Topological optical waveguide device capable of realizing OR logic gate and application

Abstract

The invention provides a topological optical waveguide device capable of realizing an OR logic gate and an application, the topological optical waveguide device comprises a first photonic crystal module TPC1 formed by periodically arranging first unit cells UC1, a second photonic crystal module TPC2 formed by periodically arranging second unit cells UC2, the first unit cells UC1 and the second unit cells UC2 are valley Hall unit cells, and the valley Hall unit cells UC1 and the valley Hall unit cells UC2 are connected with the first photonic crystal module TPC1 and the second photonic crystal module TPC2. The three dielectric cylinders in the first unit cell UC1 are arranged in a regular triangle shape, and the three dielectric cylinders in the second unit cell UC2 are arranged in an inverted triangle shape. A Y-shaped air waveguide formed by a Y-shaped air gap is constructed in the second photonic crystal module TPC2, three channels of the Y-shaped air waveguide are respectively an output channel and two input channels, and one side of each of the two input channels is provided with a beard-shaped boundary and a zigzag boundary which are formed by splicing the second photonic crystal module TPC2 and the first photonic crystal module TPC1. According to the invention, topological angular states of various different working frequency bands are realized by using different interface splicing modes, and an optical waveguide device supporting logic or functions is built by using a topological waveguide cavity coupling structure.

Description

Technical Field

[0001] The present invention relates to the application field of topological photonic crystals, and in particular to a topological optical waveguide device capable of realizing an OR logic gate and an application thereof. Background Art

[0002] Topology is an important concept in current physics and has attracted extensive attention in various fields of physics. In topological photonic insulators, photons are insulating in the bulk but conducting along the edges. Therefore, photonic topological insulators are considered a promising platform to study topologically protected transport of light. Usually, this can be achieved by using broken or preserved time-reversal symmetry. In particular, compared with broken time-reversal symmetry, topological photonic insulators with preserved time-reversal symmetry have compact footprints and lossless light transmission, making them more suitable for on-chip applications on dielectric photonic crystal platforms at telecommunication frequencies. In previous studies, topological photonics using preserved time-reversal symmetry have been explored to realize several optical degrees of freedom, including polarization in bi-anisotropic metamaterials, transverse electric TE and transverse magnetic TM modes in photonic crystals, chirality of whispering channel modes in ring resonators, p and d orbitals in artificial atoms, and valley pseudospins in photonic crystals. Compared with other methods, valley photonic crystal-based structures are widely used to build topological photonic devices due to their low loss, wide bandwidth, and compact structural design. In higher-order topological insulators, one-dimensional topological edge states and zero-dimensional topological corner states have multiple properties for propagating and localizing optical signals, which can be used for the design of robust optical waveguides and cavities in photonic crystals, respectively.

[0003] Photonic crystals with triangular valley photonic lattices can achieve two different topological properties by changing the position of the dielectric column in the unit cell. A topological corner state with strong localization of light is constructed by two photonic crystals with different topological properties. At present, the existing topological corner states realized by topological photonic crystal structures do not realize the function of logic gates. Since triangular valley Hall photonic crystals can obtain a variety of different boundary structures through whisker-type splicing or zigzag splicing, an optical waveguide device with a structure that realizes OR logic gates can be designed. Summary of the invention

[0004] In view of the shortcomings in the prior art, the present invention provides a topological optical waveguide device and application capable of realizing an OR logic gate. By using different interface splicing methods to realize topological angular states in multiple different working frequency bands, an optical waveguide device supporting logic OR function is constructed using a topological waveguide cavity coupling structure.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A topological optical waveguide device capable of realizing an OR logic gate, comprising a first photonic crystal module TPC1 formed by a periodic arrangement of first unit cells UC1, and a second photonic crystal module TPC2 formed by a periodic arrangement of second unit cells UC2, wherein the first unit cells UC1 and the second unit cells UC1 are both valley Hall unit cells, and three dielectric columns in the first unit cell UC1 are arranged in an equilateral triangle, and three dielectric columns in the second unit cell UC2 are arranged in an inverted triangle;

[0007] A Y-shaped air waveguide formed by a Y-shaped air gap is constructed in the second photonic crystal module TPC2, and the three channels of the Y-shaped air waveguide are respectively an output channel and two input channels; one side of the two input channels respectively has a whisker-shaped boundary and a zigzag boundary spliced ​​by the second photonic crystal module TPC2 and the first photonic crystal module TPC1, and the whisker-shaped boundary and the zigzag boundary have at least one acute corner.

[0008] Furthermore, the distance between the input channel and the whisker-shaped boundary or the zigzag-shaped boundary is a lattice constant a.

[0009] Furthermore, the width of the Y-shaped air waveguide is a.

[0010] Furthermore, the first photonic crystal module TPC1 spliced ​​with the second photonic crystal module TPC2 to form a whisker-shaped boundary and a zigzag-shaped boundary is embedded in the second photonic crystal module TPC2 between two input channels, and the first photonic crystal module TPC1 is one piece or two pieces divided by the second photonic crystal module TPC2.

[0011] Furthermore, the first photonic crystal module TPC1 spliced ​​with the second photonic crystal module TPC2 to form a whisker-shaped boundary and a zigzag-shaped boundary are respectively located on the same side of the two input channels.

[0012] Furthermore, the whisker-shaped boundary and / or the zigzag-shaped boundary form an equilateral triangle, which is formed by splicing a first photonic crystal module TPC1 in the form of an equilateral triangle and a second photonic crystal module TPC2 spliced ​​on the periphery thereof.

[0013] Furthermore, the side length of the equilateral triangle-shaped first photonic crystal module TPC1 forming a whisker-shaped boundary with the second photonic crystal module TPC2 is 18a, and the side length of the equilateral triangle-shaped first photonic crystal module TPC1 forming a zigzag-shaped boundary with the second photonic crystal module TPC2 is 22a.

[0014] Furthermore, the first unit cell UC1 and the second unit cell UC2 both use air as the background, and the three dielectric columns are all circular silicon dielectric columns of equal diameter, which are arranged in a centrosymmetric manner around the center of the unit cell. The lattice constant of the Valley Hall unit cell is a=246μm, and the cross-section of the unit cell is a regular hexagon.

[0015] Furthermore, the radius of the silicon dielectric column is r=0.22a; the distance between the center of the circular silicon dielectric column and the center of the unit cell in the first unit cell UC1 and the second unit cell UC1 is

[0016] The application of the topological optical waveguide device described in any of the above items is characterized in that, when used for a logic or device, the input channel adjacent to the whisker-shaped boundary can cut off light waves of 0.306 to 0.307 THz, and the input channel adjacent to the zigzag boundary can cut off light waves of 0.331 to 0.332 THz.

[0017] The topological optical waveguide device capable of realizing an OR logic gate described in the present invention is composed of two photonic crystal structures with different topological properties. The first unit cell UC1 composed of three circular dielectric columns arranged in a regular triangle around the center of the unit cell and the second unit cell UC2 composed of three circular dielectric columns arranged in an inverted triangle around the center of the unit cell have opposite valley-Chen numbers, but they have the same photonic band gap, and there is a topological phase transition between the two photonic crystal structures. Two two-dimensional photonic crystals with different topological properties can form a zero-dimensional topological angle state, and optical signals can be transmitted locally at a specific frequency, and have strong robustness to structural defects.

[0018] The input channel adjacent to the whisker-shaped boundary can cut off light waves of 0.306 to 0.307 THz, and the input channel adjacent to the zigzag boundary can cut off light waves of 0.331 to 0.332 THz. Inputting light waves of 0.331 to 0.332 THz into the input channel adjacent to the whisker-shaped boundary, or inputting light waves of 0.306 to 0.307 THz into the input channel adjacent to the zigzag boundary can both realize the OR logic gate function.

[0019] Since the splicing structures of the first photonic crystal module TPC1 and the second photonic crystal module TPC2 are different, the frequency ranges of the corresponding topological angular state localized optical signal transmission are also different, and the air waveguide can transmit optical signals within these frequency ranges. The topological optical waveguide device capable of realizing an OR logic gate described in the present invention has a first photonic crystal module TPC1 and a second photonic crystal module TPC2. Within the frequency range of the topological angular state of the first photonic crystal module TPC1 and the second photonic crystal module TPC2, the optical signal in the air waveguide will be coupled into the first photonic crystal module TPC1 and the second photonic crystal module TPC2 to achieve truncation of the optical signal; when using excitation light sources of different frequencies, the difference in coupling frequency results in different output results, thereby realizing the OR logic gate function.

[0020] The present invention is a novel topological photonic crystal structure designed based on the above concept, a circular silicon dielectric column type photonic crystal in an air background, which has a relatively simple structure and only changes the arrangement of the circular silicon dielectric columns in the unit cell, thereby obtaining two photonic crystals with different topological properties, and its combined structure can realize zero-dimensional topological angle states, so that optical signals can be localized at topological angle states within a specific frequency range, and have strong robustness to structural defects. The structural design is simple and easy to prepare, with a small volume and no waste generated during the preparation process, and has the advantages of low manufacturing cost and being conducive to integration. In addition, the optical waveguide that supports zero-dimensional topological angle states can realize logic or functions in one structure, and has great application prospects in modern integrated optical communication devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural diagram of the first unit cell UC1 and the second unit cell UC2 of the present invention; wherein: 1-first unit cell UC1; 2-second unit cell UC2; 3-circular dielectric column.

[0022] Figure 2 It is the primitive cell of the first unit cell UC1 and the second unit cell UC2 and the corresponding phase distribution diagram.

[0023] Figure 3 It is a schematic diagram of the energy band structure of the first unit cell UC1 and the second unit cell UC2.

[0024] Figure 4 (a) is a schematic diagram showing that the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is a whisker-shaped one.

[0025] Figure 4 (b) is a schematic diagram showing that the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is zigzag.

[0026] Figure 5 (a) is a schematic structural diagram of the first triangular module C1 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is a whisker type.

[0027] Figure 5 (b) is the mode field diagram corresponding to the first triangular module C1 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is a whisker type.

[0028] Figure 5 (c) is a set of next-nearest-neighbor coupling angular mode field diagrams corresponding to the first triangular module C1 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is a whisker type.

[0029] Figure 6(a) is a schematic structural diagram of the second triangular module C2 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is zigzag.

[0030] Figure 6 (b) is the mode field diagram corresponding to the second triangular module C2 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is zigzag.

[0031] Figure 6 (c) is a set of nearest neighbor coupling angular mode field diagrams corresponding to the second triangular module C2 when the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is zigzag.

[0032] Figure 7 (a) is a schematic diagram of a diamond-shaped air waveguide coupled cavity structure consisting of a first photonic crystal module TPC1 and a second photonic crystal module TPC2.

[0033] Figure 7 (b), (c), (d), (e), and (f) are electric field distribution diagrams of the topological optical waveguide device capable of realizing an OR logic gate within different frequency ranges. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0035] The topological optical waveguide device capable of realizing an OR logic gate described in this embodiment includes a first photonic crystal module TPC1 formed by a periodic arrangement of first unit cells UC1, and a second photonic crystal module TPC2 formed by a periodic arrangement of second unit cells UC2, wherein the first unit cells UC1 and the second unit cells UC1 are both Valley Hall units, and the three dielectric columns in the first unit cell UC1 are arranged in a regular triangle, and the three dielectric columns in the second unit cell UC2 are arranged in an inverted triangle. The radius of the circular dielectric column r = 0.22a, a is the lattice constant of the regular hexagonal unit cell, and the distance between the center of the circular dielectric column and the center of the regular hexagonal unit cell R = a / √3.

[0036] Figure 1 The structure diagram of the first unit cell UC1 and the second unit cell UC2 of this embodiment is shown in the figure, where a is the lattice constant, the radius of the circular dielectric column is r=0.22a, and the three dielectric columns are all circular silicon dielectric columns with equal diameters, and are arranged in a centrosymmetric manner around the center of the unit cell, ε r =12.76 is the dielectric constant of the dielectric column, ε0=1 is the dielectric constant of the air background. The lattice constants of the first unit cell UC1 and the second unit cell UC2 are both a=246μm, the cross-sections of the unit cells are both regular hexagons, and the dielectric columns in the unit cells are all circular dielectric columns made of silicon material.

[0037] Figure 2 It is the primitive cell of the first unit cell UC1 and the second unit cell UC2 and the corresponding phase distribution diagram. As shown in the figure, the vortex chirality of the eigenmode phase of the first unit cell UC1 and the second unit cell UC2 undergoes clockwise and counterclockwise reciprocity, that is, the clockwise orbital angular momentum of UC1 is converted into the counterclockwise orbital angular momentum of UC2, and the counterclockwise orbital angular momentum of UC1 is converted into the clockwise orbital angular momentum of UC2.

[0038] The valley states of the first unit cell UC1 and the second unit cell UC2 have opposite characteristics. Although they have different topological properties, they have the same band structure. Figure 3 It is a schematic diagram of the energy band structure of the first unit cell UC1 and the second unit cell UC2, as shown Figure 3 There is a topological phase transition between two photonic crystals with different topological properties, and in the combined structure composed of the two photonic crystals, light can be robustly transmitted along the interface of the two photonic crystals, and a topological corner state with strong energy localization can also be obtained.

[0039] Specifically, the electromagnetic wave studied in the present invention is the TM mode, and the lattice constant a is 245 μm; the radius of each circular silicon dielectric column is equal, and the radius of the dielectric column is 0.22a. The dielectric constant ε of the silicon material r =12.76, and the dielectric constant of the air background ε0 = 1. The frequencies of the photonic band gaps of the two photonic crystals are 0.32THz-0.36THz and 0.65THz-0.77THz. In this frequency range, photons are localized, the scattering of photons is suppressed, and the optical signal cannot propagate in the structure.

[0040] In order to obtain two sets of topological angular states with different frequencies in the same structure, the first photonic crystal module TPC1 and the second photonic crystal module TPC2 are designed to be spliced ​​to construct a crystal structure with a whisker-shaped boundary and a crystal structure with a zigzag-shaped boundary. Figure 4 (a) is a schematic diagram showing that the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is a whisker-shaped one, Figure 4 (b) is a schematic diagram showing that the splicing interface between the first photonic crystal module TPC1 and the second photonic crystal module TPC2 is zigzag.

[0041] Take a box-shaped structure of a crystal structure with a whisker-shaped boundary as an example, that is, the first photonic crystal module TPC1 is studied. The whisker-shaped boundary is an equilateral triangle, which is composed of the first photonic crystal module TPC1 in the form of an equilateral triangle and the second photonic crystal module TPC2 spliced ​​on its periphery. For the convenience of distinction, the first photonic crystal module TPC1 with a whisker-shaped boundary and an equilateral triangle is collectively referred to as the first triangle module C1. Figure 5As shown in (a), the periodic wave vector k is calculated using the COMSOL software. x Scan, solve the eigenvalue, calculate the eigenfrequency, and obtain Figure 5 (b) The mode field diagram shows that the first triangular module C1 has two sets of topological angular states, one of which is Figure 5 (c) shows that the energy is confined to a closed area at a corner where the edges intersect and the next nearest neighbor topological corner states are attenuated along the edge direction, with frequencies of 0.30681THz, 0.30683THz and 0.30684THz. The optical signals at the frequencies of 0.30681THz, 0.30683THz and 0.30684THz will be localized at the boundary intersection corner between the first triangle module C1 and the second photonic crystal module TPC2, and the optical signals cannot continue to be transmitted.

[0042] Similarly, in order to verify the effect of the combination of two photonic crystals with different topological properties on the corner states, Figure 4 (b) shows a schematic diagram of a zigzag splicing interface of the first photonic crystal module TPC1 and the second photonic crystal module TPC2. Figure 6 As shown, taking a box-shaped structure of the crystal structure with a zigzag boundary as an example, that is, taking the second photonic crystal module TPC2 for research, the zigzag boundary is an equilateral triangle, which is composed of the first photonic crystal module TPC1 in the form of an equilateral triangle and the second photonic crystal module TPC2 spliced ​​on its periphery. For the convenience of distinction, the first photonic crystal module TPC1 with a zigzag boundary and an equilateral triangle is collectively referred to as the second triangle module C2. Figure 6 As shown in (a), the periodic wave vector is scanned using the COMSOL software, the eigenvalue is solved, and the eigenfrequency is calculated. Figure 6 (b) shows that the second triangular module C2 has two sets of topological angular states, one of which is Figure 6 (c) shows the nearest neighbor topological corner state with energy confined in a corner without obvious attenuation, with frequencies of 0.33147THz, 0.33148THz and 0.33149THz. The optical signals at the frequencies of 0.33147THz, 0.33148THz and 0.33149THz will be localized at the boundary intersection corner between the second triangle module C2 and the second photonic crystal module TPC2, and the optical signals cannot continue to be transmitted.

[0043] It can be seen that the first triangle module C1 can only transmit optical signals in the frequency range of 0.306-0.307 THz, the second triangle module C2 can only transmit optical signals in the frequency range of 0.331-0.332 THz, and the air waveguide can transmit optical signals outside these frequency ranges.

[0044] In order to realize the function of logical OR, a Figure 7 The diamond-shaped air cavity coupling structure composed of the first photonic crystal module TPC1 and the second photonic crystal module TPC2 shown in (a) is only a specific embodiment. A Y-shaped air waveguide formed by a Y-shaped air gap is constructed in the second photonic crystal module TPC2, and the three channels of the Y-shaped air waveguide are an output channel O1, two input channels S1 and S2, and the width of the Y-shaped air waveguide is a. The first photonic crystal module TPC1 includes a first triangular module C1 spliced ​​with the second photonic crystal module TPC2 to form a whisker-shaped boundary, and a second triangular module C2 spliced ​​with the second photonic crystal module TPC2 to form a zigzag boundary. The first triangular module C1 and the second triangular module C2 are inlaid between the two input channels S1 and S2, and are located on the same side of the two input channels S1 and S2. The distance between the whisker-shaped boundary of the first triangular module C1 and the input channel S1 is a lattice constant a, and the distance between the zigzag boundary of the second triangular module C2 and the input channel S2 is a lattice constant a. The side length of the first triangular module C1 is 18a, and the side length of the second triangular module C2 is 22a.

[0045] In order to verify whether the above diamond air cavity coupling structure can realize the function of logical OR, a Figure 7 The electric field distribution of the structure shown in (b)-(f) in different frequency ranges is shown in the figure: Figure 7 (b) is the electric field distribution diagram of the diamond air cavity coupling structure when the frequency is 0.30681 THz and only the input channel S1 is input. The optical signal is only transmitted along the input channel S1 and is cut off in the input channel S1, and there is no signal output. Figure 7 (c) is the electric field distribution diagram of the diamond air cavity coupling structure when the frequency is 0.33148 THz and only the input channel S2 is input. The optical signal is only transmitted along the input channel S2 and is cut off in the input channel S2, and there is no signal output. Figure 7 (d) is the electric field distribution diagram of the diamond air cavity coupling structure when the frequency is 0.35 THz and the input channels S1 and S2 are input simultaneously. The optical signal is transmitted along the input channels S1 and S2, and the signal is output from the output channel O1, realizing the OR gate 1|1 input effect. Figure 7 (e) is the electric field distribution diagram of the diamond air cavity coupling structure when the frequency is 0.30681 THz and only the input channel S2 is input. The optical signal is only transmitted along the input channel S2, and the signal is output from the output channel O1, realizing the OR gate 0|1 input effect. Figure 7(f) is the electric field distribution diagram of the diamond air cavity coupling structure when the frequency is 0.33148 THz and only the input channel S1 is input. The optical signal is only transmitted along the input channel S1, and the signal is output from the output channel O1, realizing the OR gate 1|0 input effect.

[0046] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A topological optical waveguide device capable of realizing an OR logic gate, characterized in that: It includes a first photonic crystal module TPC1 formed by a periodic arrangement of first unit cells UC1, and a second photonic crystal module TPC2 formed by a periodic arrangement of second unit cells UC2, wherein the first unit cells UC1 and the second unit cells UC1 are both Valley Hall unit cells, and the three dielectric columns in the first unit cell UC1 are arranged in a regular triangle, and the three dielectric columns in the second unit cell UC2 are arranged in an inverted triangle; A Y-shaped air waveguide formed by a Y-shaped air gap is constructed in the second photonic crystal module TPC2, and the three channels of the Y-shaped air waveguide are respectively an output channel and two input channels; one side of the two input channels respectively has a whisker-shaped boundary and a zigzag boundary spliced ​​by the second photonic crystal module TPC2 and the first photonic crystal module TPC1, and the whisker-shaped boundary and the zigzag boundary have at least one acute corner.

2. The topological optical waveguide device according to claim 1, characterized in that: The distance between the input channel and the whisker-shaped boundary or the zigzag-shaped boundary is a lattice constant a.

3. The topological optical waveguide device according to claim 1, characterized in that: The width of the Y-shaped air waveguide is a.

4. The topological optical waveguide device according to claim 1, characterized in that: The first photonic crystal module TPC1 spliced ​​with the second photonic crystal module TPC2 to form a whisker-shaped boundary and a zigzag-shaped boundary is embedded in the second photonic crystal module TPC2 between two input channels. The first photonic crystal module TPC1 is one piece or two pieces divided by the second photonic crystal module TPC2.

5. The topological optical waveguide device according to claim 1, characterized in that: The first photonic crystal module TPC1 spliced ​​with the second photonic crystal module TPC2 to form a whisker-shaped boundary and a zigzag-shaped boundary are respectively located on the same side of the two input channels.

6. The topological optical waveguide device according to claim 4 or 5, characterized in that: The whisker-shaped boundary and / or zigzag-shaped boundary form an equilateral triangle, which is formed by splicing a first photonic crystal module TPC1 in the form of an equilateral triangle and a second photonic crystal module TPC2 spliced ​​on the periphery thereof.

7. The topological optical waveguide device according to claim 6, characterized in that: The side length of the equilateral triangle first photonic crystal module TPC1 forming a whisker-shaped boundary with the second photonic crystal module TPC2 is 18a, and the side length of the equilateral triangle first photonic crystal module TPC1 forming a zigzag-shaped boundary with the second photonic crystal module TPC2 is 22a.

8. The topological optical waveguide device according to claim 1, characterized in that: The first unit cell UC1 and the second unit cell UC2 both use air as the background. The three dielectric columns are all circular silicon dielectric columns of equal diameter, which are arranged in a centrosymmetric manner around the center of the unit cell. The lattice constant of the Valley Hall unit cell is a=246μm, and the cross-section of the unit cell is a regular hexagon.

9. The topological optical waveguide device according to claim 7, characterized in that: The radius of the silicon dielectric column is r=0.22a; the distance between the center of the circular silicon dielectric column and the center of the unit cell in the first unit cell UC1 and the second unit cell UC1 is 10. Use of the topological optical waveguide device according to any one of claims 1 to 9, characterized in that: For logic or devices, the input channel adjacent to the whisker-shaped boundary can cut off the light wave of 0.306~0.307THz, and the input channel adjacent to the zigzag boundary can cut off the light wave of 0.331~0.332THz.

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