Multi-junction VCSEL device, VCSEL chip, laser radar and light source thereof

Abstract

The utility model discloses a multi-junction VCSEL device, a VCSEL chip, a laser radar and a light source thereof. The multi-junction VCSEL device comprises: a substrate; the bottom reflecting mirror structure and the top reflecting mirror structure are sequentially arranged on the substrate; the resonant cavity structure comprises at least two active areas and at least one photoelectric limiting layer, the photoelectric limiting layer is arranged on one side, far away from the substrate, of the active areas, the photoelectric limiting layer is located at the wave trough of the standing wave, and the photoelectric limiting layer is used for limiting a light emitting area of the multi-junction VCSEL device; the at least one optical regulation and control layer is arranged adjacent to the photoelectric limiting layer, the optical regulation and control layer is configured to divide a light field in the resonant cavity structure into at least two sections, and the intensity of each section of the light field is different; and at least two multi-quantum well structures are arranged between the bottom reflecting mirror structure and the nearest optical regulation and control layer. According to the invention, the limiting factor of the photoelectric limiting layer can be greatly reduced, and meanwhile, the limiting factor of the active layer cannot be reduced too much.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, and particularly relates to a multi-junction VCSEL device, a VCSEL chip, a lidar and a light source thereof. Background Art

[0002] Vertical cavity surface emitting laser (VCSEL) is a new type of semiconductor laser, which is characterized by low threshold current and easy two-dimensional integration, and is widely used in the fields of optical communication, optical interconnection and optical sensing. However, due to the use of multiple oxide layers in traditional multi-junction VCSELs and the relatively high confinement factor of the multiple oxide layers, the divergence angle is relatively large. For VCSELs, the low-order mode has a lower divergence angle, and the high-order mode has a larger divergence angle. Therefore, the method to reduce the divergence angle is to suppress the high-order mode and make the low-order mode the main excitation mode. In order to suppress the high-order mode, generally, the confinement factor of the oxide layer is reduced, and the refractive index contrast between the light-emitting region and the non-light-emitting region of the VCSEL is reduced. In the prior art, mainly by increasing the overall length to reduce the confinement factor of the oxide confinement layer, but this method will also cause a serious decrease in the confinement factor of the active layer, resulting in an increase in the threshold current. Summary of the Invention

[0003] In order to solve the technical problems of serious decrease in the confinement factor of the active layer and increase in the threshold current in the prior art, the present invention provides a multi-junction VCSEL device, a VCSEL chip, a lidar and a light source thereof. The specific technical solutions are as follows:

[0004] A multi-junction VCSEL device, comprising:

[0005] A substrate;

[0006] A bottom mirror structure and a top mirror structure sequentially disposed on the substrate; the bottom mirror structure and the top mirror structure define a resonant cavity structure for generating a standing wave;

[0007] The resonant cavity structure includes at least two active regions and at least one optical confinement layer. Each active region is provided with at least one multi-quantum well structure. The active regions are connected by tunnel junctions. The optical confinement layer is disposed on the side of the active region away from the substrate. The optical confinement layer is located at the trough of the standing wave. The optical confinement layer is used to define the light-emitting region of the multi-junction VCSEL device;

[0008] At least one optical modulation layer is disposed adjacent to the optical confinement layer. The optical modulation layer is configured to divide the light field in the resonant cavity structure into at least two segments, and the intensity of each segment of the light field is different;

[0009] There are at least two of the multi-quantum well structures between the bottom mirror structure and the nearest optical modulation layer.

[0010] In one embodiment, the optical modulation layer includes a photonic crystal structure, a single-layer structure, or a periodically stacked DBR structure.

[0011] In one embodiment, when the optical modulation layer is a periodically stacked DBR structure, the number of stacking periods thereof ranges from 1 pair to 10 pairs, and each pair is alternately composed of Al x Ga (1-x) As / Al y Ga (1-y) As, where 0 ≤ x < y ≤ 1.

[0012] In one embodiment, the optical modulation layer is disposed on the left side and / or the right side of the optoelectronic confinement layer.

[0013] In one embodiment, when the optical modulation layer is disposed on the right side of the optoelectronic confinement layer, a tunnel junction is further provided between the optical modulation layer and the optoelectronic confinement layer.

[0014] In one embodiment, when the optical modulation layer is disposed on the left side and the right side of the optoelectronic confinement layer, the specific selections of the optical modulation layers on both sides are the same or different.

[0015] In one embodiment, both of the optical modulation layers on both sides are periodically stacked DBR structures or both of the optical modulation layers on both sides are photonic crystal structures.

[0016] In one embodiment, when the specific selections of the optical modulation layers on both sides are different;

[0017] the optical modulation layer near the left side of the optoelectronic confinement layer is a photonic crystal structure, and the optical modulation layer near the left side of the optoelectronic confinement layer is a periodically stacked DBR structure; or

[0018] the optical modulation layer near the left side of the optoelectronic confinement layer is a periodically stacked DBR structure, and the optical modulation layer near the left side of the optoelectronic confinement layer is a photonic crystal structure.

[0019] In one embodiment, when the optical modulation layer is disposed on the left side and the right side of the optoelectronic confinement layer, the DBR stacking periods of the optical modulation layers on both sides are different.

[0020] In one embodiment, the DBR stacking period of the optical modulation layer on the left side of the optoelectronic confinement layer is more than that of the optical modulation layer on the right side of the optoelectronic confinement layer.

[0021] In one embodiment, the number of DBR stacking periods in the optical modulation layer on the left side of the optoelectronic confinement layer is less than that in the optical modulation layer on the right side of the optoelectronic confinement layer.

[0022] In one embodiment, there are three of the multiple quantum well structures between the bottom mirror structure and the nearest optical modulation layer.

[0023] In one embodiment, the optoelectronic confinement layer includes any one of an air column type optoelectronic confinement layer, an oxidation confinement type optoelectronic confinement layer, an ion implantation type optoelectronic confinement layer, and a tunnel junction type optoelectronic confinement layer.

[0024] In one embodiment, the oxidation confinement type optoelectronic confinement layer is AlGaAs with a high Al component grown epitaxially, and an insulating aluminum oxide film layer is formed in the oxidized outer region; wherein, an effective current injection light emitting region is formed in the non-oxidized region.

[0025] In one embodiment, the tunnel junction type optoelectronic confinement layer is composed of at least one high-doped N-type structure layer and at least one high-doped P-type structure layer.

[0026] In one embodiment, the materials of the N-type structure layer and the P-type structure layer are selected as Al x Ga 1-x As (x = 0 to 1), and the doping concentration is greater than 1e 18 cm -3 .

[0027] In one embodiment, the resonant cavity structure includes three active regions and two optoelectronic confinement layers; the three active regions are respectively denoted as the first active region, the second active region, and the third active region, and the two optoelectronic confinement layers are respectively denoted as the first optoelectronic confinement layer and the second optoelectronic confinement layer;

[0028] The first active region is located on one side of the bottom mirror structure, the first optoelectronic confinement layer is disposed between the first active region and the second active region, the second optoelectronic confinement layer is disposed between the second active region and the third active region, a tunnel junction is provided between the first optoelectronic confinement layer and the second active region, and a tunnel junction is provided between the second optoelectronic confinement layer and the third active region.

[0029] In one embodiment, the first active region includes three multiple quantum well structures, the second active region includes two multiple quantum wells, and the third active region includes two multiple quantum well structures; and the multiple quantum well structures within each active region are connected by tunnel junctions.

[0030] In one embodiment, the bottom mirror structure includes a plurality of mirrors with an optical thickness of a quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices;

[0031] The top mirror structure includes a plurality of mirrors with an optical thickness of a quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices.

[0032] Based on the same inventive concept, the present application further provides a flip-chip VCSEL chip, which includes a positive electrode, a negative electrode, and the multi-junction VCSEL device described above;

[0033] Wherein, the positive electrode and the negative electrode are respectively electrically connected to the bottom mirror structure and the top mirror structure of the multi-junction VCSEL device; or

[0034] The positive electrode and the negative electrode are respectively electrically connected to the top mirror structure and the bottom mirror structure of the multi-junction VCSEL device;

[0035] The positive electrode and the negative electrode are arranged on a side opposite to the light-emitting side of the flip-chip VCSEL chip.

[0036] Based on the same inventive concept, the present application further provides a VCSEL chip, which includes at least one laser array; the laser array includes a plurality of the multi-junction VCSEL devices described above; the laser array is a regularly arranged array, or a randomly arranged array, or an array with multiple addressable sub-arrays.

[0037] Based on the same inventive concept, the present application further provides a light source for a lidar system, which includes at least one of the multi-junction VCSEL devices or at least one of the flip-chip VCSEL chips or one of the VCSEL chips described above.

[0038] Based on the same inventive concept, the present application further provides a lidar, which includes a transmitting component and a receiving component, and the transmitting component uses the light source for the lidar system described above.

[0039] The present application has at least the following technical effects: By inserting at least one optical control layer within the resonant cavity structure, the light field within the resonant cavity structure is divided into at least two segments, and the light field intensities in different segments are different. Therefore, the electric field intensity is the highest between the bottom mirror structure and the nearest optical control layer. Moreover, since there are at least two multiple quantum well structures between the bottom mirror structure and the nearest optical control layer, it is equivalent to increasing the thickness of the active region in the Z-axis direction, such that the confinement factor within the active region after being divided by the optical control layer remains basically unchanged, ensuring that the reduction of the confinement factor within the active region is relatively small. Since the optoelectronic confinement layer is at the trough of the standing wave, that is, at the position where the electric field intensity is the lowest, its confinement factor will decrease due to the reduction of the electric field intensity. Additionally, due to the light field segmentation effect of the optical control layer, the light field intensity near the optical control layer is relatively low. Placing the optoelectronic confinement layer adjacent to the optical control layer can further reduce the light field intensity of the optoelectronic confinement layer, thereby achieving the suppression of high-order modes and attaining the effect of a low divergence angle. Furthermore, placing the optical control layer adjacent to the optoelectronic confinement layer can reduce the diffusion of current within the active region after passing through the optoelectronic confinement layer, thereby allowing for the realization of a lower threshold current and a higher luminous efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the following-described drawings are merely some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0041] Figure 1 Structural diagram of a multi-junction VCSEL device of the present invention;

[0042] Figure 2 Structural diagram of another multi-junction VCSEL device of the present invention;

[0043] Figure 3 Structural diagram of yet another multi-junction VCSEL device of the present invention;

[0044] Figure 4 Diagram of the electric field intensity and refractive index variation of a multi-junction VCSEL device of the present invention, where red represents the refractive index, blue represents the light field intensity, and the vertical axis represents the distance to the substrate;

[0045] Figure 5 Structural diagram of a multi-junction VCSEL device of the present invention.

[0046] Description of the reference numerals:

[0047] 1 - Substrate, 2 - Bottom mirror structure, 3 - First active region, 3A - First multiple quantum well structure, 3B - First tunnel junction, 3C - Second multiple quantum well structure, 3D - Second tunnel junction, 3E - Third multiple quantum well structure, 4 - First optical modulation layer, 5 - First optoelectronic confinement layer, 6 - Second active region, 6A - Third tunnel junction, 6B - Fourth multiple quantum well structure, 6C - Fourth tunnel junction, 6D - Fifth multiple quantum well structure, 7 - Second optoelectronic confinement layer, 8 - Third active region, 8A - Fifth tunnel junction, 8B - Sixth multiple quantum well structure, 8C - Sixth tunnel junction, 8D - Seventh multiple quantum well structure, 9 - Third optoelectronic confinement layer, 10 - Top mirror, 11 - Second optical modulation layer. Detailed implementation manners

[0048] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are presented to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0049] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or groups.

[0050] For the sake of simplicity of the drawings, only the parts related to the present invention are schematically shown in each drawing, and they do not represent their actual structures as products. Additionally, to make the drawings simple and easy to understand, in some drawings, for components with the same structure or function, only one of them is schematically drawn, or only one of them is labeled. In this article, "one" not only means "only this one" but also means "more than one" situation.

[0051] It should be further understood that the term "and / or" used in the specification and appended claims of the present application refers to any combination and all possible combinations of one or more of the related listed items, and includes these combinations.

[0052] In addition, in the description of the present application, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other embodiments can also be obtained.

[0054] Oxidation confinement layer: By oxidizing AlGaAs with a high aluminum component in the oxidation current confinement layer (where the component of Al is generally more than 97% or even 100%, that is, pure AlAs). This layer will generate alumina material in a high-temperature water vapor environment. By etching it into a columnar platform structure, insulating alumina is formed by lateral oxidation, and the unoxidized part is still conductive AlGaAs. Such a structure can confine the current to only pass through the middle conductive part. The opening position is called the oxidation hole, which is also the light-emitting hole of the laser. The refractive indices of AlGaAs in the middle of the oxidation hole and the alumina on the outside are different. This causes a difference in the effective refractive indices inside and outside the VCSEL light-emitting hole.

[0055] Its confinement factor follows:

[0056]

[0057] Where, n1 is the refractive index of the material with a high aluminum component (such as Al 0.98 Ga 0.02 As), n2 is the refractive index of alumina. Γox is the optical confinement factor of the oxidation layer, l is the thickness of the current confinement layer in the direction from the N pole to the P pole, and p is the thickness of the entire optical field in the axial direction from the N pole to the P pole.

[0058] In the prior art, generally, by extending the value of p, specifically, by setting an extended cavity to reduce the confinement factor. As can be seen from the foregoing formula, as the value of p increases, the denominator will obviously also increase. Therefore, by setting an extended cavity, the reduction of the confinement factor can be achieved. However, in this technical solution, it simultaneously reduces the electric field strength at positions other than the non-oxidized layer, which will cause an increase in the threshold current.

[0059] At the same time, as the electric field strength increases, the growth rate of the numerator is not as fast as that of the denominator. Therefore, as the electric field strength increases, the confinement factor will also decrease accordingly.

[0060] Such as Figure 1As shown in the figure, this embodiment provides a multi-junction VCSEL device, including: a substrate 1; a bottom mirror structure 2 and a top mirror 10 structure sequentially disposed on the substrate 1; the bottom mirror structure 2 and the top mirror 10 structure define a resonant cavity structure for generating a standing wave; that is, the region between the bottom mirror structure 2 and the top mirror 10 structure is the resonant cavity. The resonant cavity is used to generate a standing wave, which is a wave formed by the superposition of two coherent waves propagating in opposite directions along the same straight line. Specifically, when the phases of the two waves are the same, their amplitudes are added to form a wave belly (i.e., a wave peak). When the phases of the two waves are opposite, their amplitudes are subtracted to form a wave node (i.e., a wave valley). Therefore, the positions of the wave peaks and wave valleys of the standing wave are fixed.

[0061] Among them, the material of the substrate 1 includes but is not limited to GaAs, InP, Si, etc. The bottom mirror structure 2 and the top mirror 10 structure may include film layers with periodically varying refractive indices to achieve efficient reflection or transmission of light within a specific wavelength range. The film layers with periodically varying refractive indices can be composed of semiconductor materials, dielectric materials, metal-dielectric hybrid materials, etc. For example, the bottom mirror structure 2 can be an N-type semiconductor layer, and the top mirror 10 structure can be a P-type semiconductor layer. Another example is that the bottom mirror structure 2 can be a P-type semiconductor layer, and the top mirror 10 structure can be an N-type semiconductor layer. Optionally, the materials of the N-type semiconductor layer and the P-type semiconductor layer can be but are not limited to GaAs, AlGaAs, etc., which are not limited here as long as they can define the resonant cavity and belong to the protection scope of this embodiment.

[0062] Please refer to Figure 2 and Figure 3 simultaneously. The resonant cavity structure may include at least two active regions and at least one optical confinement layer. In this specific embodiment, the resonant cavity structure includes three active regions, namely the first active region 3, the second active region 6, and the third active region 8; the resonant cavity structure also includes three optical confinement layers, namely the first optical confinement layer 5, the second optical confinement layer 7, and the third optical confinement layer 9. Among them, between the first active region 3 and the second active region 6, and between the second active region 6 and the third active region 8 are connected by tunnel junctions respectively.

[0063] At least one multi-quantum well structure is provided in each active region. In this specific embodiment, 3 multi-quantum well structures are provided in the first active region 3, 2 multi-quantum well structures are provided in the second active region 6, and 2 multi-quantum well structures are provided in the third active region 8.

[0064] The optoelectronic confinement layer is disposed on the side of the corresponding active region away from the substrate 1. Specifically, the first optoelectronic confinement layer 5 is disposed on the side of the first active region 3 away from the substrate 1; the second optoelectronic confinement layer 7 is disposed on the side of the second active region 6 away from the substrate 1; the third optoelectronic confinement layer 9 is disposed on the side of the third active region 9 away from the substrate 1. And the first optoelectronic confinement layer 5, the second optoelectronic confinement layer 7 and the third optoelectronic confinement layer 9 are all located at the troughs of the standing wave.

[0065] At least one optical modulation layer is disposed adjacent to the optoelectronic confinement layer. The optical modulation layer is configured to divide the optical field in the resonant cavity structure into at least two segments, and the intensity of each segment of the optical field is different; it can be understood that when there is only one optical modulation layer, the optical field in the resonant cavity structure can be divided into two segments, and when there are two optical modulation layers, the optical field in the resonant cavity structure can be divided into three segments. There are at least two of the multiple quantum well structures (the first multiple quantum well structure 3A, the second multiple quantum well structure 3C, and the third multiple quantum well structure 3E) between the bottom mirror structure 2 and the nearest optical modulation layer 4.

[0066] In this embodiment, by inserting at least one optical modulation layer in the resonant cavity structure, the optical field in the resonant cavity structure is divided into at least two segments, and the intensity of the optical field in different segments is different. Therefore, the electric field intensity between the bottom mirror structure 2 and the nearest optical modulation layer is the highest. And since there are at least two multiple quantum well structures between the bottom mirror structure 2 and the nearest optical modulation layer, it is equivalent to increasing the thickness of the active region in the Z-axis direction, so that the confinement factor in the active region after being divided by the optical modulation layer hardly changes, ensuring that the reduction of the confinement factor in the active region is small; while the optoelectronic confinement layer is at the trough of the standing wave, that is, the position where the electric field intensity is the lowest. Therefore, its confinement factor will decrease due to the decrease of the electric field intensity, so as to realize the suppression of high-order modes and achieve the effect of low divergence angle. In addition, by disposing the optical modulation layer adjacent to the optoelectronic confinement layer, the diffusion of the current in the active region after passing through the optoelectronic confinement layer can be reduced, thereby allowing the realization of a lower threshold current and a higher luminous efficiency.

[0067] In one embodiment, the resonant cavity structure includes three active regions and three optical confinement layers. Among them, the three active regions include a first active region 3, a second active region 6, and a third active region 8 arranged in sequence along the direction away from the substrate, and the three optical confinement layers include a first optical confinement layer 5, a second optical confinement layer 7, and a third optical confinement layer 9. The first optical confinement layer 5 is located between the first active region 3 and the second active region 6, the second optical confinement layer 7 is located between the second active region 6 and the third active region 8, and the third optical confinement layer 9 is located on the side of the third active region 8 close to the top mirror 10 structure. Further, the first active region 3 includes three multi-quantum well structures, the second active region 6 includes two multi-quantum well structures, and the third active region 8 includes two multi-quantum well structures. Among them, adjacent multi-quantum well structures in each active region (such as Figure 1 , 2 , the first multi-quantum well structure 3A, the second multi-quantum well structure 3C, the third multi-quantum well structure 3E, the fourth multi-quantum well structure 6B, the fifth multi-quantum well structure 6D, the sixth multi-quantum well structure 8B, and the seventh multi-quantum well structure 8D among 3, 5) are connected by tunnel junctions (such as Figure 1 , 2 , the first tunnel junction 3B, the second tunnel junction 3D, the third tunnel junction 6A, the fourth tunnel junction 6C, and the fifth tunnel junction 8A among 3, 5).

[0068] In this specific embodiment, the number of active regions can be, for example, 2, 3, 4, etc. Figure 2 and Figure 3 shows three active regions in the multi-junction VCSEL device, namely the first active region 3, the second active region 6, and the third active region 8. The active region is used to generate stimulated emission photons, and the emitted photons are continuously reflected in the resonant cavity defined by the bottom mirror structure 2 and the top mirror 10 structure, and are continuously enhanced during the reflection process, so as to finally emit laser light at a specific wavelength and with sufficient energy. The multiple active regions in the multi-junction VCSEL device can emit light simultaneously, so that the light fields can be effectively superimposed between the multiple active regions, thereby optimizing the overall distribution of the light field.

[0069] Further, according to formula (1), taking the first active region 3 as an example, when the target film layer is the first active region 3 and there are at least two multi-quantum well structures in the first active region 3, the thickness of the multi-quantum well structures in the first segment of the light field in the z-axis direction is larger, so that the integral result of the numerator in the calculation formula (1) of the confinement factor will increase accordingly, ensuring a larger confinement factor in the active region, which in turn helps photons to obtain gain more fully, enabling the multi-junction VCSEL device to emit laser light at a lower injection current.

[0070] In Figure 2 and Figure 3In the illustrated embodiment, the active region may include only one multiple quantum well structure, or may include a composite structure composed of multiple multiple quantum well structures arranged in layers. The composite structure may be, but is not limited to, composed of GaAs and AlGaAs, InGaAs and GaAsP, or InGaAs and AlGaAs material layers arranged in a stack. The multiple quantum well structure is used to convert electrical energy into light energy to generate laser light.

[0071] The first active region 3 includes three multiple quantum well structures, namely the first multiple quantum well structure 3A, the second multiple quantum well structure 3C, and the third multiple quantum well structure 3E, which are not limited in this application. It can be understood that the multiple quantum well structure is the place where laser gain amplification occurs, and the central position of the multiple quantum well structure can be aligned with the position where the optical field is the strongest to achieve a greater amplification effect. Further, in the case where a segmented optical field includes multiple multiple quantum well structures, the confinement factors of the multiple quantum well structures in the same segment of the optical field are within the same preset range, that is, the confinement factors of each multiple quantum well structure are maintained at the same level, so that the contribution of each multiple quantum well structure to light emission is similar. It can be understood that similar light emission contributions mean that the current injection into each multiple quantum well structure is more uniform, which helps to reduce the threshold current of the multi-junction VCSEL device, thereby reducing the power consumption of the multi-junction VCSEL device and extending its service life. Moreover, when the contribution of each multiple quantum well structure to light emission is similar, the distribution of carriers in each multiple quantum well structure will be more uniform, which helps to reduce the recombination loss of carriers, thereby improving the overall light emission efficiency of the multi-junction VCSEL device.

[0072] The number of optical confinement layers is not greater than the number of active regions, and may be, for example, 2, 3, 4, etc. Figure 2 and Figure 3Three optical confinement layers in a multi-junction VCSEL device are shown, namely a first optical confinement layer 5, a second optical confinement layer 7, and a third optical confinement layer 9. The optical confinement layers are used to define the light-emitting region of the multi-junction VCSEL device. For ease of description, the first optical confinement layer 5 will be used as an example in the following specific embodiments. Specifically, the first optical confinement layer 5 is located on the side of the corresponding active region (i.e., the first active region 3) away from the substrate 1 to restrict the flow of current, so that the current only flows within the light-emitting region defined by the first optical confinement layer 5, thereby reducing unnecessary energy consumption, further reducing the threshold current, and increasing the current density. Moreover, the first optical confinement layer 5 can also confine the optical field within the light-emitting region defined by the first optical confinement layer 5, reducing light scattering and diffraction, thereby optimizing the divergence angle of the VCSEL and improving the beam quality. Continuing to refer to the calculation formula (1), when the target film layer is the first optical confinement layer 5, since the first optical confinement layer 5 is disposed at the trough of the standing wave, the electric field at the first optical confinement layer 5 is small, and the electric field strength is positively correlated with the optical field strength. Therefore, the integral result of the numerator in the calculation formula (1) of the confinement factor will decrease accordingly. Since the integral result of the denominator remains basically unchanged, the confinement factor of the first optical confinement layer 5 is small. In addition, the first optical confinement layer 5 is disposed after the first optical control layer 4. Therefore, the optical field strength of the optical confinement layer 5 is further reduced. In this way, the confinement factor can be further reduced, which helps to reduce the divergence angle of the multi-junction VCSEL device.

[0073] In one embodiment, the first optical confinement layer 5 may include any one of an air-column type optical confinement layer, an oxidation confinement type optical confinement layer, an ion implantation type optical confinement layer, and a tunnel junction type optical confinement layer. Among them, the air-column type optical confinement layer realizes the confinement of current and light through air columns. The air columns are hollow structures formed by dry etching technology, and their refractive index is lower than that of the surrounding semiconductor materials, thereby effectively confining the light within the central region. The ion implantation type optical confinement layer changes its electrical properties by implanting ions into the semiconductor material to form a high-resistance region, and the high-resistance region can restrict the flow of current, thereby indirectly restricting the light generation region.

[0074] In one embodiment, continue to refer to Figure 2, the oxidation-limited optical confinement layer includes an unoxidized region made of AlGaAs with a high aluminum composition and an oxidized region made of aluminum oxide. The oxidized region is located outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection. Among them, the semiconductor layer of the unoxidized region in the first optical confinement layer 5 can be understood as an opening, and the opening is used to define the light-emitting region of the multi-junction VCSEL device. When current enters, the current can only flow through the opening in the first optical confinement layer 5 to the active region, thereby realizing the confinement of the current injection path and the optical mode field. Further, through a selective oxidation process, the AlGaAs layer with a high aluminum composition can be converted into aluminum oxide to form the peripheral unoxidized region. Furthermore, the opening sizes of different optical confinement layers can be the same or different. In the case where the openings of multiple optical confinement layers are different, the light-emitting region defined by the optical confinement layer with the smallest opening is used as the light-emitting region of the multi-junction VCSEL device.

[0075] In one embodiment, the tunnel-junction optical confinement layer includes at least one highly doped N-type structural layer and at least one highly doped P-type structural layer. Specifically, a potential barrier is formed between the highly doped N-type structural layer and the highly doped P-type structural layer, and electrons are allowed to pass through the potential barrier through the tunnel effect, thereby realizing the lateral confinement of the current. In one embodiment, the materials of the N-type structural layer and the P-type structural layer are selected as Al x Ga 1-x As, and the doping concentrations of the N-type structural layer and the P-type structural layer are greater than 1e 18 cm-3, where 0 ≤ x ≤ 1.

[0076] In one embodiment, with reference to Figure 3 , the multi-junction VCSEL device further includes at least one tunnel junction. The tunnel junction is located between two adjacent active regions, such as between the first active region 3 and the second active region 6, such as the third tunnel junction layer 6A;

[0077] Furthermore, since each active region includes at least one multi-quantum well structure, in this specific embodiment, a tunnel junction is also provided between two adjacent multi-quantum well structures, such as the first tunnel junction 3B between the first multi-quantum well structure 3A and the second multi-quantum well structure 3C, the second tunnel junction 3D between the second multi-quantum well structure 3C and the third multi-quantum well structure 3E, the third tunnel junction 6A between the third multi-quantum well structure 3E and the fourth multi-quantum well structure 6B, the fourth tunnel junction 6C between the fourth multi-quantum well structure 6B and the fifth multi-quantum well structure 6D, the fifth tunnel junction 8A between the fifth multi-quantum well structure 6D and the sixth multi-quantum well structure 8B, and the sixth tunnel junction 8C between the sixth multi-quantum well structure 8B and the seventh multi-quantum well structure 8D.

[0078] In one embodiment, the bottom mirror structure 2 includes a plurality of mirrors with an optical thickness of a quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices. The top mirror 10 structure includes a plurality of mirrors with an optical thickness of a quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices. That is to say, the bottom mirror structure 2 and the top mirror 10 structure can be respectively understood as a Bragg mirror structure. Among them, the materials of the top mirror 10 structure and the bottom mirror structure 2 can be dielectric materials with electrical insulation properties, such as silicon nitride, silicon oxide, aluminum oxide, or titanium oxide, etc. The materials of the top mirror 10 structure and the bottom mirror structure 2 can also be semiconductor materials, such as GaAs and AlGaAs.

[0079] The number of optical modulation layers is not greater than the number of optoelectronic confinement layers, for example, it can be 2, 3, 4, etc. The optical modulation layer is used to divide the optical field in the resonant cavity structure into at least two segments. Figure 2 and Figure 3 Fig. shows an optical modulation layer (i.e., the first optical modulation layer 4) in a multi-junction VCSEL device. The first optical modulation layer 4 can divide the optical field in the resonant cavity structure into two segments. The first optical modulation layer 4 is arranged adjacent to the first optoelectronic confinement layer 5. It can be understood that the closer the distance between the first optoelectronic confinement layer 5 and the first optical modulation layer 4, the greater the degree of reducing the diffusion of current on the surface of the active region after passing through the first optoelectronic confinement layer 5. Therefore, in this embodiment, by arranging the first optical modulation layer 4 between the first optoelectronic confinement layer 5 and the active region, the confinement factor of the first optoelectronic confinement layer 5 can be effectively regulated on the premise of better reducing current diffusion.

[0080] In this specific embodiment, the material of the first optical modulation layer 4 can be a photonic crystal structure or a periodically stacked DBR structure. Specifically, the periodically stacked DBR (Distributed Bragg Reflector) structure realizes the efficient reflection or transmission of light within a specific wavelength range through the periodic stacking of multiple layers of materials with different refractive indices. Among them, the optical thickness of each layer in the periodically stacked DBR structure is 1 / 4 of the lasing wavelength. The material of the periodically stacked DBR structure includes either semiconductor material or metal. Exemplarily, the DBR structure of semiconductor material is, for example, composed of alternately stacked GaAs and AlGaAs with different refractive indices, or composed of alternately stacked InGaAs and GaAsP with different refractive indices, or composed of alternately stacked InGaAs and AlGaAs with different refractive indices. The DBR structure of metal is, for example, composed of alternately stacked silver and aluminum with different refractive indices. Due to its own periodic dielectric constant change, a photonic crystal can form a photonic bandgap, and thus, by controlling the position and width of the bandgap, the reflection or transmission of light within a specific wavelength range can be achieved.

[0081] In one embodiment, the periodically stacked DBR structure is composed of alternating stacks of Al x Ga (1-x) As / Al y Ga (1-y) As, where 0 ≤ x < y ≤ 1. Specifically, by adjusting the proportion of aluminum and gallium in the AlGaAs material system, the refractive index and bandgap of the periodically stacked DBR structure can be precisely controlled, thereby achieving the reflection or transmission of light at a specific wavelength.

[0082] In one embodiment, the first optical control layer 4 can be disposed near the left side and / or the right side of the first optoelectronic confinement layer 5. That is to say, the first optical control layer 4 can be disposed on the left side of the first optoelectronic confinement layer 5, the first optical control layer 4 can also be disposed on the right side of the first optoelectronic confinement layer 5, and the first optical control layer 4 can be disposed on both the left and right sides of the first optoelectronic confinement layer 5, corresponding Figure 5 cases.

[0083] In one embodiment, when the first optical control layer 4 is disposed only near the right side of the first optoelectronic confinement layer 5, a tunnel junction, namely the third tunnel junction 6A, is further provided therebetween. The third tunnel junction 6A, as a current path, can limit the current flow position, enabling the current to flow more in the central region near the central axis of the multi-junction VCSEL device, reducing the diffusion of the current from the central region to the outside, thereby facilitating the emission of laser light from the center of the multi-junction VCSEL device. Moreover, the tunnel junction layer can also reduce the non-radiative recombination of carriers at the tunnel junction layer, ensuring that more current is used to generate useful photons, thereby increasing the probability of radiative recombination and improving the optical field quality.

[0084] Among them, by providing a tunnel junction (such as Figure 5The third tunneling junction 6A and the fifth tunneling junction 8A) provided therein can slow down the change rate of the light field intensity at the first optoelectronic confinement layer 5 and the first optical modulation layer 4, so that the light field intensity at the first optoelectronic confinement layer 5 and the first optical modulation layer 4 can continuously remain at a relatively low position. It can be understood that if the process results in a certain offset in the position of the optoelectronic confinement layer in the light field, it may cause the first optoelectronic confinement layer 5 not to be located at the trough of the standing wave. Based on the positive correlation between the confinement factor and the light field intensity, when the offset causes the light intensity at the optoelectronic confinement layer to increase, the confinement factor of the first optoelectronic confinement layer 5 will increase, thereby affecting the performance of the multi-junction VCSEL device. In addition, taking the third tunneling junction 6A adjacent to the first optoelectronic confinement layer 5 as an example, since the multi-quantum well structure on the side far from the substrate in the first active region 3 is P-type heavily doped on the side close to the first optoelectronic confinement layer 5. And in the third tunneling junction 6A adjacent to the first optoelectronic confinement layer 5, its side close to the first optoelectronic confinement layer 5 is also P-type heavily doped. Therefore, if the third tunneling junction 6A is disposed on the side of the first optoelectronic confinement layer 5 close to the substrate 1, it will cause the two P-type heavily doped regions to be too close, and the P-type heavily doped regions have certain light absorption characteristics, and the two P-type heavily doped regions with a closer distance will further enhance the light absorption, thereby resulting in a decrease in the performance of the multi-junction VCSEL device. In the embodiment of the application, the third tunneling junction 6A is disposed on the side of the first optoelectronic confinement layer 5 far from the substrate, which can effectively improve the above light absorption problem.

[0085] In one embodiment, when the first optical modulation layer 4 is disposed on both the left and right sides close to the first optoelectronic confinement layer 5, the specific selections of the first optical modulation layers 4 on both sides can be the same or different. In this specific embodiment, each first optical modulation layer 4 is composed of two Bragg reflectors, and the first optoelectronic confinement layer 5 is disposed between the Bragg reflectors. When the oxide layer is between the two Bragg reflectors, the first optoelectronic confinement layer 5 is at the lowest point of the electric field intensity. For the first optoelectronic confinement layer 5 with Bragg reflectors in the front and back, using a relatively short section of material in the front and back can make the confinement factor of the first optoelectronic confinement layer 5 reach the lowest value, and can also reduce the increase in the confinement factor of the first optoelectronic confinement layer 5 caused by process instability.

[0086] The magnitude of the refractive index of the reflector can be selected according to the actual situation. Either Bragg reflectors with the same refractive index or Bragg reflectors with different refractive indices can be used, and the specific number of stacked pairs can also be selected according to the actual situation.

[0087] Furthermore, the first optical modulation layers 4 disposed on both sides can both be periodically stacked DBR structures or both be photonic crystal structures. The present application does not make further limitations in this regard.

[0088] In one embodiment, when the specific selections of the first optical modulation layers 4 provided on both sides are different; the first optical modulation layer 4 near the left side of the first optoelectronic confinement layer 5 can be a photonic crystal structure, and the first optical modulation layer 4 near the right side of the first optoelectronic confinement layer 5 can be a periodically stacked DBR structure; or the first optical modulation layer 4 near the left side of the first optoelectronic confinement layer 5 can be a periodically stacked DBR structure, and the first optical modulation layer 4 near the right side of the first optoelectronic confinement layer 5 is a photonic crystal structure. Here, the photonic crystal structure refers to an artificial periodic dielectric structure with photonic band-gap (abbreviated as PBG) characteristics. The photonic band-gap means that waves in a certain frequency range cannot propagate in this periodic structure. At the same time, other structures can also be selected according to actual needs.

[0089] In one of the embodiments, reference may be made to Figure 5 , when the first optical modulation layers 4 are provided on both the left and right sides of the first optoelectronic confinement layer 5, the DBR stacking periods in the first optical modulation layers 4 on both sides can be different. In other words, the first optical modulation layers 4 with different refractive indexes can be used. It can have a stronger refractive index on the left side or a stronger refractive index on the right side, and it can be selected according to the actual situation. By setting the structure and / or composition of the first optical modulation layers 4 on both sides of the first optoelectronic confinement layer 5, flexible adjustment of the optical field intensity of each segment of the optical field can be achieved. Exemplarily, the two first optical modulation layers 4 can both be composed of alternately stacked Al0.25Ga0.75As / Al0.5Ga0.5As. Based on different optical field distributions, different scenario applications can be realized, thereby improving the applicability of the multi-junction VCSEL device to different scenarios. It should be noted that the optical field intensities on both sides of one first optical modulation layer 4 can be the same or different, which can be specifically determined according to the actual scenario requirements and are not limited here. The intensity peaks of each segment of the optical field in the resonant cavity structure can also be the same or different, which are not limited here.

[0090] Furthermore, the stacking periods of the first optical modulation layers 4 on both sides of the first optoelectronic confinement layer 5 can be between 1 pair and 10 pairs, and further preferably between 1 pair and 5 pairs. Here, one pair includes two adjacent film layers with different refractive indexes. For example, if the stacking period of the first optical modulation layer 4 on the left side is 2 pairs, then the DBR structure of the first optical modulation layer 4 includes an Al x Ga (1-x) As layer, an Al y Ga (1-y) As layer, an Al x Ga (1-x) As layer, and an Al y Ga (1-y)As layer. It can be understood that, the more the number of stacking periods of the DBR structure of the first optical modulation layer 4, the lower the confinement factor of the first optoelectronic confinement layer 5 can be made. However, it will also exacerbate the problem of current spreading, thereby having a greater impact on the light-emitting efficiency of the active region after the first optoelectronic confinement layer 5. Therefore, in this embodiment, the first optical modulation layer 4 is provided to include 1 to 5 pairs of stacking periods respectively, which can have a lower confinement factor of the optoelectronic confinement layer on the premise that the current spreading problem is controllable. It should be noted that the number of stacking periods of the DBR structure of each first optical modulation layer 4 can be the same or different, and can be specifically set according to the requirements of the optical field, which is not limited here.

[0091] The different numbers of stacking periods of the DBR structures of the first optical modulation layers 4 on both sides can be that the number of stacking periods of the DBR structure of the first optical modulation layer 4 closer to the substrate 1 is greater than that of the DBR structure of the first optical modulation layer 4 farther from the substrate 1, or the number of stacking periods of the DBR structure of the first optical modulation layer 4 farther from the substrate 1 is greater than that of the DBR structure of the first optical modulation layer 4 closer to the substrate 1, which is not limited here. It can be understood that, the larger the number of stacking periods of the DBR structure of the first optical modulation layer 4, the more interfaces the photons will reflect at, that is, the reflection coefficient of the modulation sub-layer will be changed. Therefore, the different numbers of stacking periods of the DBR structures of the first optical modulation layers 4 on both sides mean that the reflection coefficients of the two first optical modulation layers 4 are different, so that after the photons generated in the active region obtain the required gain, they are emitted from the modulation sub-layer on one side to achieve flexible control of the optical field intensity. In the embodiments of the application, by changing the numbers of stacking periods of the DBR structures of the first optical modulation layers 4 on both sides, the adjustment of the optical field intensity in each optical field segment can be realized to meet different application scenarios.

[0092] In one embodiment, when the first optical modulation layer 4 includes a periodically stacked DBR structure, the refractive index stacking orders of the DBR structures of the first optical modulation layer 4 on both sides of the first optoelectronic confinement layer 5 are opposite. For example, for the first optical modulation layer 4 close to the substrate 1, the film layer closest to the substrate 1 on one side of the first optical modulation layer 4 is a high refractive index film layer, and is stacked in the order of high-low-high-low along the direction away from the substrate 1. While for the first optical modulation layer 4 away from the substrate 1, the film layer closest to the substrate 1 on one side of the first optical modulation layer 4 is a low refractive index film layer, and is stacked in the order of low-high-low-high along the direction away from the substrate 1. Another example is that for the first optical modulation layer 4 close to the substrate 1, the film layer closest to the substrate 1 on one side of the first optical modulation layer 4 is a low refractive index film layer, and is stacked in the order of low-high-low-high along the direction away from the substrate 1. While for one first optical modulation layer 4 away from the substrate 1, the film layer closest to the substrate 1 on one side of the first optical modulation layer 4 is a high refractive index film layer, and is stacked in the order of high-low-high-low along the direction away from the substrate 1. In the embodiments of the application, by adjusting the refractive index stacking orders of the DBR structures of the first optical modulation layer 4 on both sides of the first optoelectronic confinement layer 5, the phases of the light of the first optical modulation layer 4 on both sides of the first optoelectronic confinement layer 5 can be made opposite, so as to achieve that the light field intensities at the first optical modulation layer 4 and the first optoelectronic confinement layer 5 are lower than the light field intensity of any adjacent active region.

[0093] In some embodiments, the first optical modulation layer 4 can also be composed of dielectric materials, metal-dielectric hybrid materials, etc., which are not limited herein.

[0094] Furthermore, the specific stacking pairs of the first optical modulation layer 4 on both sides of the first optoelectronic confinement layer 5 can be the same or different. The two Bragg reflectors in the first optical modulation layer 4 on the left side of the first optoelectronic confinement layer 5 and the first optical modulation layer 4 on the right side of the first optoelectronic confinement layer 5 are 2 pairs and 3 pairs respectively from bottom to top; 4 pairs and 3 pairs; 1 pair and 3 pairs; 1 pair and 3 pairs.

[0095] Furthermore, as Figure 5 shown, if there is a second optoelectronic confinement layer 7, and second optical modulation layers 11 are respectively provided on both sides of the second optoelectronic confinement layer 7, based on the same description above, the four Bragg reflectors in the first optical modulation layer 4 on the left side of the first optoelectronic confinement layer 5, the first optical modulation layer 4 on the right side of the first optoelectronic confinement layer 5, the second optical modulation layer 11 on the left side of the second optoelectronic confinement layer 7, and the second optical modulation layer 11 on the right side of the second optoelectronic confinement layer 11 are 2 pairs, 3 pairs, 2 pairs, and 3 pairs respectively from bottom to top; 4 pairs, 3 pairs, 4 pairs, and 3 pairs; 1 pair, 3 pairs, 3 pairs, and 1 pair; 1 pair, 3 pairs, 1 pair, and 3 pairs. Different pair distributions will generate different light field distributions and achieve different scenario applications.

[0096] In one embodiment, the number of DBR stacking periods in the optical modulation layer located on the left side of the optoelectronic confinement layer is more than that in the optical modulation layer located on the right side of the optoelectronic confinement layer; or, the number of DBR stacking periods in the optical modulation layer located on the left side of the optoelectronic confinement layer is less than that in the optical modulation layer located on the right side of the optoelectronic confinement layer.

[0097] It should be noted that the specific structures of different optical modulation layers can be set as needed. Specifically, each modulation sub-layer in each optical modulation layer can adopt either a photonic crystal structure or a periodically stacked DBR structure. In the case of both adopting a periodically stacked DBR structure, the refractive indices of the first DBR functional layers of the modulation sub-layers in different optical modulation layers can be the same or different, and the refractive indices of the second DBR functional layers of the modulation sub-layers in different optical modulation layers can be the same or different, which are not limited in the embodiments of the present application.

[0098] As Figure 4 shown, when the above design method is adopted, it can be clearly seen that its refractive index, as shown by the red line, is effectively controlled. More specifically, it can be clearly seen that the waveforms of the refractive index in the two electric field segments are basically the same, thereby ensuring that the confinement factor differences of the quantum wells are relatively small, making the contributions of each multi-quantum well to luminescence basically the same. At the same time, the oxide layers are all at the standing wave troughs of the refractive index curve, that is, at the places with lower confinement factors, so as to suppress the high-order modes as much as possible and achieve the effect of a low divergence angle.

[0099] The embodiments of the present application also provide a VCSEL chip, which can be a flip-chip VCSEL chip. The VCSEL chip includes a positive electrode, a negative electrode, and the multi-junction VCSEL device as described above. Exemplarily, the positive electrode and the negative electrode are respectively electrically connected to the bottom mirror structure 2 and the top mirror 10 structure of the multi-junction VCSEL device, and the positive electrode and the negative electrode are located on the side opposite to the light-emitting side of the VCSEL chip. Another exemplarily, the positive electrode and the negative electrode are respectively electrically connected to the top mirror 10 structure and the bottom mirror structure 2 of the multi-junction VCSEL device, and the positive electrode and the negative electrode are located on the side opposite to the light-emitting side of the VCSEL chip. Based on the foregoing multi-junction VCSEL device, the VCSEL chip of this embodiment can have better performance in terms of divergence angle and threshold current. In addition, the flip-chip VCSEL chip can connect the chip to the substrate and the carrier through bumps, which can reduce the need for wire bonding, thereby not only simplifying the packaging technology but also reducing the system inductance of the flip-chip VCSEL chip, helping to improve the overall optoelectronic conversion efficiency of the flip-chip VCSEL chip.

[0100] The embodiment of the present application further provides a VCSEL chip, which includes at least one laser array. The laser array includes a plurality of multi-junction VCSEL devices as described above. The laser array is a regularly arranged array, or a randomly arranged array, or an array with multiple addressable sub-arrays. Based on the foregoing multi-junction VCSEL devices, the VCSEL chip of this embodiment can have better performance in terms of divergence angle and threshold current.

[0101] The embodiment of the present application further provides a light source for a lidar system, which includes at least one multi-junction VCSEL device as described above or at least one VCSEL chip as described above.

[0102] The embodiment of the present application further provides a lidar system, which includes a transmitting component and a receiving component. The transmitting component uses the light source for a lidar system as described above.

[0103] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0104] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-junction VCSEL device, characterized in that, Comprising: A substrate; A bottom mirror structure and a top mirror structure sequentially disposed on the substrate; The bottom mirror structure and the top mirror structure define a resonant cavity structure for generating a standing wave; The resonant cavity structure includes at least two active regions and at least one optical confinement layer. At least one multi-quantum well structure is provided in each active region, and the active regions are connected by tunnel junctions. The optical confinement layer is disposed on a side of the active region away from the substrate, and the optical confinement layer is located at a trough of the standing wave. The optical confinement layer is used to define a light-emitting region of the multi-junction VCSEL device; At least one optical modulation layer is disposed adjacent to the optical confinement layer. The optical modulation layer is configured to divide an optical field in the resonant cavity structure into at least two segments, and the intensity of each segment of the optical field is different; There are at least two of the multi-quantum well structures between the bottom mirror structure and the nearest optical modulation layer.

2. The multi-junction VCSEL device according to claim 1, wherein The optical modulation layer includes a photonic crystal structure or a single-layer structure or a periodically stacked DBR structure.

3. The multi-junction VCSEL device according to claim 2, characterized in that, When the optical modulation layer is a periodically stacked DBR structure, the number of stacking periods is between 1 pair and 10 pairs, and each pair is alternately composed of Al x Ga (1-x) As / Al y Ga (1-y) As, where 0 ≤ x < y ≤ 1.

4. The multi-junction VCSEL device according to claim 2, wherein, The optical modulation layer is disposed on the left side and / or the right side close to the optical confinement layer.

5. The multi-junction VCSEL device according to claim 4, wherein, When the optical modulation layer is disposed on the right side close to the optical confinement layer, a tunnel junction is further provided between the optical modulation layer and the optical confinement layer.

6. The multi-junction VCSEL device according to claim 4, wherein When the optical modulation layer is disposed on the left side and the right side close to the optical confinement layer, the specific selections of the optical modulation layers on both sides are the same or different.

7. The multi-junction VCSEL device according to claim 6, characterized in that, Both of the optical modulation layers on both sides are periodically stacked DBR structures or both of the optical modulation layers on both sides are photonic crystal structures.

8. The multi-junction VCSEL device according to claim 6, wherein When the specific selections of the optical modulation layers on both sides are different; The optical modulation layer close to the left side of the optical confinement layer is a photonic crystal structure, and the optical modulation layer close to the left side of the optical confinement layer is a periodically stacked DBR structure; or The optical modulation layer close to the left side of the optical confinement layer is a periodically stacked DBR structure, and the optical modulation layer close to the left side of the optical confinement layer is a photonic crystal structure.

9. The multi-junction VCSEL device according to claim 4, wherein, When the optical modulation layer is disposed on the left side and the right side close to the optical confinement layer, the DBR stacking periods in the optical modulation layers on both sides are different.

10. The multi-junction VCSEL device according to claim 8, characterized in that, The DBR stacking period in the optical modulation layer on the left side of the optical confinement layer is more than that in the optical modulation layer on the right side of the optical confinement layer.

11. The multi-junction VCSEL device according to claim 8, wherein, The DBR stacking period in the optical modulation layer on the left side of the optical confinement layer is less than that in the optical modulation layer on the right side of the optical confinement layer.

12. The multi-junction VCSEL device according to claim 1, wherein There are three of the multi-quantum well structures between the bottom mirror structure and the nearest optical modulation layer.

13. The multi-junction VCSEL device according to any one of claims 1-12, characterized in that, The optical confinement layer includes any one of an air-column type optical confinement layer, an oxidation confinement type optical confinement layer, an ion implantation type optical confinement layer, and a tunnel junction type optical confinement layer.

14. The multi-junction VCSEL device according to claim 13, wherein, The oxidation confinement type optical confinement layer is an epitaxially grown AlGaAs with a high Al component, and an insulating alumina film layer is formed in an oxidized region on its outer side; wherein, an unoxidized region forms a light-emitting region for effective current injection.

15. The multi-junction VCSEL device according to claim 13, wherein, The tunnel junction type optical confinement layer is composed of at least one high-doped N-type structural layer and at least one high-doped P-type structural layer.

16. The multi-junction VCSEL device according to claim 15, wherein The materials of the N-type structure layer and the P-type structure layer are selected as Al x Ga 1-x As (x = 0 to 1), and the doping concentration is greater than 1e 18 cm -3 .

17. The multi-junction VCSEL device according to any one of claims 1-12, characterized in that, The resonant cavity structure includes three active regions and two optical confinement layers; the three active regions are respectively denoted as the first active region, the second active region, and the third active region, and the two optical confinement layers are respectively denoted as the first optical confinement layer and the second optical confinement layer; The first active region is located on one side of the bottom mirror structure, the first optical confinement layer is disposed between the first active region and the second active region, the second optical confinement layer is disposed between the second active region and the third active region, a tunnel junction is provided between the first optical confinement layer and the second active region, and a tunnel junction is provided between the second optical confinement layer and the third active region.

18. The multi-junction VCSEL device according to claim 17, characterized in that, The first active region includes three multiple quantum well structures, the second active region includes two multiple quantum wells, and the third active region includes two multiple quantum well structures; and the multiple quantum well structures within each active region are connected by tunnel junctions.

19. The multi-junction VCSEL device according to any one of claims 1-12, characterized in that, The bottom mirror structure includes a plurality of mirrors with an optical thickness of one-quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices; The top mirror structure includes a plurality of mirrors with an optical thickness of one-quarter of the lasing wavelength, and the plurality of mirrors are arranged alternately with high and low refractive indices.

20. An inverted VCSEL chip, characterized in that, The flip-chip VCSEL chip includes a positive electrode, a negative electrode, and a multi-junction VCSEL device according to any one of claims 1-19; wherein, the positive electrode and the negative electrode are respectively electrically connected to the bottom mirror structure and the top mirror structure of the multi-junction VCSEL device; or The positive electrode and the negative electrode are respectively electrically connected to the top mirror structure and the bottom mirror structure of the multi-junction VCSEL device; The positive electrode and the negative electrode are disposed on a side opposite to the light-emitting side of the flip-chip VCSEL chip.

21. A VCSEL chip, characterized in that, Comprising at least one laser array; the laser array includes a plurality of multi-junction VCSEL devices according to any one of claims 1-19; the laser array is a regularly arranged array, or a randomly arranged array, or an array having a plurality of addressable sub-arrays.

22. A light source for a lidar system, characterized in that, Comprising at least one multi-junction VCSEL device according to any one of claims 1-19, or at least one flip-chip VCSEL chip according to claim 20, or a VCSEL chip according to claim 21.

23. A lidar, characterized in that, Comprising a transmitting component and a receiving component, and the transmitting component uses the light source for a lidar system according to claim 22.

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