Resonator, Laser Unit, Laser, and Lidar

Abstract

A resonant cavity, a laser unit, a laser, and a lidar, the resonant cavity comprising: a first mirror and a second mirror that are relatively spaced apart; an active structure located between the first mirror and the second mirror; the active structure includes a plurality of functional stacks including a light-emitting layer, namely the first functional stack, the second functional stack... the Nth functional stack, and at least the first functional stack and the Nth functional stack further include: a current confinement layer; in the same functional stack, the distance between the current confinement layer and the light-emitting layer is a conduction spacing; the conduction spacing of the first functional stack is greater than the conduction spacing of the Nth functional stack. By arranging functional stacks with uneven conduction spacings in the active structure, it is possible to suppress the current concentration effect at the boundary position and the increase in the current density in the central region, both of which can effectively increase the fundamental mode intensity and suppress the excitation of higher-order modes, and can effectively reduce the divergence angle of the laser.

Description

Technical Field

[0001] The present invention relates to the field of lasers, and particularly to a resonant cavity, a laser unit, a laser, and a lidar. Background Art

[0002] A lidar is a commonly used ranging sensor, which has the characteristics of long detection distance, high resolution, and little environmental interference, and is widely used in the fields of intelligent robots, unmanned aerial vehicles, autonomous driving, etc. In recent years, the development of autonomous driving technology has been rapid, and the lidar, as the core sensor for distance perception, has become indispensable. The laser, as one of the core components of the lidar, has a great impact on the performance of the lidar.

[0003] A traditional vertical cavity surface emitting laser (VCSEL) generally includes a lower distributed Bragg reflector (DBR), an active region, a current confinement layer, and an upper DBR that are sequentially epitaxially grown on an N-type doped substrate. Among them, the current is injected into the active region through the current confinement layer by an electrode; the material in the active region is excited to emit light, and resonates in the resonant cavity formed by the upper DBR and the lower DBR, forming a strong light beam with the same propagation direction, frequency, and phase.

[0004] In a VCSEL, in order to improve the overall gain to achieve high-power output, the active region is often set as a structure of multiple stacked multi quantum wells (MQWs); at the same time, in order to increase the current density and reduce the current spreading effect, a current confinement layer is arranged between adjacent multi quantum well structures to drive the current to concentrate at the central position.

[0005] However, when a resonant cavity structure that includes both a current confinement layer and multiple multi quantum well structures emits light, problems such as high-order modes being excited and a large laser divergence angle being generated are likely to occur. Summary of the Invention

[0006] The problem solved by the present invention is to provide a resonant cavity, a laser unit, a laser, and a lidar to suppress high-order modes and control the laser divergence angle.

[0007] To solve the above problems, the present invention provides a resonant cavity, comprising: a first mirror and a second mirror, the first mirror and the second mirror are arranged opposite to each other at an interval, and the direction of the first mirror pointing to the second mirror is consistent with the current direction; an active structure, the active structure is located between the first mirror and the second mirror; the active structure includes a plurality of functional stacks, and the functional stack includes a light-emitting layer; along the direction of the first mirror pointing to the second mirror, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack, the second functional stack... the Nth functional stack, where N is the number of functional stacks in the active structure, and at least the first functional stack and the Nth functional stack further include: a current confinement layer; in the same functional stack, the distance between the current confinement layer and the light-emitting layer is the conduction distance; the conduction distance of the first functional stack is greater than the conduction distance of the Nth functional stack.

[0008] Optionally, the optical path difference between the conduction distance of the first functional stack and the conduction distance of the Nth functional stack is an integer multiple of half the wavelength of the light generated by the active structure.

[0009] Optionally, the integer is greater than or equal to 2.

[0010] Optionally, each of the stacks includes a current confinement layer and a light-emitting layer arranged in sequence along the current direction.

[0011] Optionally, along the direction from the first functional stack to the second functional stack, the conduction distance decreases.

[0012] Optionally, the conduction distance of the first functional stack is greater than the conduction distance of the second functional stack.

[0013] Optionally, the conduction distance of the Nth functional stack is less than the conduction distance of the N-1th functional stack.

[0014] Optionally, the conduction distance of any one of the first functional stack, the second functional stack,..., the Xth functional stack is greater than the conduction distance of any one of the X+1th functional stack, the X+2th functional stack,..., the Nth functional stack.

[0015] Optionally, the conduction distance of the first functional stack is greater than 0.75λ, where λ is the wavelength of the light generated by the active structure.

[0016] Optionally, the conduction distance of the Nth functional stack is less than 0.75λ, where λ is the wavelength of the light generated by the active structure.

[0017] Optionally, the light-emitting layer is a quantum well structure.

[0018] Optionally, the first mirror is a P-type doped mirror; the second mirror is an N-type doped mirror.

[0019] Correspondingly, a lidar includes: a resonant cavity, which is the resonant cavity of the present invention; a first electrode, which is electrically connected to the resonant cavity; and a second electrode, which is electrically connected to the resonant cavity.

[0020] Optionally, the first electrode includes: an opening penetrating the first electrode; the current limiting layer includes: a conductive region and an insulating region filled between the conductive regions, wherein the conductive region penetrates the current limiting layer along the current direction; and the projection of the conductive region on the surface of the first electrode is within the range of the opening.

[0021] Optionally, the first electrode is a P electrode; the second electrode is an N electrode.

[0022] Moreover, the present invention also provides a laser unit, including: a laser unit, which is the laser unit of the present invention.

[0023] Optionally, the laser is a vertical cavity surface emitting laser.

[0024] Optionally, the laser is a top-emitting vertical cavity surface emitting laser or a back-emitting vertical cavity surface emitting laser.

[0025] In addition, the present invention also provides a lidar, including: a light source, and the light source includes the laser of the present invention.

[0026] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0027] In the technical solution of the present invention, the conduction spacing of the first functional stack is greater than that of the Nth functional stack. Increasing the conduction spacing of the first functional stack can extend the current path from the current limiting layer of the first functional stack to the light emitting layer, making the diffusion of current to the central region more sufficient, thereby effectively suppressing the current concentration effect at the boundary position between the insulating region and the conductive region of the current limiting layer; reducing the conduction spacing of the Nth functional stack shortens the current path from the current limiting layer of the Nth functional stack to the light emitting layer, thereby improving the current diffusion effect and increasing the current density in the central region; the suppression of the current concentration effect at the boundary position and the increase of the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser. Description of the Drawings

[0028] Figure 1 is a schematic cross-sectional structure diagram of a VCSEL unit;

[0029] Figure 2It is a schematic cross-sectional structure diagram of a VCSEL unit including a multi-quantum well structure with multiple junctions;

[0030] Figure 3 is Figure 2 A schematic diagram of the light intensity distribution in the active region of the VCSEL unit shown;

[0031] Figure 4 It is a schematic diagram of the light intensity distribution after the superposition of the fundamental mode and the high-order mode in the active region of two VCSEL units;

[0032] Figure 5 is Figure 2 The current distribution in the 5th multi-quantum well structure 22e1 upstream of the current in the VCSEL unit shown;

[0033] Figure 6 is Figure 2 The current distribution in the 1st multi-quantum well structure 22a1 downstream of the current in the VCSEL unit shown;

[0034] Figure 7 It is a schematic cross-sectional structure diagram of an embodiment of the resonant cavity of the present invention;

[0035] Figure 8 It is a schematic cross-sectional structure diagram of another embodiment of the resonant cavity of the present invention;

[0036] Figure 9 is Figure 8 A schematic diagram of the waveform of the standing wave formed between the first mirror and the second mirror in the shown embodiment of the resonant cavity;

[0037] Figure 10 is Figure 8 The current distribution in the light-emitting layer 121 of the 1st functional stack 101 upstream of the current in the shown embodiment of the resonant cavity;

[0038] Figure 11 is Figure 8 The current distribution in the light-emitting layer 125 of the 5th functional stack 105 downstream of the current in the shown embodiment of the resonant cavity;

[0039] Figure 12 It is a schematic cross-sectional structure diagram of another embodiment of the laser unit of the present invention. Detailed implementation manners

[0040] As can be seen from the background art, when a resonant cavity structure that includes both a current confinement layer and multiple multi-quantum well structures emits light, due to the uneven current distribution, problems such as the excitation of high-order modes and a relatively large laser divergence angle are likely to occur. Now, in combination with the structure of a resonant cavity, the reasons for the problems of high-order mode excitation and large laser divergence angle are analyzed:

[0041] Refer toFigure 1 , showing a schematic cross-sectional structure diagram of a VCSEL unit.

[0042] The VCSEL laser chip includes a plurality of VCSEL units. As Figure 1 shown, between the annular upper electrode 15 and the lower electrode 16, the device structure of the VCSEL unit includes: a lower DBR 11, an active region 12, a current confinement layer 13, and an upper DBR 14 that are sequentially epitaxially grown on the substrate 10. Each epitaxial layer is obtained by epitaxial growth on the substrate 10 by Metal-Organic Chemical Vapour Deposition (MOCVD) technology.

[0043] In each VCSEL unit, current is injected into the active region 12 through the upper electrode 15; the material of the active region 12 is excited to emit light, and resonates in the resonant cavity formed by the upper DBR 14 and the lower DBR 11, forming a strong light beam with the same propagation direction, frequency, and phase. Figure 1 Shown is a front-emitting VCSEL unit, where the upper DBR 14 has a smaller number of periods and a slightly lower reflectivity than the lower DBR 11, so that most of the light is transmitted upward through the upper DBR 14 to become useful laser light.

[0044] To improve the overall gain and achieve high-power output, a multi-junction multi-quantum well structure, or a multi-junction VCSEL, is provided in the active region of each VCSEL unit, as Figure 2 shown. Figure 2 That is, it shows a schematic cross-sectional structure diagram of a VCSEL unit including a multi-junction multi-quantum well structure. To reduce the current spreading effect, a current confinement layer is provided between two adjacent multi-quantum well structures in the active region to concentrate the current towards the central position.

[0045] As Figure 2The VCSEL unit shown, the active region includes a plurality of multi-quantum well structures, the first multi-quantum well structure 22a1, the second multi-quantum well structure 22b1, the third multi-quantum well structure 22c1, the fourth multi-quantum well structure 22d1, and the fifth multi-quantum well structure 22e1. A current confinement layer is disposed between two adjacent multi-quantum well structures, that is, the first current confinement layer 22a2 between the first multi-quantum well structure 22a1 and the second multi-quantum well structure 22b1, the second current confinement layer 22b2 between the second multi-quantum well structure 22b1 and the third multi-quantum well structure 22c1, the third current confinement layer 22c2 between the third multi-quantum well structure 22c1 and the fourth multi-quantum well structure 22d1, the fourth current confinement layer 22d2 between the fourth multi-quantum well structure 22d1 and the fifth multi-quantum well structure 22e1, and the fifth current confinement layer 22e2 between the fifth multi-quantum well structure 22e1 and the upper electrode 25.

[0046] In addition, Figure 2 in, the upper electrode 25 is a P-type electrode, and the lower electrode 26 is an N-type electrode. Therefore, Figure 2 in the VCSEL unit shown, the current flows in the direction from the upper electrode 25 to the lower electrode 26 (as Figure 2 shown by the arrow i in). In order to better confine the current flowing into each multi-quantum well structure, the current confinement layer is usually disposed on the side of each multi-quantum well structure facing the P-type electrode, that is, each current confinement layer is located on the side of each multi-quantum well structure facing the upper electrode 25.

[0047] Figure 2 In the active region of the VCSEL structure shown, usually the distribution of the multi-quantum well structures and the current confinement layers is uniform. That is to say, the distance L between different multi-quantum well structures and the corresponding current confinement layers is uniform, that is, L1 = L2 = L3 = L4 = L5, and the distance between adjacent multi-quantum well structures is also uniform, that is, D1 = D2 = D3 = D4. However, it has been found through research that such a uniform structure will cause the current distribution in the active region to be non-uniform, resulting in the excitation of higher-order modes in the VCSEL unit, an increase in the divergence angle of the laser, and thus limiting the application of the laser.

[0048] Combined with reference to Figure 3 and Figure 4 , where Figure 3 shows Figure 2 a schematic diagram of the optical intensity distribution of the fundamental mode and higher-order modes in the active region of the VCSEL unit shown, Figure 4 schematically shows a schematic diagram of the optical intensity distribution after the superposition of the fundamental mode and higher-order modes in the active region of two VCSEL units. The abscissa is the distance r from the geometric center of the VCSEL unit in the plane perpendicular to the direction from the upper electrode 25 to the lower electrode 26, and the ordinate represents the normalized optical intensity I. Figure 3 In, the graph line 31 representsFigure 2 Schematic diagram of the optical intensity distribution of the fundamental mode in the active region of the VCSEL unit shown, where the curve 32 represents Figure 2 Schematic diagram of the optical intensity distribution of the high-order mode in the active region of the VCSEL unit shown; Figure 4 In the figure, the curve 41 represents Figure 2 Schematic diagram of the optical intensity distribution generated in the active region of the VCSEL unit shown.

[0049] The light emitted by the VCSEL unit is a light beam with a circular cross-section centered on the geometric center of the VCSEL unit, and the divergence angle is obtained based on the spot size where the light intensity decreases from the strongest value at the center to 1 / e 2 . In an ideal state, the light should be a fundamental mode spot, that is, the light at the center of the spot corresponding to the geometric center of the VCSEL unit is the strongest and decreases rapidly towards the edge. In this case, it is easy to obtain a relatively small divergence angle. The distribution of current in the active region is preferably such that the curve of the intensity varying with distance conforms to the shape of the fundamental mode intensity curve, which can enable the active region to emit fundamental mode light.

[0050] However, as Figure 3 and Figure 4 shown, Figure 2 the light emitted by the active region in the VCSEL unit shown has multiple modes, and the optical intensity of each mode basically follows a Gaussian distribution. Among them, the light of the fundamental mode is the strongest at the geometric center of the VCSEL unit and gradually weakens towards both sides. As Figure 3 shown, a high-order mode is the strongest at a position far from the geometric center of the VCSEL unit (as shown within the circle 32 in Figure 3 ). However, after the superposition of the fundamental mode and the high-order mode, there are additional regions with relatively strong light emission in the light generated by the entire VCSEL unit at positions deviating from the geometric center (such as the region indicated by the arrow T1 in Figure 4 ).

[0051] Refer to Figure 5 and Figure 6 , where Figure 5 is Figure 2 the current distribution in the 5th multiple quantum well structure 22e1 upstream of the current in the VCSEL unit shown, Figure 6 and Figure 2 is

[0052] In the figure, the abscissa is the distance (unit: μm) from the geometric center of the VCSEL unit in the plane perpendicular to the upper electrode 25 pointing towards the lower electrode 26, and the ordinate represents the total current density in the multiple quantum well structure (unit: 10 4 A / cm 2);In addition, the dashed line on the vertical horizontal axis in the figure represents the boundary position between the conductive region and the insulating region in the corresponding current limiting layer (i.e., Figure 2 the position shown by the dashed line a1a2 in

[0053] As Figure 5 and Figure 6 shown, within the first multiple quantum well structure 22a1 and within the fifth multiple quantum well structure 22e1, the current density is relatively high at the geometric center position of the VCSEL unit, and as the distance from the geometric center increases, the current density gradually decreases.

[0054] However, as Figure 5 shown, in the fifth multiple quantum well structure 22e1 upstream of the current path, there is an aggregation effect of current at the boundary position between the conductive region and the insulating region, and at this position, the current density even exceeds the current density at the geometric center position. At a position 1 μm away from the geometric center beyond the boundary position between the conductive region and the insulating region, the current density decreases from 2×10 4 A / cm 2 to a level close to zero. As Figure 6 shown, in the first multiple quantum well structure 22a1 downstream of the current path, there is a more obvious current diffusion effect, that is, the current diffuses to the current limiting layer part, and at a position 1 μm away from the boundary position between the conductive region and the insulating region, the current density decreases from 1×10 4 A / cm 2 to a level close to zero.

[0055] Top-emitting VCSEL units usually use an N-type substrate. The lower electrode 26 connected to the substrate is an N-type electrode, and the lower electrode 26 is grounded. The upper electrode 25 is a P-type electrode connected to the positive pole of the power supply. Among them, the shape of the upper electrode 25 is annular.

[0056] In order to increase the current density at the geometric center position of the VCSEL unit, the size of the insulating region in the current limiting layer is relatively large, and the size of the conductive region is relatively small; on the other hand, in order to prevent blocking the light emission, the width of the P-type electrode is relatively small. Therefore, in the resonant cavity, the width of the insulating region of the current limiting layer is generally greater than the width of the upper electrode 25. The current flows out from the upper electrode 25, passes through the current limiting layer, diffuses towards the geometric center of the VCSEL unit and then passes through the active region, and is led out from the lower electrode 26. Such a path makes the current easily aggregate at the edge of the topmost current limiting layer on the path, such as the edge of the fifth current limiting layer 22e2, and continue to diffuse towards the edge of the resonant cavity after passing through multiple multiple quantum well structures (between the first current limiting layer 22a2 and the first multiple quantum well structure 22a1), thus causing the Figure 5 current aggregation effect shown in Figure 6 and the

[0057] current diffusion effect shown inFigure 3 As shown, since the current density is relatively high at the boundary between the conductive region and the insulating region in the current confinement layer, it is easy to excite high-order modes with relatively high light intensity at this position, so that the light generated by the VCSEL unit is a superposition of the fundamental mode and the high-order mode, resulting in a phenomenon of relatively high light intensity at a position deviating from the center, causing the light spot to continue to spread outward, and further resulting in the problem of an increased divergence angle.

[0058] To solve the above technical problems, the present invention provides a resonant cavity, including: a first mirror and a second mirror, the first mirror and the second mirror are arranged opposite to each other at intervals, and the direction of the first mirror pointing to the second mirror is the same as the current direction; an active structure, the active structure is located between the first mirror and the second mirror; the active structure includes a plurality of functional stacks, the functional stack includes a light-emitting layer; along the direction of the first mirror pointing to the second mirror, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack, the second functional stack... the Nth functional stack, where N is the number of functional stacks in the active structure, and at least the first functional stack and the Nth functional stack further include: a current confinement layer; in the same functional stack, the distance between the current confinement layer and the light-emitting layer is the conduction spacing; the conduction spacing of the first functional stack is greater than the conduction spacing of the Nth functional stack.

[0059] In the technical solution of the present invention, increasing the conduction spacing of the first functional stack can extend the current path from the current confinement layer of the first functional stack to the light-emitting layer, making the diffusion of current to the central region more sufficient, thereby effectively suppressing the current accumulation effect at the boundary between the insulating region and the conductive region of the current confinement layer; reducing the conduction spacing of the Nth functional stack shortens the current path from the current confinement layer of the Nth functional stack to the light-emitting layer, thereby improving the current diffusion effect and increasing the current density in the central region; the suppression of the current accumulation effect at the boundary between the insulating region and the conductive region of the current confinement layer and the increase in the current density in the geometric central region of the VCSEL unit can both effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser.

[0060] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings.

[0061] Refer to Figure 7 , which shows a schematic cross-sectional structure diagram of an embodiment of the resonant cavity of the present invention.

[0062] The resonant cavity includes:

[0063] A first reflector 110 and a second reflector 140, the first reflector 110 and the second reflector 140 are arranged at a relative interval, and the direction of the first reflector 110 pointing to the second reflector 140 is consistent with the current direction; an active structure (not labeled in the figure), the active structure is located between the first reflector 110 and the second reflector 140; the active structure includes a plurality of functional stacks, and the functional stack includes a light-emitting layer; along the direction of the first reflector 110 pointing to the second reflector 140, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack 101, the second functional stack 102,..., the Nth functional stack, where N is the number of functional stacks in the active structure, and at least the first functional stack and the Nth functional stack further include: a current confinement layer; in the same functional stack, the distance between the current confinement layer and the light-emitting layer is the conduction spacing; the conduction spacing of the first functional stack 101 is greater than the conduction spacing of the Nth functional stack.

[0064] By providing functional stacks with uneven conduction spacings in the active structure, on the one hand, increasing the conduction spacing of the first functional stack 101 to make the conduction spacing of the functional stacks in the current injection direction larger can extend the current path from the current confinement layer 131 to the light-emitting layer 121 of the first functional stack 101, making the diffusion of current into the central region more sufficient, thereby effectively suppressing the current concentration effect at the boundary between the insulating region and the conductive region of the current confinement layer; on the other hand, reducing the conduction spacing of the Nth functional stack to make the conduction spacing of the functional stacks in the current extraction direction smaller can shorten the current path from the current confinement layer to the light-emitting layer of the Nth functional stack, thereby improving the current diffusion effect and increasing the current density in the central region; the suppression of the current concentration effect at the boundary position and the increase in the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser.

[0065] It should be noted that in this embodiment, the resonant cavity is the resonant cavity of a vertical cavity surface emitting laser.

[0066] It should also be noted that in the technical solution of the present invention, the spacing between material film layers refers to the spacing between the centers of the material film layers. Therefore, the conduction spacing refers to the spacing between the center line of the current confinement layer and the center line of the light-emitting layer in the same functional stack.

[0067] The embodiments of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0068] The relatively spaced first reflector 110 and second reflector 140 respectively serve as the two cavity mirrors of the resonant cavity, and light travels back and forth between the first reflector 110 and the second reflector 140.

[0069] In some embodiments of the present invention, the first reflector 110 and the second reflector 140 are Bragg reflectors (Distributed Bragg Reflector, referred to as DBR), and the first reflector 110 and the second reflector 140 both include a high refractive index film and a low refractive index film, and the high refractive index film and the low refractive index film are alternately arranged. Adjacent high refractive index films and low refractive index films form a period. The reflectivity of the distributed Bragg reflector is related to the number of periods of the high and low refractive index films. For example, the first reflector 110 and the second reflector 140 can be Al2O3 films arranged alternately in sequence. x Ga 1-x As / Al 1-y Ga y As film, where the values ​​of x and y can be different.

[0070] In order to ensure the gain of the resonant cavity, the first reflector 110 and the second reflector 140 must have a considerable number of periods to meet the requirement of high reflectivity. In addition, in order to ensure that the emitted laser has a narrow line width, the light forms a standing wave in the resonant cavity after being reflected multiple times by the first reflector 110 and the second reflector 140. Therefore, the first reflector 110 and the second reflector 140 need to have a considerable reflectivity.

[0071] In this embodiment, the reflectivity of the second reflector 140 is greater than or equal to 99.9%, and the number of periods of the second reflector 140 is greater than or equal to 30, so as to meet the high reflectivity requirement of the resonant cavity; the reflectivity of the first reflector 110 is greater than or equal to 98%, and the number of periods of the first reflector 110 is greater than or equal to 11. Ensuring the overall number of periods of the first reflector 110 and the second reflector 140 can ensure that the first reflector 110 and the second reflector 140 meet the high reflectivity requirement to form a resonant cavity, and can ensure the gain of the resonant cavity and the luminous intensity.

[0072] It should be noted that, in this embodiment, the reflectivity of the first reflector 110 is lower than that of the second reflector 140, so the direction in which the second reflector 140 points to the first reflector 110 is consistent with the laser emission direction. Specifically, the reflectivity of the second reflector 140 reaches more than 99.9% to minimize the light energy loss caused by the generated laser passing through the second reflector 140.

[0073] It should also be noted that, since the direction in which the first reflector 110 points to the second reflector 140 is consistent with the current, the first reflector 110 is a P-type doped reflector, and the second reflector 140 is an N-type doped reflector.

[0074] The active structure (not shown in the figure) has a gain medium capable of achieving population inversion to produce stimulated emission amplification effect.

[0075] The active structure includes a plurality of functional laminates. Along the direction from the first mirror 110 to the second mirror 140, the plurality of functional laminates are arranged in sequence and are respectively the first functional laminate, the second functional laminate... the Nth functional laminate, where N is the number of functional laminates in the active structure.

[0076] Specifically, as Figure 7 shown, the active structure includes 5 functional laminates. Along the direction from the first mirror 110 to the second mirror 140, they are respectively the first functional laminate 101, the second functional laminate 102, the third functional laminate 103, the fourth functional laminate 104, and the fifth functional laminate 105 in sequence.

[0077] At least the first functional laminate 101 and the Nth functional laminate 102 further include: a current confinement layer. In some embodiments of the present invention, the current confinement layer is located between the light-emitting layer and the first mirror in the same functional laminate, that is, the direction of the current confinement layer pointing to the light-emitting layer in the same functional laminate is consistent with the current direction.

[0078] In this embodiment, the first functional laminate 101 includes a light-emitting layer 131 and a current confinement layer 131, and the current confinement layer 131 and the light-emitting layer 121 are arranged in sequence along the current direction I (i.e., the direction from the first mirror 110 to the second mirror 140); the fifth functional laminate 105 includes a light-emitting layer 135 and a current confinement layer 135, and the current confinement layer 135 and the light-emitting layer 125 are arranged in sequence along the current direction I.

[0079] As Figure 7 shown, the distance between the current confinement layer 131 and the light-emitting layer 121 is the conduction spacing L1 of the first functional laminate 101; the distance between the current confinement layer 135 and the light-emitting layer 125 is the conduction spacing L5 of the fifth functional laminate 105. The conduction spacing of the first functional laminate 101 is greater than the conduction spacing of the fifth functional laminate 105, that is, L1 > L5.

[0080] A functional stack with uneven conduction spacing is arranged in the active structure. On the one hand, the conduction spacing L1 of the first functional stack 101 can be increased so that the conduction spacing of the functional stack in the starting current injection direction (i.e., the current upstream) is larger, which can extend the current path from the current limiting layer 131 to the light emitting layer 121 of the first functional stack 101, make the diffusion of current to the central region more sufficient, and thus effectively suppress the current concentration effect at the boundary between the insulating region and the conductive region of the current limiting layer. On the other hand, the conduction spacing of the Nth functional stack can be reduced so that the conduction spacing of the functional stack in the current extraction direction (i.e., the current downstream) is smaller, which can shorten the current path from the current limiting layer of the Nth functional stack to the light emitting layer, thereby improving the current diffusion effect and increasing the current density in the central region. The suppression of the current concentration effect at the boundary position and the increase in the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser.

[0081] It should be noted that in this embodiment, the spacing between adjacent light emitting layers is equal, that is, as Figure 7 shown, the spacing D1 between the light emitting layer of the first functional stack 101 and the light emitting layer of the second functional stack 102, the spacing D2 between the light emitting layer of the second functional stack 102 and the light emitting layer of the third functional stack 103, the spacing D3 between the light emitting layer of the third functional stack 103 and the light emitting layer of the fourth functional stack 104, and the spacing D4 between the light emitting layer of the fourth functional stack 104 and the light emitting layer of the fifth functional stack 105 are equal, that is, D1 = D2 = D3 = D4. Refer to Figure 8 , which shows a schematic cross-sectional structure diagram of another embodiment of the resonator of the present invention.

[0082] The resonator includes: a first mirror 110 and a second mirror 140, the first mirror 110 and the second mirror 140 are arranged at intervals relative to each other, and the direction of the first mirror 110 pointing to the second mirror 140 is the same as the current direction; an active structure (not marked in the figure), the active structure is located between the first mirror 110 and the second mirror 140; the active structure includes a plurality of functional stacks, each functional stack includes a current limiting layer and a light emitting layer arranged in sequence along the current direction, and the distance between the current limiting layer and the light emitting layer is the conduction spacing; along the direction of the first mirror 110 pointing to the second mirror 140, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack 101, the second functional stack 102,..., the Nth functional stack, where N is the number of functional stacks in the active structure; the conduction spacing of the first functional stack 101 is greater than the conduction spacing of the Nth functional stack.

[0083] A functional stack with uneven conduction spacing is arranged in the active structure. On the one hand, increasing the conduction spacing of the first functional stack 101 so that the conduction spacing of the functional stack in the current injection direction is larger can extend the current path from the current conduction layer 131 of the first functional stack 101 to the light-emitting layer 121, making the diffusion of current into the central region more sufficient, thereby effectively suppressing the current concentration effect at the boundary between the insulating region and the conductive region of the current confinement layer; on the other hand, reducing the conduction spacing of the Nth functional stack so that the conduction spacing of the functional stack in the current extraction direction is smaller can shorten the current path from the current conduction layer of the Nth functional stack to the light-emitting layer, thereby improving the current diffusion effect and increasing the current density in the central region; the suppression of the current concentration effect at the boundary position and the increase in the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser.

[0084] The active structure (not labeled in the figure) has a gain medium capable of achieving population inversion to produce stimulated emission amplification.

[0085] The active structure includes a plurality of functional stacks. Along the direction from the first mirror 110 to the second mirror 140, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack, the second functional stack... the Nth functional stack, where N is the number of functional stacks in the active structure.

[0086] Specifically, as Figure 8 shown, the active structure includes 5 functional stacks. Along the direction from the first mirror 110 to the second mirror 140, they are respectively the first functional stack 101, the second functional stack 102, the third functional stack 103, the fourth functional stack 104, and the fifth functional stack 105 in sequence.

[0087] Each functional stack includes a current confinement layer and a light-emitting layer arranged in sequence along the current direction.

[0088] The current confinement layer is suitable for restricting the distribution range of current and suppressing the current dispersion effect, thereby increasing the current density in the light-emitting region within the active structure to improve the gain. In some embodiments of the present invention, the current confinement layer includes a conductive region and an insulating region outside the conductive region, where the conductive region penetrates the current confinement layer along the current direction.

[0089] The light-emitting layer has a gain medium, which can generate stimulated emission amplification under the pumping of voltage. In some embodiments of the present invention, the light-emitting layer is a quantum well structure, that is, the light-emitting layer is a quantum well structure formed by alternately growing thin films of two materials with a narrow bandgap and a wide bandgap. In this embodiment, the light-emitting layer is a multi-quantum well structure, that is, the light-emitting layer includes multiple groups of quantum well structures. For example, when the resonant cavity is the resonant cavity of a 940 nm laser, the quantum well structure is an InGaAs / GaAs quantum well structure or an InGaAs / GaAsP quantum well structure.

[0090] Specifically, as Figure 8 shown, in this embodiment, in the active structure, the first functional stack 101 includes a first current confinement layer 131 and a first light-emitting layer 121 arranged in sequence along the current direction I (that is, the direction from the first mirror 110 to the second mirror 140), the second functional stack 102 includes a second current confinement layer 132 and a second light-emitting layer 122 arranged in sequence along the current direction I, the third functional stack 103 includes a third current confinement layer 133 and a third light-emitting layer 123 arranged in sequence along the current direction I, the fourth functional stack 104 includes a fourth current confinement layer 134 and a fourth light-emitting layer 124 arranged in sequence along the current direction I, and the fifth functional stack 105 includes a fifth current confinement layer 135 and a fifth light-emitting layer 125 arranged in sequence along the current direction I.

[0091] In each of the functional stacks, the distance between the current confinement layer and the light-emitting layer is the conduction distance L. Specifically, as Figure 8 shown, the distance between the first current confinement layer 131 and the first light-emitting layer 121 is the conduction distance L1 of the first functional stack 101; the distance between the second current confinement layer 132 and the second light-emitting layer 122 is the conduction distance L2 of the second functional stack 102; the distance between the third current confinement layer 133 and the third light-emitting layer 123 is the conduction distance L3 of the third functional stack 103; the distance between the fourth current confinement layer 134 and the fourth light-emitting layer 124 is the conduction distance L4 of the fourth functional stack 104; the distance between the fifth current confinement layer 135 and the fifth light-emitting layer 125 is the conduction distance L5 of the fifth functional stack 105.

[0092] It should be noted that in the technical solution of the present invention, the distance between material film layers refers to the distance between the centers of the material film layers. Therefore, the conduction distance refers to the distance between the center line of the current confinement layer and the center line of the light-emitting layer in the same functional stack.

[0093] The conduction distance L1 of the first functional stack is greater than the conduction distance of the Nth functional stack. Specifically, as Figure 8As shown, the conduction pitch L1 of the first functional stack is greater than the conduction pitch L5 of the fifth functional stack.

[0094] Functional stacks with uneven conduction spacing are arranged in the active structure. On the one hand, the conduction spacing of the first functional stack 101 can be increased, so that the conduction spacing of the functional stack in the direction of initial current injection is larger, and the current path from the current limiting layer 131 of the first functional stack 101 to the light-emitting layer 121 can be extended, so that the current diffuses more fully to the central area, thereby effectively suppressing the current concentration effect at the boundary between the insulating area and the conductive area of ​​the current limiting layer; on the other hand, the conduction spacing of the Nth functional stack can be reduced to make the conduction spacing of the functional stack in the direction of current extraction smaller, and the current path from the current limiting layer to the light-emitting layer of the Nth functional stack can be shortened, thereby improving the current diffusion effect and increasing the current density in the central area; the suppression of the current concentration effect at the boundary and the increase of the current density in the central area can effectively increase the fundamental mode strength, suppress the excitation of high-order modes, and effectively reduce the divergence angle of the laser.

[0095] It should be noted that, in this embodiment, the spacing between adjacent light-emitting layers is equal, that is, Figure 8 As shown, the distance D1 between the light-emitting layer of the first functional stack 101 and the light-emitting layer of the second functional stack 102, the distance D2 between the light-emitting layer of the second functional stack 102 and the light-emitting layer of the third functional stack 103, the distance D3 between the light-emitting layer of the third functional stack 103 and the light-emitting layer of the fourth functional stack 104, and the distance D4 between the light-emitting layer of the fourth functional stack 104 and the light-emitting layer of the fifth functional stack 105 are equal, that is, D1=D2=D3=D4.

[0096] It should be noted that the light generated by the active structure is reflected back and forth between the first reflector 110 and the second reflector 140, and the reflected light will interfere with each other, thereby forming a standing wave in the resonant cavity (such as Figure 9 As shown in the figure, the amplitudes of the standing waves at different points are not equal. The position with zero amplitude is called a node, and the position with the largest amplitude is an antinode. The distance between two adjacent antinodes and the distance between two adjacent nodes are both λ / 2.

[0097] Since the amplitude of the standing wave is the largest at the antinode, the electric field intensity of the light wave is the largest at the antinode, and the light intensity of the light wave is the largest. Therefore, the light emitting layer is located at the antinode of the standing wave, so that the light generated by the light emitting layer can achieve the maximum degree of resonance amplification. On the other hand, the insulating region of the current limiting layer is generally an oxide (for example, Al 1- x Ga xFor O, x≥0), the oxide will absorb light and easily cause a large loss in the resonant cavity. Therefore, the current limiting layer is located at the node position of the standing wave to reduce the light absorption and loss of the current limiting layer.

[0098] Therefore, the distances between adjacent two light-emitting layers and between adjacent two current limiting layers should satisfy the following relationship:

[0099]

[0100] Where λ is the central wavelength of the light generated by the light-emitting layer, n is the refractive index of the light-emitting layer material for light with wavelength λ, and N is a positive integer. That is to say, the optical path between adjacent two light-emitting layers and between adjacent two current limiting layers should both be an integer multiple of half the wavelength of the light generated by the active structure.

[0101] Increasing the conduction spacing L1 of the first functional stack 101 or decreasing the conduction spacing of the Nth functional stack can make the conduction spacings of multiple functional stacks of the active structure uneven. Therefore, either the increase amount of the conduction spacing L1 of the first functional stack 101 or the decrease amount of the conduction spacing of the Nth functional stack should satisfy the above relationship, that is, either the increase amount of the conduction spacing L1 of the first functional stack 101 or the decrease amount of the conduction spacing of the Nth functional stack should be an integer multiple of half the wavelength of the generated light. That is to say, the optical path difference caused by the change in the conduction spacing in the functional stack is an integer multiple of half the wavelength of the generated light, that is:

[0102]

[0103] Where λ is the central wavelength of the light generated by the light-emitting layer, n is the refractive index of the light-emitting layer material for light with wavelength λ, and N is a positive integer.

[0104] Therefore, the optical path difference between the conduction spacing of the first functional stack and that of the Nth functional stack is an integer multiple of half the wavelength of the light generated by the active structure. As Figure 8 shown, in this embodiment, the optical path difference between the conduction spacing L1 of the first functional stack 101 and the conduction spacing L5 of the fifth functional stack 105 is an integer multiple of half the wavelength of the light generated by the active structure, that is:

[0105]

[0106] Where λ is the central wavelength of the light generated by the light-emitting layer, n is the refractive index of the light-emitting layer material for light with wavelength λ, and N is a positive integer.

[0107] Specifically, in order to better suppress the current concentration effect at the boundary position and increase the current density in the central region, the optical path difference between the conduction spacing of the first functional stack and the conduction spacing of the Nth functional stack is an integer multiple of half the wavelength of the light generated by the active structure, where the integer is greater than or equal to 2. That is to say, the optical path difference between the conduction spacing of the first functional stack and the conduction spacing of the Nth functional stack is more than twice the half wavelength of the light generated by the active structure.

[0108] As a specific embodiment, the conduction spacing of each of the second to (N - 1)th functional stacks is 0.75λ. The conduction spacing L1 of the first functional stack 101 and the conduction spacing of the Nth functional stack both deviate from 0.75λ, thereby forming a non-uniformly distributed active structure. Specifically, the conduction spacing L1 of the first functional stack is greater than 0.75λ, where λ is the wavelength of the light generated by the active structure; the conduction spacing of the Nth functional stack is less than 0.75λ, where λ is the wavelength of the light generated by the active structure.

[0109] On the one hand, it enables the current to more fully diffuse towards the geometric center of the VCSEL unit on the current path, and on the other hand, it suppresses the current diffusion effect downstream of the current path, thereby increasing the current density at the geometric center and reducing the current density at positions far from the geometric center, ultimately achieving the purpose of suppressing the excitation of high-order modes and reducing the divergence angle of the generated laser.

[0110] In some embodiments of the present invention, along the direction from the first functional stack to the second functional stack, the conduction spacing decreases. That is to say, along the direction of the current I, the conduction spacing in each of the sequentially arranged functional stacks decreases.

[0111] As Figure 8 shown, in this embodiment, the conduction spacing L1 of the first functional stack is greater than the conduction spacing L2 of the second functional stack, that is, the conduction spacing of the functional stack in the current injection direction is increased by increasing the conduction spacing of the first functional stack 101, and the current path from the current confinement layer 131 to the light-emitting layer 121 of the first functional stack 101 is extended, so that the current diffuses more fully towards the central region to suppress the current concentration effect at the boundary position.

[0112] Moreover, the conduction spacing of the Nth functional stack is less than the conduction spacing of the (N - 1)th functional stack. In this embodiment, N = 5. That is to say, the conduction spacing L5 of the fifth functional stack is less than the conduction spacing L4 of the fourth functional stack, that is, the conduction spacing of the functional stack in the current extraction direction is reduced by reducing the conduction spacing of the Nth functional stack, and the current path from the current confinement layer of the Nth functional stack to the light-emitting layer is shortened, and the current diffusion effect is improved to increase the current density in the central region.

[0113] Therefore, as Figure 8As described above, in this embodiment, the conduction spacing L1 of the first functional stack, the conduction spacing L2 of the second functional stack, the conduction spacing L3 of the third functional stack, the conduction spacing L4 of the fourth functional stack to the conduction spacing L5 of the fifth functional stack decrease in sequence, that is, L1 > L2 > L3 > L4 > L5.

[0114] The method of making the conduction spacings of multiple functional stacks decrease in sequence is only an example. In addition, in some embodiments of the present invention, the conduction spacing of any one of the first functional stack, the second functional stack, ……, the Xth functional stack is greater than the conduction spacing of any one of the (X + 1)th functional stack, the (X + 2)th functional stack, ……, the Nth functional stack.

[0115] For example, in some embodiments of the present invention, the conduction spacing of only the first functional stack can be increased without changing the conduction spacings of other functional stacks, that is, L1 > L2 = L3 = … = LN; in other embodiments of the present invention, the conduction spacing of only the Nth functional stack can also be decreased without changing the conduction spacings of other functional stacks, that is, L1 = L2 = L3 = … = LN - 1 > LN. It is also possible to increase the conduction spacing of the first functional stack and decrease the conduction spacing of the Nth functional stack at the same time, that is, L1 > L2 = L3 = … = L(N - 1) > LN. Increasing the conduction spacing of the first functional stack upstream of the current path and decreasing the conduction spacing of the Nth functional stack downstream of the current path can both improve the current distribution in the active structure, can suppress the excitation of higher-order modes, and reduce the divergence angle of the generated laser.

[0116] In addition, in some other embodiments of the present invention, the conduction spacings of multiple functional stacks upstream of the current path can be increased. Taking the active structure including 5 functional stacks as an example for illustration, the conduction spacings of only the first functional stack and the second functional stack can also be increased, that is, L1 = L2 > L3 = L4 = L5; or the conduction spacings of only the first functional stack, the second functional stack and the third functional stack can be increased, that is, L1 = L2 = L3 > L4 = L5; or the conduction spacings of only the first functional stack, the second functional stack, the third functional stack and the fourth functional stack can be increased, that is, L1 = L2 = L3 = L4 > L5.

[0117] Combined with reference Figure 10 and Figure 11 , where Figure 10 is Figure 8 the current distribution in the light-emitting layer 121 of the first functional stack 101 upstream of the current in the resonant cavity embodiment shown; Figure 11 is Figure 8 the current distribution in the light-emitting layer 125 of the fifth functional stack 105 downstream of the current in the resonant cavity embodiment shown.

[0118] In the figure, the abscissa is the distance between the geometric center and the light-emitting layer (unit: μm), and the ordinate represents the total current density in the light-emitting layer (unit: 10 4 A / cm 2 ); in addition, the dashed line perpendicular to the horizontal axis in the figure represents the boundary position between the conductive region and the insulating region in the corresponding current confinement layer (i.e., the position shown by the dashed line A1A2 in Figure 8 ).

[0119] As Figure 10 shown, after increasing the conduction spacing L1 of the first functional stack, at the position corresponding to the boundary between the conductive region and the insulating region in the current confinement layer, the current density in the light-emitting layer is reduced to 1.5×10 4 A / cm 2 , which is close to the current density at the geometric center position, indicating that the current distribution in the light-emitting area is more uniform, and the current concentration effect at the boundary position is improved.

[0120] As Figure 11 shown, after reducing the conduction spacing LN of the Nth functional stack, at the position corresponding to the boundary between the conductive region and the insulating region in the current confinement layer, the current density in the light-emitting layer decreases, and the diffusion effect of the current towards the boundary position weakens, and the current density at the geometric center increases by about 0.15×10 4 A / cm 2 .

[0121] Combined with reference Figure 4 , where the abscissa is the distance r between the geometric center of the VCSEL unit and the plane perpendicular to the upper electrode 25 and pointing towards the lower electrode 26, and the ordinate represents the light intensity I. Figure 4 The graph line 42 in Figure 8 shows the schematic diagram of the light intensity distribution generated in the resonant cavity active structure shown in Figure 4 . It can be seen that the fundamental mode light is enhanced and the high-order mode light is weakened. The light generated by the overall resonant cavity has a weakened light intensity at the place deviating from the geometric center (such as the region shown by the arrow T2 in Figure 4 ), and the beam divergence angle decreases.

[0122] Correspondingly, the present invention also provides a laser unit.

[0123] Reference Figure 8 shows a schematic cross-sectional structure diagram of an embodiment of the laser unit of the present invention. The laser unit includes: a resonant cavity, which is the resonant cavity of the present invention; a first electrode 150 and a second electrode 160 electrically connected to the resonant cavity.

[0124] It should be noted that in this embodiment, the laser unit is the laser unit of a vertical cavity surface emitting laser.

[0125] Specifically, for the specific technical solution of the resonant cavity, reference can be made to the embodiments of the resonant cavity described above, and details are not repeated herein. Increasing the conduction distance of the first functional stack can extend the current path from the current limiting layer of the first functional stack to the light emitting layer, enabling more sufficient diffusion of the current towards the central region, thereby effectively suppressing the current concentration effect at the boundary between the insulating region and the conductive region of the current limiting layer; reducing the conduction distance of the Nth functional stack shortens the current path from the current limiting layer of the Nth functional stack to the light emitting layer, thus improving the current diffusion effect and increasing the current density in the central region; suppressing the current concentration effect at the boundary position and increasing the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of higher order modes, and can effectively reduce the divergence angle of the laser.

[0126] The first electrode 150 and the second electrode 160 respectively connect the resonant cavity to an external circuit to supply power to the resonant cavity.

[0127] In some embodiments of the present invention, the first electrode 150 and the second electrode 160 are electrically connected to the resonant cavity by being respectively electrically connected to the mirrors. As Figure 8 described, the first electrode 150 is electrically connected to the first mirror 110, and the second electrode 160 is electrically connected to the second mirror 140.

[0128] Therefore, in order to ensure a single current flow direction, the conduction types of the first electrode 150 and the second electrode 160 need to be consistent with the conduction types of the connected mirrors. As Figure 8 shown, the conduction type of the first electrode 150 is the same as that of the first mirror 110; the conduction type of the second electrode 160 is the same as that of the second mirror 140.

[0129] In this embodiment, the first mirror 110 is a P-type doped mirror; the second mirror 140 is an N-type doped mirror, so the first electrode 150 is a P electrode; the second electrode 160 is an N electrode.

[0130] In this embodiment, the direction in which the second mirror 140 points to the first mirror 110 is the same as the laser output direction. Therefore, the first electrode 150 includes: an opening penetrating through the first electrode 150. As Figure 8 shown, the projection of the conductive region of the current limiting layer on the surface of the first electrode 150 is within the range of the opening to avoid the electrode blocking the light output.

[0131] Refer to Figure 12 , which shows a cross-sectional structural schematic diagram of another embodiment of the laser unit of the present invention.

[0132] The difference between this embodiment and the foregoing embodiments is that, in this embodiment, the laser unit is a backlight-emitting laser unit. The laser unit includes: the resonant cavity of the present invention, and a first electrode 250 and a second electrode 260 electrically connected to the resonant cavity.

[0133] The resonant cavity is the resonant cavity of the present invention. For the specific technical solution of the resonant cavity, reference may be made to the embodiments of the resonant cavity described above, and the present invention will not elaborate herein. The resonant cavity includes a first reflector (not labeled in the figure), an active structure, and a second reflector 240 that are sequentially located on a substrate 200; wherein the active structure includes a current confinement layer 231 and a light-emitting layer 221 of the first functional stack, a current confinement layer 232 and a light-emitting layer 222 of the second functional stack, a current confinement layer 233 and a light-emitting layer 223 of the third functional stack, a current confinement layer 234 and a light-emitting layer 224 of the fourth functional stack, and a current confinement layer 235 and a light-emitting layer 225 of the fifth functional stack, which are arranged along the direction from the first reflector to the second reflector 240.

[0134] It should be noted that, in this embodiment, the first reflector includes a first reflecting portion 211 and a second reflecting portion 212 that are sequentially arranged along the direction pointing to the active structure. Among them, the material of the first reflecting portion 211 is an intrinsic material (that is, the material of the first reflecting portion 211 is an undoped material), the material of the second reflecting portion 212 is a doped material, and a current conduction layer 213 is arranged between the first reflecting portion 211 and the second reflecting portion 212 to realize the electrical connection between the active structure and an external current.

[0135] It should also be noted that, in this embodiment, the material of the second reflecting portion 212 of the first reflector is a P-type doped material, and the material of the second reflector 240 is an N-type doped material. Therefore, the first electrode 250 electrically connected to the first reflector is a P electrode, and the second electrode electrically connected to the second reflector 240 is an N electrode.

[0136] In addition, as Figure 12 shown, in some embodiments of the present invention, in the plane perpendicular to the light-emitting direction, the laser unit includes: a core region 201 and an extended region 202, and the resonant cavity is located in the core region 201.

[0137] The current conduction layer 213 extends into the extended region 202, the first electrode 250 is located on the surface of the current conduction layer 213 in the extended region 202 facing the second reflector 240; the second electrode 260 is located on the surface of the second reflector 240. The shape of the second electrode 260 can be planar or disc-shaped. The current conduction layer 213 can realize the lateral conduction of current. Therefore, this structure can make the first electrode 250 and the second electrode 260 face the same side, so as to reduce the difficulty of subsequent circuit connection.

[0138] In addition, the current conduction layer 213 can also serve as an etching stop layer during the formation of the resonant cavity, that is, during the formation of the resonant cavity, the etching step stops on the surface of the current conduction layer 213 or within the current conduction layer 213. Therefore, as Figure 12 shown, the thickness of the current conduction layer 213 in the extended region 202 is less than or equal to the thickness of the current conduction layer 213 in the core region 201, and the surface of the current conduction layer 213 facing the active structure is planar or stepped.

[0139] In another embodiment of the present invention, the material of the second reflection portion 212 of the first mirror is an N-type doped material, and the material of the second mirror 240 is a P-type doped material. Therefore, the first electrode 250 electrically connected to the first mirror is an N electrode, and the second electrode electrically connected to the second mirror 240 is a P electrode.

[0140] At this time, the current flows from the second electrode 260 to the first electrode 250. The active structure includes a current confinement layer and a light-emitting layer of the first functional stack, a current confinement layer and a light-emitting layer of the second functional stack, a current confinement layer and a light-emitting layer of the third functional stack, a current confinement layer and a light-emitting layer of the fourth functional stack, and a current confinement layer and a light-emitting layer of the fifth functional stack (not shown in the figure) arranged in sequence along the current direction.

[0141] In addition, the present invention also provides a laser, specifically including: a laser unit, and the laser unit is the laser unit of the present invention.

[0142] Since the laser unit is the laser unit of the present invention, therefore, for the specific technical solution of the laser unit, reference can be made to the embodiments of the foregoing laser unit, and the present invention will not elaborate herein.

[0143] In this embodiment, the laser is a vertical cavity surface emitting laser. Specifically, the laser is a top-emitting vertical cavity surface emitting laser or a back-emitting vertical cavity surface emitting laser.

[0144] The conduction spacings of the functional stacks in the active structure of the resonant cavity are non-uniformly distributed: increasing the conduction spacing of the first functional stack can extend the current path from the current confinement layer to the light-emitting layer of the first functional stack, making the current diffusion to the central region more sufficient, thereby effectively suppressing the current concentration effect at the boundary between the insulating region and the conductive region of the current confinement layer; reducing the conduction spacing of the Nth functional stack shortens the current path from the current confinement layer to the light-emitting layer of the Nth functional stack, thereby improving the current diffusion effect and increasing the current density in the central region; both the suppression of the current concentration effect at the boundary position and the increase in the current density in the central region can effectively increase the fundamental mode intensity and suppress the excitation of high-order modes, and can effectively reduce the divergence angle of the laser.

[0145] In addition, the present invention also provides a lidar, specifically including: a light source, and the light source includes the laser of the present invention.

[0146] Since the resonant cavity of the laser of the present invention can suppress the current concentration effect at the boundary position and increase the current density in the central region, the fundamental mode intensity of the resonant cavity is relatively large and the excitation of higher-order modes is suppressed. Therefore, the divergence angle of the laser generated by the laser is relatively small.

[0147] In summary, increasing the conduction spacing of the first functional laminate can extend the current path from the current limiting layer of the first functional laminate to the light emitting layer, making the diffusion of current into the central region more sufficient, thereby effectively suppressing the current concentration effect at the boundary between the insulating region and the conductive region of the current limiting layer; reducing the conduction spacing of the Nth functional laminate shortens the current path from the current limiting layer of the Nth functional laminate to the light emitting layer, thereby improving the current diffusion effect and increasing the current density in the central region; the suppression of the current concentration effect at the boundary position and the increase in the current density in the central region can both effectively increase the fundamental mode intensity and suppress the excitation of higher-order modes, and can effectively reduce the divergence angle of the laser.

[0148] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A resonant cavity, characterized in that, it includes: a first mirror and a second mirror, the first mirror and the second mirror are arranged at a relative interval, and the direction of the first mirror pointing to the second mirror is consistent with the current direction; an active structure, the active structure is located between the first mirror and the second mirror; the active structure includes a plurality of functional stacks, and the functional stack includes a light-emitting layer; Along the direction from the first mirror to the second mirror, the plurality of functional stacks are arranged in sequence and are respectively the first functional stack, the second functional stack... the Nth functional stack, where N is the number of functional stacks in the active structure, and at least the first functional stack and the Nth functional stack further include: a current confinement layer; In the same functional stack, the distance between the current confinement layer and the light-emitting layer is the conduction distance; The conduction distance of the first functional stack is greater than the conduction distance of the Nth functional stack.

2. The resonant cavity according to claim 1, characterized in that, The optical path difference between the conduction distance of the first functional stack and the conduction distance of the Nth functional stack is an integer multiple of half the wavelength of the light generated by the active structure.

3. The resonant cavity according to claim 2, characterized in that, The integer is greater than or equal to 2.

4. The resonant cavity according to claim 1, characterized in that, Each of the functional stacks includes a current confinement layer and a light-emitting layer arranged in sequence along the current direction.

5. The resonant cavity according to claim 4, characterized in that, Along the direction from the first functional stack to the second functional stack, the conduction distance decreases.

6. The resonant cavity according to claim 5, characterized in that, The conduction distance of the first functional stack is greater than the conduction distance of the second functional stack.

7. The resonant cavity according to claim 5, characterized in that, The conduction distance of the Nth functional stack is less than the conduction distance of the N-1th functional stack.

8. The resonant cavity according to claim 4, characterized in that, The conduction distance of any one of the first functional stack, the second functional stack,..., the Xth functional stack is greater than the conduction distance of any one of the X+1th functional stack, the X+2th functional stack,..., the Nth functional stack.

9. The resonant cavity according to claim 1, characterized in that, The conduction distance of the first functional stack is greater than 0.75λ, where λ is the wavelength of the light generated by the active structure.

10. The resonant cavity according to claim 1, characterized in that, The conduction distance of the Nth functional stack is less than 0.75λ, where λ is the wavelength of the light generated by the active structure.

11. The resonant cavity according to claim 1, characterized in that, The light-emitting layer is a quantum well structure.

12. The resonant cavity according to claim 1, characterized in that, The first mirror is a P-type doped mirror; the second mirror is an N-type doped mirror.

13. A laser unit, characterized in that, it includes: a resonant cavity, the resonant cavity is the resonant cavity according to any one of claims 1 to 12; a first electrode, the first electrode is electrically connected to the resonant cavity; a second electrode, the second electrode is electrically connected to the resonant cavity.

14. The laser unit according to claim 13, wherein, the first electrode includes: an opening penetrating the first electrode; the current limiting layer includes: a conductive region and an insulating region outside the conductive region, wherein the conductive region penetrates the current limiting layer along the current direction; a projection of the conductive region on the surface of the first electrode is within the range of the opening.

15. The laser unit according to claim 13 or 14, wherein, the first electrode is a P electrode; the second electrode is an N electrode.

16. A laser, wherein, it includes: a laser unit, and the laser unit is the laser unit according to any one of claims 13 to 15.

17. The laser according to claim 16, wherein, the laser is a vertical cavity surface emitting laser.

18. The laser according to claim 17, wherein, the laser is a top-emitting vertical cavity surface emitting laser or a back-emitting vertical cavity surface emitting laser.

19. A lidar, wherein, it includes: a light source, and the light source includes the laser according to any one of claims 16 to 18.

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