A kagome photonic crystal

Abstract

The application discloses a Kagome photonic crystal, belongs to the technical field of lasers, and is used for constructing a topological laser, wherein the Kagome photonic crystal comprises a plurality of supercells, each supercell comprises three hexapole cavities, and the plurality of supercells are periodically arranged along a first direction and a second direction, so that all the hexapole cavities form a Kagome lattice structure as a whole. The technical scheme provided by the application constructs a Kagome supercell through the hexapole cavities, the momentum space of the Kagome lattice has a flat-band energy band with close-to-zero dispersion, the photon group velocity in the flat band tends to be zero, the interaction between light and matter is enhanced, and the Kagome photonic crystal has a natural advantage of constructing a two-dimensional topological laser. Through design of lattice parameters, a single light field mode that can be adjusted and controlled appears in a forbidden band, the band edge mode competition problem of a traditional semiconductor laser is effectively inhibited, and a stable single-mode laser with a high quality factor is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional topological photonic crystal cavities, and particularly relates to a Kagome photonic crystal. BACKGROUND

[0002] Semiconductor topological lasers have advantages of high efficiency, miniaturization, long service life, low cost and easy modulation, but have problems of mode competition and low power of single device.

[0003] One-dimensional Bragg grating distributed feedback lasers and vertical cavity surface emitting lasers generally have the problem of band edge mode competition output, and it is difficult to realize stable single mode output, therefore, it is particularly important to design a two-dimensional photonic crystal cavity laser with single mode characteristics and robust performance. Generally, the lattice parameters are adjusted to improve the single mode characteristics. Since the periodicity of the lattice determines the rules of photon motion and the energy band structure, adjusting the lattice constant and the radius of the air hole (primitive cell) can change the energy band and the range of the photonic band gap to a certain extent. However, there are many modes in the common lattice structure, which is difficult to directly apply to single mode lasers. In the prior art, a photonic structure based on a limited Su-Schrieffer-Heeger (SSH) model can realize single mode transmission in a nanocavity array, but since the model is essentially one-dimensional, the integration degree is low, and therefore it is difficult to realize a topological laser.

[0004] The Kagome lattice is a highly symmetrical structure composed of alternating hexagons and triangles, and its momentum space has a flat band energy band close to zero dispersion. The group velocity of photons in the flat band tends to zero, which is beneficial to enhance the interaction between light and matter, and has the natural advantage of constructing a two-dimensional topological laser. However, the stability of the flat band of the Kagome photonic crystal is highly dependent on the long-range order of the lattice. If the lattice structure has defects or disorder, the strict periodicity will be destroyed, which will change the dispersion relation of the flat band, thereby weakening or even eliminating the unique flat band energy characteristics of the Kagome photonic crystal. SUMMARY

[0005] Therefore, the technical scheme of the application provides a Kagome photonic crystal, which cleverly constructs a supercell containing a hexapole cavity, so that the supercell is periodically arranged in two directions to form a long-range ordered Kagome photonic crystal, thereby solving the problem of single mode stability of a high-quality topological laser.

[0006] In order to achieve the above purpose, the application discloses a Kagome photonic crystal for constructing a topological laser, comprising a plurality of supercells, each supercell comprising three hexapole cavities, and a plurality of supercells being periodically arranged along a first direction and a second direction, so that all the hexapole cavities form a Kagome lattice structure as a whole.

[0007] Further, the supercell is a regular hexagon, the first direction is a direction perpendicular to one side of the regular hexagon, the second direction is a direction perpendicular to another side of the regular hexagon, and a lattice constant of the Kagome photonic crystal along the first direction is equal to a lattice constant of the supercell along the second direction.

[0008] Further, in each supercell, three hexapole cavities are symmetrically distributed about a center of the supercell, two of the hexapole cavities are arranged along the first direction, and a distance between the hexapole cavities is half of a lattice constant of the Kagome photonic crystal.

[0009] Preferably, the supercell further comprises a base and a primitive, the base has a lattice point arranged thereon, the lattice point is periodically arranged along a third direction and a fourth direction to form a lattice array, the primitive is arranged on the lattice point, the third direction is an extension direction of the one side of the regular hexagon, and the fourth direction is an extension direction of the another side of the regular hexagon.

[0010] Specifically, each hexapole cavity comprises six cavity primitives, the six cavity primitives are symmetrically distributed relative to a cavity center of the hexapole cavity, a distance between the six cavity primitives relative to the cavity center of the hexapole cavity is greater than a lattice constant of the lattice array, and a radius of the cavity primitive is less than a radius of the primitive.

[0011] Further, in each hexapole cavity, a position of the cavity center coincides with a position of the lattice point, and at least one cavity primitive is parallel to the third direction or the fourth direction relative to an extension direction of the cavity center.

[0012] The application further provides a Kagome photonic crystal device, the device uses the Kagome photonic crystal as described above, and the device comprises an upper cladding layer, a core layer and a lower cladding layer, the core layer is arranged between the upper cladding layer and the lower cladding layer, and the core layer is the Kagome photonic crystal.

[0013] Specifically, the upper cladding layer comprises a first material, and the lower cladding layer comprises a fourth material; the first material is an n-type semiconductor, and the fourth material is a p-type semiconductor.

[0014] Preferably, the device further comprises an upper electrode and a lower electrode, the upper electrode is arranged on the upper cladding layer, and the lower electrode is arranged on the lower cladding layer; the upper electrode and the lower electrode are used to inject carriers to construct an electrically driven topological laser.

[0015] The application further provides a laser, the laser uses the Kagome photonic crystal device as described above to construct a laser cavity.

[0016] The present application achieves the beneficial effects of the above technical solutions:

[0017] (1) By utilizing the inherent translational symmetry of the Kagome lattice, a Kagome supercell is designed to form a large-area Kagome crystal structure through periodic translation. The technical solution provided by the present application not only is easy to implement, but also effectively ensures the long-range order of the lattice, thereby being applicable to the construction of a large-area, uniform emission topological laser, solving the problems of the prior art.

[0018] (2) Based on the unique energy band structure of the Kagome supercell, a single optical field mode is obtained in the photonic band gap by adjusting the lattice parameters. The stability is good, and the multimode competition is effectively suppressed, and a stable single-mode topological laser can be further realized.

[0019] (3) By introducing a hexapole cavity to construct the Kagome supercell, the high quality factor Q value characteristics of the hexapole cavity are combined with the energy band structure of the Kagome, and the localization of the optical field and the laser quality factor Q value are enhanced. In the simulation debugging process, if the output wavelength deviates from the design value, the lattice constant or the primitive radius can be adjusted. If the quality factor Q value does not reach the expected value, the cavity primitive radius and the offset length of the hexapole cavity are adjusted. This clear parameter-performance relationship can guide the simulation to be optimized efficiently, so as to obtain a stable single-mode laser with a high quality factor. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of a Kagome photonic crystal of an embodiment of the present application.

[0021] Figure 2 is a directional schematic diagram of a supercell hexagon of the Kagome photonic crystal of the embodiment of the present application.

[0022] Figure 3 is a design process conceptual diagram of the supercell of the embodiment of the present application. Figure 3 (a) is a conceptual diagram of selecting and constructing the cavity center of the hexapole cavity; Figure 3 (b) is a conceptual diagram of selecting and constructing the cavity primitive of the hexapole cavity; Figure 3 (c) is a structural diagram of constructing the supercell from the hexapole cavity.

[0023] Figure 4 is a three-dimensional structural schematic diagram of an electrically pumped Kagome photonic crystal device of an embodiment of the present application.

[0024] Figure 5 is Figure 4 is a cross-sectional structural schematic diagram of the electrically pumped Kagome photonic crystal device shown in (a).

[0025] Figure 6is a spatial electric field distribution diagram of a prior art sextupole cavity.

[0026] Figure 7 is Figure 6 is a quality factor Q value discrete frequency spectrum distribution diagram of the sextupole cavity shown in

[0027] Figure 8 is a simulated two-dimensional band diagram of a Kagome photonic crystal of an embodiment of the present application.

[0028] Figure 9 is a measured three-dimensional band diagram of a Kagome photonic crystal of an embodiment of the present application.

[0029] Figure 10 is a spatial electric field distribution diagram of a supercell of a Kagome photonic crystal of an embodiment of the present application.

[0030] In the figure, the respective labels represent: 1, a first direction; 2, a second direction; 3, a third direction; 4, a fourth direction; 5, an upper electrode; 6, an upper cladding layer; 7, a second material; 8, a third material; 9, a lower cladding layer; 10, a lower electrode; 11, a supercell; 12, a sextupole cavity; 101, one of the edges; 102, another of the edges; 110, a primitive; 120, a cavity primitive; 80, a flat band; 20, a Γ point; 21, an M point; 22, a K point. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present application clearer, the specific embodiments of the present application are described in further detail below. It should be understood that the embodiments described herein are only used to explain the present application, but not to limit the scope of the present application.

[0032] Please refer to the accompanying drawings Figure 1 , Figure 1 is a structural schematic diagram of a Kagome photonic crystal of an embodiment of the present application. As can be seen from the figure, the Kagome photonic crystal of the embodiment of the present application comprises a plurality of supercells 11, each of the supercells 11 comprises three sextupole cavities 12, and the plurality of supercells 11 are periodically arranged along a first direction 1 and a second direction 2, so that all the sextupole cavities 12 form a Kagome lattice structure as a whole.

[0033] In particular, the supercell 11 of the embodiment of the present application is a regular hexagon, and has four different directions with respect to the regular hexagon. Please refer to the accompanying drawings Figure 2 , Figure 2is a schematic diagram of the direction of the supercell hexagon of the Kagome photonic crystal of the embodiment of the present application. As shown in the figure, the first direction 1 is the vertical direction of one side 101 of the regular hexagon, and the second direction 2 is the vertical direction of one side 102 of the regular hexagon, that is, the included angle between the first direction 1 and the second direction 2 is 60°. The third direction 3 is the extension direction of the one side 101 of the regular hexagon, and the fourth direction 4 is the extension direction of the one side 102 of the regular hexagon.

[0034] As shown in the figure, Figure 1 As shown in the figure, Figure 2 It can be seen that the supercell 11 further comprises a base and a unit cell 110, and the base is provided with a lattice point, and the lattice points are periodically arranged along the third direction 3 and the fourth direction 4 to form a lattice array. The lattice constant of the lattice point is set as a, and the unit cell 110 is arranged on the lattice point. In the embodiment of the present application, the lattice constant a of the unit cell 110 is taken as 380 nm corresponding to the laser with a target lasing wavelength of 1550 nm, and the radius of the unit cell 110 is set as 0.25a. In one or other embodiments of the present application, the value range of the lattice constant a of the unit cell 110 can be 330 nm to 400 nm corresponding to the laser with a target lasing wavelength of 1550 nm.

[0035] As shown in the figure, Figure 3 , Figure 3 is a design process conceptual diagram of the supercell of the embodiment of the present application. Figure 3 (a) is a conceptual diagram of selecting and constructing the cavity center of the hexapole cavity. In the design, the unit cell 110 is selected and removed as the cavity center. In the actual etching process, the position of the unit cell 110 is punched, and the cavity center is left blank and not processed. Figure 3 (b) is a conceptual diagram of selecting and constructing the cavity unit of the hexapole cavity. As shown in the figure, the production of the cavity unit 120 is equivalent to reducing the radius of the six unit cells 110 adjacent to the cavity center and translating outward along the radial direction of the cavity center by an offset amount, forming six smaller unit cells 110, that is, six cavity units 120, so that the radius of the cavity unit 120 is smaller than the radius of the unit cell 110. In the embodiment of the present application, the radius of the cavity unit 120 is taken as 0.20a, and the offset amount is taken as 0.18a. Figure 3 (c) is a structural diagram of constructing the supercell from the hexapole cavity. As shown in the figure, in each of the supercells 11, three hexapole cavities 12 are symmetrically distributed about the center of the supercell 11, and as shown in the figure, Figure 2 It can be seen that two of the hexapole cavities 12 are arranged along the first direction 1, and the distance B between the hexapole cavities 12 is half of the lattice constant A of the supercell 11, and in the embodiment of the present application, B=3a.

[0036] Each of the sextupole cavity 12 includes six cavity units 120, the six cavity units 120 are symmetrically distributed relative to the cavity center of the sextupole cavity 12, and the distance between the six cavity units 120 and the cavity center of the sextupole cavity 12 is greater than the lattice constant a of the unit 110. The cavity center of each of the sextupole cavities 12 coincides with the lattice point. In combination with the drawings Figure 2 It can be seen that at least one of the cavity units 120 is parallel to the third direction 3 or the fourth direction 4 relative to the extension direction of the cavity center.

[0037] After the supercell 11 structure is designed, the preparation steps of the Kagome crystal structure are as follows:

[0038] Step 1: After the cleaning and pretreatment steps, the impurities and oxides on the surface of the substrate are effectively removed to ensure that the substrate has good flatness and cleanliness.

[0039] Step 2: Using precise micro-nano processing technologies such as photolithography or nano-imprinting, photoresist is coated on the substrate, exposure and development are performed using a mask, patterns are formed, and dry or wet etching processes are used to transfer the patterns of the supercell 11 to the substrate to complete the production of a single supercell 11.

[0040] Step 3: According to the translational and rotational symmetry requirements of the Kagome photonic crystal, the above prepared multiple independent supercells 11 are arranged in a two-dimensional array. In this process, precise docking technology based on optical vision or mechanical precise positioning is used to ensure the accuracy of the relative position and orientation of each supercell 11, so that the final formed overall structure has strict periodicity and high consistency, thereby constructing a large-area Kagome photonic crystal.

[0041] Please refer to the drawings Figure 4 and the drawings Figure 5 , Figure 4 is a schematic diagram of the three-dimensional structure of the electrically pumped Kagome photonic crystal device according to an embodiment of the present application, Figure 5 is Figure 4The cross-sectional structure of the electrically pumped Kagome photonic crystal device is shown. As can be seen from the figure, the electrically pumped Kagome photonic crystal device comprises an upper electrode 5, an upper cladding layer 6, a core layer, a lower cladding layer 9 and a lower electrode 10. The upper electrode 5 is arranged on the upper cladding layer 6, and the lower electrode 10 is arranged on the lower cladding layer 9. The core layer is arranged between the upper cladding layer 6 and the lower cladding layer 9, and the core layer is a Kagome photonic crystal structure. The upper cladding layer 6 comprises a first material, the core layer comprises a unit cell 110, a cavity unit cell 120 and a substrate, the unit cell 110 and the cavity unit cell 120 are a second material 7, the substrate is a third material 8, and the lower cladding layer 9 comprises a fourth material. In the embodiment of the present application, the upper cladding layer 6 is an n-type semiconductor, and the lower cladding layer 9 is a p-type semiconductor, wherein the n-type semiconductor is a semiconductor material doped with a pentavalent impurity such as phosphorus (P) and arsenic (As), and the p-type semiconductor is a semiconductor material doped with a trivalent impurity such as boron (B) and aluminum (Al). The upper electrode 5 and the lower electrode 10 are used to inject carriers to build an electrically driven topological laser. In particular, in the embodiment of the present application, the core layer comprises a substrate and a unit cell 110, and the substrate is a semiconductor material, which can be selected from a group consisting of III-V, II-VI or IV semiconductor materials. For example, it can be a single-element semiconductor such as silicon (Si) or germanium (Ge); or it can be a compound semiconductor such as gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), indium phosphide (InP) and ternary or quaternary compounds thereof (for example, InGaP, InGaAs, AlGaAs, InAlGaN, InGaAsP, etc.). The unit cell 110 is air.

[0042] In one or other embodiments of the present application, the Kagome photonic crystal can be used to manufacture an optically pumped Kagome photonic crystal device. Compared with the electrically pumped Kagome photonic crystal device, the optically pumped Kagome photonic crystal device does not comprise the upper electrode 5 and the lower electrode 10, and the other structures are consistent. Through the irradiation of an external light source, energy is injected into the core layer, so that the atoms inside the core layer are pumped from a low-energy state to a high-energy state, thereby realizing population inversion and reserving energy for laser generation.

[0043] The Kagome photonic crystal device of the embodiment of the present application can be used to construct a laser cavity.

[0044] In particular, a direct current forward bias is applied between the upper electrode 5 and the lower electrode 10, so that the potential of the upper electrode 5 is lower than that of the lower electrode 10. Under the driving of the forward bias, the majority carrier electrons from the upper cladding layer 6 are driven by the electric field to inject downward into the core layer. The majority carrier holes from the lower cladding layer 9 are driven by the electric field to inject upward into the core layer. Through parameter design, the band gap width of the core layer can be made smaller than the upper cladding layer 6 and the lower cladding layer 9, so as to effectively confine the injected electrons and holes inside the Kagome photonic crystal structure. The electrons and holes confined in the core layer radiate and recombine, and the energy is released in the form of photons, realizing electroluminescence and providing an initial light field for laser oscillation. The generated light field is confined in the flat band 80 for transmission, thereby forming a single-mode electrically driven topological laser device. Such a multi-layer structure design not only increases the structural complexity of the laser, but also brings more performance optimization space. For example, by selecting materials with different refractive indices for combination, precise control of the output wavelength of the laser can be achieved. At the same time, the interaction between different layers can also bring new physical phenomena and effects, providing new ideas for performance improvement of the laser.

[0045] The supercell 11 of the embodiment of the present application is a region surrounded by a hexagon boundary in the first Brillouin zone in momentum space. Among them, the Γ point 20 is located at the center of the Brillouin zone, the K point 22 is located at the six vertices of the hexagon, and the M point 21 is located at the midpoint of each side of the hexagon. The first Brillouin zone of the hexagon reflects the periodic symmetry characteristics of the Kagome photonic crystal. Different wave vector paths from the Γ point 20 to the M point 21 and the K point 22 can demonstrate the energy band characteristics of the Kagome photonic crystal in different propagation directions.

[0046] In particular, after the Kagome photonic crystal of the embodiment of the present application removes the hexapole cavity 12, there is a forbidden band in the first Brillouin zone band diagram of the lattice array formed by the pure primitive cell 110, ranging from 190 THz to 210 THz. The embodiment of the present application changes the energy band structure by constructing the Kagome structure of the hexapole cavity 12, so that a topological flat band 80 appears in the frequency range originally in the forbidden band. Moreover, the flat band 80 has a high quality factor Q value, which can be used to realize single-mode laser.

[0047] Please refer to the accompanying drawings Figure 6 and the accompanying drawings Figure 7 , Figure 6 is a spatial electric field distribution diagram of the prior art hexapole cavity, Figure 7 is Figure 6 a quality factor Q value discrete frequency spectrum distribution diagram of the hexapole cavity shown in FIG. 8. Figure 6In the figure, the horizontal and vertical coordinates are spatial position x and spatial position y, respectively, both in units of microns, which shows the electric field distribution of the cavity structure in a two-dimensional plane when the characteristic frequency is 199.83 THz. In the figure, the color scale from blue to red represents the electric field strength from low to high, and the numerical range is from 0 to about V / m. As can be seen from the figure, the electric field strength of the hexapole cavity 12 is highly localized in the central region of the cavity, and the field strength rapidly decays at the edge of the cavity, showing a typical hexapole symmetric distribution mode. This shows that the hexapole cavity 12 structure can effectively confine the electromagnetic field in the defect cavity region. Figure 7 In the figure, the horizontal axis is the electric field frequency, and the vertical axis is the quality factor Q value. As can be seen from the figure, the hexapole cavity 12 only excites a resonance mode with a Q value of about 10 at two specific frequency points, about 199 THz and 201 THz. It can be seen that the hexapole cavity 12 not only has a high quality factor Q value, but also can confine the specific frequency optical field in a very small local area, and there is no stability problem of multi-mode competition.

[0048] Please refer to the accompanying Figure 8 and the accompanying Figure 9 , Figure 8 is a simulated two-dimensional band diagram of the Kagome photonic crystal of the embodiment of the present application, Figure 9 is a measured three-dimensional band diagram of the Kagome photonic crystal of the embodiment of the present application. Figure 8 In the figure, the vertical coordinate represents the frequency (unit: THz), and the horizontal coordinate represents the wave vector path along the first Brillouin zone high symmetry point path. As can be seen from the figure, there is an obvious flat band 80 in the frequency range of 190 THz to 210 THz. Figure 9 In the figure, the vertical coordinate represents the frequency (unit: THz), and the horizontal coordinate represents the wave vector path along the first Brillouin zone high symmetry point path, and the color bar represents the quality factor Q value. In particular, the value 0 of the wave vector path corresponds to the Γ point 20, 1 corresponds to the M point 21, 2 corresponds to the K point 22, 3 corresponds to the Γ point 20, and 1 corresponds to the Γ point 20 to form a complete closed path.

[0049] Exemplarily, in the embodiment of the present application Figure 9 In the actual test corresponding to the embodiment of the present application, the key performance indicators of the laser are mainly evaluated by a spectrum analyzer, a laser power meter and the like to characterize the optical performance of the laser, and then the single mode characteristics, the output power stability and the beam quality of the laser are comprehensively evaluated. In the embodiment of the present application, the test parameters include output wavelength, output power and far field divergence angle and the like. In addition, the cavity ring-down method is used to test the quality factor Q value of the laser to evaluate the energy storage capacity and the photoelectric conversion efficiency of the laser constructed by the Kagome photonic crystal provided by the present application.

[0050] Based on the test data, the parameters of the Kagome crystal structure are optimized in the embodiment of the present application. In particular, if the laser output wavelength deviates from the target value, the lattice constant a of the unit cell 110 and / or the radius r of the unit cell 110 are adjusted. If the quality factor Q value does not reach the preset value, the radius or offset of the unit cell 110 of the sextupole cavity 12 is adjusted. In this way, through multiple structure optimization and iterative testing, the overall performance of the laser is finally optimized. In the embodiment of the present application Figure 9 corresponding to the case where the target wavelength of the laser is 1550 nm, the lattice constant of the unit cell 110 of the Kagome photonic crystal is set to 380 nm, the lattice constant of the supercell 11 is set to 2280 nm, the radius of the unit cell 110 is 95 nm, the radius of the cavity unit cell 120 is 76 nm, and the offset of the cavity unit cell 120 is 68.4 nm.

[0051] From Figure 9 it can be seen that there is a clear flat-band feature at a frequency of 225 THz, and the flat-band 80 maintains a highly stable frequency characteristic on the entire high-symmetry point path from 0 to 3. In the vicinity of the flat-band 80, the quality factor Q value reaches a maximum of . It can be seen that the Kagome photonic crystal provided by the technical scheme of the present application can be used to realize high-Q single-mode laser output.

[0052] Please refer to the accompanying Figure 10 , Figure 10 is a spatial electric field distribution diagram of the Kagome photonic crystal supercell 11 in the embodiment of the present application. Both the horizontal and vertical coordinates in the diagram represent real space positions in microns, and the color bar represents the electric field intensity distribution in V / m. Figure 10 In the diagram, the red and yellow areas indicate places with high electric field intensity, and the surrounding blue areas indicate places with extremely small or close-to-zero electric field intensity. As can be seen from the diagram, the Kagome photonic crystal in the embodiment of the present application highly localizes the photonic energy in a very small spatial range, and has extremely high spatial localization characteristics. Compared with the electric field intensity distribution diagram of the ordinary sextupole cavity 12 shown in Figure 6 , the Kagome photonic crystal provided by the embodiment of the present application has a larger mode field area under the same working conditions, and can realize high-efficiency laser emission.

[0053] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical scheme of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical scheme of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A Kagome photonic crystal for constructing a topological laser, characterized in that, It includes several supercells, each supercell comprising three hexapole cavities, and the supercells are periodically arranged along a first direction and a second direction, such that all the hexapole cavities as a whole form a Kagome lattice structure; Wherein, the supercell is a regular hexagon, the first direction is the perpendicular direction of one side of the regular hexagon, and the second direction is the perpendicular direction of the other side of the regular hexagon.

2. The Kagome photonic crystal according to claim 1, characterized in that, The lattice constant of the Kagome photonic crystal along the first direction is equal to the lattice constant of the supercell along the second direction.

3. The Kagome photonic crystal according to claim 2, characterized in that, In each of the supercells, three hexapole cavities are symmetrically distributed about the center of the supercell, with two of the hexapole cavities arranged along the first direction, and the spacing between the hexapole cavities is half the lattice constant of the Kagome photonic crystal.

4. The Kagome photonic crystal according to claim 3, characterized in that, The supercell further includes a substrate and basic units. Grid points are disposed on the substrate, and the grid points are periodically arranged along a third direction and a fourth direction to form a lattice array. The basic units are disposed on the grid points. The third direction is the extension direction of one of the sides of the regular hexagon, and the fourth direction is the extension direction of the other side of the regular hexagon.

5. The Kagome photonic crystal according to claim 4, characterized in that, Each of the six-pole sub-cavities comprises six cavity elements, which are symmetrically distributed with respect to the cavity center of the six-pole sub-cavity. The distance between the six cavity elements and the cavity center of the six-pole sub-cavity is greater than the lattice constant of the lattice array, and the radius of each cavity element is smaller than the radius of the element.

6. The Kagome photonic crystal according to claim 5, characterized in that, In each of the hexapole subcavities, the position of the cavity center coincides with the position of the lattice point, and at least one of the cavity primitives extends in a direction parallel to the third or fourth direction relative to the cavity center.

7. A Kagome photonic crystal device, said device using the Kagome photonic crystal as described in claim 1, characterized in that, The device includes an upper cladding layer, a core layer, and a lower cladding layer, wherein the core layer is disposed between the upper cladding layer and the lower cladding layer, and the core layer is the Kagome photonic crystal.

8. The Kagome photonic crystal device according to claim 7, characterized in that, The upper cladding layer includes a first material, and the lower cladding layer includes a fourth material; the first material is an n-type semiconductor, and the fourth material is a p-type semiconductor.

9. The Kagome photonic crystal device according to claim 8, characterized in that, It also includes an upper electrode and a lower electrode, the upper electrode being disposed on the upper cladding and the lower electrode being disposed on the lower cladding; the upper electrode and the lower electrode are used to inject charge carriers to construct an electrically driven topological laser.

10. A laser, characterized in that, The laser uses the Kagome photonic crystal device of claim 7 to construct the laser cavity.

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