A two-dimensional perovskite topological photonic crystal laser

Abstract

The application belongs to the technical field of nanometer laser, and discloses a two-dimensional perovskite topological photonic crystal laser, which comprises a two-dimensional perovskite film, the two-dimensional perovskite film is bounded by triangular domain walls, and a first energy valley photonic crystal and a second energy valley photonic crystal are arranged in the inside and outside respectively to form a laser cavity, the first energy valley photonic crystal comprises a plurality of first hexagonal air holes, the second energy valley photonic crystal comprises a plurality of second hexagonal air holes, the centers of the first hexagonal air holes and the second hexagonal air holes are arranged in a triangular lattice shape, and the directions of the first hexagonal air holes and the second hexagonal air holes are opposite, so that the topological properties of the first energy valley photonic crystal and the second energy valley photonic crystal are opposite. The application has high Q value and is robust to defects or impurities.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanolaser, and particularly relates to a two-dimensional perovskite topological photonic crystal laser with defect immunity. BACKGROUND

[0002] In recent years, perovskite materials have become a highly competitive material in the field of light-emitting devices. The environmental stability of three-dimensional perovskite materials is poor, and they are easily decomposed in ultraviolet irradiation, high temperature and water environment, thereby causing a substantial reduction in the performance of light-emitting devices. The introduction of large hydrophobic organic cations into the composition of perovskite can form a two-dimensional perovskite with excellent environmental stability. Compared with three-dimensional perovskite, the new two-dimensional perovskite has advantages including solution-processable, excellent film-forming property, excellent light stability, ultra-low self-doping behavior, low defect density and significantly reduced ion migration effect, and other outstanding optical properties. The two-dimensional perovskite can not only adjust the light-emitting wavelength by adjusting the layer number, but also achieve a greater range of light-emitting wavelength adjustment by adjusting the composition.

[0003] A photonic crystal is an artificial micro-nano structure with photonic band gap characteristics. According to the periodicity and band gap characteristics of the spatial structure distribution of the photonic crystal, it can be divided into one-dimensional photonic crystal, two-dimensional photonic crystal and three-dimensional photonic crystal. Compared with one-dimensional photonic crystal, two-dimensional photonic crystal has more physical quantities to be controlled, and at the same time, it can be processed using the mature semiconductor micro-nano processing technology; compared with the complex three-dimensional photonic crystal, the two-dimensional photonic crystal device is relatively simple to prepare. By introducing the two-dimensional photonic crystal structure into the semiconductor laser, the refractive index is periodically arranged in two different directions in the plane, and the direction perpendicular to the plane is uniform. By using the band gap effect and light localization characteristics of the two-dimensional photonic crystal, light can be restricted from two directions of the plane, which is helpful to construct a high-quality factor (Q) resonant cavity.

[0004] Perovskite photonic crystal lasers have shown advantages such as high Q value, small mode volume and low threshold. In 2017, Pourdavoud et al. (Pourdavoud N, Wang S, Mayer A, et al. Photonic nanostructures patterned by thermal nanoimprint directly into organo-metal halide perovskites. Advanced Materials, 2017, 29(12): 1605003.) of Wuppertal University in Germany used thermal nanoimprint technology to process air columns with a period of 450 nm and a thickness of 230 nm on a MAPbI3 perovskite film, forming a two-dimensional photonic crystal laser cavity, and realizing a pulse energy density of 3.8 µJ / cm2 by photonic band gap mode.-2 Diguna et al. (see Diguna L J, Hardhienata H, Birowosuto M D. Design of perovskite photonic crystals for emission control. Journal of Physics: Conference Series, 2019, 1170(1): 012003) studied the emission control of two-dimensional photonic crystal lasers based on MAPbI3 perovskite materials in 2019. The lattice constant of the photonic crystal in the laser cavity is 360 nm, the air hole radius is 108 nm, and the average thickness is 198 nm. The structure has a Purcell factor of 199.6 and a Q value of 1560 at a wavelength of 779 nm.

[0005] The structure of the perovskite photonic crystal laser is currently in the micron or nanometer scale, and defects, impurities and other defects in the processing process of the laser cavity will greatly affect the optical performance of the laser. Therefore, the structure of the photonic crystal laser needs to be improved to improve its defect resistance. SUMMARY

[0006] The present application overcomes the shortcomings of the prior art photonic crystal laser, and solves the technical problem of providing a two-dimensional perovskite topological photonic crystal laser with high Q value and immunity to defects or impurities.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a two-dimensional perovskite topological photonic crystal laser, comprising a two-dimensional perovskite film, the two-dimensional perovskite film is bounded by a triangular domain wall, and a first energy valley photonic crystal and a second energy valley photonic crystal are arranged inside and outside the two-dimensional perovskite film respectively to form a laser cavity, the first energy valley photonic crystal comprises a plurality of first hexagonal air holes, the second energy valley photonic crystal comprises a plurality of second hexagonal air holes, the centers of the first hexagonal air holes and the second hexagonal air holes are arranged in a triangular lattice, and the directions of the first hexagonal air holes and the second hexagonal air holes are opposite, so that the topological properties of the first energy valley photonic crystal and the second energy valley photonic crystal are opposite.

[0008] The first hexagonal air hole and the second hexagonal air hole each comprise three equal short sides and three equal long sides, the three short sides and the three long sides are arranged at intervals, and are arranged in 120° rotational symmetry.

[0009] The length of the three short sides is 0.2-0.3 times the length a, and the length of the three long sides is 0.5-0.6 times the length a, where a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole and the second hexagonal air hole.

[0010] The length of the three short sides is d1=0.26*a, and the length of the three long sides is d2=0.58*a, wherein a represents a lattice constant of a triangular lattice formed by the first hexagonal air hole and the second hexagonal air hole.

[0011] The domain wall is an equilateral triangle, the triangle formed by the straight line on which the three long sides of the first hexagonal air hole are located is arranged in the same direction as the triangle in which the domain wall is located, and the triangle formed by the straight line on which the three long sides of the second hexagonal air hole are located is arranged in the opposite direction of the triangle in which the domain wall is located.

[0012] The length of the domain wall is 20~25*a, and a represents a lattice constant of a triangular lattice formed by the first hexagonal air hole and the second hexagonal air hole.

[0013] The lattice constant a of the first hexagonal air hole and the second hexagonal air hole is 150~200nm.

[0014] The thickness of the two-dimensional perovskite film is H=100 nm, the refractive index is 2.29, and the chemical formula is (PEA)2FA7Pb8Br 25 , the bottom is provided with a metal layer, and the position other than the top air hole is also provided with a metal layer.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] 1. The present application provides a two-dimensional perovskite topological photonic crystal laser, which combines two-dimensional perovskite material with photonic crystal laser, and through appropriate resonant cavity design, a laser with structure size in micro-nanometer or even nanometer size and high Q value can be obtained. And the refractive index contrast between two-dimensional perovskite and air makes the light wave be limited in the photonic crystal layer in the vertical direction due to total internal reflection, and the limitation on light is stronger.

[0017] 2. Based on the optical quantum valley Hall effect, the present application introduces the valley degree of freedom into the photonic crystal, breaks the spatial inversion symmetry of the structure to occur topological phase transition, realizes the controllable band gap of different topological phases of the transmitted light, forms the topological edge state which inhibits backscattering, has high emission efficiency, greatly improves the laser performance, and uses the topological edge state to form a triangular ring-shaped topological waveguide, and simulation of a two-dimensional structure calculates that the Q value can reach 4.5*10 4 .

[0018] 3.Because of the robustness of the two-dimensional topological photonic crystal edge mode, electromagnetic waves can still propagate smoothly along the domain wall between two topologically different photonic crystals even if there are defects, disorder or sharp corners. Therefore, the photonic crystal laser of the present application is robust to defects, perturbations and the like, has low loss and is compact in structure. Moreover, experiments have shown that introducing a topologically protected mode in a laser cavity structure introduces defects in the laser cavity and destroys the periodic structure of the photonic crystal, but does not affect the optical performance of the laser, indicating that the photonic crystal laser of the present application has a high tolerance to the requirements of the processing process, and errors and defects generated during the processing process will not significantly affect the optical transmission characteristics of the structure. Therefore, the photonic crystal laser of the present application can be experimentally produced using the current mature semiconductor micro-nano processing technology.

[0019] In summary, the present application uses the topological protection of the topological optical mode to construct a two-dimensional perovskite topological photonic laser, which can greatly improve the laser performance and realize a high-Q value laser that is robust to defects or impurities. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structure schematic diagram of the two-dimensional perovskite topological photonic crystal laser provided by the embodiment of the present application is shown in the figure;

[0021] Figure 2 A setting schematic diagram of the hexagonal air hole in the photonic crystal in the embodiment of the present application is shown in the figure;

[0022] Figure 3 A band schematic diagram of the two-dimensional perovskite topological photonic crystal in the embodiment of the present application is shown in the figure;

[0023] Figure 4 A cross-sectional structure schematic diagram of the two-dimensional perovskite topological photonic crystal laser provided by the embodiment of the present application is shown in the figure;

[0024] Figure 5 A two-dimensional perovskite topological photonic crystal and its electric field distribution diagram (a), a photonic crystal with a side defect and its electric field distribution diagram (b), and a photonic crystal after adding an angle defect and its electric field distribution diagram (c) in the embodiment of the present application are shown in the figure. DETAILED DESCRIPTION

[0025] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0026] As Figure 1As shown in the figure, the embodiment of the present application provides a two-dimensional perovskite topological photonic crystal laser, which comprises a two-dimensional perovskite thin film 1, the two-dimensional perovskite thin film 1 is bounded by a triangular domain wall 2, and a first energy valley photonic crystal 3 and a second energy valley photonic crystal 4 are arranged in the inside and outside of the two-dimensional perovskite thin film 1 respectively to form a laser cavity, the first energy valley photonic crystal 3 comprises a plurality of first hexagonal air holes 5, the second energy valley photonic crystal 4 comprises a plurality of second hexagonal air holes 6, the centers of the first hexagonal air holes 5 and the second hexagonal air holes 6 are arranged in a triangular lattice, and the directions of the first hexagonal air holes 5 and the second hexagonal air holes 6 are opposite, so that the topological properties of the first energy valley photonic crystal 3 and the second energy valley photonic crystal 4 are opposite. The first hexagonal air holes 5 and the second hexagonal air holes 6 are hollow and filled with air, and the refractive index is 1.

[0027] Specifically, in the embodiment, as shown in the figure, Figure 2 In the embodiment, the first hexagonal air hole 5 and the second hexagonal air hole 6 each comprise three equal short sides and three equal long sides, the three short sides and the three long sides are arranged at intervals, and are arranged in 120° rotational symmetry.

[0028] Specifically, in the embodiment, the length of the three short sides is 0.2-0.3 times the length a, and the length of the three long sides is 0.5-0.6 times the length a, wherein a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole 5 and the second hexagonal air hole 6.

[0029] Preferably, in the embodiment, the length of the three short sides is d1=0.26*a, and the length of the three long sides is d2=0.58*a, wherein a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole 5 and the second hexagonal air hole 6.

[0030] Specifically, in the embodiment, the domain wall 2 is an equilateral triangle, the triangle formed by the straight line on which the three long sides of the first hexagonal air hole 5 are located is arranged in the same direction as the triangle on which the domain wall 2 is located, that is, parallelly arranged; the triangle formed by the straight line on which the three long sides of the second hexagonal air hole 6 are located is arranged in the opposite direction to the triangle on which the domain wall 2 is located, that is, symmetrically arranged.

[0031] Specifically, in the embodiment, the length of the side of the domain wall 2 is 20-25*a, and a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole 5 and the second hexagonal air hole 6. Preferably, the length of the side of the domain wall 2 is 21*a.

[0032] Specifically, in the embodiment, the lattice constant a of the first hexagonal air hole 5 and the second hexagonal air hole 6 is 150-200 nm. Preferably, the lattice constant a is 180 nm.

[0033] As shown in the figure, Figure 3As shown, in the embodiment, the lattice constant a is 180 nm, the side length of the domain wall 2 is 21*a, the irregular hexagon side length is d1=0.26*a and d2=0.58*a, and the two-dimensional perovskite topological photonic crystal band gap is 487-547 THz obtained by simulation calculation.

[0034] Specifically, in the embodiment, the thickness of the two-dimensional perovskite film (1) is H=100 nm, and the refractive index is 2.29, and the two-dimensional perovskite (PEA)2FA7Pb8Br 25 with a lasing wavelength of about 550 nm, and green light emission can be achieved. Figure 4 As shown, the two-dimensional perovskite film is a rectangle with a length of about 8 µm (8.1 µm) and a width of about 7.92 µm. The bottom is provided with a metal layer, and the position outside the air hole on the top is also provided with a metal layer. When there is no defect or impurity, the laser cavity electric field diagram is a relatively uniform ring-shaped triangle, as shown in Figure 5 (a).

[0035] The defects or impurities in the laser cavity are generally air holes connected or air holes missing caused by errors in the processing and manufacturing process. As shown in Figure 5 (b)~(c), the defects are placed on the side or corner of the triangular domain wall, destroying the periodic arrangement structure of the laser cavity. The defect is set as a rectangle with a length of 370 nm and a width of 320 nm, and 2 complete air columns are missing inside, and 6 air columns around are partially missing, and all are set as two-dimensional perovskite. In addition, it should be pointed out that the internal material of the defect is set as two-dimensional perovskite to simulate air hole missing or set as air to simulate air hole connection, and the results are basically the same. The defect does not affect the light emitting performance of the laser, and the electric field diagram is still a relatively uniform ring-shaped triangle. The Q values after adding the side defect and the corner defect are 45258 and 45507, respectively, which are almost unchanged compared with the Q value 45368 when there is no defect. The above results show that in the present application, the size of the defect and the impurity within a certain range does not affect the optical performance of the laser cavity.

[0036] In summary, the present application provides a two-dimensional perovskite topological photonic crystal laser, which is designed based on the optical quantum valley Hall effect. The two-dimensional perovskite is combined with the topological photonic crystal laser, and finally a laser with robustness to defects or impurities and high Q value is obtained, which provides a solution to the influence of current processing precision on laser performance.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A two-dimensional perovskite topological photonic crystal laser, characterized in that, The system includes a two-dimensional perovskite thin film (1), on which a first valley photonic crystal (3) and a second valley photonic crystal (4) are respectively arranged inside and outside the two-dimensional perovskite thin film (1) with triangular domain walls (2) as boundaries to form a laser cavity. The first valley photonic crystal (3) includes a plurality of first hexagonal air holes (5), and the second valley photonic crystal (4) includes a plurality of second hexagonal air holes (6). The centers of the first hexagonal air holes (5) and the second hexagonal air holes (6) are arranged in a triangular lattice, and the directions of the first hexagonal air holes (5) and the second hexagonal air holes (6) are opposite, so that the topological properties of the first valley photonic crystal (3) and the second valley photonic crystal (4) are opposite. The first hexagonal air holes (5) and the second hexagonal air holes (6) each include three equal short sides and three equal long sides, which are arranged alternately and 120° rotationally symmetrically.

2. The two-dimensional perovskite topological photonic crystal laser according to claim 1, characterized in that, The length of the three short sides is 0.2 to 0.3 times a, and the length of the three long sides is 0.5 to 0.6 times a, where a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole (5) and the second hexagonal air hole (6).

3. A two-dimensional perovskite topological photonic crystal laser according to claim 2, characterized in that, The length of the three shorter sides is d1 = 0.

26. a, the length of the three longer sides is d² = 0.58 a, where a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole (5) and the second hexagonal air hole (6).

4. A two-dimensional perovskite topological photonic crystal laser according to claim 1, characterized in that, The domain wall (2) is an equilateral triangle. The triangle formed by the three long sides of the first hexagonal air hole (5) is arranged in the same direction as the triangle where the domain wall (2) is located. The triangle formed by the three long sides of the second hexagonal air hole (6) is arranged in the opposite direction to the triangle where the domain wall (2) is located.

5. A two-dimensional perovskite topological photonic crystal laser according to claim 4, characterized in that, The side length of the domain wall (2) is 20~25. a, a represents the lattice constant of the triangular lattice formed by the first hexagonal air hole (5) and the second hexagonal air hole (6).

6. A two-dimensional perovskite topological photonic crystal laser according to claim 1, characterized in that, The lattice constant a of the first hexagonal air hole (5) and the second hexagonal air hole (6) is 150~200nm.

7. A two-dimensional perovskite topological photonic crystal laser according to claim 1, characterized in that, The two-dimensional perovskite thin film (1) has a thickness of H = 100 nm, a refractive index of 2.29, and a chemical formula of (PEA)2FA7Pb8Br. 25 A metal layer (7) is provided at the bottom and a metal layer (7) is also provided at the top except for the air hole.

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