gap, and does not contact the first chiral medium 1-1 or the second chiral medium 1-2. The scatterer 3 can be made of an isotropic dielectric material, such as aluminum oxide.

[0043] One implementation method Figure 4 This is the fourth example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field, and there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0044] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0045] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1 and a second chiral medium 1-2. The first chiral medium 1-1 and the second chiral medium 1-2 are cubic blocks of equal size. The first chiral medium 1-1 and the second chiral medium 1-2 are respectively attached to the upper and lower sides of the inner cavity of the insulating shell 4, forming a connected air layer 2 with an H-shaped cross-section. The first chiral medium 1-1 and the air layer 2 are in direct contact and form a heterogeneous structure; the second chiral medium 1-2 and the air layer 2 are also in direct contact and form a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1 and the second chiral medium 1-2 can be the same or different, and they can each be independently selected from magnetoelectric coupling parameters of different symbols, such as metals like copper and gold, silicon dioxide, and silicon.

[0046] Within this T-shaped air layer 2, a scatterer 3 is disposed within the first air gap, and does not contact the first chiral medium 1-1 or the second chiral medium 1-2. The scatterer 3 can be made of an isotropic dielectric material, such as aluminum oxide.

[0047] One implementation method Figure 5 This is the fifth example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field; there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0048] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0049] For example, in this embodiment, the chiral medium 1 is a cubic block, but it has a structural defect of a cubic structure on its top. The chiral medium 1 is closely attached to the lower side of the inner cavity of the insulating shell 4, and the chiral medium 1, the top layer of the insulating shell 4, and at least one side form a communicating air layer 2. The chiral medium 1 and the air layer 2 are in direct contact and form a heterogeneous structure. Preferably, the chiral medium 1 is selected from copper, a metal material with a positive sign direction magnetoelectric coupling parameter. The air layer 2 includes a cross-shaped air layer and a longitudinal strip-shaped air layer that are connected. The left arm of the cross-shaped air layer is connected to the top of the longitudinal strip-shaped air layer, and the bottom of the longitudinal strip-shaped air layer contacts the bottom of the inner cavity of the insulating shell 4.

[0050] Within this air layer 2, a scatterer 3 is positioned within the left arm of the cross-shaped air layer, without contacting the chiral medium 1. The scatterer 3 can be made of an isotropic dielectric material, such as aluminum oxide.

[0051] One implementation method Figure 6 This is the sixth example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field, and there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0052] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0053] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1 and a second chiral medium 1-2. The first chiral medium 1-1 and the second chiral medium 1-2 are respectively attached to the inner cavity of the insulating shell 4, and there is a connected air layer 2 with a Z-shaped cross-section between them. One end of the Z-shaped air layer 2 points to and contacts one side wall of the inner cavity of the insulating shell 4, and the other end points to and contacts the opposite side wall of the inner cavity of the insulating shell 4. The first chiral medium 1-1 and the air layer 2 are in direct contact and form a heterogeneous structure; the second chiral medium 1-2 and the air layer 2 are in direct contact and form a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1 and the second chiral medium 1-2 can be the same or different, and they can be independently selected from magnetoelectric coupling parameters of different symbols, such as metals such as copper and gold, silicon dioxide, and silicon.

[0054] Within this T-shaped air layer 2, a scatterer 3 is disposed within the air layer 2, without contacting the first chiral medium 1-1 or the second chiral medium 1-2. The scatterer 3 can be made of an isotropic dielectric material, such as aluminum oxide.

[0055] One implementation method Figure 7 This is the seventh example of a topological photonic switch with an adjustable bandgap range. The topological photonic switch in this embodiment includes: an insulating housing 4, a chiral medium 1 disposed inside the insulating housing 4, and an air layer 2 containing a scatterer 3. The chiral medium does not require an external magnetic field; there is an interface state with an adjustable bandgap range between it and the air layer. The different frequencies of the chiral medium and the air layer result in different bandgap ranges. Light waves within the different bandgap ranges achieve a topological switching effect through the scatterer within the air layer.

[0056] For example, in this embodiment, the insulating shell 4 is a sealed space, which is made of insulating material, such as resin material, plastic, etc., to form an insulating isolation from the outside world.

[0057] For example, in this embodiment, the chiral medium 1 includes a first chiral medium 1-1, a second chiral medium 1-2, a third chiral medium 1-3, and a fourth chiral medium 1-4. The first chiral medium 1-1 has a C-shaped structure. The second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 are cubic blocks, which can be of equal or unequal size. The second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 are located at the C-shaped opening of the first chiral medium 1-1, thus forming an air layer 2 with an E-shaped cross-section. The first chiral medium 1-1 and the air layer 2 are in direct contact and form a heterogeneous structure; the second chiral medium 1-2 and the air layer 2 are in direct contact and form a heterogeneous structure; the third chiral medium 1-3 and the air layer 2 are in direct contact and form a heterogeneous structure; and the fourth chiral medium 1-4 and the air layer 2 are in direct contact and form a heterogeneous structure. Preferably, the topological properties of the first chiral medium 1-1, the second chiral medium 1-2, the third chiral medium 1-3, and the fourth chiral medium 1-4 may be the same or different, and they may be independently selected from magnetoelectric coupling parameters of different symbols, such as metals like copper and gold, silicon dioxide, and silicon.

[0058] Within this air layer 2, two scatterers 3 are positioned, corresponding to the locations of the structural defects. The scatterers 3 can be made of isotropic dielectric materials, such as aluminum oxide.

[0059] The following example uses a bulk chiral medium in direct contact with an air layer. In this embodiment, the chiral medium has a constant permeability of μ=1, a magnetoelectric coupling coefficient |g|=0.5, and a dielectric parameter of transverse permittivity ε. t =1.5, longitudinal permittivity ε z =1-1 / ω 2 ω is the operating frequency. Based on the premise of breaking the spatial inversion symmetry induced by the magnetoelectric coupling effect in the chiral medium, the chiral medium has Berry fluxes in different directions, and the topological invariant formed by the inwardly converging Berry flux is defined as negative.

[0060] Figure 8 Figure (a) shows the evolution phase diagram of the topological bandgap range with respect to the operating parameter ω within a certain range of operating parameters, calculated according to the present invention. The shaded area represents the topological bandgap. From the specific locations of the upper and lower boundaries of the topological bandgap in the figure, it can be seen that the range of the topological bandgap increases with the increase of the operating parameter. Figure 8 Figure (b) shows the specific distribution of the chiral medium isofrequency surface and topological boundary states in this invention as the chiral medium operating frequency changes. The blue-green curve represents the chiral medium isofrequency surface, the gray dashed line represents air, and the red curve represents the topological boundary states. As can be seen from the specific distribution in the figure, the topological bandgap and boundary states can exist stably under certain operating parameters, and the range of the topological bandgap will also change, which is a prerequisite for realizing a topological photonic switch with an adjustable bandgap range.

[0061] Figure 9 (a)- Figure 9 (f) shows the numerical simulation results of the topological photonic switch in the chiral medium of this invention, where multiple different ports are defined (e.g., Figure 9 (b) Ports 1-8) Qualitative analysis of the controllable light output characteristics of the topological photonic switch. In the figure, chiral medium 1-1 is a chiral medium with a magnetoelectric coupling parameter greater than 0 (e.g., copper), and chiral medium 1-2 is a chiral medium with a magnetoelectric coupling parameter less than 0 (e.g., copper). The sign of the magnetoelectric coupling parameter can be adjusted by the helical direction of the helical structures of the chiral medium, and its magnitude is related to the helical density of the helical structures. From... Figure 9 Electromagnetic simulation results show that by changing the relative spatial positions of the operating air and the chiral medium, topological photonic switches with different port outputs can be realized. Furthermore, by changing the spatial positions and number of scatterers in the device, multi-port controllable topological photonic switches can be designed and implemented, such as… Figure 9 (b) and Figure 9 As shown in (f).

[0062] Figure 10 (a)- Figure 9 (c) shows the specific one-dimensional normalized electric field intensity distribution of the topological photonic switch composed of air, scatterer, and chiral medium in this invention, where interface cutoffs 1-3 correspond to... Figure 9 (b) Results. Figure 10 In diagrams (b) and (c), the normalized electric field intensity exists only at output ports 6 or 8 (corresponding to the "on" state of the switch), while ports 5 and 7 show no electromagnetic wave output (corresponding to the "off" state of the switch). The distribution results are consistent with... Figure 9 The electromagnetic numerical simulation results in (b) are consistent, and the reason for this type of topological switch is due to the unidirectional coupling between the boundary states and the scatterer. Therefore, the unidirectional coupling direction between the boundary states and the scatterer can be controlled by adjusting the magnetoelectric coupling parameters of each chiral medium, thereby achieving the open state of a specified port. Further analysis... Figure 10 The normalized electric field intensity distribution proves that the topological photonic switch in this invention can achieve multi-port controllable output and realize a topological photonic device with multiplexing function under magnetic field-free conditions.

[0063] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A topological photonic switch with tunable bandgap range, characterized in that, The heterostructure is composed of at least one chiral medium and an air layer containing scatterers; wherein the interface state between the chiral medium and the air layer has a band gap range that can be adjusted, the chiral medium and the air layer have different band gap ranges due to different frequencies, and the light waves in the band gap range pass through the scatterers in the air layer to realize the topological switching effect.

2. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, The chiral medium is free of dependence on an external magnetic field.

3. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, By adjusting the relative spatial positions of the air layer and the chiral medium in the photonic switching device, the interface state light output can be controlled.

4. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, If there are two or more chiral media, there is an air layer between adjacent chiral media.

5. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, If there are two or more chiral media, the topological properties of adjacent chiral media are the same or different.

6. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, Since the topological photonic switch of the application is directly contacted by air and chiral medium, the interface state of the topological photonic switch can realize wave vector direction locking output.

7. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, The chiral medium is a bulk material described by an equivalent electromagnetic tensor, and the non-trivial topological response is induced by a non-zero magneto-electric coupling parameter; the non-zero topological invariant in the chiral medium is caused by the Berry curvature.

8. The topological photonic switch with adjustable bandgap range according to claim 7, wherein, When the operating parameter ω of the chiral medium changes, the Berry flux distribution and topological invariant of the chiral medium also exhibit corresponding changes.

9. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, At least one type of structural defect is introduced at the interface between the chiral medium and the air layer.

10. The topological photonic switch with adjustable bandgap range according to claim 1, wherein, The interface state in the topological photonic switch is excited by an excitation source at the interface.

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