Vertical-cavity surface-emitting laser and vertical-cavity surface-emitting laser chip

Abstract

This application discloses a vertical-cavity surface-emitting laser (VCSEL) and a VCSEL chip. The VCSEL includes: a first distributed Bragg reflector region, an active region, and a second distributed Bragg reflector region. The active region includes at least one active sub-region. Each active sub-region includes a quantum well and a corresponding light-emitting aperture layer. A space layer is disposed between the quantum well and the light-emitting aperture layer. The thickness of the space layer is set to be between 100 nm and 1000 nm.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to a vertical cavity surface-emitting laser and a vertical cavity surface-emitting laser chip. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in many fields, such as 3D sensing, LiDAR, and optical communication, due to their advantages of miniaturization, high efficiency, and ease of integration. However, traditional single-junction or multi-junction VCSELs often have a large divergence angle due to their structural characteristics. Specifically, the divergence angle of traditional VCSELs is typically about 20° to 30°. For LiDAR systems that require high resolution and long-range detection, this large divergence angle leads to energy dispersion, reduces the signal-to-noise ratio, and affects the overall performance of the system.

[0003] To reduce the divergence angle of VCSELs, existing technologies typically employ methods such as extending the length of the laser resonator to reduce the effective refractive index difference inside and outside the emission aperture, thereby suppressing the generation of higher-order modes. Higher-order modes typically have larger divergence angles; suppressing these modes retains only lower-order modes, resulting in a smaller divergence angle. Existing technologies usually extend the length of the laser resonator by incorporating a storage layer or an extension layer within the VCSEL structure.

[0004] While the methods described above can reduce the divergence angle to some extent, they also introduce new challenges, such as increased manufacturing complexity and cost. Therefore, effectively reducing the divergence angle of VCSELs without significantly increasing manufacturing difficulty and cost remains a pressing technical problem to be solved. Utility Model Content

[0005] This application provides a vertical cavity surface-emitting laser and its chip. By optimizing the thickness and refractive index of the space layer and precisely controlling the relative position of the active region and the standing wave field, the divergence angle of the laser is effectively reduced while maintaining high efficiency, thus solving the problem of large divergence angle in traditional VCSELs.

[0006] The first aspect of this application discloses a vertical cavity surface-emitting laser, comprising: a first distributed Bragg reflector region, an active region, and a second distributed Bragg reflector region. The active region includes at least one active sub-region, each active sub-region including a quantum well and a corresponding light-emitting aperture layer. A space layer is disposed between the quantum well and the light-emitting aperture layer, wherein the thickness of the space layer is set to be between 100 nm and 1000 nm.

[0007] According to the vertical cavity surface-emitting laser of this application, by adjusting the thickness of the space layer, the distribution of electric field intensity in the cavity can be effectively controlled, thereby changing the light confinement factor of the light-emitting aperture layer and the effective refractive index difference inside and outside the light-emitting aperture, thus reducing the divergence angle of the VCSEL.

[0008] In the vertical cavity surface-emitting laser disclosed in this application, the thickness of the spatial layer is preferably set to be between 200 nm and 1000 nm.

[0009] According to the vertical cavity surface-emitting laser of this application, by setting the thickness of the space layer in the range of 200nm to 1000nm, the electric field intensity distribution can be optimized more effectively, and the divergence angle can be further reduced.

[0010] In the vertical cavity surface-emitting laser disclosed in this application, the refractive index of the spatial layer is set to between 3 and 3.5.

[0011] In the vertical-cavity surface-emitting laser disclosed in this application, the refractive index of the spatial layer is greater than the refractive index of the low-refractive-index layer in the distributed Bragg reflector, and the refractive index of the spatial layer is less than the refractive index of the high-refractive-index layer in the distributed Bragg reflector.

[0012] In the vertical-cavity surface-emitting laser disclosed in this application, the refractive index of the space layer is greater than the refractive index of the light-emitting aperture layer, and the refractive index of the space layer is less than the refractive index of the quantum well.

[0013] According to the vertical cavity surface-emitting laser of this application, the refractive index of the space layer is set such that the electric field intensity is increased when moving from a high refractive index medium to a low refractive index medium, and the thickness of the space layer is set to be thicker, thereby increasing the integral value of the electric field intensity of the entire optical field. This can change the light confinement factor of the emission aperture layer and the effective refractive index difference inside and outside the emission aperture, thereby reducing the divergence angle of the VCSEL.

[0014] In the vertical cavity surface-emitting laser disclosed in this application, two adjacent active sub-regions are connected by a tunnel junction.

[0015] According to the vertical cavity surface-emitting laser of this application, a multi-junction VCSEL structure can be realized by connecting adjacent active sub-regions through a tunnel junction, thereby improving the output power of the laser.

[0016] In the vertical-cavity surface-emitting laser disclosed in this application, the vertical-cavity surface-emitting laser forms a standing-wave optical field between a first distributed Bragg reflection region and a second distributed Bragg reflection region. The optical path distance between the thickness center of the quantum well and the antinode of the standing-wave optical field is less than one-tenth of the laser wavelength. Preferably, the thickness center of the quantum well is located at the antinode of the standing-wave optical field. Furthermore, the optical path distance between the thickness center of the light-emitting aperture layer and the node of the standing-wave optical field is less than one-tenth of the laser wavelength. Preferably, the thickness center of the light-emitting aperture layer is located at the node of the standing-wave optical field.

[0017] In the vertical-cavity surface-emitting laser disclosed in this application, the vertical-cavity surface-emitting laser forms a standing-wave optical field between the first distributed Bragg reflection region and the second distributed Bragg reflection region. The optical path distance between the thickness center position of the tunnel junction and the node position of the standing-wave optical field is less than one-tenth of the laser wavelength. Preferably, the thickness center position of the tunnel junction is located at the node position of the standing-wave optical field.

[0018] According to the vertical cavity surface-emitting laser of this application, by reasonably setting the thickness of the spatial layer, the quantum well is placed at the antinode of the standing wave optical field, and the light-emitting aperture layer and tunnel junction are placed at the node of the standing wave optical field, thereby reducing the divergence angle and improving the luminous efficiency of the laser.

[0019] In the vertical-cavity surface-emitting laser disclosed in this application, the laser wavelength of the vertical-cavity surface-emitting laser is 350 to 530 nm, or 500 to 1000 nm, or 1000 to 1600 nm.

[0020] The vertical cavity surface-emitting laser of this application reduces the divergence angle by adjusting the thickness of the space layer, and can also utilize different semiconductor materials to fabricate quantum wells, enabling the laser to emit lasers of different wavelengths, suitable for different application needs.

[0021] A second aspect of this application discloses a vertical-cavity surface-emitting laser chip, comprising at least one laser array, the laser array comprising a plurality of the aforementioned vertical-cavity surface-emitting lasers.

[0022] Compared with existing technologies, this application effectively reduces the divergence angle of VCSELs by optimizing the thickness and refractive index of the space layer without adding additional layers and processes. Furthermore, by optimizing the thickness of the space layer, the relative positions of the quantum well, the light-emitting aperture layer, and the tunnel junction with the standing wave light field can be precisely controlled, while maintaining high luminous efficiency. It does not require the growth of additional complex structures, has a simple manufacturing process, low cost, and is applicable to a variety of wavelength ranges, making it widely applicable. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the resonant cavity structure of a vertical cavity surface-emitting laser according to one embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the resonant cavity structure of a vertical cavity surface-emitting laser according to another embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the refractive index and electric field intensity within the resonant cavity of the vertical cavity surface-emitting laser involved in this application. Detailed Implementation

[0026] The present application will be further described below with reference to specific embodiments and accompanying drawings. It is to be understood that the illustrative embodiments of this disclosure are merely for explaining the present application and not for limiting it. Furthermore, for ease of description, the accompanying drawings show only the parts relevant to the present application, and not all of the structures or processes.

[0027] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0028] Unless the context otherwise specifies, the terms “contains,” “has,” and “includes” are synonyms. The phrase “A / B” means “A or B.” The phrase “A and / or B” means “(A and B) or (A or B).”

[0029] It should be understood that although terms such as "first," "second," etc., may be used herein to describe various components, units, or data, these components, units, or data should not be limited by these terms. These terms are used merely to distinguish one feature from another. For example, without departing from the scope of the exemplary embodiments, a first feature may be referred to as a second feature, and similarly, a second feature may be referred to as a first feature.

[0030] It should be understood that although directional terms such as "up," "down," "left," and "right" may be used here to describe the positional relationship between the various components, these directional terms are only for the convenience of understanding and are not intended to limit the scope of protection of this application.

[0031] It should be noted that in this specification, similar reference numerals and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of the resonant cavity structure of a vertical-cavity surface-emitting laser according to one embodiment of this application. Figure 1 As shown, the vertical-cavity surface-emitting laser involved in this application includes: a first distributed Bragg reflector 1, an active region 2, and a second distributed Bragg reflector 3. In this embodiment, the active region 2 includes only one active sub-region, which includes a quantum well 4 and a corresponding light-emitting aperture layer (also referred to as an oxide layer or a current-confining layer) 5, and a space layer 6 is disposed between the quantum well 4 and the light-emitting aperture layer 5. Figure 2 This is a schematic diagram of the resonant cavity of a vertical cavity surface-emitting laser according to another embodiment of this application. Figure 2 In the embodiment shown, the active region 2 includes three active sub-regions 21, and the structure of each active sub-region 21 is the same as that of the active region 21. Figure 1 Each active sub-region is identical, and adjacent active sub-regions are connected by tunnel junctions 8.

[0034] It should be pointed out that, Figure 1 and Figure 2 The structure of the VCSEL resonant cavity is only schematically shown; that is, only a portion of the VCSEL structure is shown, excluding components such as the substrate, electrodes, and external packaging. It should also be noted that... Figure 1 and Figure 2 The thicknesses of the layers shown are for illustrative purposes only, and the thickness ratios in the figures do not represent the actual thickness ratios between the layers.

[0035] Here, we take the most common 850nm VCSEL as an example for explanation. VCSELs are generally fabricated by epitaxially growing functional layers on a semiconductor substrate, which is usually a GaAs (gallium arsenide) substrate. The first distributed Bragg reflector region 1 is an N-type distributed Bragg reflector region, composed of multiple layers of N-type doped AlGaAs (aluminum gallium arsenide) material with alternating high and low refractive indices. The refractive index of each layer is determined by the Al content; the higher the Al content, the lower the refractive index of the AlGaAs material layer, and vice versa. Typically, the refractive index of the high-refractive-index AlGaAs material layer in the distributed Bragg reflector region is set to around 3.5, and the refractive index of the low-refractive-index AlGaAs material layer is set to around 3. The second distributed Bragg reflector region 3 is a P-type distributed Bragg reflector region, composed of multiple layers of P-type doped AlGaAs material with periodically varying refractive indices.

[0036] The active region 2 of the VCSEL is the core region in the laser that generates optical gain. In this region, electrical energy is converted into optical energy to achieve laser radiation. Each active sub-region 21 within the active region 2 has a quantum well 4, which consists of alternating quantum well layers and barrier layers. The quantum well layers have a small band gap, while the barrier layers have a large band gap. This structure forms a potential well, which can effectively confine electrons and holes, improve radiative recombination efficiency, and thus enhance optical gain. The quantum well layer material is typically GaAs, while the barrier layer material can be AlGaAs (aluminum gallium arsenide) or GaAsP (gallium arsenide phosphide).

[0037] The light-emitting hole layer 5 is a key structure in VCSELs that defines the laser emission region. Located near the quantum well 4, its core function is to control the carrier injection region and optical field distribution through current confinement and optical confinement. The most common fabrication method for the light-emitting hole layer 5 is oxidation: first, a high-alumina-content (>90%) AlGaAs layer is epitaxially grown, then selectively wet-oxidized to transform the edge region into insulating alumina, preventing current and laser transmission. The unoxidized central region remains conductive, forming a current channel and allowing laser transmission, thus forming the light-emitting hole 51. The light-emitting hole 51 in the middle of the light-emitting hole layer 5 has a different refractive index between AlGaAs and the outer alumina, resulting in a difference in effective refractive index between the inside and outside of the VCSEL light-emitting hole 51. In VCSELs, this difference in effective refractive index is a key factor affecting the divergence angle. The effective refractive index difference inside and outside the emission aperture in the emission aperture layer 5 is positively correlated with the optical confinement factor of the emission aperture layer. The smaller the optical confinement factor, the smaller the effective refractive index difference inside and outside the emission aperture, which can suppress the generation of higher-order modes of the VCSEL and limit the divergence angle of the VCSEL. The magnitude of the optical confinement factor of the emission aperture layer is inversely correlated with the integral value of the electric field intensity of the entire optical field. Therefore, by increasing the electric field intensity in the active region, the integral value of the electric field intensity of the entire optical field can be increased, thereby reducing the optical confinement factor of the emission aperture layer and thus limiting the divergence angle of the VCSEL.

[0038] In this application, a space layer 6 is disposed between the quantum well 4 and the light-emitting aperture layer 5. The thickness of the space layer 6 is set between 100 nm and 1000 nm, preferably between 200 nm and 1000 nm. The material of the space layer 6 is AlGaAs, and its refractive index is set between 3 and 3.5. That is, the refractive index of the AlGaAs space layer 6 is greater than the refractive index of the low refractive index layer in the distributed Bragg reflector (around 3), and the refractive index of the AlGaAs space layer 6 is less than the refractive index of the high refractive index layer in the distributed Bragg reflector (around 3.5). The refractive index of the quantum well 4 is around 3.6. When the electric field enters the low refractive index (relative to the refractive index of the quantum well 4) AlGaAs space layer 6 from the high refractive index quantum well 4, the electric field strength becomes stronger. Furthermore, by increasing the thickness of the space layer 6, the electric field strength in the active region is increased, and the light confinement factor of the light-emitting aperture layer is reduced, thereby limiting the divergence angle of the VCSEL.

[0039] Figure 3 This is a schematic diagram showing the refractive index and electric field intensity within the resonant cavity of the vertical-cavity surface-emitting laser (VCSEL) involved in this application. Figure 3As shown, a standing wave optical field is formed between the first and second distributed Bragg reflection regions. The thickness of the spatial layer 6 is approximately 200 nm. By increasing the thickness of the spatial layer 6, the electric field intensity within the active region is enhanced, thereby reducing the light confinement factor of the emission aperture layer and limiting the divergence angle of the VCSEL. The refractive index of the spatial layer 6 is greater than that of the emission aperture layer 5, and less than that of the quantum well 4.

[0040] The thicknesses of the quantum well 4, the light-emitting aperture layer 5, and the tunnel junction 8 are typically between a few nanometers and tens of nanometers. To improve the luminous efficiency of the VCSEL, the quantum well 4 needs to be positioned at the antinode of the standing wave optical field, and the light-emitting aperture layer and the tunnel junction need to be positioned at the node of the standing wave optical field. Figure 1-3 As shown, the active region 2 of the VCSEL also includes other filling layers 7. The material of the other filling layers 7 can be AlGaAs. In this application, by reasonably setting the thickness of the space layer 6 and the other filling layers 7, the optical path distance between the thickness center position of the quantum well 4 and the antinode position of the standing wave field is less than one-tenth of the laser wavelength. Preferably, the thickness center position of the quantum well 4 is located at the antinode position of the standing wave field. Furthermore, the optical path distance between the thickness center position of the light-emitting aperture layer 5 and the node position of the standing wave field is less than one-tenth of the laser wavelength. Preferably, the thickness center position of the light-emitting aperture layer 5 is located at the node position of the standing wave field. Moreover, the optical path distance between the thickness center position of the tunnel junction 8 and the node position of the standing wave field is less than one-tenth of the laser wavelength. Preferably, the thickness center position of the tunnel junction 8 is located at the node position of the standing wave field.

[0041] In this application, by optimizing the thickness and refractive index of the space layer between the high-refractive-index quantum well and the low-refractive-index light-emitting aperture layer, and utilizing the characteristic that the electric field intensity increases when the electric field enters the low-refractive-index medium from the high-refractive-index medium, compared with the case where the thickness of the filling layer is less than 100 nm in the conventional technology, the thickness of the space layer is increased to between 100 nm and 1000 nm, preferably between 200 nm and 1000 nm. This effectively increases the electric field intensity in the active region, increases the integral value of the electric field intensity of the entire optical field, and thus reduces the light confinement factor of the light-emitting aperture layer. Therefore, without adding additional layers and processes, the divergence angle of the VCSEL is effectively reduced. For example, the divergence angle of the conventional VCSEL can be reduced from 20° to 30° to 15° to 18°. Furthermore, by optimizing the thickness of the space layer and other filling layers, the relative positions of the quantum well, the light-emitting hole layer, and the tunnel junction with the standing wave light field can be precisely controlled, while maintaining high luminous efficiency. No additional complex structures need to be grown, the manufacturing process is simple and low-cost, and it is applicable to a variety of wavelengths, making it widely applicable.

[0042] In the embodiments described above, the first distributed Bragg reflection zone 1 is an N-type distributed Bragg reflection zone and the second distributed Bragg reflection zone 3 is a P-type distributed Bragg reflection zone. However, this application is not limited to this. The first distributed Bragg reflection zone 1 can also be a P-type distributed Bragg reflection zone, and correspondingly, the second distributed Bragg reflection zone 3 can be an N-type distributed Bragg reflection zone.

[0043] In addition, different materials can be used to prepare VCSELs with different laser wavelengths in this application. Laser wavelengths in the 350-530nm range (blue-violet band) mainly correspond to GaN (gallium nitride) based material systems. Laser wavelengths in the 500-1000nm range (red-near-infrared band) mainly correspond to GaAs (gallium arsenide) based material systems. Laser wavelengths in the 1000-1600nm range (near-infrared-communication band) mainly correspond to InP (indium phosphide) based material systems.

[0044] This application also provides a vertical-cavity surface-emitting laser (VCSEL) chip with an integrated design, comprising at least one VCSEL array, each VCSEL array consisting of multiple VCSELs of the aforementioned optimized design. The array can be arranged in a regular pattern (such as a square, hexagonal grid, or triangle), randomly, or divided into multiple independently addressable subarrays to meet the needs of different application scenarios, such as lidar, 3D sensing, and optical communication systems.

[0045] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Where there is no conflict, the embodiments and features described in the embodiments of this application can be combined with each other. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, include: The system comprises a first distributed Bragg reflector region, an active region, and a second distributed Bragg reflector region. The active region includes at least one active sub-region, each active sub-region including a quantum well and a corresponding light-emitting aperture layer. A space layer is disposed between the quantum well and the light-emitting aperture layer, wherein the thickness of the space layer is set to be between 100 nm and 1000 nm.

2. The vertical cavity surface emitting laser according to claim 1, characterized in that The thickness of the space layer is set to be between 200 nm and 1000 nm.

3. The vertical cavity surface emitting laser of claim 1, wherein, The refractive index of the space layer is set to be between 3 and 3.

5.

4. The vertical cavity surface emitting laser of claim 1, wherein, The refractive index of the space layer is greater than that of the low-refractive-index layer in the distributed Bragg reflection zone, and the refractive index of the space layer is less than that of the high-refractive-index layer in the distributed Bragg reflection zone.

5. The vertical cavity surface emitting laser of claim 1, wherein, The refractive index of the space layer is greater than that of the light-emitting hole layer, and the refractive index of the space layer is less than that of the quantum well.

6. The vertical cavity surface emitting laser of claim 1, wherein, The two adjacent active sub-regions are connected by a tunnel junction.

7. The vertical cavity surface emitting laser of claim 1, wherein, The vertical-cavity surface-emitting laser forms a standing-wave optical field between the first distributed Bragg reflection region and the second distributed Bragg reflection region, wherein, The optical path distance between the center of the quantum well's thickness and the antinode of the standing wave field is less than one-tenth of the laser wavelength; and... The optical path distance between the center of the thickness of the light-emitting hole layer and the node position of the standing wave light field is less than one-tenth of the laser wavelength.

8. The vertical cavity surface emitting laser of claim 7, wherein, The thickness center of the quantum well is located at the antinode of the standing wave light field; and the thickness center of the light-emitting aperture layer is located at the node of the standing wave light field.

9. The vertical cavity surface emitting laser of claim 6, wherein, The vertical cavity surface-emitting laser forms a standing wave optical field between the first distributed Bragg reflection region and the second distributed Bragg reflection region, and the optical path distance between the thickness center of the tunnel junction and the node position of the standing wave optical field is less than one-tenth of the laser wavelength.

10. The vertical cavity surface emitting laser of claim 9, wherein, The thickness center of the tunnel junction is located at the node position of the standing wave optical field.

11. The vertical cavity surface emitting laser of claim 1, wherein, The laser wavelength of the vertical cavity surface-emitting laser is 350 to 530 nm, or 500 to 1000 nm, or 1000 to 1600 nm.

12. A vertical cavity surface emitting laser chip, characterized by It includes at least one laser array, the laser array comprising a plurality of vertical cavity surface-emitting lasers as described in any one of claims 1-11.

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