Surface emitting laser

Abstract

The invention discloses a surface emitting laser which solves the problems that a laser is poor in single-mode working stability and high in preparation process difficulty. The surface emitting laser comprises a substrate and an epitaxial structure which are arranged in a stacked mode, the epitaxial structure is provided with a plurality of holes, the section of each hole is roughly in a T shape, the sections are parallel to the substrate, filler is arranged in the holes, and the refractive index of the filler is different from that of the epitaxial structure. Under the same mode field area and surface emission coupling efficiency, the threshold gain difference between the base mode and the high-order resonance mode of the laser is large, and the stability of the single-mode working state is high. And the hole machining difficulty of the T-shaped structure is low.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor lasers, and in particular to a surface emitting laser. Background Art

[0002] Semiconductor lasers have been widely used in many fields such as laser processing, communications, and lighting due to their advantages of small size, high electro-optical conversion efficiency, and low cost. However, the far-field divergence angle of traditional edge-emitting or vertical cavity surface-emitting semiconductor lasers in single-mode operation is usually large, which makes optical path design and system integration more difficult, thereby increasing the overall cost and reliability of the system. Therefore, a photonic crystal surface-emitting laser (PCSEL) is proposed to reduce the far-field divergence angle of the laser. However, the photonic crystal resonant cavity of PCSEL has problems such as high processing difficulty or poor single-mode stability. Therefore, it is urgent to provide a semiconductor laser with good single-mode working stability and low process preparation difficulty. Summary of the Invention

[0003] The surface emitting laser provided in the present application solves the problems of poor stability of single-mode operation of the laser and high difficulty in the preparation process.

[0004] A surface-emitting laser provided in the present application includes a stacked substrate and an epitaxial structure, wherein the epitaxial structure has a plurality of holes, each of the holes having a roughly T-shaped cross-section parallel to the substrate, and a filler provided in the hole, wherein the refractive index of the filler is different from the refractive index of the epitaxial structure.

[0005] In the above-described embodiment, the epitaxial structure has a hole with a roughly T-shaped cross section, which reduces the processing difficulty compared to hole structures with a combination of an ellipse and a circle, or a combination of a large circle and a small circle, as used in related art. Because the hole has a roughly T-shaped cross section and the filler fills the hole, the shape of the filler inside it is also roughly T-shaped. The refractive index of the filler differs from that of the epitaxial structure. Compared to holes with isosceles triangle cross sections in related art, under the same mode field area and surface emission coupling efficiency, the threshold gain difference between the fundamental mode and higher-order resonant modes of the laser of this application is larger, and the stability of the single-mode operation state is high.

[0006] In one embodiment, the epitaxial structure includes a stacked photonic crystal layer and a p-doped cladding layer, and the hole is located in the photonic crystal layer.

[0007] In one embodiment, each of the holes extends at least partially into the p-doped cladding layer.

[0008] In one embodiment, the photonic crystal layer includes a plurality of unit cells arranged in a lattice, the unit cells are periodically repeated along a first direction and a second direction, each of the unit cells includes a hole, and the cross-section of each hole is symmetrical along a third direction. The first direction, the second direction, and the third direction are all parallel to the substrate, the first direction is perpendicular to the second direction, and the third direction forms an angle of 45° with the first direction and the second direction, respectively.

[0009] In one embodiment, along a direction perpendicular to the substrate, a depth d of the hole satisfies: 50 nm ≤ d ≤ 500 nm.

[0010] In one embodiment, the cross section includes a first portion and a second portion connected to each other, and an area of ​​the first portion is greater than an area of ​​the second portion;

[0011] The length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.35a≤L1≤1.1a, 0.1a≤H1≤0.65a, 0.05a≤L2≤0.35a, 0.05a≤H2≤0.35a, where a is the lattice constant.

[0012] In one embodiment, the first part is elliptical, the second part is rectangular, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.55a≤L1≤0.85a, 0.2a≤H1≤0.5a, 0.1a≤L2≤0.35a, and 0.1a≤H2≤0.35a.

[0013] In one embodiment, the first part is a rhombus, the second part is a rectangle, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.7a≤L1≤1.1a, 0.3a≤H1≤0.65a, 0.1a≤L2≤0.35a, and 0.05a≤H2≤0.3a.

[0014] In one embodiment, the first part is a rectangle, the second part is also a rectangle, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.5a≤L1≤0.8a, 0.1a≤H1≤0.4a, 0.1a≤L2≤0.35a, and 0.1a≤H2≤0.35a.

[0015] In one embodiment, the first part is roughly elliptical, including oppositely arranged long sides and oppositely arranged arcuate edges, the arcuate edges are bent inward, and the curvature of the arcuate edges is 0rad~2rad, the second part is rectangular, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.35a≤L1≤0.85a, 0.15a≤H1≤0.4a, 0.1a≤L2≤0.35a, 0.1a≤H2≤0.35a. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a single-mode photonic crystal resonant cavity in the related art;

[0017] Figure 2 Schematic diagram of another single-mode photonic crystal resonant cavity in the related art;

[0018] Figure 3 Schematic diagram of another single-mode photonic crystal resonant cavity in the related art;

[0019] Figure 4 A schematic structural diagram of a surface emitting laser provided in one embodiment of the present application;

[0020] Figure 5 A cross-sectional view of an epitaxial structure provided in accordance with an embodiment of the present application, parallel to the substrate;

[0021] Figure 6 A schematic structural diagram of a surface emitting laser provided in another embodiment of the present application;

[0022] Figure 7 A schematic structural diagram of a surface emitting laser provided in another embodiment of the present application;

[0023] Figure 8 A top view of a surface emitting laser provided in accordance with an embodiment of the present application;

[0024] Figure 9 A schematic structural diagram of a surface emitting laser provided in another embodiment of the present application;

[0025] Figure 10 A top view of a surface emitting laser provided in accordance with an embodiment of the present application;

[0026] Figure 11 for Figure 5 A-A' cross-sectional view;

[0027] Figure 12 A mode threshold gain diagram of a surface emitting laser provided in accordance with an embodiment of the present application;

[0028] Figure 13 A vertical radiation constant diagram of a surface emitting laser provided for one embodiment of the present application;

[0029] Figure 14 A resonant mode distribution diagram of a surface emitting laser provided in one embodiment of the present application;

[0030] Figure 15 A far-field diagram corresponding to the fundamental mode of a surface-emitting laser provided in one embodiment of the present application;

[0031] Figure 16 A near-field diagram corresponding to the fundamental mode of a surface-emitting laser provided in one embodiment of the present application;

[0032] Figure 17 is a resonant mode distribution diagram of a laser in the related art;

[0033] Figure 18 A cross-sectional view of an epitaxial structure parallel to a substrate provided in another embodiment of the present application;

[0034] Figure 19 A cross-sectional view of an epitaxial structure parallel to a substrate provided in another embodiment of the present application;

[0035] Figure 20 A cross-sectional view of an epitaxial structure parallel to a substrate provided in another embodiment of the present application;

[0036] Figure 21 A cross-sectional view of an epitaxial structure parallel to a substrate is provided for another embodiment of the present application.

[0037] Reference numerals:

[0038] 10-substrate; 20-epitaxial structure; 201-hole; 202-filler; 1-n-doped cladding; 2-active layer; 3-photonic crystal layer; 4-p-doped cladding; 5-p-doped contact layer; 6-first metal film layer; 7-second metal film layer; 8-electrically insulating layer; 9-transparent conductive layer; 2011-first part; 2012-second part. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of this application clearer, the present application is further described in detail with reference to the accompanying drawings.

[0040] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and appended claims of this application, the singular expressions "a", "an", "said", "above", "the", and "this" are intended to also include expressions such as "one or more", unless the context clearly indicates otherwise.

[0041] References in this specification to "one embodiment" or "a specific embodiment" mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. The terms "including," "comprising," "having," and their variations all mean "including but not limited to," unless otherwise specifically stated.

[0042] The mode field refers to the cross-sectional distribution of the fundamental mode electromagnetic field in an optical waveguide or laser. It reflects the spatial concentration and propagation characteristics of optical energy. The mode field distribution directly affects the divergence angle and brightness of the beam. Specifically, the smaller the mode field diameter, the stronger the diffraction effect, and the larger the far-field divergence angle.

[0043] Because traditional edge-emitting or vertical-cavity surface-emitting semiconductor lasers have a small single-mode mode area, their far-field divergence angle is large when operating in single-mode mode, typically exceeding 10°. Photonic crystal surface-emitting lasers (PCSELs) use a two-dimensional photonic crystal as a resonant cavity to achieve laser oscillation and surface-emitting output. They can maintain stable single-mode operation with a larger mode area (e.g., a diameter of 500 microns or more), and their far-field divergence angle can be less than 1°, significantly reducing the laser's far-field divergence angle.

[0044] Photonic crystals are periodic dielectric materials with photonic band gaps. The so-called photonic band gap is the result of the spatial periodicity of the dielectric constants, resulting from the periodic arrangement of materials with different dielectric constants. This creates a periodic distribution of the refractive index of light, creating an energy band structure as light propagates through it, and photons with frequencies within the band gap are prohibited from propagating. This unique optical property is determined by the composition of the electromagnetic field in the photonic crystal, and therefore the transmission of light can be controlled by designing the structure of the photonic crystal.

[0045] In the design of a photonic crystal resonant cavity, it is necessary to precisely control the geometric parameters and structural configuration of the photonic crystal so that the difference in threshold gain between the fundamental mode and the higher-order resonant modes (higher-order modes) in the resonant cavity is significant enough. Figure 1 Schematic diagram of a single-mode photonic crystal resonant cavity in related art. Figure 2 Schematic diagram of another single-mode photonic crystal resonant cavity in the related art. Figure 3 FIG. 1 is a schematic diagram of another single-mode photonic crystal resonant cavity in the related art. Figure 1 and Figure 2 As shown, in the related art, there are two main structures of single-mode photonic crystal resonant cavity: one is a photonic crystal structure based on a double lattice, which usually adopts "ellipse + circle" ( Figure 1 ) or "big circle + small circle" ( Figure 2) hole shape configuration, but the requirements for the hole spacing and hole size in the unit cell of the photonic crystal are extremely strict, and the process tolerance is only a few nanometers. In addition, the etching process at the micro-nano scale places higher requirements on the precise control of the hole shape and size, making it difficult to control the distribution difference between the hole depths of the double lattice structure, and directly affecting the subsequent batch preparation process (such as nanoimprinting), thus bringing huge challenges to the reliability of the overall process. Figure 3 As shown, the other is based on an isosceles triangle photonic crystal structure. This design is more ideal than the double lattice structure in terms of process difficulty and process stability. However, under the same mode field area and surface emission coupling efficiency, the threshold gain difference between the fundamental mode and the high-order resonant mode is smaller, and the single-mode stability will be inferior to the former.

[0046] In view of this, the embodiments of the present application provide a surface emitting laser that solves the problems of poor single-mode working stability and high difficulty in manufacturing process. The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0047] Figure 4 A schematic structural diagram of a surface emitting laser provided in one embodiment of the present application is shown. Figure 5 A cross-sectional view of an epitaxial structure parallel to the substrate is provided for one embodiment of the present application. Figure 4 and Figure 5 As shown, an embodiment of the present application provides a surface-emitting laser including a stacked substrate 10 and an epitaxial structure 20. The epitaxial structure 20 has a plurality of holes 201, each of which has a substantially T-shaped cross-section parallel to the substrate 10. A filler 202 is provided in the hole 201, and the refractive index of the filler 202 is different from that of the epitaxial structure 20.

[0048] In the above embodiment, the epitaxial structure 20 has a hole 201 with a substantially T-shaped cross section. Figure 1 or Figure 2 The hole structure of the combination of ellipse and circle or large circle and small circle in the related art shown reduces the difficulty of processing. Since the cross section of the hole 201 is roughly T-shaped, the filler 202 fills the hole 201, so the shape of the filler 202 inside it is also roughly T-shaped. The refractive index of the filler 202 is different from the refractive index of the epitaxial structure 20. Compared with the related art such as Figure 3 The cross section shown is an isosceles triangle hole. Under the same mode field area and surface emission coupling efficiency, the threshold gain difference between the fundamental mode and the high-order resonant mode of the surface emitting laser of the present application is large, and the stability of the single-mode working state is high.

[0049] In one embodiment, the filler 202 may be a gas, such as air, nitrogen, etc. The hole 201 may also be filled with a semiconductor material, a metal material, or an insulating material.

[0050] Figure 6 A schematic structural diagram of a surface emitting laser provided in another embodiment of the present application is shown in FIG. Figure 6 As shown, in one embodiment, the substrate 10 can be specifically an n-doped substrate, and the epitaxial structure 20 can include a plurality of stacked epitaxial layers. Specifically, the epitaxial structure 20 includes an n-doped cladding 1, an active layer 2, a photonic crystal layer 3, a p-doped cladding 4 and a p-doped contact layer 5 stacked in sequence. The above-mentioned n-doped cladding 1, active layer 2, photonic crystal layer 3, p-doped cladding 4 and p-doped contact layer 5 are all epitaxial layers. Among them, the photonic crystal layer 3 is the resonant cavity of the laser, which is used to regulate the internal light field of the laser and construct a resonant cavity mode with a large threshold gain difference. The material of the photonic crystal layer 3 can be GaAs, InP, AlGaAs, GaAsP, InAlGaAs, InGaAsP, etc. The active layer 2 is used to continuously amplify the selected fundamental mode resonant mode to achieve laser lasing. The active layer 2 can be made of semiconductor materials, such as quantum wells, quantum dots or quantum cascade structure materials, and can be specifically InGaAs multiple quantum wells. The material of the p-doped cladding 4 is Al 0.4 Ga 0.6 As. The material of the p-doped contact layer 5 is GaAs. The material of the n-doped cladding layer 1 is Al 0.6 Ga 0.4 As.

[0051] Photonic crystals can be classified into one-dimensional, two-dimensional, and three-dimensional photonic crystals, depending on the spatial dimension of the periodic variation in refractive index. In the embodiment of the present application, the photonic crystal layer 3 is a two-dimensional photonic crystal layer, and the aforementioned hole 201 is located in the photonic crystal layer 3. The unique structural design of the roughly T-shaped filler 202 can control the optical field within the laser, constructing a resonant cavity mode with a large threshold gain difference.

[0052] Experiments have shown that, compared to conventional fillers 202 with circular or rectangular geometric patterns, the roughly T-shaped filler 202 of the photonic crystal layer 3 in this application significantly enhances the selectivity of the photonic crystal resonator for different resonant modes. Furthermore, this structure effectively suppresses the destructive interference effect of the oscillating light field within the resonator, significantly increasing the proportion of vertically coupled laser output. A surface-emitting laser based on this photonic crystal layer 3 structure can maintain the device's single-mode operating characteristics despite a large mode field area, thereby achieving high-power single-mode surface-emitting laser output.

[0053] Figure 7 This is a schematic diagram of the structure of a surface emitting laser provided in another embodiment of the present application. Figure 7As shown, in one embodiment, each hole 201 extends at least partially to the p-doped cladding 4, that is, the hole 201 is located in the photonic crystal layer 3 and the p-doped cladding 4, and the filler 202 is located in both the photonic crystal layer 3 and the p-doped cladding 4. When preparing the hole 201, the hole 201 can extend from the photonic crystal layer 3 to the p-doped cladding 4 in a direction perpendicular to the substrate 10. Correspondingly, the filler 202 also extends to the p-doped cladding 4. By extending the hole 201 to the p-doped cladding 4 to increase the hole depth, the optical field distribution ratio inside the hole 201 can be improved, thereby achieving better single-mode control of the optical mode in the resonant cavity.

[0054] Please continue to refer to Figure 5 In one embodiment, the photonic crystal layer 3 includes a plurality of unit cells arranged in a lattice, and the unit cells are periodically repeated along the first direction X and the second direction Y. Each unit cell (i.e., each repeating unit) in the photonic crystal layer 3 contains a hole 201 and a filler 202 corresponding to the hole 201. The filler 202 has a different refractive index from the parent material of the photonic crystal layer 3. The cross section of each hole 201 is symmetrical along the third direction Z, and the cross section is parallel to the substrate 10. The first direction X, the second direction Y, and the third direction Z are all parallel to the substrate 10, the first direction is perpendicular to the second direction, and the third direction is at an angle of 45° to the first direction and the second direction, respectively. In other words, a figure with a roughly T-shaped cross section is an axially symmetrical figure, and the angle between the axis of symmetry and the first direction X or the second direction Y is 45°. The pattern can be formed by splicing two geometric figures, such as splicing an ellipse and a rectangle. The area of ​​the ellipse is larger than the area of ​​the rectangle. By adopting this design method of introducing additional small-scale structures (such as rectangles) on a basic shape with rotational symmetry (such as an ellipse), it is possible to achieve fine control of the electromagnetic field distribution of the resonant mode in the photonic crystal resonator (such as the symmetry of the electromagnetic field distribution, and the position of the antinodes and nodes of the electromagnetic field), thereby enhancing the selectivity of the fundamental mode and high-order modes in the photonic crystal cavity and achieving stable single-mode resonance of the laser over a large area. In addition, this structure can also effectively improve the vertical radiation loss of the photonic crystal cavity, which is conducive to increasing the surface emission output power and slope efficiency of the laser.

[0055] The lattice structure of the photonic crystal layer 3 is a square lattice, that is, it has the same lattice constant a in two mutually perpendicular periodic arrangement directions (the first direction X and the second direction Y), and the lattice constant is numerically the same as the lasing wavelength λ of the laser involved in this embodiment in the material. n In this embodiment, the lattice constant can be set to 298 nm, and the corresponding target operating wavelength of the laser is about 980 nm.

[0056] In one embodiment, the photonic crystal layer 3 is a square with a side length of 600 μm. In other embodiments, the diameter of the photonic crystal layer 3 can be designed to be 1 mm or 3 mm according to different output power design requirements of the laser.

[0057] Continue to refer Figure 6 In one embodiment, a first metal film layer 6 is provided on the side of the p-doped contact layer 5 facing away from the p-doped cladding layer 4, and a second metal film layer 7 is provided on the side of the n-doped substrate 10 facing away from the n-doped cladding layer 1. The first metal film layer 6 and the second metal film layer 7 can be prepared using a deposition process. The first metal film layer 6 can specifically be a Ti / Pt / Au composite metal film layer. The second metal film layer 7 can specifically be a Ni / Au-Ge / Ni / Au composite metal film layer. The first metal film layer 6 and the second metal film layer 7 are used for electrical conduction to enable current to be injected into the laser.

[0058] In one embodiment, the p-doped cladding layer 4 and the p-doped contact layer 5 are combined together and can be referred to as a p-doped semiconductor material layer. The p-doped cladding layer 4 and the p-doped contact layer 5 are arranged in a stepped manner. The area of ​​the p-doped contact layer 5 is smaller than that of the p-doped cladding layer 4, and the p-doped contact layer 5 is arranged in the middle area of ​​the p-doped cladding layer 4. The first metal film layer 6 is wrapped around the side of the p-doped semiconductor material layer facing away from the substrate 10. An electrical insulating layer 8 is provided between the first metal film layer 6 and the p-doped semiconductor material layer, and the electrical insulating layer 8 is located at the edge of the p-doped semiconductor material layer. The material of the electrical insulating layer 8 is silicon oxide or silicon nitride. By providing the electrical insulating layer 8 in the edge area of ​​the device, the flow of current along the edge path can be blocked, so that the current is limited to the central area of ​​the device for injection.

[0059] Figure 8 A top view of a surface emitting laser provided in an embodiment of the present application, combined with Figures 6 to 8 In one embodiment, a light exit hole is provided at the center of the second metal film. The shape of the light exit hole can be circular or square, etc., and this application does not impose any specific restrictions. In this embodiment, the laser output direction is from the substrate side.

[0060] Figure 9 A schematic structural diagram of a surface emitting laser provided in another embodiment of the present application is shown. Figure 10 A top view of a surface emitting laser provided in accordance with an embodiment of the present application. Figure 9 and Figure 10In another embodiment, a light exit hole is provided at the center of the first metal film. The shape of the light exit hole can be circular or square, etc., and this application does not impose any specific restrictions. In this embodiment, the direction in which the laser outputs the laser is from the epitaxial side. In this embodiment, a transparent conductive layer 9 can be provided at the corresponding position of the p-doped contact layer 5 and the light exit hole. The transparent conductive layer 9 can allow current to pass through, so that it can be better injected into the device, and will not block the light output of the device.

[0061] In one embodiment, the depth d of the hole 201, along a direction perpendicular to the substrate 10, satisfies the following: 50 nm ≤ d ≤ 500 nm. By precisely adjusting the hole structure's depth and optimizing its optical field confinement factor and mode loss, single-mode operation conditions can be better met for the laser under different epitaxial layer configurations.

[0062] Figure 11 for Figure 5 The A-A' cross-sectional view is as follows: Figure 11 As shown, in one embodiment, along the direction perpendicular to the substrate 10, that is, the depth direction of the hole 201. The cross-sectional shape of the hole 201 can be rectangular, conical (not shown in the figure), trapezoidal (not shown in the figure) or teardrop-shaped (not shown in the figure), preferably rectangular.

[0063] The cross section of the hole 201 parallel to the substrate 10 is described in detail below:

[0064] Please continue to refer to Figure 5 In one embodiment, the cross section includes a first portion 2011 and a second portion 2012 connected to each other, with the area of ​​the first portion 2011 being greater than the area of ​​the second portion 2012. Along a direction perpendicular to a third direction Z, the length L1 of the first portion 2011 and the length L2 of the second portion 2012 are defined; along the third direction Z, the widths H1 and H2 of the first portion 2011 and the second portion 2012 are defined. The following conditions are satisfied: 0.35a ≤ L1 ≤ 1.1a, 0.1a ≤ H1 ≤ 0.65a, 0.05a ≤ L2 ≤ 0.35a, and 0.05a ≤ H2 ≤ 0.35a, where a is the lattice constant. The value of L1 can be, for example, 0.35a, 0.4a, 0.5a, 0.7a, 1.0a, or 1.1a, but is not limited to these values. The value of H1 can be, for example, 0.1a, 0.2a, 0.4a, 0.5a, 0.6a, 0.65a, but is not limited to these values. The value of L2 can be, for example, 0.05a, 0.1a, 0.15a, 0.2a, 0.3a, 0.35a, but is not limited to these values. The value of H2 can be, for example, 0.05a, 0.1a, 0.15a, 0.2a, 0.3a, 0.35a, but is not limited to these values.

[0065] Figure 12A threshold gain diagram of a surface emitting laser provided in one embodiment of the present application is provided. Figure 13 A vertical radiation constant diagram of a surface emitting laser provided in an embodiment of the present application. Figure 5 、 Figure 12 and Figure 13 In a further embodiment, the first portion 2011 is specifically an ellipse, and the second portion 2012 is specifically a rectangle. The length L1 of the first portion 2011, the width H1 of the first portion 2011, the length L2 of the second portion 2012, and the width H2 of the second portion 2012 satisfy the following conditions: 0.55a≤L1≤0.85a, 0.2a≤H1≤0.5a, 0.1a≤L2≤0.35a, and 0.1a≤H2≤0.35a. Specifically, the width H1 of the ellipse is set to 0.39a, and the length L2 of the rectangle is set to 0.18a. Of the two structural parameters (H2 and L1) used as variables, the mode threshold gain difference of the laser is mainly affected by the width H2 of the rectangle, while its vertical radiation constant is more affected by the length L1 of the ellipse. When the length L1 of the ellipse is 0.7a and the width H2 of the rectangle is 0.2a, the mode threshold gain difference of the laser reaches a maximum value of 33cm. -1 . And its vertical radiation constant is moderate, about 20cm -1 . In addition, it can be found that within a larger adjustment range, the mode threshold gain difference of the laser can maintain a large value, thereby supporting high-power single-mode operation of the device. The value of L1 can also be 0.55a, 0.6a, 0.65a, 0.75a, 0.8a, 0.85a, but not limited to these values. The value of H1 can also be 0.2a, 0.25a, ​​0.3a, 0.35a, 0.4a, 0.45a, 0.5a, but not limited to these values. The value of L2 can also be 0.1a, 0.15a, 0.2a, 0.25a, ​​0.3a, 0.35a, but not limited to these values. The value of H2 can also be 0.1a, 0.15a, 0.25a, ​​0.3a, 0.35a, but not limited to these values.

[0066] Figure 14 A resonant mode distribution diagram of a surface emitting laser provided in one embodiment of the present application is shown. Figure 15 The far-field diagram corresponding to the fundamental mode of the surface-emitting laser provided in one embodiment of the present application is: Figure 16 The near-field diagram corresponding to the fundamental mode of the surface emitting laser provided in one embodiment of the present application is shown in FIG. Figures 14 to 16 As shown, for the structure of the above embodiment, the corresponding resonant mode distribution and the far-field and near-field patterns corresponding to the fundamental mode are calculated. Figure 14The circle pointed by the arrow in the figure is the fundamental mode. The fundamental mode is the lowest order mode transmitted in the waveguide structure, and has unique light field distribution and transmission characteristics. In semiconductor lasers, the fundamental mode is usually manifested as a single light spot in the energy distribution on the cross section, while the higher order mode has multiple light spots on the cross section. In addition to the fundamental mode, there are also higher order modes in semiconductor lasers. The energy distribution of the higher order mode on the cross section will have multiple light spots. Figure 14 As shown in the figure, there is a large difference in threshold gain between the fundamental mode with the lowest threshold gain (the circle pointed by the arrow in the left column) and other modes (such as the high-order modes in the middle column and the high-order modes in the right column). This structure can achieve a laser far-field divergence angle much smaller than 1° ( Figure 15 As shown), and has a Gaussian distribution of the intracavity electromagnetic field intensity ( Figure 16 shown).

[0067] Figure 17 FIG. 1 is a diagram showing the distribution of the resonant modes of the laser in the relevant embodiment. Figure 3 、 Figure 14 and Figure 17 , as a comparative example, Figure 3 A photonic crystal structure with an isosceles triangle hole cross section in the related art is shown. As can be seen, Figure 14 As shown, the difference in mode threshold gain of the comparative example under the same resonant cavity size is much smaller than the difference in mode threshold gain of the embodiment of the present application.

[0068] Figure 18 A cross-sectional view of an epitaxial structure parallel to the substrate is provided for another embodiment of the present application, such as Figure 18 As shown, in another embodiment, the first portion 2011 is a diamond shape, and the second portion 2012 is a rectangle. The length L1 of the first portion 2011, the width H1 of the first portion 2011, the length L2 of the second portion 2012, and the width H2 of the second portion 2012 satisfy the following: 0.7a≤L1≤1.1a, 0.3a≤H1≤0.65a, 0.1a≤L2≤0.35a, and 0.05a≤H2≤0.3a. The value of L1 can be, for example, 0.7a, 0.8a, 0.9a, 1.0a, or 1.1a, but are not limited to these values. The value of H1 can be, for example, 0.3a, 0.35a, 0.4a, 0.5a, 0.6a, or 0.65a, but are not limited to these values. The value of L2 can be, for example, 0.1a, 0.2a, 0.3a, or 0.35a, but are not limited to these values. The value of H2 may be, for example, 0.05a, 0.1a, 0.2a, or 0.3a, but is not limited to these values.

[0069] Figure 19 A cross-sectional view of an epitaxial structure parallel to the substrate is provided for another embodiment of the present application, such as Figure 19As shown, in another embodiment, the first portion 2011 is rectangular, and the second portion 2012 is also rectangular. The length L1 of the first portion 2011, the width H1 of the first portion 2011, the length L2 of the second portion 2012, and the width H2 of the second portion 2012 satisfy the following: 0.5a≤L1≤0.8a, 0.1a≤H1≤0.4a, 0.1a≤L2≤0.35a, and 0.1a≤H2≤0.35a. The value of L1 can be, for example, 0.5a, 0.6a, 0.7a, or 0.8a, but is not limited to these values. The value of H1 can be, for example, 0.1a, 0.2a, 0.3a, or 0.4a, but is not limited to these values. The value of L2 can be, for example, 0.1a, 0.2a, 0.3a, or 0.35a, but is not limited to these values. The value of H2 may be, for example, 0.1a, 0.2a, 0.3a, or 0.35a, but is not limited to these values.

[0070] Figure 20 A cross-sectional view of an epitaxial structure parallel to the substrate is provided for another embodiment of the present application, such as Figure 20 As shown, in another embodiment, the first portion 2011 is generally elliptical, including oppositely disposed long sides and oppositely disposed curved edges, the curved edges curving inward, similar to a runway shape. The radian of the curved edges is 0 rad to 2 rad. The second portion 2012 is rectangular, and the length L1 of the first portion 2011, the width H1 of the first portion 2011, the length L2 of the second portion 2012, and the width H2 of the second portion 2012 satisfy the following conditions: 0.35a ≤ L1 ≤ 0.85a, 0.15a ≤ H1 ≤ 0.4a, 0.1a ≤ L2 ≤ 0.35a, and 0.1a ≤ H2 ≤ 0.35a. The value of L1 can be, for example, 0.35a, 0.4a, 0.5a, 0.6a, 0.7a, 0.8a, or 0.85a, but is not limited to these values. The value of H1 can be, for example, 0.15a, 0.2a, 0.3a, 0.4a, but is not limited to these values. The value of L2 can be, for example, 0.1a, 0.2a, 0.3a, 0.35a, but is not limited to these values. The value of H2 can be, for example, 0.1a, 0.2a, 0.3a, 0.35a, but is not limited to these values.

[0071] Figure 21 A cross-sectional view of an epitaxial structure parallel to the substrate is provided for another embodiment of the present application, such as Figure 21 As shown, in another embodiment, the first portion 2011 can also be a semicircle, and the second portion 2012 can also be a rectangle. Or in other embodiments, the T-shaped pattern can also be composed of other graphics, which is not specifically limited in this application.

[0072] In one embodiment, the right angles, acute angles, or obtuse angles in the hole 201 and the filler 202 are all chamfered to meet processing requirements.

[0073] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A surface emitting laser, characterized in that: The invention comprises a stacked substrate and an epitaxial structure, wherein the epitaxial structure has a plurality of holes, each hole has a roughly T-shaped cross section parallel to the substrate, and a filler is provided in the hole, and the refractive index of the filler is different from that of the epitaxial structure.

2. The surface emitting laser according to claim 1, wherein The epitaxial structure includes a photonic crystal layer and a p-doped cladding layer which are stacked, and the hole is located in the photonic crystal layer.

3. The surface emitting laser according to claim 2, wherein Each of the holes extends at least partially into the p-doped cladding layer.

4. The surface emitting laser according to claim 2, wherein The photonic crystal layer includes a plurality of unit cells arranged in a lattice, the unit cells are periodically repeated along a first direction and a second direction, each of the unit cells includes a hole, and the cross-section of each hole is symmetrical along a third direction. The first direction, the second direction, and the third direction are all parallel to the substrate, the first direction is perpendicular to the second direction, and the third direction forms an angle of 45° with the first direction and the second direction, respectively.

5. The surface emitting laser according to claim 1, wherein Along a direction perpendicular to the substrate, the depth d of the hole satisfies: 50 nm ≤ d ≤ 500 nm.

6. The surface emitting laser according to claim 4, wherein The cross section of the hole includes a first portion and a second portion connected to each other, and the area of ​​the first portion is larger than the area of ​​the second portion; The length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.35a≤L1≤1.1a, 0.1a≤H1≤0.65a, 0.05a≤L2≤0.35a, 0.05a≤H2≤0.35a, where a is the lattice constant.

7. The surface emitting laser according to claim 6, wherein The first part is elliptical, the second part is rectangular, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.55a≤L1≤0.85a, 0.2a≤H1≤0.5a, 0.1a≤L2≤0.35a, 0.1a≤H2≤0.35a.

8. The surface emitting laser according to claim 6, wherein The first part is a rhombus, the second part is a rectangle, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.7a≤L1≤1.1a, 0.3a≤H1≤0.65a, 0.1a≤L2≤0.35a, and 0.05a≤H2≤0.3a.

9. The surface emitting laser according to claim 6, wherein The first part is a rectangle, the second part is also a rectangle, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.5a≤L1≤0.8a, 0.1a≤H1≤0.4a, 0.1a≤L2≤0.35a, 0.1a≤H2≤0.35a.

10. The surface emitting laser according to claim 6, wherein The first part is roughly an ellipse, including relatively long sides and relatively arcuate edges, the arcuate edges are bent inward, and the curvature of the arcuate edges is 0rad~2rad. The second part is a rectangle, and the length L1 of the first part, the width H1 of the first part, the length L2 of the second part, and the width H2 of the second part satisfy: 0.35a≤L1≤0.85a, 0.15a≤H1≤0.4a, 0.1a≤L2≤0.35a, 0.1a≤H2≤0.35a.

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