Photonic Dirac waveguide for synthesizing pseudo magnetic field based on photonic crystal and application

Abstract

The invention provides a photonic Dirac waveguide based on a pseudo magnetic field synthesized by a photonic crystal and an application of the photonic Dirac waveguide. Comprising a photon Dirac waveguide I, a photon Dirac waveguide II and a photon Dirac waveguide III. The photonic Dirac waveguide I is composed of a gradient photonic crystal A1, a photonic crystal O and a gradient photonic crystal A2; the photon Dirac waveguide II is composed of a gradient photonic crystal A3, a photonic crystal O and a gradient photonic crystal A4; the photon Dirac waveguide III is composed of a gradient photonic crystal A5, a photonic crystal O and a gradient photonic crystal A6. According to the invention, the photonic Dirac waveguide is designed by using the photonic crystal with linear gradient change of the angle. The waveguide is based on large-area bulk transmission, and has the excellent characteristics of easy preparation and low scattering loss. And a plurality of transmission channels are generated by changing the rotation angle of the embedded body in the photonic crystal in a linear gradient manner, so that the information transmission capacity is improved, and the requirement of high-capacity information transmission in a photonic device can be met.

Description

Technical Field

[0001] The present invention belongs to the field of photonic integrated devices, and in particular relates to a photon Dirac waveguide based on photonic crystal synthetic pseudomagnetic field and its application. Background Art

[0002] Research on optical communications has always been the core of modern physics and engineering applications. Compared with electrons, light transmits information at a higher rate and with a higher amount of information, with lower loss and stronger anti-interference. These excellent properties make photons widely used in information processing, communication, and computing.

[0003] As a structure for guiding electromagnetic waves, waveguides can effectively limit and guide electromagnetic waves to propagate along a specific path, reduce the loss of electromagnetic waves during transmission, and allow electromagnetic waves to be manipulated in a specific direction. However, traditional waveguides are limited by the influence of materials and devices themselves, and face some problems in terms of size, manufacturing process, flexibility and adjustability. As a metamaterial with a periodic structure, photonic crystals have the advantages of low loss, high controllable freedom and easy implementation. This makes waveguides constructed from photonic crystals more advantageous in improving information transmission performance.

[0004] As an artificially synthesized gauge field, pseudomagnetic field can control electrons like a real magnetic field. Unlike a real magnetic field, a pseudomagnetic field does not destroy the time reversal symmetry of the system. This provides a new mechanism for controlling the behavior of photons, thereby realizing Landau level quantization and quantum Hall effect in a system without an external magnetic field. Unlike electrons, photons, as a neutral particle, are inert to an external magnetic field. Many novel physical phenomena of electrons in a magnetic field cannot be realized in a classical wave system. How to efficiently control photons is the focus of today's optical research field. Therefore, constructing pseudomagnetic fields in artificial periodic structures has aroused great research interest. In 2017, Professor Christian Brendel of the University of Erlangen-Nuremberg in Germany applied a single-direction deformation in a nanometer-sized phononic crystal to achieve a pseudomagnetic field (Natl. Acad. Sci. 114 3390 (2017)). Professor Qiu Chunyin's research team at Wuhan University experimentally observed the quantization of Landau levels and quantum-like Hall boundary states in phononic crystals with pseudomagnetic fields (Nat.Phys.15 352(2019)). Research on artificial synthetic gauge fields has become increasingly in-depth. Recently, researchers have used inhomogeneous artificial surface plasmon metasurfaces to construct in-plane pseudomagnetic fields. This strong pseudomagnetic field leads to the appearance of chiral zero-order Landau levels. The results show that photonic Dirac waveguides designed based on in-plane pseudomagnetic fields can guide electromagnetic modes unidirectionally and achieve high-capacity energy transmission. Designing a new type of large-area bulk transmission photonic Dirac waveguide will play an important role in promoting the development and application of future photonic integrated devices. Summary of the invention

[0005] The purpose of the present invention is to provide a photonic Dirac waveguide based on a photonic crystal synthetic pseudomagnetic field and its application. The present invention uses a photonic crystal with a linear gradient change in angle to design a photonic Dirac waveguide to achieve signal splitting and centralized transmission. This Dirac waveguide is based on large-area bulk transmission, has the excellent characteristics of easy preparation and low scattering loss, and can generate multiple transmission channels by changing the rotation angle of the chimera in the photonic crystal with a linear gradient, has a higher degree of operational freedom, improves the information transmission capacity, and can meet the needs of high-capacity information transmission in photonic devices.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention relates to a photon Dirac waveguide based on photon crystal synthetic pseudomagnetic field, comprising photon Dirac waveguide I, photon Dirac waveguide II and photon Dirac waveguide III;

[0008] in,

[0009] The photon Dirac waveguide I is composed of gradient photonic crystal A1, photonic crystal O and gradient photonic crystal A2, and is arranged in a sandwich structure of A1OA2;

[0010] The photon Dirac waveguide II is composed of gradient photonic crystal A3, photonic crystal O and gradient photonic crystal A4, and is arranged in a sandwich structure with A3OA4;

[0011] The photon Dirac waveguide III is composed of gradient photonic crystal A5, photonic crystal O and gradient photonic crystal A6, and is arranged in a sandwich structure with A5OA6.

[0012] Preferably, each of A1OA2, A3OA4 and A5OA6 has a lateral interface state transmission channel.

[0013] Preferably, the left side of the lateral interface state transmission channel is the information input port P1, and the rightmost side thereof is the information output port P2.

[0014] Preferably, the photonic crystal O, gradient photonic crystal A1, gradient photonic crystal A2, gradient photonic crystal A3, gradient photonic crystal A4, gradient photonic crystal A5 and gradient photonic crystal A6 are periodically arranged in the X-axis and Y-axis directions in a rectangular coordinate system to form a triangular lattice, and the lattice constant of the triangular lattice is a=36.8mm.

[0015] Preferably, the unit cell of the triangular lattice is a mosaic composed of a metal cylinder with a radius of r1=3.68 mm and three identical metal cuboids with a length of l=7.95 mm and a width of w=2.21 mm and an interval of 60°.

[0016] Preferably, the rotation angle θ of the chimera is the angle of rotation of the chimera around the center of the primitive cell. When the chimera is centrally symmetric about the y-axis and the rectangular part points to the positive direction of the y-axis, the rotation angle θ is 0°.

[0017] Preferably, the chimera is made of metal material, and the background material of the chimera is air, and the relative dielectric constant and relative magnetic permeability of air are both 1.

[0018] The triangular lattice photonic crystal composed of the metal mosaic of the present invention satisfies C 6V Symmetry; when the chimera rotates at an angle of θ=30°, the first and second energy bands of the photonic crystal become degenerate at K and K' to form Dirac points, called photonic crystal O; by rotating the chimera and adjusting the angle θ, the degenerate Dirac points will open and form a complete band gap; when the rotation angles are 0°≤θ<30° and 30°<θ≤60°, the topological Chern numbers of the two photonic crystals are opposite, and topological boundary states will appear on their common interface.

[0019] The present invention reduces the symmetry of the photonic crystal by rotating the angle of the chimera, so that the degenerate energy valleys at the K and K' points in the momentum space open a band gap, and the width of the band gap changes with the change of the angle; the photonic crystal chimera is manipulated to make its rotation angle change linearly in the y-axis direction, which will produce a change in the vector potential A; according to the relationship between the magnetic field B and the vector potential A A uniform synthetic pseudomagnetic field in a plane can be generated in the photonic crystal structure. This in-plane pseudomagnetic field leads to the linear dispersion of the zero-order Landau level. Unlike the localized topological boundary state in the quantum spin Hall system, the chiral zero-order chiral Landau level is a bulk mode state, which is distributed in a large area in the middle of the photonic crystal waveguide.

[0020] Preferably, the gradient photonic crystal A1 has 15 primitive cells in the y direction, and the rotation angle of the chimera in each layer of primitive cells changes linearly along the y direction, that is, θ n1 =2n°, where 0≤n<15, n is the number of layers of the primitive cell;

[0021] The gradient photonic crystal A2 has 15 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n2 =2n°, where 15<n≤30; n is the number of layers of the primitive cell;

[0022] The gradient photonic crystal A3 has 5 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n3 =6n°, where 0≤n<5; n is the number of layers of the primitive cell;

[0023] The gradient photonic crystal A4 has 9 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n4 =6n°, where 5<n<15; n is the number of layers of the primitive cell;

[0024] The gradient photonic crystal A5 has 9 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n5 =6n°, where 15<n<25; n is the number of layers of the primitive cell;

[0025] The gradient photonic crystal A6 has 5 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n6 =6n°, where (25<n≤30); n is the number of layers of the primitive cell;

[0026] The mosaic in the photonic crystal O is rotated 30° around the center of the primitive cell, and the width of the photonic crystal O in the y direction is the size of a primitive cell.

[0027] The present invention also relates to the application of the aforementioned photonic Dirac waveguide based on the synthetic pseudomagnetic field of photonic crystals, and changes the rotation angle of each layer of the chimera in the photonic crystal along the linear gradient of the y direction to construct gradient photonic crystals A1, gradient photonic crystals A2, gradient photonic crystals A3, gradient photonic crystals A4, gradient photonic crystals A5 and gradient photonic crystals A6, so that after the broadband electromagnetic wave enters the photonic crystal interface state transmission channel, it is divided into two upper and lower electromagnetic waves, which are respectively transmitted in the two interface state channels and then gathered into one beam, thereby realizing the control of electromagnetic wave splitting and focusing.

[0028] Preferably, the excitation source of the light source is a linear polarization source; the excitation source is placed at the left end of the photonic crystal O.

[0029] The working principle of the present invention is as follows: a light source constructs gradient photonic crystals A1, A2, A3, A4, A5 and A6 by changing the rotation angle of each layer of mosaics in the photonic crystal along the linear gradient of the y direction, so that after a broadband electromagnetic wave enters the transverse interface state transmission channel in the photonic Dirac waveguide I, it is divided into two upper and lower electromagnetic waves, which are respectively transmitted through the transverse interface state transmission channel in the Dirac waveguide II and the transverse interface state transmission channel in the photonic Dirac waveguide III, and then gathered into one beam, thereby realizing the control of electromagnetic wave splitting and aggregation.

[0030] The present invention has the following advantages:

[0031] (1) The present invention constructs a uniform in-plane synthetic pseudomagnetic field in the gradient photonic crystal by adjusting the rotation angle of each layer of the chimera with a linear gradient, resulting in the appearance of a chiral zero-order Landau energy level distributed in the photonic crystal; different from the localized topological interface state, the mode of this chiral zero-order Landau energy level is a bulk state with a large area; the photonic crystal Dirac waveguide designed by the present invention can store more electromagnetic wave energy.

[0032] (2) The present invention utilizes different rotation gradients to cause different intensities of the synthetic pseudomagnetic field. The position where the large-area body state appears in the photonic crystal can be controlled, thereby achieving the purpose of arbitrarily controlling the position of electromagnetic wave transmission.

[0033] (3) The photon Dirac waveguide designed by the present invention can separate and gather electromagnetic waves, thereby achieving the purpose of controlling signal transmission. Compared with the traditional waveguide structure, the present invention is based on a photon Dirac waveguide that integrates beam splitting and focusing, and has the advantages of high flexibility, low loss and easy control. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The overall structure schematic diagram of the photon Dirac waveguide based on photonic crystal to synthesize pseudomagnetic field of the present invention;

[0035] Figure 2 Schematic diagram of the energy band structure of the photonic crystal mosaic of the present invention when the rotation angles are 0°, 30° and 60°;

[0036] Figure 3 The projected energy band and intrinsic electric field distribution diagram of the photon Dirac waveguide I, photon Dirac waveguide II and photon Dirac waveguide III of the present invention;

[0037] Figure 4 This is the electric field distribution diagram of the photon Dirac waveguide in the present invention when f=10.34 GHz;

[0038] The accompanying drawings are marked with: 1 is a gradient photonic crystal A1, 2 is a gradient photonic crystal A2, 3 is a gradient photonic crystal A3, 4 is a gradient photonic crystal A4, 5 is a gradient photonic crystal A5, 6 is a gradient photonic crystal A6, 7 is a photonic crystal O, 8 is an excitation source, 9 is a photonic crystal with a rotation angle of 0°, 10 is a photonic crystal with a rotation angle of 30°; 11 is an input port P1, and 12 is an output port P2. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments are only further descriptions of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0040] Example

[0041] This embodiment relates to a photonic Dirac waveguide based on a photonic crystal synthetic pseudomagnetic field. Figure 1 As shown, it includes photon Dirac waveguide I, photon Dirac waveguide II and photon Dirac waveguide III;

[0042] in,

[0043] The photon Dirac waveguide I is composed of gradient photonic crystal A1 1, photonic crystal O 7 and gradient photonic crystal A2 2, and is arranged in A1OA2 to form a sandwich structure; the photon Dirac waveguide I is distributed on the left side of the photon Dirac waveguide II and the photon Dirac waveguide III; the photon Dirac waveguide II and the photon Dirac waveguide III are arranged up and down.

[0044] The photon Dirac waveguide II is composed of gradient photonic crystal A3 3, photonic crystal O 7 and gradient photonic crystal A4 4, and is arranged in a sandwich structure with A3OA4;

[0045] The photon Dirac waveguide III is composed of gradient photonic crystal A5 5, photonic crystal O 7 and gradient photonic crystal A6 6, and is arranged in a sandwich structure with A5OA6;

[0046] A1OA2, A3OA4 and A5OA6 each have a lateral interface state transmission channel.

[0047] The left side of the transverse interface state transmission channel of the photonic Dirac waveguide I is an information input port P1 11 , and the rightmost side thereof is an information output port P2 12 .

[0048] The photonic crystal O 7, gradient photonic crystal A1 1, gradient photonic crystal A2 2, gradient photonic crystal A3 3, gradient photonic crystal A4 4, gradient photonic crystal A5 5 and gradient photonic crystal A6 6 are periodically arranged in the X-axis and Y-axis directions in a rectangular coordinate system to form a triangular lattice, and the lattice constant of the triangular lattice is a=36.8mm.

[0049] The primitive cell of the triangular lattice is a mosaic composed of a metal cylinder with a radius of r1 = 3.68 mm and three identical metal cuboids with a length of l = 7.95 mm and a width of w = 2.21 mm and an interval of 60°.

[0050] The rotation angle θ of the chimera is the angle of rotation of the chimera around the center of the primitive cell. When the chimera is centrally symmetric about the y-axis and the rectangular part points to the positive direction of the y-axis, the rotation angle θ is 0°.

[0051] The chimera is made of metal material, and the background material of the chimera is air, and the relative dielectric constant and relative magnetic permeability of air are both 1.

[0052] See Figure 1 The illustrations on the right are schematic diagrams of the photonic crystal unit cell structure with the chimera rotated at 0° and 30°. The chimera consists of a cylinder and three cuboids, and the chimera is distributed in the middle of the unit cell. The lattice constant is a = 36.8 mm.

[0053] See Figure 2 The figure shows the energy band structure of the photonic crystal mosaic when the rotation angles are 0°, 30° and 60°. The horizontal axis is the high symmetry points K and M in the first Brillouin zone of the triangular lattice; the vertical axis is the frequency, in GHz. Figure 2 (a) When the chimera is rotated by 30°, the first energy band of the photonic crystal degenerates with the second energy band. The inset shows the unit cell and the first Brillouin zone of the metal chimera. When the chimera is rotated by an angle greater than or less than 30 degrees, the degenerate Dirac point will be opened to form a band gap. It is worth noting that when the rotation angle reaches the maximum or minimum, that is, θ=0° or θ=60°, the band structures of the two are the same, see Figure 2 (b) is a schematic diagram of the energy band of the photonic crystal mosaic with a rotation angle of 30°, and the inset is a schematic diagram of the primitive cell structure; see Figure 2 (c) is a schematic diagram of the energy band of the photonic crystal chimera when it is rotated by 60°, and the inset is a schematic diagram of the primitive cell structure; the topological Chern numbers of the two are different, which ensures the existence of topologically protected boundary states at the interface of the two photonic crystals.

[0054] like Figure 3 The diagram shows the projected energy band and intrinsic electric field distribution of the photon Dirac waveguide I, photon Dirac waveguide II and photon Dirac waveguide III of the present invention; (a) is the projected energy band and intrinsic electric field distribution of the photon Dirac waveguide I; (b) is the projected energy band and intrinsic electric field distribution of the photon Dirac waveguide II and photon Dirac waveguide III; from the calculated one-dimensional energy band dispersion of the photonic crystal supercell structure, it can be seen that by rotating the angle of the photonic crystal chimera with a linear gradient in the y direction, a spatially uniformly distributed synthetic pseudomagnetic field can be constructed. The existence of this strong pseudomagnetic field leads to the quantization of the Landau level in the photonic crystal. It is worth noting that the zero-order Landau level here is a chiral interface state dispersion. Figure 3 The horizontal coordinate is the reciprocal space k x Directional wave vector, the ordinate is frequency, the unit is GHz. In the numerical simulation calculation, the left and right sides of the supercell are set as periodic boundaries, and the upper and lower sides are set as scattering boundary conditions. This means that this structure is infinite along the x direction and finite along the y direction. Figure 3 The inset in (a) shows that there are 30 primitive cells in the y direction, and the chimera rotates uniformly along the y direction with a rotation gradient of Δθ = 2°, with a rotation range of 0-60°. The inset on the right shows the wave vector k x =0.7(π / a), the intrinsic electric field distribution at frequency f=10.334GHz, the electric field is localized on the photonic crystal in the middle. Figure 3 The rotation angle gradient Δθ of the chimera in the supercell of (b) is 6°, that is, the rotation angle range is 0-180°, and two energy band dispersions appear in the calculated projected energy band. As the degree of rotation increases, the interface state dispersion slope will also increase, and the number of interface channels will also increase accordingly. This means that a beam of electromagnetic waves incident therein can be divided into multiple beams as needed, and the transmission rate of the electromagnetic waves can be manipulated. This provides a theoretical basis for the successful design of the photonic Dirac waveguide of the present invention.

[0055] like Figure 4 As shown in the figure, the electric field distribution diagram of the photonic Dirac waveguide. When a broadband electromagnetic wave is incident on the photonic crystal from the P1 11 port, the electromagnetic wave will propagate in the middle area of ​​the photonic crystal waveguide I; it will be divided into two beams after passing through the photonic crystal waveguide II and the photonic crystal waveguide III, and will be transmitted at the upper and lower interfaces; finally, it will be concentrated in the middle area of ​​the photonic crystal waveguide I on the right and will be emitted from the P2 12 port.

[0056] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which will not affect the essence of the present invention.

Claims

1. A photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field, characterized in that: Including photon Dirac waveguide I, photon Dirac waveguide II and photon Dirac waveguide III; in, The photon Dirac waveguide I is composed of gradient photonic crystal A1, photonic crystal O and gradient photonic crystal A2, and is arranged in a sandwich structure of A1OA2; The photon Dirac waveguide II is composed of gradient photonic crystal A3, photonic crystal O and gradient photonic crystal A4, and is arranged in a sandwich structure with A3OA4; The photon Dirac waveguide III is composed of gradient photonic crystal A5, photonic crystal O and gradient photonic crystal A6, and is arranged in a sandwich structure with A5OA6.

2. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 1, characterized in that: A1OA2, A3OA4 and A5OA6 each have a lateral interface state transmission channel.

3. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 2, characterized in that: The left side of the lateral interface state transmission channel is the information input port P1, and the rightmost side thereof is the information output port P2.

4. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 1, characterized in that: The photonic crystal O, gradient photonic crystal A1, gradient photonic crystal A2, gradient photonic crystal A3, gradient photonic crystal A4, gradient photonic crystal A5 and gradient photonic crystal A6 are periodically arranged in the X-axis and Y-axis directions in a rectangular coordinate system to form a triangular lattice, and the lattice constant of the triangular lattice is a=36.8mm.

5. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 4, characterized in that: The primitive cell of the triangular lattice is a mosaic composed of a metal cylinder with a radius of r1 = 3.68 mm and three identical metal cuboids with a length of 7.95 mm and a width of 2.21 mm and an interval of 60°.

6. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 5, characterized in that: The rotation angle θ of the chimera is 0°.

7. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 5, characterized in that: The chimera is made of metal material, and the background material of the chimera is air, and the relative dielectric constant and relative magnetic permeability of air are both 1.

8. The photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 1, characterized in that: The gradient photonic crystal A1 has 15 primitive cells in the y direction, and the rotation angle of the chimera in each layer of primitive cells changes linearly along the y direction, that is, θ n1 =2n°, where 0≤n<15, n is the number of layers of the primitive cell; The gradient photonic crystal A2 has 15 primitive cells in the y direction, and the rotation angle θ of each layer of mosaic is n2 =2n°, where 15<n≤30; n is the number of layers of the primitive cell; The gradient photonic crystal A3 has 5 primitive cells in the y direction, and the rotation angle θ of each layer of mosaic is n3 =6n°, where 0≤n<5; n is the number of layers of the primitive cell; The gradient photonic crystal A4 has 9 primitive cells in the y direction, and the rotation angle of each layer of the mosaic is θ n4 =6n°, where 5<n<15; n is the number of layers of the primitive cell; The gradient photonic crystal A5 has 9 primitive cells in the y direction, and the rotation angle θ of each layer of the mosaic is n5 =6n°, where 15<n<25; n is the number of layers of the primitive cell; The gradient photonic crystal A6 has 5 primitive cells in the y direction, and the rotation angle θ of each layer of the mosaic is n6 =6n°, where 25<n≤30; n is the number of layers of the primitive cell; The mosaic in the photonic crystal O is rotated 30° around the center of the primitive cell, and the width of the photonic crystal O in the y direction is the size of one primitive cell.

9. An application of the photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 1, characterized in that: By changing the rotation angle of each layer of the chimera in the photonic crystal along the linear gradient of the y direction, gradient photonic crystal A1, gradient photonic crystal A2, gradient photonic crystal A3, gradient photonic crystal A4, gradient photonic crystal A5 and gradient photonic crystal A6 are constructed, so that after the broadband electromagnetic wave enters the transverse interface state transmission channel in the photonic Dirac waveguide I, it is divided into two beams of electromagnetic waves, an upper beam and a lower beam, which are respectively transmitted through the transverse interface state transmission channel in the Dirac waveguide II and the transverse interface state transmission channel in the photonic Dirac waveguide III, and then converge into one beam, thereby realizing the control of electromagnetic wave splitting and focusing.

10. The application of the photonic Dirac waveguide based on photonic crystal synthetic pseudomagnetic field as claimed in claim 1, characterized in that: The excitation source of the light source is a linear polarization source; the excitation source is placed at the left end of the photonic crystal O.

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