All-silicon terahertz multiplexing chip based on valley hall topological phase transition

Abstract

The application discloses a full-silicon terahertz multiplex chip based on valley Hall topological phase transition, and belongs to the technical field of terahertz on-chip passive devices, wherein the multiplex chip is a double-layer structure, the double-layer structure comprises an upper waveguide and a lower waveguide in a fishhook structure, the working state of the chip can be regulated by controlling the distance between the upper waveguide and the lower waveguide in the fishhook structure, and then controllable terahertz on-chip channel switching is realized; the working state comprises two working states of coupling and decoupling. The upper and lower photonic crystal waveguiders of the application can control the two working states of coupling and decoupling of the double-layer waveguide by adjusting the distance between the double-layer waveguide, realize the conversion of the transmission path, and then realize the switching of the on-chip channel.

Description

Technical Field

[0001] This invention belongs to the field of terahertz on-chip passive device technology, specifically relating to an all-silicon terahertz multiplexed chip based on valley-Hall topological phase transition. Background Technology

[0002] Terahertz spectrum lies between microwave and infrared, possessing characteristics of both electronics and photonics. Compared to existing microwave communication, terahertz communication, due to its higher carrier frequency and richer spectrum resources, can achieve ultra-high-speed, low-latency data transmission and is considered an important air interface for next-generation communication technology (6G). Developing integrated, chip-based terahertz functional devices is of great significance for building terahertz communication systems and has become a key research topic both domestically and internationally in recent years.

[0003] As a key component of communication systems, flexible multiplexers enable on-demand channel switching, effectively improving spectrum utilization efficiency and flexibility. However, due to functional failures caused by semiconductor material dispersion at terahertz frequencies and the lack of on-chip control methods for photonic systems, currently reported terahertz multiplexing chips remain unadjustable, making it difficult to achieve flexible multiplexing functionality. Summary of the Invention

[0004] To address the functional limitations and other shortcomings of existing terahertz on-chip devices, this invention provides an all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition. The multiplexing chip is a double-layer harpoon waveguide, and the chip's operating state is switched by adjusting the spacing between the two harpoon waveguides, thereby achieving controllable on-chip terahertz channel switching.

[0005] The principle of an all-silicon terahertz flexible multiplexing chip based on valley-Hall topological phase transition of the present invention is as follows:

[0006] At the junction of two photonic crystals with different topological phases, a boundary is formed, where electromagnetic waves of a specific frequency can be transmitted. For a double-layer photonic crystal with a boundary, when the interlayer spacing is small, the two photonic crystals will couple, making the overall effect of the double-layer photonic crystal a superposition of the two layers, which is basically unrelated to the transmission effect of a single layer. Therefore, the transmission path can be changed by designing specific photonic crystals. When the interlayer spacing is large, the coupling effect of the two photonic crystals is small, making the transmission effect of the double-layer photonic crystal consistent with that of a single-layer photonic crystal. Therefore, electromagnetic waves can be transmitted at the transmission boundary of each layer.

[0007] This invention is achieved through the following technical solution:

[0008] A silicon-based terahertz multiplexing chip based on valley-Hall topological phase transition is disclosed. The multiplexing chip has a two-layer structure, which includes an upper waveguide and a lower waveguide of a harpoon-shaped structure. By controlling the spacing between the upper and lower waveguides of the harpoon-shaped structure, the operating state of the chip can be adjusted, thereby realizing controllable on-chip terahertz channel switching. The operating state includes two modes: coupling and decoupling.

[0009] Furthermore, the coupling state refers to the situation where the distance between two harpoon-shaped waveguides is 0.05-0.10 mm, and the waveguides are coupled together, so that the overall transmission path is a superposition of the two waveguides; decoupling refers to the situation where the distance between two harpoon-shaped waveguides is 0.80-1.00 mm, and the coupling between the waveguides is small and can be ignored, so that the overall transmission path is consistent with the transmission path of a single waveguide.

[0010] Furthermore, both the upper and lower waveguides are composed of periodically arranged equilateral triangular air holes. These equilateral triangular air holes include four types of triangles with varying side lengths, from largest to smallest: Type I, Type II, Type III, and Type IV triangular air holes. The Type I and Type IV triangular air holes form a unit cell, arranged in a honeycomb structure to form a first-type valley photonic crystal (VPC1). Interchanging the positions of the triangular air holes in the first-type valley photonic crystal forms a second-type valley photonic crystal. (VPC2), the type II and type III triangular air holes form a unit cell, which is arranged in a honeycomb structure to form a third type of valley photonic crystal (VPC3). The positions of the triangular air holes in the third type of valley photonic crystal are interchanged to form a fourth type of valley photonic crystal (VPC4). The first type of valley photonic crystal, the second type of valley photonic crystal, and the third type of valley photonic crystal are combined in a harpoon-shaped structure to form an upper waveguide. The fourth type of valley photonic crystal, the third type of valley photonic crystal, and the second type of valley photonic crystal are combined in a harpoon-shaped structure to form a lower waveguide.

[0011] Furthermore, in the first type of valley photonic crystal (VPC1), type I triangular air holes are distributed on the top edge of the hexagonal honeycomb structure, and type IV triangular air holes are distributed on the bottom edge of the hexagonal honeycomb structure; in the third type of valley photonic crystal (VPC3), type II triangular air holes are distributed on the top edge of the hexagonal honeycomb structure, and type III triangular air holes are distributed on the bottom edge of the hexagonal honeycomb structure.

[0012] Furthermore, both the upper and lower waveguides are composed of high-resistivity silicon with a relative permittivity of 11.7-12.0.

[0013] Furthermore, the thickness of both the upper and lower waveguides is 0.18-0.22 mm.

[0014] Furthermore, the cell lattice constant a is 0.7-0.8 mm, the side length of the type I triangular air hole is 0.49-0.54 mm, the side length of the type II triangular air hole is 0.21-0.26 mm, the side length of the type III triangular air hole is 0.38-0.43 mm, and the side length of the type IV triangular air hole is 0.32-0.37 mm.

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] 1. The two different photonic crystal waveguides of the present invention control the coupling and decoupling working states of the two waveguides by adjusting the distance between the two waveguides, thereby realizing the conversion of the transmission path and the switching of the on-chip channel;

[0017] 2. The device structure and materials proposed in this invention are compatible with existing CMOS processing technology, enabling large-scale integration and mass production. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0019] Figure 1 (a) is a schematic diagram of the upper harpoon waveguide structure of the present invention;

[0020] Figure 1 (b) is a schematic diagram of the lower-layer harpoon waveguide structure of the present invention;

[0021] Figure 1 (c) represents the composite topological phase of the present invention when the spacing between the two-layer waveguides is 0.05 mm. The black solid line indicates that electromagnetic waves can be transmitted.

[0022] Figure 2 (a) is the xy cross-sectional view of the upper harpoon waveguide of the present invention;

[0023] Figure 2 (b) is the xy cross-sectional view of the lower harpoon waveguide of the present invention;

[0024] Figure 3 (a) is a graph showing the variation of the band gap of the monolayer valley photonic crystal of the present invention with the difference in the side length of the two triangular air holes in the unit cell, and the lattice constant a is 0.75 mm;

[0025] Figure 3(b) is a graph showing the band gap of the bilayer valley photonic crystal of the present invention as a function of the difference in side length of the two triangular air holes in the unit cell when the spacing is 0.05 mm, and the lattice constant a is 0.75 mm;

[0026] Figure 4 (a) is an overall device diagram of an embodiment of the present invention in a coupled working state;

[0027] Figure 4 (b) shows the S-parameter transmission spectrum of the embodiment with a spacing of 0.05 mm between the two waveguide layers;

[0028] Figure 4 (c) is the Hz (A / m) distribution diagram of the upper waveguide in the coupled working state of the present invention;

[0029] Figure 4 (d) is the Hz (A / m) distribution diagram of the lower waveguide in the coupled working state of the present invention;

[0030] Figure 5 (a) is an overall device diagram of an embodiment of the present invention in a decoupled working state;

[0031] Figure 5 (b) shows the S-parameter transmission spectrum of the embodiment with a spacing of 1 mm between the two waveguide layers;

[0032] Figure 5 (c) is the Hz (A / m) distribution diagram of the upper waveguide in the decoupled working state of the present invention;

[0033] Figure 5 (d) is the Hz (A / m) distribution diagram of the lower waveguide in the decoupled working state of the present invention. Detailed Implementation

[0034] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0035] Example 1

[0036] like Figure 4 As shown in (a), this embodiment provides an all-silicon terahertz multiplexing chip based on valley-Hall topology phase transition operation in a coupled state. The chip consists of a double-layer harpoon waveguide and a triangular coupling plate, wherein the triangular coupling plate is directly connected to the harpoon waveguide. During use, the triangular coupling plate needs to be inserted into the WR-8 standard rectangular waveguide port. The double-layer harpoon waveguide includes an upper waveguide with a harpoon structure (e.g., Figure 1 (as shown in (a)) and the lower waveguide (as shown in (a)) Figure 1As shown in (b), by controlling the spacing between the upper and lower waveguides of the harpoon-shaped structure, the operating state of the chip can be adjusted, thereby achieving controllable on-chip terahertz channel switching; the operating state includes two types: coupling and decoupling. Figure 1 (c) represents the synthesized topological phase when the spacing between the two waveguides in this embodiment is 0.05 mm. The black solid line indicates that electromagnetic waves can be transmitted.

[0037] In this embodiment, both the upper and lower waveguides are composed of periodically arranged equilateral triangular air holes. The equilateral triangular air holes include four types of triangles with different side lengths, which are classified as type I, type II, type III, and type IV triangular air holes, from longest to shortest side length.

[0038] like Figure 2 Figure (a) shows the xy-section of the upper harpoon-shaped waveguide in this embodiment. Type I triangular air holes and Type IV triangular air holes form a unit cell, which is arranged in a honeycomb structure to form a first type valley photonic crystal (VPC1). The positions of the triangular air holes in the first type valley photonic crystal are interchanged to form a second type valley photonic crystal (VPC2). The type II triangular air holes and Type III triangular air holes form a unit cell, which is arranged in a honeycomb structure to form a third type valley photonic crystal (VPC3). The positions of the triangular air holes in the third type valley photonic crystal are interchanged to form a fourth type valley photonic crystal (VPC4). The first type valley photonic crystal, the second type valley photonic crystal, and the third type valley photonic crystal are combined in a harpoon-shaped structure to form the upper waveguide.

[0039] like Figure 2 Figure (b) shows the xy cross-section of the lower harpoon waveguide in this embodiment. The fourth type valley photonic crystal, the third type valley photonic crystal, and the second type valley photonic crystal are combined in a harpoon structure to form the lower waveguide.

[0040] like Figure 3 (a) is a graph showing the band gap of the single-layer valley photonic crystal in this embodiment as a function of the difference in side length of the two types of triangular air holes in the unit cell, with a lattice constant a of 0.75 mm. (b) is a graph showing the band gap of the double-layer valley photonic crystal of this invention as a function of the difference in side length of the two types of triangular air holes in the unit cell when the spacing is 0.05 mm.

[0041] In this embodiment, the triangular coupling sheet is composed of high-resistivity silicon with a base of 0.8 mm, a height of 5 mm, and a thickness of 0.2 mm, using silicon material with a relative permittivity of 11.9. Both the upper and lower waveguides are composed of honeycomb structure photonic crystals with a spacing of 0.05 mm, 52 periods in the x-axis direction, 62 periods in the y-axis direction, and a lattice constant α of 0.75 mm. The side length of the type I triangular air hole is 0.52 mm, the side length of the type II triangular air hole is 0.24 mm, the side length of the type III triangular air hole is 0.40 mm, and the side length of the type IV triangular air hole is 0.34 mm.

[0042] When the interlayer spacing between the two waveguides is 0.05 mm, and the thickness of both the upper and lower waveguides is 0.2 mm, the coupling between the two waveguides dominates. This causes the transmission channel for electromagnetic waves to differ from the transmission boundary of a single-layer photonic crystal, instead aligning with the transmission boundary resulting from the coupling between the two waveguides. The overall effect is as follows: Figure 1 As shown in (c), the transmission paths between the upper and lower waveguides are as follows: Figure 4 As shown in (c) and (d).

[0043] like Figure 4 As shown in (b), observing the transmission spectra of S21 and S31, it is found that electromagnetic waves are transmitted through the boundary connecting port 1 and port 3, while the loss at port 2 is very large, and almost no electromagnetic waves pass through. The results show that the coupling effect between the two waveguides is greater than the effect of a single waveguide. The effective working state corresponds to the frequency shown in the gray shaded area in the figure.

[0044] Example 2

[0045] like Figure 5 As shown in (a), this embodiment provides an all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition operation in a decoupled state. The chip consists of a double-layer harpoon waveguide and a triangular coupling plate, wherein the triangular coupling plate is directly connected to the harpoon waveguide. During use, the triangular coupling plate needs to be inserted into the port of the WR-8 standard rectangular waveguide.

[0046] In this embodiment, the upper and lower waveguides are the same as in Embodiment 1, but the distance between the two waveguides is adjusted to 1 mm. At the same time, the transmission frequency band and the operating channel are changed.

[0047] When the interlayer spacing between two waveguides is 1 mm, and the thickness of both the upper and lower waveguides is 0.2 mm, the transmission channel of a single-layer waveguide dominates. The channel for transmitting electromagnetic waves in each layer coincides with the transmission boundary of that photonic crystal layer, and the overall effect is as follows: Figure 1 As shown in (a) and (b), the solid black lines indicate that electromagnetic waves can be transmitted, and the dashed black lines indicate that electromagnetic waves cannot be transmitted.

[0048] like Figure 5 As shown in (b), observing the transmission spectra of S21 and S31 reveals that the electromagnetic wave propagates through the boundary connecting port 1 and port 2, while the transmission loss at port 3 is significant. The results indicate that the coupling effect between the two waveguide layers is far less than that of a single waveguide layer, and the effective decoupling operating frequency is shown by the gray shading in the figure.

[0049] The above analysis shows that when the spacing between the upper and lower waveguides is less than or close to the thickness of the single-layer waveguide, the coupling between the waveguides can determine the topology transmission path; when the spacing between the upper and lower waveguides is greater than the thickness of the single-layer waveguide, the transmission boundary of the single-layer waveguide can determine the topology transmission path.

[0050] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0051] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0052] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A fully silicon terahertz multiplexed chip based on valley-Hall topological phase transition, characterized in that, The multiplexing chip has a two-layer structure, which includes an upper waveguide and a lower waveguide of a harpoon-shaped structure. By controlling the spacing between the upper and lower waveguides of the harpoon-shaped structure, the operating state of the chip can be adjusted, thereby realizing controllable on-chip terahertz channel switching. The operating state includes two types: coupling and decoupling. The coupling state refers to the situation where the distance between two harpoon-shaped waveguides is 0.05-0.10 mm, and the waveguides are coupled together, so that the overall transmission path is a superposition of the two waveguides; the decoupling state refers to the situation where the distance between two harpoon-shaped waveguides is 0.80-1.00 mm, so that the overall transmission path is consistent with the transmission path of a single waveguide. Both the upper and lower waveguides are composed of periodically arranged equilateral triangular air holes. These equilateral triangular air holes include four types of triangles with varying side lengths, from largest to smallest: Type I, Type II, Type III, and Type IV triangular air holes. The Type I and Type IV triangular air holes form a unit cell, arranged in a honeycomb structure to form a first-type valley photonic crystal (VPC1). By swapping the positions of the triangular air holes in the first-type valley photonic crystal, a second-type valley photonic crystal (VP) is formed. C2), the type II and type III triangular air holes form a unit cell, which is arranged in a honeycomb structure to form a third type valley photonic crystal (VPC3). The positions of the triangular air holes in the third type valley photonic crystal are interchanged to form a fourth type valley photonic crystal (VPC4). The first type valley photonic crystal, the second type valley photonic crystal, and the third type valley photonic crystal are combined in a harpoon-shaped structure to form an upper waveguide. The fourth type valley photonic crystal, the third type valley photonic crystal, and the second type valley photonic crystal are combined in a harpoon-shaped structure to form a lower waveguide.

2. The all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition as described in claim 1, characterized in that, In the first type of valley photonic crystal (VPC1), type I triangular air holes are distributed on the top edge of the hexagonal honeycomb structure, and type IV triangular air holes are distributed on the bottom edge of the hexagonal honeycomb structure; in the third type of valley photonic crystal (VPC3), type II triangular air holes are distributed on the top edge of the hexagonal honeycomb structure, and type III triangular air holes are distributed on the bottom edge of the hexagonal honeycomb structure.

3. The all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition as described in claim 1, characterized in that, Both the upper and lower waveguides are composed of high-resistivity silicon with a relative permittivity of 11.7-12.

0.

4. The all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition as described in claim 1, characterized in that, The thickness of both the upper and lower waveguides is 0.18-0.22 mm.

5. The all-silicon terahertz multiplexing chip based on valley-Hall topological phase transition as described in claim 1, characterized in that, The lattice constant α of the unit cell is 0.7-0.8 mm, the side length of the type I triangular air hole is 0.49-0.54 mm, the side length of the type II triangular air hole is 0.21-0.26 mm, the side length of the type III triangular air hole is 0.38-0.43 mm, and the side length of the type IV triangular air hole is 0.32-0.37 mm.

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