Multi-wavelength topological surface-emitting laser array

Abstract

This application relates to a monolithically integrated multi-wavelength topological cavity surface-emitting laser (PCSEL) array. According to one embodiment, a monolithically integrated PCSEL array includes multiple PCSELs formed from the same semiconductor layer, at least one layer of which is formed as a photonic crystal layer, or the laser also includes a separate photonic crystal layer. The photonic crystal layer includes multiple supercell structures, each with substructures having multiple independent one-dimensional parameters. At least two independent one-dimensional parameters of one or more substructures are modulated to be greater than or less than their equilibrium position to open the Dirac point of the supercell's bandgap at the equilibrium position. Around any point in the photonic crystal layer, the modulation of the two independent one-dimensional parameters of the supercell forms a vortex structure, which corresponds in parameter space to one or more turns around the equilibrium position. The supercell lattice constants of the two lasers can be different to emit lasers of different wavelengths.

Description

Technical Field

[0001] This application generally relates to the semiconductor field, and more particularly to a monolithic integrated topological cavity surface-emitting laser array that supports multiple wavelengths. Background Technology

[0002] Semiconductor lasers have become the preferred light source in many applications due to their small size, high efficiency, and low cost. To compensate for the insufficient power of a single semiconductor laser, it is desirable to form arrays of multiple semiconductor lasers. Based on the laser emission method, semiconductor lasers can be divided into edge-emitting lasers (PELs) where the laser emits from the edge of the resonant cavity and vertical-cavity surface-emitting lasers (VCSELs) where the laser emits perpendicularly from the top surface of the resonant cavity. Manufacturing edge-emitting lasers requires cutting the substrate containing the resonant cavity structure layer, with the laser emanating from the cut surface. Therefore, monolithically integrated edge-emitting laser arrays are one-dimensional. Two-dimensional arrays require assembling multiple cut, discrete one-dimensional arrays, resulting in a larger overall size, lower integration density, higher packaging requirements, and generally greater difficulty in precisely aligning the laser emission directions of multiple discrete one-dimensional edge-emitting arrays. Unlike edge-emitting lasers, vertical-cavity surface-emitting lasers (VCSELs) do not require dicing because the laser emitted perpendicularly from the top surface. Multiple VCSELs can be fabricated in a two-dimensional array on a single semiconductor substrate and wafer using the same process flow, without needing to be cut apart. This allows for a very small overall size and high integration. Furthermore, the laser emission directions of each laser in the array are consistent, all perpendicular to the top surface of the resonant cavity. Due to these advantages, monolithically integrated VCSEL arrays are widely used in portable electronic devices such as mobile phones.

[0003] However, current vertical-cavity surface-emitting laser (VCSEL) arrays still have several weaknesses. For example, the size of a single laser is generally less than 10 μm, the emission power is generally difficult to exceed 10 mW, and the divergence angle is generally above 15°. Further improvements in laser emission power and reduction in emission angle are still desired. Increasing the laser size to increase emission power leads to multimode lasing, severely affecting beam quality. Furthermore, in monolithically integrated VCSEL arrays, the wavelengths are generally identical, determined by the VCS structure, as the VCS is fabricated during the epitaxial growth of the entire wafer. For these reasons, the wavelength, power, beam quality, and other properties of each laser in the array are essentially the same, making it difficult to obtain laser arrays with different properties, such as different emission wavelengths, through modulation or other means. This significantly limits the application areas of such laser arrays. For example, in the field of optical communication, there is a desire to provide monolithically integrated VCSEL arrays with multiple output wavelengths for multi-wavelength fiber optic communication. Using multiple wavelengths of laser light simultaneously for communication within a single fiber can greatly increase the total amount of data transmitted through that fiber. Furthermore, in fields such as lidar or detection, there is a desire to use multi-wavelength lasers for scanning, as they can provide more information than single-wavelength lasers. For example, they can not only determine the distance to the scanned object but also determine the material properties of the scanned object through spectral information. Additionally, optical coherence tomography (OCT), widely used in ophthalmology, also requires broadband coherent light sources. Summary of the Invention

[0004] This application is made in response to one or more of the above-mentioned problems.

[0005] According to one embodiment, a monolithically integrated topological cavity surface-emitting laser (PCSEL) array is provided, comprising multiple PCSELs formed from the same semiconductor layer. Each PCSEL includes a first semiconductor layer, an active layer disposed on the first semiconductor layer, a second semiconductor layer disposed on the active layer, and a first electrode and a second electrode respectively disposed on the first semiconductor layer and the second semiconductor layer. At least one of the first electrode, the first semiconductor layer, the active layer, the second semiconductor layer, and the second electrode is formed as a photonic crystal layer, or the PCSEL further includes a separate photonic crystal layer. The photonic crystal layer includes multiple supercell structures, each supercell having one or more substructures, each substructure having multiple independent one-dimensional parameters. At least two independent one-dimensional parameters of one or more substructures of the supercell are modulated to be greater than or less than their equilibrium position to open the Dirac point of the energy band of the supercell at the equilibrium position. The modulation of the two independent one-dimensional parameters of the supercell forms a vortex structure, which corresponds to one or more turns around the equilibrium position in a two-dimensional parameter space composed of the two independent one-dimensional parameters.

[0006] In some embodiments, the independent one-dimensional parameters of the substructure include size, shape, and displacement.

[0007] In some embodiments, modulation of at least two independent one-dimensional parameters of one or more substructures of the supercell structure includes: modulating at least two independent one-dimensional parameters of one substructure respectively; or modulating at least one independent one-dimensional parameter of each of two or more substructures.

[0008] In some embodiments, around a point in the photonic crystal layer, each of the two independent one-dimensional parameters of the supercell structure is modulated for an integer number of periods.

[0009] In some embodiments, the photonic crystal layers of two or more topological cavity surface-emitting lasers have different supercell lattice constants.

[0010] In some embodiments, the maximum difference in the supercell lattice constants of the photonic crystal layers of the two or more topological cavity surface-emitting lasers is within 50% of their maximum lattice constant, preferably within 30% of their maximum lattice constant.

[0011] In some embodiments, the supercell lattice constant of the photonic crystal layer is in the range of 50 nm to 500 μm.

[0012] In some embodiments, the maximum in-plane size of the photonic crystal in the photonic crystal layer of each topological cavity surface-emitting laser is greater than 10 μm and less than or equal to 10 cm, preferably greater than 50 μm and less than or equal to 1 cm.

[0013] In some embodiments, the individual photonic crystal layer is disposed between any two adjacent layers among the first electrode, the first semiconductor layer, the active layer, the second semiconductor layer, and the second electrode, or disposed in the same layer as the first electrode or the second electrode.

[0014] According to another embodiment, an electronic device is provided, which includes the above-described monolithic integrated topological cavity surface-emitting laser array. The electronic device may be an optical communication device, a lidar device, a detection and sensing device, a laser processing device, a laser medical device, a laser weapon device, a lighting device, or a display device.

[0015] The above and other features and advantages of this application will become apparent from the following description of exemplary embodiments. Attached Figure Description

[0016] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0017] Figure 1 A schematic diagram of a monolithic integrated topological cavity surface-emitting laser array according to an embodiment of this application is shown.

[0018] Figure 2A A plan view of a photonic crystal layer according to an embodiment of this application is shown.

[0019] Figure 2B Show Figure 2A A cross-sectional view of a photonic crystal layer.

[0020] Figure 2C Show Figure 2A A schematic diagram of the supercell structure of a photonic crystal layer.

[0021] Figure 2D The energy band diagram of the supercell structure of the photonic crystal layer is shown.

[0022] Figure 3A A schematic diagram of two-dimensional modulation of a supercell structure according to an embodiment of this application is shown.

[0023] Figure 3B Shown in parameter space Figure 3A A schematic diagram of two-dimensional modulation.

[0024] Figure 4A A plan view of a photonic crystal layer according to another embodiment of this application is shown.

[0025] Figure 4B Show Figure 4A A schematic diagram of the supercell structure of a photonic crystal layer.

[0026] Figure 4C Show Figure 4A A schematic diagram of substructure modulation in the supercell structure of a photonic crystal layer.

[0027] Figure 5A A plan view of a photonic crystal layer according to another embodiment of this application is shown.

[0028] Figure 5B Show Figure 5A A schematic diagram of the supercell structure of a photonic crystal layer.

[0029] Figure 5C Show Figure 5A A schematic diagram of substructure modulation in the supercell structure of a photonic crystal layer.

[0030] Figure 6 A schematic diagram of a laser including a photonic crystal layer is shown.

[0031] Figures 7A to 7E A schematic diagram of a laser including a photonic crystal layer according to some embodiments of this application is shown.

[0032] Figure 8 A schematic diagram showing the performance of a laser including a photonic crystal layer according to an embodiment of this application is illustrated.

[0033] Figure 9 A schematic diagram showing the luminescence performance of a plurality of lasers with different lattice constants according to an embodiment of the present application is provided.

[0034] Figure 10 A schematic diagram illustrating the characteristics of lasers of different sizes according to some embodiments of this application is shown. Detailed Implementation

[0035] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0036] Figure 1 A schematic diagram of a monolithic integrated topological cavity surface-emitting laser array according to an embodiment of this application is shown. Figure 1As shown, the monolithically integrated topological cavity surface-emitting laser array 10 may include multiple semiconductor lasers 20. In this invention, the semiconductor lasers 20 include a photonic crystal layer to form a topological cavity surface-emitting laser structure, and are therefore also referred to as topological cavity surface-emitting lasers 20. Figure 1 Only two semiconductor lasers 20 are schematically shown. It is understood that multiple semiconductor lasers 20 can be arranged in a desired shape, such as an array of rows and columns, or a circular arrangement, etc. A desired spacing can be maintained between adjacent lasers 20, which can be determined taking into account factors such as desired integration density, heat dissipation space, and wiring space. Each semiconductor laser 20 can have a desired shape. Figure 1 The shape shown is a disk, but it can also be other shapes such as rectangle, square, ellipse, regular hexagon, etc. The semiconductor laser 20 can be based on various commonly used semiconductor material systems, such as GaAs, InP, GaN, etc. The following description uses specific materials as examples, but it should be understood that the invention is not limited to these material examples.

[0037] The semiconductor laser 20 may include a first semiconductor layer 22, an active layer 23, and a second semiconductor layer 25. The first semiconductor layer 22 and the second semiconductor layer 25 may have different conductivity types; for example, the first semiconductor layer 22 may be an N-type doped semiconductor layer, and the second semiconductor layer 25 may be a P-type doped semiconductor layer, or vice versa, thereby injecting N-type and P-type charge carriers into the active layer 23, respectively. In some embodiments, the first semiconductor layer 22 may be an InP, GaAs, or GaN substrate, etc., and it may be N-type doped with dopants such as S or Si, with a doping concentration of, for example, 2-8 × 10⁻⁶. 18 The range is defined as follows. The second semiconductor layer 25 can be a semiconductor layer such as InGaAsP, InGaAs, or AlGaAs epitaxially grown on the active layer 23, and it can be p-type doped with, for example, Zn, with a doping concentration of, for example, 1*10⁻⁶. 19 The active layer 23 can employ a multi-quantum-well structure, comprising alternating barrier layers and quantum well layers. For example, when the first semiconductor layer 22 is an InP substrate, the active layer 23 may include multiple InGaAsP barrier layers and quantum well layers epitaxially grown thereon, with the barrier layers and quantum well layers formed by adjusting the atomic ratio of each element, and each quantum well layer sandwiched between adjacent barrier layers.

[0038] The semiconductor laser 20 also includes a first electrode 21 formed on a first semiconductor layer 22 and a second electrode 27 formed on a second semiconductor layer 25. The first electrode 21 and the second electrode 27 can be formed of a metal with good conductivity, such as Au, Ag, Ti-Au alloy, In-Au alloy, etc., and can also have a multilayer structure. Figure 1In the illustrated embodiment, the second electrode 27 is located on the light-emitting side, and therefore can be a structure with a light-emitting window for the laser to be emitted vertically from the window. The window can also be filled with a transparent material such as SiO2 to protect the underlying semiconductor layer. In some embodiments, the second electrode 27 can also be formed of a transparent conductive material such as ITO or IZO. The first electrode 21 can be located on the side of the first semiconductor layer 22 opposite to the active layer 23. In addition to injecting current into the first semiconductor layer 22, it can also reflect downward-emitted light upward to improve the luminous efficiency of the laser 20. In some embodiments, the first electrode 21 can also be formed on the same side of the first semiconductor layer 22 as the active layer 23. For example, the first electrode 21 can be formed on the first semiconductor layer 22 as a ring electrode surrounding the active layer 23, but spaced apart from the active layer 23 by a distance. In this case, an additional reflective layer can also be formed to reflect downward-emitted light upward. For example, a high-reflectivity film can be provided on the lower surface of the first semiconductor layer 22, or a Bragg mirror (DBR) can be formed in the first semiconductor layer 22.

[0039] exist Figure 1 In the laser array 10 shown, the first electrode 21 and the first semiconductor layer 22 of each laser 20 can be continuous layers, while the active layer 23, the second semiconductor layer 25, and the second electrode 27 can be separated from each other by etching or by other processing methods to make them electrically isolated from each other. It should be understood that Figure 1 Only the main functional layers in laser 20 are shown, while some layers such as buffer layers and waveguide cladding are omitted.

[0040] In some embodiments of the present invention, at least one of the first electrode 21, the first semiconductor layer 22, the active layer 23, the second semiconductor layer 25, and the second electrode 27 may be formed as a photonic crystal layer, or the laser 20 may include a separate photonic crystal layer to form a topological cavity surface emission structure. The separate photonic crystal layer may be formed between any two adjacent layers of the first electrode 21, the first semiconductor layer 22, the active layer 23, the second semiconductor layer 25, and the second electrode 27, or it may be formed in the same layer as the first electrode 21 or the second electrode 27. These will be described in detail below.

[0041] Figure 2A This shows a top plan view of a photonic crystal layer 30 according to an embodiment of this application. Figure 2B This is a cross-sectional view of photonic crystal layer 30. Figure 2C A schematic diagram of the supercell structure 31 in the photonic crystal layer 30 is shown. Figure 2D The band structure of the supercell is shown. First, refer to... Figure 2A The photonic crystal layer 30 may include multiple supercell structures 31, which are repeating structural units in the photonic crystal layer 30, as shown in the magnified view. Figure 2C The supercell structure 31 can have a regular hexagonal shape and be arranged in a honeycomb pattern. Each supercell structure 31 may include three parallelogram-shaped primitive cells, and each primitive cell may include multiple substructures, such as the black circular substructure 32 and gray circular substructure 34 illustrated. It should be understood that the circular substructures here are merely examples, and substructures 32 and 34 can have any other shape. Each primitive cell may include more substructures, or the primitive cell body material surrounding substructures 32 and 34 can also be considered as constituting a substructure of the primitive cell. It should be understood that the supercells, primitive cells, and substructures shown herein are merely examples, and the photonic crystal layer 30 may include supercells, primitive cells, and substructures of any other shape and layout, as long as they do not depart from the principles of the invention described herein.

[0042] Reference Figure 2B Substructures 32 and 34 can be formed by etching the main material of the photonic crystal layer 30 to form circular air holes, or the circular air holes can be filled with a material with a different dielectric constant or refractive index than the main material of the photonic crystal layer 30. Here, the main material of the photonic crystal layer 30 can be referred to as the first refractive index material, and the material of the circular substructures 32 and 34 of the photonic crystal layer 30 can be referred to as the second refractive index material. The photonic crystal layer 30 may also include a third refractive index material; for example, substructures 32 and 34 can be formed from different materials with different refractive indices. These materials forming the photonic crystal layer 30 can be appropriately selected according to the position of the photonic crystal layer 30 in the laser 20, as will be described in detail below. It is understood that the supercells, primitive cells, and substructures described here are not crystal structures formed by the repeating arrangement of atoms in crystalline materials, but rather repeating microstructures artificially formed through processes such as etching or other methods (e.g., 3D printing). These are determined by the designer and realized through specific manufacturing processes. Because they have repeating arrangement characteristics similar to unit cells, the terms "supercell" and "primary cell" from the crystal field are used here for description. Although the accompanying drawings show a hexagonal supercell, a parallelogram-shaped primitive cell, and a circular substructure, they can also have other shapes and layouts.

[0043] In the photonic crystal layer 30, one or more substructures of each supercell 31 are modulated in two dimensions. Figure 2CA specific example of two-dimensional modulation is illustrated. Specifically, each substructure 32, 34 can have multiple independent one-dimensional parameters. An independent one-dimensional parameter is a parameter that can be modulated independently in one dimension, examples of which include the size, shape, and displacement of the substructure. For example, the size of a substructure can be modulated to increase or decrease in the size dimension, thus size is an independent one-dimensional parameter of the substructure. As another example, the position of a substructure, such as its centroid position, can be modulated to shift from its equilibrium position; the displacement of the centroid along a one-dimensional line is an independent one-dimensional parameter. If the centroid is displaced in a two-dimensional plane—that is, if this displacement can be represented by displacement in different directions, or by displacement amplitude and displacement argument—and the displacement in different directions or displacement amplitude and displacement argument can be modulated independently of each other, then the displacement in each direction (which is equivalent to a one-dimensional displacement), as well as the displacement amplitude and displacement argument, are each independent one-dimensional parameters of the substructure. For example, the displacement of a substructure can be represented by displacement along the x-axis and displacement along the y-axis. The xy-plane is the layer plane of the photonic crystal layer, and the x-direction displacement and y-direction displacement can be modulated independently of each other. Therefore, each x-direction displacement and y-direction displacement can be considered an independent one-dimensional parameter, which can also be understood as an independent one-dimensional parameter of displacement amplitude in a fixed direction. Furthermore, the shape of the substructure can change from its initial shape to any shape; therefore, each change in shape can be considered an independent one-dimensional parameter, which can be represented by a specially defined shape factor. For example, changing the shape between a triangle and a circle can be considered an independent one-dimensional structural parameter, and changing the shape between a triangle and a square can be considered another independent one-dimensional structural parameter. Besides the examples of independent one-dimensional parameters described here, substructures can also have other independent one-dimensional parameters, which are not listed here. Two-dimensional modulation of the supercell structure can include the modulation of two independent one-dimensional parameters of any one substructure separately, or the modulation of one independent one-dimensional parameter of each of the two substructures. Figure 2C In the illustrated embodiment, the supercell structure has a lattice constant α, where each substructure 32 and 34 has a circular shape with a radius r. The dashed circle represents the equilibrium position of substructure 34, which can be a position symmetrical to substructure 32. In this embodiment, the displacement amplitude m0 and displacement argument φ0 of substructure 34 are modulated to achieve two-dimensional modulation of supercell structure 31. Of course, two-dimensional modulation of supercell structure 31 can also be achieved in other ways as described above.

[0044] Two-dimensional modulation of the supercell structure 31 can open the Dirac point in its band structure. When the supercell structure 31 is not modulated, that is, when its independent one-dimensional parameters are all in equilibrium, the band structure 31 has a double Dirac point, such as... Figure 2DAs shown in the left figure. When the supercell structure 31 is modulated in two dimensions, that is, when its two independent one-dimensional parameters are modulated to be greater than or less than its equilibrium position, the double Dirac point in the band diagram of the supercell structure 31 will be opened, as shown in the left figure. Figure 2D As shown in the right figure. By opening double Dirac points at all locations around the photonic crystal layer, this application realizes a two-dimensional topological photonic crystal cavity, also known as a Dirac vortex cavity, which has the characteristics of large mode field area, large free spectral range, narrow beam divergence angle, arbitrary mode degeneracy, and compatibility with various substrate materials, as described in detail below.

[0045] exist Figure 2A In the photonic crystal layer 30 shown, any point is selected as the center, and a circle is drawn around it. The circle can be circular, elliptical, or any curved shape. The modulation of two independent one-dimensional parameters of multiple supercell structures 31 (i.e., the aforementioned two-dimensional modulation) forms a vortex structure. In other words, the modulation of the two independent one-dimensional parameters of the supercell structure 31 changes periodically with the angle around the center point. Thus, in the two-dimensional parameter space composed of these two independent one-dimensional parameters, the two-dimensionally modulated vortex structure corresponds to one or more circles around the equilibrium position. Figure 3A and 3B An example of this vortex structure is shown, in which Figure 3A This is a schematic diagram of a two-dimensional modulated vortex structure in real space. Figure 3B This is a schematic diagram of a two-dimensional modulated vortex structure in parameter space. Figure 3A and 3B In the illustrated embodiment, the modulation of the position of a substructure 32 or 34 in each unit cell, for example, the centroid in both the x-axis and y-axis dimensions, is taken as an example. First, refer to... Figure 3A It shows five supercell structures from left to right, corresponding to the surrounding structures. Figure 2AThe supercell structure 31 at any point on the photonic crystal layer 30, at five angular positions: 0°, 90°, 180°, 270°, and 360°, is shown. The large dashed circle represents the equilibrium position of the substructure whose centroid is modulated, and the small dashed circle represents the centroid modulation trajectory of the substructure. The black dot on the dashed circle represents the centroid of the substructure. In the first supercell structure at 0°, the centroid of the substructure shifts from its equilibrium position to the position indicated by the black dot, corresponding to an x-axis offset and a y-axis offset. In the second supercell structure at 90°, the centroid of the substructure rotates 90° counterclockwise along the trajectory indicated by the dashed circle, thus changing both its x-axis and y-axis offset values. Similarly, in the three supercell structures at the 180°, 270°, and 360° positions, the centroid offset position of the substructure rotates counterclockwise by 90° on the trajectory shown by the dashed circle, corresponding to the changes in the x-axis and y-axis offset values ​​of the centroid. At the 360° position, the two-dimensional modulation of the centroid completes an integer number of cycles (1 in this example), returning to the same centroid position as the supercell structure at the 0° position. Figure 3B This shows the two-dimensional parameter space defined by the centroid positions along the x-axis and y-axis. Figure 3A A schematic diagram of centroid modulation is shown, where the circular black dots represent the points in parameter space corresponding to the combination of the centroid's x-axis and y-axis positions. This can be understood as... Figure 3A The two-dimensional modulated vortex structure of the substructure's centroid in real space shown corresponds to... Figure 3B The point of mass in the parameter space revolves around the central equilibrium position (the position where the mass offset is zero). This can be understood as... Figure 3A In real space, orbiting any point on the photonic crystal layer, the two-dimensional modulation of the centroid of the substructure can vary by more integer periods, such as 2 periods, 3 periods, etc., which corresponds to... Figure 3B In the parameter space, the center of mass position rotates around the central equilibrium position more times, such as 2 times, 3 times, etc. It should also be understood that in... Figure 3B In the parameter space, depending on the phase difference of two independent one-dimensional parameters being modulated, i.e., the phase difference of their oscillations around the equilibrium position, the trajectory of the point formed by the combination of these two independent one-dimensional parameters in the parameter space is not necessarily... Figure 3B The dotted line indicates a circular trajectory, but it could also be an ellipse, or in extreme cases, a straight trajectory oscillating around the central equilibrium position. These trajectories can all be considered as one or more revolutions around the equilibrium position.

[0046] Figure 3A and 3BThe illustrated two-dimensional modulation of the centroid is merely an example; other independent one-dimensional parameters of one or more substructures within the supercell structure can also be modulated. For instance, the one-dimensional position and size of a substructure can be modulated separately; the shape of a substructure can be modulated in a specific manner while simultaneously modulating its size; or the shapes of two substructures can be modulated differently, for example, the shape of the first substructure varying between a first shape (e.g., a circle) and a second shape (e.g., a square) around an equilibrium position shape (e.g., a square), and the shape of the second substructure varying between a first shape (e.g., a horizontal stripe) and a second shape (e.g., a vertical stripe) around an equilibrium position shape (e.g., a square), and so on. All these modulations fall within the scope of the two-dimensional modulation of this application. The two-dimensional modulation of this application encompasses any form of modulation of two or more independent one-dimensional parameters of one or more substructures of the supercell structure, as long as it can open the double Dirac points of the supercell's band structure.

[0047] As mentioned earlier, the supercell structure of photonic crystal layers is not limited to the examples described above. Figures 4A to 4C A schematic diagram illustrating the modulation of a photonic crystal layer and its substructures according to another embodiment of the present invention is shown, wherein... Figure 4A A plan view of the photonic crystal layer is shown. Figure 4B A schematic diagram of the supercell structure in a photonic crystal layer is shown. (Example) Figure 4A As shown, the photonic crystal layer may include a triangular structure formed of a first high-refractive-index material, and a second low-refractive-index material surrounding the triangular structure. Specifically, the triangular structure itself may be an air pore, without being filled with other material. (See reference...) Figure 4B The supercell of the photonic crystal layer may include three primitive cells A1, A2 and A3. Each primitive cell includes three branch structures, and each branch structure contains a triangle with equal base sides. The vertices of the three branch structures coincide to form an equilateral triangle. Figure 4C The modulation of the branch structure is shown. Before modulation, the vertices and bottom edges of the branch structure can have the same height t0, meaning the three branch structures are identical. a R b and R c The combined vector is located at the central equilibrium position. The height of each branch structure triangle can be modulated to t. a t b and t c This causes the centroid of the unit cell to shift by an amplitude of δ and an angle of displacement of θ. In this way, the substructures (or unit cells) within the supercell structure can be similarly modulated in two dimensions to achieve... Figure 4AThe photonic crystal layer shown opens the double Dirac points of the supercell's energy bands at each position around the center point.

[0048] Figures 5A to 5C A schematic diagram of the modulation of a photonic crystal layer and its substructures according to another embodiment of the present invention is shown, which is the same as the modulation principle described above, except that the substructures in the supercell are arranged differently. Figure 5A A plan view of the photonic crystal layer is shown. Figure 5B A schematic diagram of the supercell structure in a photonic crystal layer is shown. (Example) Figure 5A As shown, the photonic crystal layer may include an isosceles right-angled triangle structure formed of a first high-refractive-index material, and a second low-refractive-index material surrounding the isosceles right-angled triangle structure. Specifically, the isosceles right-angled triangle structure itself may be an air pore, without being filled with other material. (Refer to...) Figure 5B The supercell of the photonic crystal layer may include right-angled sides with lengths L0 and L... a An isosceles right triangle structure. Figure 5C This illustrates the modulation of the supercell structure. Before modulation, the centers of the two isosceles right-angled triangles are located at their respective equilibrium positions. During modulation, the length of the right-angled side is L. a If the center of an isosceles right triangle remains unchanged, the lengths of the two legs of this isosceles right triangle can be expressed as L. b With L c The position of the center of the isosceles right triangle, whose side length is L0, remains constant while the triangle's position varies within the range of δ and -δ. This allows for similar two-dimensional modulation of substructures (e.g., primitive cells) within a supercell structure.

[0049] The embodiments of photonic crystal layers have been discussed above. As previously mentioned, the photonic crystal layer can be applied to each layer in laser 20, or laser 20 can include a single photonic crystal layer. See below for further details. Figure 6 Explain the principle of a laser that includes a photonic crystal layer. Figure 6In the example, a photonic crystal layer is formed above a multiple quantum well (MQW) active layer, which can be located on an InP substrate, where the active layer is the gain region. The guided mode field at least partially overlaps the photonic crystal layer in the vertical direction, so that photons generated in the active layer can be selectively confined within the gain region by the photonic crystal layer, forming resonant amplification. The photon resonance direction is in the layer plane direction, but a vertical component is generated. The photonic crystal layer selectively amplifies specific wavelengths, ultimately generating laser light that is vertically emitted from the upper surface. The vertically downward emitted laser light can be reflected back to the upper surface by a reflective structure to improve light emission efficiency. It is understood that the photonic crystal layer can be located anywhere in the laser 20, as long as it at least partially overlaps with the guided mode field; of course, it is preferred that the photonic crystal layer and the guided mode field overlap more, so the photonic crystal layer can be formed in or as close as possible to the active layer.

[0050] Figures 7A to 7E A schematic diagram of a laser including photonic crystal layers according to some embodiments of this application is shown. As previously described, each layer in laser 20 can be formed as a photonic crystal layer, or laser 20 can include separate photonic crystal layers, provided that the formed photonic crystal layers overlap with the guided mode field portion. Figure 7A In the illustrated embodiment, the first electrode 21 can be formed as a photonic crystal layer, or a separate photonic crystal layer can be formed in the same layer as the first electrode 21. For example, the metal layer of the first electrode 21 can be etched with a number of pores, which can be filled with materials of different dielectric constants, such as SiO2, or left unfilled to form air pores, thereby forming a supercell structure. Such a photonic crystal layer formed in a metal electrode layer is particularly suitable for the terahertz band. Alternatively, the first electrode 21 can be formed as a ring electrode, and a separate photonic crystal layer can be formed in the central opening region of the ring electrode. It is understood that when the first electrode 21 includes a photonic crystal layer, a high-reflectivity film 24 can also be formed below the first electrode 21 to reflect downward-emitted laser light as upward-emitted light, thereby improving the luminous efficiency of the laser 20. It is understood that in some embodiments, the second electrode 27 may also be formed as a photonic crystal layer, or a separate photonic crystal layer may be formed in the light-emitting window of the annular second electrode 27, which may be similar to the photonic crystal layer described above with respect to the first electrode 21, and therefore will not be described again.

[0051] Figure 7BAn embodiment in which the first semiconductor layer 22 is formed as a photonic crystal layer is illustrated. For example, a plurality of pores can be etched into the first semiconductor layer 22, and these pores can be filled with materials of different dielectric constants, such as SiO2, or left unfilled to form air pores, thereby forming a supercell structure. Then, a buffer layer and an active layer can be epitaxially grown on the first semiconductor layer 22. Even if the first semiconductor layer 22 includes air pores, lateral epitaxial growth of the material can cover the air pores, forming a continuous epitaxial layer on top for forming subsequent, such as, active layers. Similarly, the active layer 23 and the second semiconductor layer 25 can also be formed as photonic crystal layers, which will not be described again here.

[0052] Figure 7C An embodiment of a laser 20 including a separate photonic crystal layer 26 is shown. In this embodiment, the photonic crystal layer 26 is located between the active layer 23 and the second semiconductor layer 25, but it can also be located at other positions as long as it overlaps with the guided mode field in the vertical direction. The photonic crystal layer 26 can be formed by epitaxially growing a semiconductor layer on the active layer 23, etching holes in the epitaxial layer, and then filling the holes with a material or air of different refractive indices. The second semiconductor layer 25 can then be epitaxially grown on the photonic crystal layer 26.

[0053] Figure 7D Another specific embodiment of a photonic crystal layer 26 formed between an active layer 23 and a second semiconductor layer 25 is shown. A portion of the active layer 23 may be etched to form apertures, which may be filled with a material of a different refractive index or air, and then the second semiconductor layer 25 may be epitaxially grown thereon. Thus, the photonic crystal layer 26 includes a portion 26a of the same material as the active layer 23 and a portion 26b filled with a material of a different refractive index.

[0054] Figure 7E Another specific embodiment of a photonic crystal layer 26 formed between an active layer 23 and a second semiconductor layer 25 is shown. A portion of the active layer 23 can be etched to form apertures, and then the second semiconductor layer 25 can be epitaxially grown directly on the active layer 23 with the apertures. A conformal epitaxial process can be used such that the material of the second semiconductor layer 25 fills the apertures in the active layer 23, so that the photonic crystal layer 26 includes a material portion 26a identical to that of the active layer 23 and a material portion 26b identical to that of the second semiconductor layer 25. Since the second semiconductor layer 25 has a different material or material composition than the active layer 23, the material portions 26a and 26b have different refractive indices.

[0055] The above describes some embodiments of the laser 20 including a photonic crystal layer. The laser 20 of this application, including a photonic crystal layer, can achieve many excellent technical effects. The cavity diameter of conventional vertical-plane emitting lasers is generally less than 10 μm. When it exceeds 10 μm, multimode lasing occurs, affecting the laser quality. Due to the size limitation of the laser, the output power is generally less than 10 mW, while the divergence angle is generally greater than 15°. In this invention, by employing the above-mentioned photonic crystal layer, the laser 20 can be formed with a larger size of more than 10 μm, for example, greater than 20 μm, or even greater than 50 μm. Considering power density and heat dissipation, the size of the laser 20 can be less than 10 cm, or less than 5 cm, preferably less than 1 cm. Or, more precisely, the maximum in-plane dimension of the photonic crystal in the photonic crystal layer of each laser, such as diameter, length, or major axis, can be more than 10 μm, preferably more than 20 μm, more preferably more than 50 μm, and can be less than 10 cm, preferably less than 5 cm, more preferably less than 1 cm. Figure 8 A performance schematic diagram of a laser including a photonic crystal layer according to an embodiment of this application is shown. The laser sample includes a 320 nm thick InGaAsP / InP photonic crystal layer above a 225 nm thick InGaAsP multiple quantum well active layer. The active layer has a diameter of 500 μm, significantly larger than the less than 10 μm diameter of conventional lasers. The photonic crystal layer employs... Figure 3A The supercell two-dimensional modulation shown has a supercell lattice constant a of 325 nm and a ratio r / a = 0.32 between the substructure radius r and the supercell lattice constant a. Figure 8 Figure (a) shows micrographs of multiple samples, with five samples prepared for substructure displacement amplitudes m equal to 0.1a, 0.13a, 0.16a, 0.19a and 0.22a. Figure 8 Figure (b) illustrates the optical output characteristics of these five samples. It can be seen that optimizing the displacement amplitude m can increase the maximum optical output power. However, if the displacement amplitude m is further increased, the gaps between adjacent substructures tend to connect, ultimately leading to a decrease in slope efficiency. In the two samples with m values ​​of 0.19a and 0.22a, far-field peak power exceeding 10W was achieved, far exceeding that of current commercial lasers. Under higher pump conditions, the output power reaches saturation due to thermal effects. Figure 8 The illustration in (b) shows the spectrum and side-mode suppression ratio (SMR) characteristics measured using a spectrometer with a resolution of 0.01 nm. When the output power is below 1 W, the output spectrum of laser 20 maintains good single-mode characteristics, with an SMR exceeding 55 dB and a full width at half maximum (FWHM) of 0.03 nm. If the spectral resolution is increased to 1 nm, the SMR can reach over 60 dB due to the increased signal intensity. Figure 8Figure (c) shows the output spectra under different pump conditions when m = 0.19a. It can be seen that under high pump conditions, the laser spectrum exhibits a redshift due to the increase in refractive index with increasing temperature. When the output power exceeds 1W, the laser linewidth broadens due to various nonlinear effects, a common phenomenon in semiconductor lasers. Figure 8 Figure (d) shows the far-field image captured by an infrared camera. It can be seen that the laser's divergence angle is around 1°, far less than the minimum of 15° for traditional lasers. Therefore, laser 20 exhibits excellent collimation characteristics, which can reduce the size, complexity, and cost of system integration. The far-field beam is a ring-shaped vector beam with radial polarization, consistent with theoretical calculations. Figure 8 Figure (e) is a magnified version of Figure (b) near the laser threshold. It can be seen that lasers with different m values ​​all exhibit a clear lasing threshold, demonstrating the stability of the design.

[0056] It is understood that multiple lasers 20 in the laser array 10 can be formed in the same steps. When forming the photonic crystal layer of each laser 20, different photoresist mask patterns can be used to form different supercell structures through an etching process. For example, the primitive cell and substructure patterns or the size of the supercell structure, i.e., its lattice constant, can be different from each other. Generally, the lattice constant of the supercell structure can be in the range of 50 nm to 500 μm, preferably in the range of 50 nm to 100 μm. The approximate range of the supercell lattice constant can be selected based on the material used to form the laser 20. The photonic crystal layers of multiple lasers 20 can have different supercell lattice constants. For multiple lasers 20 formed from the same material in the same laser array 10, the maximum difference in their supercell lattice constants can generally be within 50% of the maximum lattice constant, preferably within 30%. Figure 9 The emission characteristics of each laser 20 in the laser array 10 with different supercell lattice constants are shown. When the supercell lattice constants are 315 nm, 320 nm, 325 nm, 330 nm, 335 nm, and 340 nm, the corresponding laser emission wavelength increases linearly from 1512 nm to 1616 nm, demonstrating the multi-wavelength capability of the laser array 10. Figure 9 Figure (a) shows that all six lasers can stably achieve single-mode operation, with side-mode suppression ratios (SMSRs) all greater than 50 dB, and the highest SSR reaching 60 dB, making it the lowest threshold device. Its laser wavelength is closest to the photoluminescence (PL) peak. Figure 9The laser emission threshold shown in Figure (b) allows estimation that laser 20 can operate at shorter wavelengths, spanning a wider spectrum than the 100 nm span shown here. This multi-wavelength vertical-cavity surface-emitting laser array has the potential to increase the power and bandwidth of wavelength division multiplexing (WDM) technology used in optical communication devices for high-capacity signal transmission, and can also be applied to sensing applications such as optical coherence tomography (OTC) and multispectral lidar.

[0057] Figure 10 A schematic diagram illustrating the characteristics of lasers of different sizes according to some embodiments of this application is shown. Figure 10 Figure (a) shows micrographs of multiple samples with device dimensions (diameters) of 200 μm, 300 μm, 400 μm, and 500 μm. Each sample comprises a 225 nm thick InGaAsP multiple quantum well active layer and a 320 nm thick InGaAsP / InP photonic crystal layer thereon. The photonic crystal layer employs... Figure 3A The supercell two-dimensional modulation shown has a supercell lattice constant a of 325 nm and a ratio r / a = 0.32 between the substructure radius r and the supercell lattice constant a. Figure 10 Figure (b) shows the optical output characteristics of these four samples, demonstrating that stable lasing can be achieved for devices of all sizes. The output power increases with increasing cavity size. Due to thermal effects, the output power saturates after increasing pump power. Compared to larger devices, smaller devices reach output power saturation more easily. Figure 10 Figure (c) shows the characteristics near the laser threshold. All samples exhibit a clear threshold, further demonstrating the stability of lasing. Figure 10 Figure (d) shows the output spectra of devices of different sizes under the same pumping conditions. It can be seen that the laser exhibits good single-mode performance across different device sizes. Figure 10 Figure (e) shows a far-field image captured by an infrared camera. The unique far-field structure further confirms that the lasing mode is a topological mode, consistent with theoretical calculations. It can be seen that, compared to conventional lasers with dimensions below 10 μm, the laser according to the embodiments of this application achieves a significantly larger laser size by utilizing a topological photonic crystal layer, thereby increasing the emission power while maintaining excellent single-mode characteristics and a small far-field emission angle. Therefore, it greatly improves laser performance and has very promising application prospects in various laser-related fields.

[0058] Some exemplary embodiments of this application also provide an electronic device including the above-described monolithically integrated semiconductor laser array 10. Such an electronic device can be, for example, an optical communication device, a lidar device, a detection sensing device, a laser processing device, a laser medical device, a laser weapon device, a lighting device, or a display device, wherein the laser array 10 can be used as a multi-wavelength light source. For example, in an optical communication device, the laser array 10 not only improves signal transmission power, but its multi-wavelength capability also helps to achieve multi-wavelength signal transmission, thereby increasing data transmission bandwidth. In lidar devices and detection sensing devices, the laser array 10 can utilize its multi-wavelength capability to perform spectral analysis of the scanned / detected object, for example, determining whether the scanned object is metal, such as a car or a pedestrian. In lighting or display devices, the laser array 10 can provide lighting / display capabilities of different colors.

[0059] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0060] The above description has been given for illustrative and descriptive purposes. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A monolithically integrated topological cavity surface-emitting laser array, comprising a plurality of topological cavity surface-emitting lasers formed from the same semiconductor layer, wherein each topological cavity surface-emitting laser includes a first semiconductor layer, an active layer disposed on the first semiconductor layer, a second semiconductor layer disposed on the active layer, and a first electrode and a second electrode respectively disposed on the first semiconductor layer and the second semiconductor layer. in, At least one of the first electrode, the first semiconductor layer, the active layer, the second semiconductor layer, and the second electrode is formed as a photonic crystal layer, or the topological cavity surface-emitting laser further includes a separate photonic crystal layer. The photonic crystal layer includes multiple supercell structures, each supercell having one or more substructures, each substructure having multiple independent one-dimensional parameters. At least two independent one-dimensional parameters of one or more substructures of the supercell are modulated to be greater than or less than their equilibrium positions to open the Dirac point of the supercell's energy band at the equilibrium position. The double Dirac point of the supercell is opened at all positions in any loop around a point in the photonic crystal layer. The modulation of the two independent one-dimensional parameters of the supercell forms a vortex structure, which corresponds to one or more loops around the equilibrium position in a two-dimensional parameter space composed of the two independent one-dimensional parameters.

2. The monolithically integrated topological cavity surface-emitting laser array as described in claim 1, wherein, The independent one-dimensional parameters of the substructure include size, shape, and displacement.

3. The monolithically integrated topological cavity surface-emitting laser array as described in claim 1, wherein, The modulation of at least two independent one-dimensional parameters of one or more substructures of the supercell includes: Modulate at least two independent one-dimensional parameters of a substructure; or Modulate at least one independent one-dimensional parameter of each of two or more substructures.

4. The monolithic integrated topological cavity surface-emitting laser array as described in claim 1, wherein, Two or more topological cavity surface-emitting lasers have photonic crystal layers with different supercell lattice constants.

5. The monolithically integrated topological cavity surface-emitting laser array as described in claim 4, wherein, The maximum difference in the supercell lattice constants of the photonic crystal layers of the two or more topological cavity surface-emitting lasers is within 50% of their maximum lattice constants.

6. The monolithically integrated topological cavity surface-emitting laser array as described in claim 5, wherein, The maximum difference in the supercell lattice constants of the photonic crystal layers of the two or more topological cavity surface-emitting lasers is within 30% of their maximum lattice constant.

7. The monolithic integrated topological cavity surface-emitting laser array as described in claim 1, wherein, The supercell lattice constant of the photonic crystal layer is in the range of 50 nm to 500 μm.

8. The monolithic integrated topological cavity surface-emitting laser array as described in claim 1, wherein, The maximum in-plane size of the photonic crystal in the photonic crystal layer of each topological cavity surface-emitting laser is greater than 10 μm and less than or equal to 10 cm.

9. The monolithically integrated topological cavity surface-emitting laser array as described in claim 8, wherein, The maximum in-plane size of the photonic crystal in the photonic crystal layer of each topological cavity surface-emitting laser is greater than 50 μm and less than or equal to 1 cm.

10. The monolithic integrated topological cavity surface-emitting laser array as described in claim 1, wherein, The individual photonic crystal layer is disposed between any two adjacent layers among the first electrode, the first semiconductor layer, the active layer, the second semiconductor layer, and the second electrode, or disposed in the same layer as the first electrode or the second electrode.

11. An electronic device comprising a monolithic integrated topological cavity surface-emitting laser array as described in any one of claims 1 to 10.

12. The electronic device of claim 11, wherein, The electronic device is an optical communication device, a lidar device, a detection and sensing device, a laser processing device, a laser medical device, a laser weapon device, a lighting device, or a display device.

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