Photonic crystal wavelength division multiplexer based on high-order topology double angular states

Abstract

The invention discloses a photonic crystal wavelength division multiplexer based on high-order topology double angular states. The photonic crystal wavelength division multiplexer comprises a first strip-shaped waveguide, a second strip-shaped waveguide, a third strip-shaped waveguide, a first defect waveguide, a second defect waveguide, a third defect waveguide, a first photonic crystal dielectric flat plate and a second photonic crystal dielectric flat plate, the first photonic crystal dielectric flat plate and the second photonic crystal dielectric flat plate are located on the same horizontal plane, a first defect waveguide and a second defect waveguide are arranged on the first photonic crystal dielectric flat plate, the first defect waveguide is connected to a first strip-shaped waveguide, and the second defect waveguide is connected to a second strip-shaped waveguide; the second photonic crystal dielectric flat plate is provided with a third defect waveguide which is connected to the third strip-shaped waveguide. Compared with the prior art, the method has the outstanding advantages of being simple in design method, novel in design thought, low in performance index crosstalk value and the like.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano and integrated optoelectronic technology, and more specifically, to a photonic crystal wavelength division multiplexer based on a high-order topological double-angle state. Background Art

[0002] With the development of information technology, more flexible light field control and optical information processing methods have received widespread attention. Photonic crystals are artificial optical materials formed by the periodic arrangement of two or more materials with different refractive indices. Due to their unique photonic bandgap properties, they can be used to make photonic crystal microcavities, filters, multiplexers and other photonic devices. Among them, wavelength division multiplexers are used to realize the multiplexing or demultiplexing of two or more different wavelengths of light.

[0003] However, due to errors in the device preparation process and limitations in process precision, energy loss caused by energy scattering is inevitable at the corners of the device and in local microcavities. In addition to continuously improving the preparation process, we can also find ways to solve the problem from physical principles, and topological photonics is one of the solutions to overcome this type of energy loss problem. Current research mainly uses the coupling between waveguide modes and microcavity modes to realize wavelength division multiplexers on photonic crystal slabs. There are still some limitations in the application of topological photonic crystals in on-chip photonic devices. There are few studies on the application of photonic devices based on corner-state microcavities, such as wavelength division multiplexers, and less attention is paid to the directional selectivity of corner-state excitation, which limits the expansion of topological photonic crystals to more on-chip optical devices.

[0004] Topological photonics uses quantities that remain unchanged in a series of continuous transformations to make the global structure robust to local perturbations or defects, thereby providing a new anti-scattering mechanism physically and having great development potential in improving the performance of photonic devices.

[0005] The prior art discloses a wavelength division multiplexer design method and system based on topological photonic crystals, the method comprising: obtaining three photonic crystal primitive cells after topological optimization, the photonic crystal primitive cells including PC1 primitive cell, PC3 primitive cell and PC4 primitive cell; combining the three photonic crystal primitive cells in pairs to obtain different super cells; determining the boundary state and transmission efficiency of each super cell; designing four directional point sources at the junction of PC3 primitive cell and PC4 primitive cell to verify whether the structure composed of the three photonic crystal primitive cells can produce a composite effect of unidirectional propagation, boundary state and wavelength division multiplexing to obtain a wavelength division multiplexer; destroying the structure of each super cell to determine that the overall effect of the wavelength division multiplexer is not affected. The defect of this method is that it is wavelength division multiplexing realized by unidirectional transmission of boundary state, and is not suitable for the situation where wavelength division multiplexing is required in two-directional waveguides.

[0006] To this end, in combination with the above requirements and the defects of the prior art, the present application proposes a photonic crystal wavelength division multiplexer based on high-order topological double-angle states. Summary of the invention

[0007] The present invention provides a photonic crystal wavelength division multiplexer based on a high-order topological dual-angle state, which changes the angle θ between a waveguide and a horizontal direction, thereby changing the coupling efficiency, thereby obtaining a wavelength division multiplexer with lower crosstalk.

[0008] The primary purpose of the present invention is to solve the above technical problems. The technical solution of the present invention is as follows:

[0009] A first aspect of the present invention provides a photonic crystal wavelength division multiplexer based on a high-order topological dual-angle state, comprising: a first strip waveguide, a second strip waveguide, a third strip waveguide, a first defect waveguide, a second defect waveguide, a third defect waveguide, a first photonic crystal dielectric slab, and a second photonic crystal dielectric slab.

[0010] The first photonic crystal dielectric slab and the second photonic crystal dielectric slab are in the same horizontal plane and are connected to each other through two connecting boundaries, and the intersection of the two connecting boundaries constitutes a corner structure with a high-order topological dual-angle state; a first defect waveguide and a second defect waveguide are arranged on the first photonic crystal dielectric slab, wherein one end of the first defect waveguide is at a distance L1 from the corner structure, and the other end extends out of the first photonic crystal dielectric slab and is connected to the first strip waveguide, and one end of the second defect waveguide is at a distance L2 from the corner structure, and the other end extends out of the first photonic crystal dielectric slab and is connected to the second strip waveguide; a third defect waveguide is arranged on the second photonic crystal dielectric slab, and one end of the third defect waveguide is at a distance L3 from the corner structure, and the other end extends out of the second photonic crystal dielectric slab and is connected to the third strip waveguide.

[0011] Furthermore, the first photonic crystal dielectric slab is composed of a periodic arrangement of first unit cells, and the second photonic crystal dielectric slab is composed of a periodic arrangement of second unit cells; the first unit cell and the second unit cell are both Kagome lattice photonic crystals and have an initial shape of a regular hexagon, a first air hole is provided at the center of the first unit cell, and second air holes are provided at three non-adjacent vertices of the second unit cell.

[0012] Furthermore, the first defect waveguide and the second defect waveguide are obtained by filling part of the first air holes in the first photonic crystal dielectric slab with photonic crystal dielectric, and the third defect waveguide is obtained by filling part of the second air holes in the second photonic crystal dielectric slab with photonic crystal dielectric.

[0013] Further, the first air holes of the first unit cell are configured as regular hexagonal holes, and the second air holes of the second unit cell are configured as rhombus holes.

[0014] Furthermore, the side lengths of the first air hole and the second air hole are both 0.28a, where a represents a lattice constant.

[0015] Furthermore, the overall size of the first photonic crystal dielectric slab and the second photonic crystal dielectric slab is

[0016] Furthermore, the width of the first defect waveguide is The length is 38a; the width of the second defect waveguide is The width of the third defect waveguide is a and its length is

[0017] Furthermore, the width of the first strip waveguide is The length is 20a; the width of the second strip waveguide is The width of the third strip waveguide is 2a and the length is 20a.

[0018] Furthermore, the input port of the first strip waveguide is used to receive light containing two wavelengths and transmit it to the first defect waveguide, and then excite two localized corner modes at the corner structure to separate the two wavelengths of light, wherein the light of the first wavelength is coupled into the third defect waveguide through a boundary with a length of L3 and is output from the output port of the third strip waveguide, and the light of the second wavelength is coupled into the second defect waveguide through a boundary with a length of L2 and is output from the output port of the second strip waveguide.

[0019] Furthermore, the transmission peak efficiency is changed by adjusting the angle θ between the second strip waveguide and the second defect waveguide and the horizontal direction, thereby adjusting the demultiplexing effect of the wavelength division multiplexer, and the optimal coupling angle is θ=30°.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] The present invention provides a photonic crystal wavelength division multiplexer based on high-order topological dual-angle states. By using the principle of topological optics to predict the localized mode of the topological dual-angle states, a topologically protected photonic crystal wavelength division multiplexer is designed. By changing the angle θ between the waveguide and the horizontal direction, the coupling efficiency is changed, thereby obtaining a wavelength division multiplexer with low crosstalk. It has outstanding advantages such as simple design principle and novel design ideas, and is expected to provide new ideas for guiding the design of topological photonic wavelength division multiplexers, and has potential applications in wavelength division multiplexing systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The schematic diagram of the photonic crystal wavelength division multiplexer based on high-order topological dual-angle states of the present invention.

[0023] Figure 2 FIG. 1 is an xy cross-sectional schematic diagram of a photonic crystal wavelength division multiplexer in an embodiment of the present invention.

[0024] Figure 3 This is a diagram of magnetic field energy distribution during transmission of an input wavelength division multiplexer in an embodiment of the present invention.

[0025] Figure 4 This is a transmission spectrum of a photonic crystal wavelength division multiplexer with a rotation angle θ=0° in an embodiment of the present invention.

[0026] Figure 5 This is a transmission spectrum of a photonic crystal wavelength division multiplexer with a rotation angle of θ=30° in an embodiment of the present invention.

[0027] Figure 6 This is the transmission spectrum of the photonic crystal wavelength division multiplexer with a rotation angle of θ=45° according to the present invention. DETAILED DESCRIPTION

[0028] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0030] Before describing the specific embodiments, the terms involved in the present invention are explained as follows:

[0031] Bandwidth (BW): It is defined as the bandwidth when the transmittance of the transmission signal in the wavelength division multiplexer is reduced to half. It is used to indicate the frequency width occupied by the transmission signal, and half of the power is concentrated in this bandwidth. In logarithmic coordinates, the half-power point corresponds to the position of -3dB, and the bandwidth defined in this invention can be considered to be the 3dB bandwidth. In optical fiber transmission, the size of the bandwidth is used to indicate the ability of the line to transmit data.

[0032] Free Spectral Range (FSR): It is defined as the difference in wavelengths corresponding to the output signals of the two output ports of a wavelength division multiplexer. It refers to the wavelength interval between two adjacent resonant modes in the resonant cavity, which can be used as an important indicator for wavelength selection. Its size can determine whether light waves of different wavelengths can be selected for transmission. FSR is a key parameter in the field of laser and optical fiber communications. A larger free spectral range can improve the communication performance of optical devices.

[0033] Crosstalk: It is defined as the influence of interference light on transmission light in the transmission channel. Its calculation formula is the logarithm of the ratio of the interference light transmittance to the transmission light transmittance in the transmission channel, multiplied by a coefficient of 10. It can be understood that the smaller the channel crosstalk, the smaller the ratio of interference light to transmission light, and the better the WDM multiplexing effect.

[0034] Example 1

[0035] like Figure 1 As shown, the present invention provides a photonic crystal wavelength division multiplexer based on a high-order topological dual-angle state, comprising: a first strip waveguide 1, a second strip waveguide 2, a third strip waveguide 3, a first defect waveguide 4, a second defect waveguide 5, a third defect waveguide 6, a first photonic crystal dielectric slab 8 and a second photonic crystal dielectric slab 9.

[0036] The first photonic crystal dielectric slab 8 and the second photonic crystal dielectric slab 9 are in the same horizontal plane and are connected to each other through two connecting boundaries, and the intersection of the two connecting boundaries constitutes a corner structure 7 with a high-order topological dual-angle state; a first defect waveguide 4 and a second defect waveguide 5 are arranged on the first photonic crystal dielectric slab 8, wherein one end of the first defect waveguide 4 is at a distance L1 from the corner structure 7, and the other end extends out of the first photonic crystal dielectric slab 8 and is connected to the first strip waveguide 1, and one end of the second defect waveguide 5 is at a distance L2 from the corner structure 7, and the other end extends out of the first photonic crystal dielectric slab 8 and is connected to the second strip waveguide 2; a third defect waveguide 6 is arranged on the second photonic crystal dielectric slab 9, and one end of the third defect waveguide 6 is at a distance L3 from the corner structure 7, and the other end extends out of the second photonic crystal dielectric slab 9 and is connected to the third strip waveguide 3.

[0037] like Figure 2 As shown, the first photonic crystal dielectric slab 8 is composed of a periodically arranged first unit cell 10, and the second photonic crystal dielectric slab 9 is composed of a periodically arranged second unit cell 11; the first unit cell 10 and the second unit cell 11 are both Kagome lattice photonic crystals and have an initial shape of a regular hexagon, a first air hole is provided at the center of the first unit cell 10, and second air holes are provided at three non-adjacent vertices of the second unit cell 11.

[0038] The first defect waveguide 4 and the second defect waveguide 5 are obtained by filling part of the first air holes in the first photonic crystal dielectric slab 8 with photonic crystal dielectric, and the third defect waveguide 6 is obtained by filling part of the second air holes in the second photonic crystal dielectric slab 9 with photonic crystal dielectric.

[0039] The first air holes of the first unit cell 10 are arranged as regular hexagonal holes, and the second air holes of the second unit cell 11 are arranged as rhombus holes. The side lengths of the first air holes and the second air holes are both 0.28a, where a represents the lattice constant.

[0040] In a specific embodiment, the lattice constant a=407nm. The two-dimensional Zach phase of the first unit cell 10 is (0,0), that is, the first unit cell 10 is a trivial topological phase, and the two-dimensional Zach phase of the second unit cell 11 is (π,π), that is, the second unit cell 11 is a non-trivial topological phase.

[0041] The overall size of the first photonic crystal dielectric slab 8 and the second photonic crystal dielectric slab 9 is: The width of the first defect waveguide 4 is The length is 38a; the width of the second defect waveguide 5 is The width of the third defect waveguide 6 is a, and the length is The width of the first strip waveguide 1 is The length is 20a; the width of the second strip waveguide 2 is The third strip waveguide 3 has a width of 2a and a length of 20a.

[0042] In a specific embodiment, the first photonic crystal dielectric slab 8, the second photonic crystal dielectric slab 9, the first strip waveguide 1, the second strip waveguide 2, the third strip waveguide 3 and the first defect waveguide 4, the second defect waveguide 5, and the third defect waveguide 6 are all made of silicon, and its refractive index is 3.464.

[0043] Example 2

[0044] Based on the above embodiment 1, combined with Figure 3 , this embodiment describes the working principle of the present invention in detail.

[0045] like Figure 3As shown, the input port of the first strip waveguide 1 is used to receive light containing two wavelengths λ3 and λ4 and transmit it to the first defect waveguide 4, and then excite two localized corner modes at the corner structure 7 to separate the two wavelengths of light, wherein the light of the first wavelength λ3 is coupled into the third defect waveguide 6 through a boundary with a length of L3 and output from the output port of the third strip waveguide 3, and the light of the second wavelength λ4 is coupled into the second defect waveguide 5 through a boundary with a length of L2 and output from the output port of the second strip waveguide 2.

[0046] Example 3

[0047] Based on the above-mentioned embodiment 1 and embodiment 2, as Figure 4-Figure 6 As shown, the embodiment of the present invention describes the demultiplexing process of the present invention in detail.

[0048] The photonic crystal wavelength division multiplexer of the present invention changes the transmission peak efficiency by adjusting the angle θ between the second strip waveguide 2 and the second defect waveguide 5 and the horizontal direction, thereby adjusting the demultiplexing effect of the wavelength division multiplexer, and the optimal coupling angle is θ=30°.

[0049] like Figure 4 As shown, when θ=0° (less than the optimal coupling angle), Port 2 can achieve a signal output with a bandwidth of 0.235 nm, and Port 3 can achieve a signal output with a bandwidth of 0.178 nm.

[0050] like Figure 5 As shown, when θ=30° (equal to the optimal coupling angle), Port 2 can achieve a signal output with a bandwidth of 0.235 nm, and Port 3 can achieve a signal output with a bandwidth of 0.178 nm.

[0051] like Figure 6 As shown, when θ=45° (greater than the optimal coupling angle), Port 2 can achieve a signal output with a bandwidth of 0.353 nm, and Port 3 can achieve a signal output with a bandwidth of 0.297 nm.

[0052] It can be seen that when θ=0° (less than the optimal coupling angle) or θ=45° (greater than the optimal coupling angle), the transmittance is lower than θ=30° (equal to the optimal coupling angle).

[0053] In a specific embodiment, the free spectral range of the output signal of the wavelength division multiplexer based on the high-order topological double-angle state is simulated and calculated, and the effect is as follows Figure 4 , 5and 6. When θ = 0° (less than the optimal coupling angle), the free spectral range of the two ports is 7.38 nm; when θ = 45° (greater than the optimal coupling angle), the free spectral range of the two ports is 7.14 nm; when θ = 30° (equal to the optimal coupling angle), the free spectral range of the two ports is 7.38 nm.

[0054] Furthermore, the channel crosstalk of the wavelength division multiplexer based on the high-order topological dual-angle state is simulated and calculated, and the calculation formula is C=10log(I ′ out / I out ). When θ = 0° (less than the optimal coupling angle), the crosstalk C = 5.9142; when θ = 45° (greater than the optimal coupling angle), the crosstalk C = -0.9337; when θ = 30° (equal to the optimal coupling angle), the crosstalk C = -12.8038.

[0055] In the embodiments provided in the present application, it should be understood that the disclosed systems and methods can be implemented in other ways. A person of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium, which, when executed, executes the steps of the above method embodiments; and the aforementioned storage medium includes: a mobile storage device, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media capable of storing program codes.

[0056] Alternatively, if the above-mentioned embodiments of the present invention are implemented in the form of software function modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiments of the present invention can be essentially or partly reflected in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device to execute all or part of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media capable of storing program codes, such as mobile storage devices, ROM, RAM, magnetic disks or optical disks.

[0057] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. The icons describing the structural positional relationships in the accompanying drawings are only used for exemplary purposes and are not to be construed as limiting the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and is not possible to list all the embodiments here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A photonic crystal wavelength division multiplexer based on high-order topological double-angle states, characterized in that: The invention comprises: a first strip waveguide (1), a second strip waveguide (2), a third strip waveguide (3), a first defect waveguide (4), a second defect waveguide (5), a third defect waveguide (6), a first photonic crystal dielectric slab (8) and a second photonic crystal dielectric slab (9); The first photonic crystal dielectric slab (8) and the second photonic crystal dielectric slab (9) are located in the same horizontal plane and are connected to each other via two connection boundaries, and the intersection of the two connection boundaries forms a corner structure (7) having a high-order topological double-angle state; a first defect waveguide (4) and a second defect waveguide (5) are arranged on the first photonic crystal dielectric slab (8), wherein one end of the first defect waveguide (4) is at a distance L1 from the corner structure (7), and the other end is epitaxially extended toward the first photonic crystal dielectric slab (8). The first photonic crystal dielectric slab (8) is provided with a third defect waveguide (6), one end of the third defect waveguide (6) is at a distance L3 from the corner structure (7), and the other end thereof is extended to the outside of the second photonic crystal dielectric slab (9) and connected to the second strip waveguide (2).

2. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 1, characterized in that: The first photonic crystal dielectric slab (8) is composed of first unit cells (10) arranged periodically, and the second photonic crystal dielectric slab (9) is composed of second unit cells (11) arranged periodically; the first unit cell (10) and the second unit cell (11) are both Kagome lattice photonic crystals and have an initial shape of a regular hexagon, a first air hole is provided at the center of the first unit cell (10), and second air holes are provided at three non-adjacent vertices of the second unit cell (11).

3. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 2, characterized in that: The first defect waveguide (4) and the second defect waveguide (5) are obtained by filling a portion of the first air holes of the first photonic crystal dielectric slab (8) with a photonic crystal dielectric, and the third defect waveguide (6) is obtained by filling a portion of the second air holes of the second photonic crystal dielectric slab (9) with a photonic crystal dielectric.

4. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 3, characterized in that: The first air holes of the first unit cell (10) are arranged as regular hexagonal holes, and the second air holes of the second unit cell (11) are arranged as rhombus holes.

5. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 4, characterized in that: The side lengths of the first air hole and the second air hole are both 0.28a, where a represents the lattice constant.

6. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 5, characterized in that: The overall size of the first photonic crystal dielectric slab (8) and the second photonic crystal dielectric slab (9) is 7. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 6, characterized in that: The width of the first defect waveguide (4) is The length is 38a; the width of the second defect waveguide (5) is The width of the third defect waveguide (6) is a and the length is 8. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 7, characterized in that: The width of the first strip waveguide (1) is The length is 20a; the width of the second strip waveguide (2) is The width of the third strip waveguide (3) is 2a and the length is 20a.

9. A photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to any one of claims 1 to 8, characterized in that: The input port of the first strip waveguide (1) is used to receive light containing two wavelengths and transmit it to the first defect waveguide (4), and then excite two localized corner modes at the corner structure (7) to separate the two wavelengths of light, wherein the light of the first wavelength is coupled into the third defect waveguide (6) through a boundary with a length of L3 and is output from the output port of the third strip waveguide (3), and the light of the second wavelength is coupled into the second defect waveguide (5) through a boundary with a length of L2 and is output from the output port of the second strip waveguide (2).

10. The photonic crystal wavelength division multiplexer based on high-order topological double-angle states according to claim 9, characterized in that: The transmission peak efficiency is changed by adjusting the angle θ between the second strip waveguide (2) and the second defect waveguide (5) and the horizontal direction, thereby adjusting the demultiplexing effect of the wavelength division multiplexer, and the optimal coupling angle is θ=30°.

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