Wide channel one-way waveguide

Abstract

The application discloses a wide-channel unidirectional waveguide, which comprises a dielectric column array, a parallel-plate waveguide and a metal domain wall, the dielectric column array is a semi-infinite quasi-two-dimensional structure composed of circular dielectric columns arranged in a triangular lattice, the upper and lower surfaces of the dielectric column array are metal domain walls, the first row and the last row of dielectric columns are composed of semicircular dielectric columns split along the central axis, and the metal domain wall is arranged on the cutting plane; the dielectric column array and the metal domain wall are arranged between the parallel-plate waveguides; electromagnetic excitation sources capable of generating left-handed / right-handed polarization are arranged between two rows of dielectric columns of the dielectric column array. The wide-channel unidirectional waveguide is designed to realize the wide-channel unidirectional transmission of electromagnetic waves by inducing chiral transmission modes through the metal domain wall. The wide-channel unidirectional waveguide has the advantages of simple principle, compact structure, wide transmission channel, small electromagnetic loss, and the like. The geometric size can be changed through the scale invariance to transplant the waveguide to the optical wave band.

Description

Technical Field

[0001] This invention relates to the field of photonic crystals and photonic devices, and to a photonic crystal structure for unidirectional electromagnetic wave transmission, which can realize wide-channel, low-loss unidirectional propagation of electromagnetic waves. Background Technology

[0002] Reciprocity is a fundamental principle of electromagnetism. However, in optical devices such as beam splitters and optical fibers, it is desirable for electromagnetic waves to propagate in a single direction and minimize backscattering. Currently, there are many methods to achieve unidirectional electromagnetic wave propagation, including utilizing magnetic surface plasmons, nonlinear gain or loss, microcavity waveguide coupling, and topological boundary states. While these methods each have their advantages, they also suffer from problems such as complex structures, high manufacturing costs, difficult integration, weak anti-interference capabilities, limited transmission channel range, and low uniformity, hindering the development of non-reciprocal optical devices.

[0003] To address the aforementioned shortcomings, this invention designs a wide-channel unidirectional waveguide. This waveguide is based on a triangular lattice dielectric pillar array and utilizes chiral bulk states induced by metallic domain walls to achieve wide-channel unidirectional propagation of electromagnetic waves. It offers advantages such as simple structure, wide transmission channel, and resistance to bending loss. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a wide-channel unidirectional waveguide with a simple structure, wide transmission channel, and resistance to bending loss.

[0005] Technical Solution: The present invention provides a wide-channel unidirectional waveguide, comprising a dielectric pillar array, a parallel plate waveguide, and metal domain walls. The dielectric pillar array is a semi-infinite quasi-two-dimensional structure composed of circular dielectric pillars arranged in a triangular lattice. The upper and lower surfaces of the dielectric pillar array are metal domain walls. The first and last rows of dielectric pillars are composed of semi-circular dielectric pillars cut in half along the central axis, with metal domain walls placed on the cutting plane. Both the dielectric pillar array and the metal domain walls are placed between the parallel plate waveguide. An electromagnetic excitation source capable of generating left-handed / right-handed polarization is provided between the two rows of dielectric pillars in the dielectric pillar array.

[0006] In a specific embodiment, the dielectric column array is provided with at least four rows of dielectric columns.

[0007] Preferably, the dielectric pillars in the dielectric pillar array are ceramic cylinders.

[0008] Preferably, the dielectric pillar array satisfies lattice translation symmetry, and the lattice constant a of the dielectric pillar array structure is , the height h = 0.625a, and the radius r of the dielectric pillar is 0.1a.

[0009] Preferably, the electromagnetic excitation source is placed above or below the middle row of dielectric columns.

[0010] Preferably, the electromagnetic excitation source consists of four phase-differential sources. A point source can be used to generate an excitation source with left-handed / right-handed polarized electromagnetic waves.

[0011] The wide-channel microwave unidirectional waveguide design proposed in this invention prohibits the propagation of electromagnetic waves with normal components (exhibiting even symmetry in bulk mode) in the dielectric pillar array through metal domain walls, while allowing the propagation of electromagnetic waves with radial components (exhibiting odd symmetry in bulk mode). Addressing the characteristic of electromagnetic waves with different energy flow vortex directions propagating along different channels in the dielectric pillar array, left-handed (right-handed) polarized excitation sources can be used to selectively excite wide-channel unidirectional waveguides with different propagation directions.

[0012] Beneficial effects: Compared with existing technologies, the wide-channel unidirectional waveguide proposed in this invention has a simple structure and can realize wide-channel transmission of electromagnetic waves. Due to the protection of valley degrees of freedom, electromagnetic wave transmission can ignore weak disorder or curvature, has low requirements for manufacturing precision, and is suitable for various integrated photonic devices. Because the dielectric pillar array has scale invariance, the operating frequency can be directly transferred to the terahertz band or optical band by changing the geometric dimensions, exhibiting broad applicability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the three-dimensional model structure of an embodiment of the present invention.

[0014] Figure 2 This is a schematic diagram of a dielectric pillar array according to an embodiment of the present invention, consisting of four phase-differential arrays. The excitation source, consisting of point sources, is placed at the center of the array.

[0015] Figure 3 Is with Figure 2 The corresponding photon projection band structure, where the dashed lines represent the chiral bulk band structure induced by the metal domain walls.

[0016] Figure 4 This is an electric field distribution diagram under a left-handed polarized excitation source according to an embodiment of the present invention, in which electromagnetic waves propagate unidirectionally in the +x direction.

[0017] Figure 5 This is an electric field distribution diagram under a right-handed polarized excitation source according to an embodiment of the present invention, in which electromagnetic waves propagate unidirectionally in the -x direction.

[0018] Figure 6 yes Figure 4 The relationship between the Poynting vector integral and frequency of electromagnetic waves along the ±x direction. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

[0020] This invention discloses a wide-channel unidirectional waveguide, comprising a dielectric pillar array 1, a parallel plate waveguide 2, and a metal domain wall 3. The dielectric pillar array is a semi-infinite quasi-two-dimensional structure composed of a dielectric pillar triangular lattice. The top and bottom surfaces of the dielectric pillar array are metal domain walls. Both the dielectric pillar array and the metal domain walls are disposed between two parallel plate waveguides. The parallel plate waveguides are aluminum plates; the metal domain walls are aluminum strips with dimensions of 300mm × 30mm × 10mm; the dielectric pillars are ceramic pillars, primarily composed of alumina, with a relative permittivity of 12.4.

[0021] like Figure 1 As shown, the wide-channel microwave unidirectional waveguide design proposed in this embodiment of the invention is based on a two-dimensional triangular lattice dielectric pillar array. The dielectric pillar array is composed of ceramic pillars with a dielectric constant of 12.4, a radius r = 0.1a, and a height h = 0.625a arranged in a triangular lattice, with a lattice constant of a (a = 16 mm in this example). Along the y-direction, the dielectric pillar array at y = 0 mm and... The plane terminates at the metallic domain wall. The dielectric pillar array has a length along the y-direction of... Extending infinitely along the x-direction. Increasing the number of dielectric pillars leads to a slow decrease in the operating frequency range of the wide-channel unidirectional waveguide.

[0022] like Figure 2 As shown, the main body of the dielectric pillar array is composed of a complete arrangement of dielectric pillars, with the upper and lower edges formed by semi-circular dielectric pillars. The electromagnetic wave excitation source 4 is placed between two rows of dielectric pillars, consisting of four phase-differential... The point source is formed. When the phase of the point source is... The sequence changes counterclockwise (clockwise), and the excitation source generates electromagnetic waves with left (right) rotational polarization characteristics.

[0023] Figure 3 for Figure 2The diagram shows the photon projection band structure corresponding to the dielectric pillar array. The dashed lines represent the chiral bulk bands induced by the metal domain walls. These chiral bulk bands connect the valence and conduction bands, and their slopes have opposite signs at the high-symmetry points K and K' in the Brillouin zone, indicating that the chiral bulk modes have opposite group velocity directions at K and K'. K and K' represent different electromagnetic wave propagation paths in the dielectric pillar array. The metal domain walls prohibit the propagation of electromagnetic waves with normal components (exhibiting even symmetry in the bulk mode) and only allow the propagation of electromagnetic waves with radial components (exhibiting odd symmetry in the bulk mode). Since inter-valley scattering is negligible, similar to the propagation of electromagnetic waves along the material edges in conventional valley topological insulators, the propagation of electromagnetic waves in the dielectric pillar array exhibits unidirectionality and robustness. Furthermore, compared to electromagnetic waves that can only propagate along narrow boundaries in conventional topological materials, the wide-channel unidirectional waveguide structure proposed in this invention allows electromagnetic waves to propagate along the main body of the dielectric pillar array, not just limited to the boundaries, greatly widening the transmission path.

[0024] Figure 4 This invention demonstrates that in the wide-channel microwave unidirectional waveguide design proposed in this invention, the electromagnetic waves generated by the left-handed polarization excitation source excite the electromagnetic wave transmission channel corresponding to the K valley, which then propagates unidirectionally along the +x direction.

[0025] Figure 5 This invention demonstrates that in the wide-channel microwave unidirectional waveguide design proposed in this invention, the electromagnetic waves generated by the right-hand polarization excitation source excite the electromagnetic wave transmission channel corresponding to the K' valley, which then propagates unidirectionally along the -x direction.

[0026] Figure 6 The relationship between the Poynting vector integral and frequency of electromagnetic waves along the ±x directions under a left-handed polarized excitation source is shown. The energy flux intensity of the electromagnetic wave along the +x direction is significantly higher than that along the -x direction, demonstrating the excellent unidirectionality of electromagnetic wave transmission in the wide-channel unidirectional waveguide proposed in this invention.

[0027] Because dielectric pillar arrays are scale invariant, the operating frequency can be shifted to the terahertz band or optical band by directly changing the geometry.

[0028] The above description is only a preferred embodiment of the present invention. Since the dielectric pillar array has scale invariance, the operating frequency can be transferred to the terahertz or visible light band by directly changing the geometric size.

Claims

1. A wide-channel unidirectional waveguide, characterized in that, The structure includes a dielectric pillar array, a parallel plate waveguide, and a metal domain wall. The dielectric pillar array is a semi-infinite quasi-two-dimensional structure composed of circular dielectric pillars arranged in a triangular lattice. Metal domain walls are set on the edges of the first and last rows of the dielectric pillar array. The first and last rows of dielectric pillars are composed of semi-circular dielectric pillars cut in half along the central axis, and the metal domain wall is placed on the outermost edge of the cutting plane. The dielectric pillar array and the metal domain wall are both placed between parallel plate waveguides arranged in parallel in the vertical direction. An electromagnetic excitation source capable of generating left-handed / right-handed polarization is provided between the two rows of dielectric pillars in the dielectric pillar array.

2. The wide-channel unidirectional waveguide according to claim 1, characterized in that, The dielectric column array has at least four rows of dielectric columns.

3. The wide-channel unidirectional waveguide according to claim 1, characterized in that, The dielectric column is a ceramic cylinder.

4. The wide-channel unidirectional waveguide according to claim 1, characterized in that, The dielectric pillar array satisfies lattice translation symmetry.

5. The wide-channel unidirectional waveguide according to claim 1, characterized in that, The electromagnetic excitation source is placed above or below the middle row of dielectric columns.

6. The wide-channel unidirectional waveguide according to claim 1, characterized in that, The electromagnetic excitation source is composed of four point sources with different phases, which can generate electromagnetic waves with left-handed / right-handed polarization.

7. The wide-channel unidirectional waveguide according to any one of claims 1-6, characterized in that, Metal domain walls prohibit the transmission of electromagnetic waves with normal components in a dielectric column array, allowing electromagnetic waves to propagate only radially.

8. The wide-channel unidirectional waveguide according to claim 7, characterized in that, Metallic domain walls suppress even modes in bulk states, retaining only odd modes; in odd modes, only electromagnetic waves with radial components are allowed to propagate, while electromagnetic waves with normal components are prohibited from propagating.

9. The wide-channel unidirectional waveguide according to claim 8, characterized in that, In a dielectric pillar array, electromagnetic waves have two different transmission channels, which allow electromagnetic waves with different energy flow vortices to propagate in a single direction.

Images