A vertical cavity surface emitting laser

Abstract

The application discloses a vertical cavity surface emitting laser, comprising: a substrate; a first distributed Bragg reflector arranged on the substrate; an active region arranged on the first distributed Bragg reflector; a second distributed Bragg reflector arranged on the active region; and at least one tunnel junction; wherein the distance between the tunnel junction and the active region is adjusted to regulate the lateral distribution of carriers, so that the far-field light field distribution of the vertical cavity surface emitting laser presents a Gaussian-like distribution.

Description

Technical Field

[0001] This application relates to the field of semiconductor optoelectronic device technology, specifically to a vertical cavity surface emitting laser (VCSEL). Background Technology

[0002] Vertical cavity surface-emitting lasers (VCSELs) have been widely used in optical communication, optical interconnection, 3D sensing and lidar due to their advantages such as low threshold current, high modulation rate, easy two-dimensional integration and low cost.

[0003] Traditional VCSEL devices typically employ a structure with an N-type distributed Bragg reflector (N-DBR) at the bottom, an active region / oxide layer in the middle, and a P-type distributed Bragg reflector (P-DBR) at the top. In this structure, the hole mobility in the P-type semiconductor material is much lower than the electron mobility in the N-type material, resulting in a relatively high lateral resistance of the P-DBR layer. When current is injected from the top P-type electrode, the current tends to flow along the path of least resistance, i.e., vertically towards the active region through the aperture defined by the oxide layer. This current conduction method easily leads to current concentration at the edge region of the oxide aperture, forming the so-called "current congestion" effect.

[0004] Non-uniform current distribution directly affects carrier concentration and gain distribution in the active region. Specifically, the current mainly concentrates in the annular region at the edge of the aperture, while the current density in the central region is lower. This non-uniform current injection leads to non-uniform transverse gain distribution, which in turn affects transverse mode competition. Ultimately, this results in the far-field (FF) optical field distribution of the VCSEL exhibiting a saddle shape (or annular, donut shape), meaning the optical field intensity is weaker in the central region and stronger at the edge region.

[0005] This saddle-shaped far-field optical field distribution has obvious drawbacks: First, its beam quality is poor and the divergence angle is large, which is not conducive to the efficient collimation and coupling of subsequent optical systems (such as lenses), increasing the complexity and cost of optical system design; Second, the concentration of current at the edge of the light-emitting aperture will form local hot spots, exacerbating the thermal effect of VCSEL and affecting its long-term reliability and lifespan.

[0006] Therefore, there is an urgent need for a VCSEL design scheme that can effectively control the lateral distribution of charge carriers, thereby transforming the far-field optical field distribution from a saddle shape to a Gaussian-like distribution. Summary of the Invention

[0007] This application discloses a vertical-cavity surface-emitting laser, comprising: a substrate; a first distributed Bragg mirror disposed on the substrate; an active region disposed on the first distributed Bragg mirror; a second distributed Bragg mirror disposed on the active region; and at least one tunnel junction; wherein, by adjusting the distance between the tunnel junction and the active region, the lateral distribution of charge carriers is modulated, thereby causing the far-field optical field distribution of the vertical-cavity surface-emitting laser to exhibit a Gaussian-like distribution.

[0008] According to the vertical-cavity surface-emitting laser of this application, by setting at least one tunnel junction and adjusting the distance between the tunnel junction and the active region, the lateral distribution of carriers injected into the active region can be effectively controlled. The tunnel junction converts part or all of the P-type layer (or P-type DBR) into an N-type layer (or N-type DBR). Utilizing the physical properties that electron mobility is much higher than hole mobility and the lateral resistance of the N-type layer is significantly lower than that of the P-type layer, the injected current can diffuse more uniformly in the lateral direction, thereby effectively suppressing the current congestion effect caused by the low hole mobility in traditional structures. On this basis, the uniform current density distribution promotes the uniformity of the lateral gain distribution, thereby optimizing the lateral mode competition mechanism and transforming the far-field optical field distribution of the device from the saddle-shaped (ring-shaped) distribution of the traditional structure to a Gaussian-like distribution.

[0009] In the vertical cavity surface-emitting laser disclosed in this application, the first distributed Bragg mirror and the second distributed Bragg mirror are N-type distributed Bragg mirrors; the tunnel junction is disposed between the second distributed Bragg mirror and the active region.

[0010] According to the vertical-cavity surface-emitting laser of this application, a structure is adopted in which both the first and second DBRs are N-type DBRs, and a tunnel junction is placed between the second DBR and the active region. In this structure, the tunneling effect of the tunnel junction enables the effective injection of charge carriers from the N-type region to the active region, making all the top DBRs N-type DBRs. This fully utilizes the advantages of low resistance and high carrier mobility of N-type materials, maximizing the uniformity of lateral current diffusion, thereby further optimizing the current density distribution injected into the active region, making the Gaussian-like characteristics of the far-field optical field distribution more significant, and effectively reducing the series resistance and Joule heating effect of the device.

[0011] In the vertical cavity surface-emitting laser disclosed in this application, the first distributed Bragg mirror is an N-type distributed Bragg mirror; the tunnel junction is disposed inside the second distributed Bragg mirror, dividing the second distributed Bragg mirror into a P-type mirror region located below the tunnel junction and an N-type mirror region located above the tunnel junction.

[0012] According to the vertical-cavity surface-emitting laser of this application, a tunnel junction is placed inside a second vertical beam backlight (DBR), dividing the second DBR into a P-type mirror region below the tunnel junction and an N-type mirror region above it. In this structural configuration, the P-type mirror region below the tunnel junction maintains a smaller number of P-type DBR logs, reducing the resistive contribution of the P-type material; while the N-type mirror region above the tunnel junction utilizes the high conductivity of the N-type material to significantly improve the lateral current spread at the top. By adjusting the specific position of the tunnel junction in the second DBR (i.e., the thickness of the P-type mirror region), the lateral carrier distribution can be flexibly controlled, thereby achieving customized adjustment of the far-field optical field distribution to meet the beam quality requirements of different application scenarios.

[0013] In the vertical cavity surface-emitting laser disclosed in this application, the second distributed Bragg reflector is an N-type distributed Bragg reflector; the tunnel junction is disposed inside the first distributed Bragg reflector, dividing the first distributed Bragg reflector into an N-type reflector region located below the tunnel junction and a P-type reflector region located above the tunnel junction.

[0014] According to the vertical-cavity surface-emitting laser of this application, a tunnel junction is disposed inside a first damping beam (DBR), such that the first DBR is divided into an N-type mirror region located below the tunnel junction and a P-type mirror region located above the tunnel junction, while the second DBR is an N-type DBR. In this structure with the tunnel junction at the bottom, the P-type mirror region is only part of the first DBR located above the tunnel junction, which greatly reduces the contribution of the P-type material to the series resistance of the entire device, while the top N-type DBR provides an excellent lateral diffusion path for current injected from the upper electrode.

[0015] In the vertical cavity surface-emitting laser disclosed in this application, the first distributed Bragg mirror is an N-type distributed Bragg mirror; the tunnel junction is multiple and disposed within the second distributed Bragg mirror, dividing the second distributed Bragg mirror into mutually spaced N-type mirror regions and P-type mirror regions.

[0016] According to the vertical-cavity surface-emitting laser of this application, by setting multiple tunnel junctions inside the second vertical-cavity reflector (DBR), the second DBR is divided into alternating N-type and P-type reflector regions. The cascaded arrangement of multiple tunnel junctions can further reduce the series resistance of the device through the cascade tunneling effect. Furthermore, through the synergistic effect of multiple tunnel junctions, the lateral distribution of charge carriers can be more precisely and hierarchically controlled. Compared to a single tunnel junction, the multi-tunnel junction structure provides more design freedom—designers can optimize the current distribution by adjusting the position and spacing of each tunnel junction, resulting in a more uniform current density distribution injected into the active region and further improvement in the Gaussian-like properties of the far-field optical field distribution.

[0017] In the vertical cavity surface-emitting laser disclosed in this application, there are multiple tunnel junctions, which are respectively disposed in the first distributed Bragg mirror and the second distributed Bragg mirror, dividing the first distributed Bragg mirror and the second distributed Bragg mirror into mutually spaced N-type mirror regions and P-type mirror regions.

[0018] According to the vertical-cavity surface-emitting laser of this application, by incorporating multiple tunnel junctions in both the first and second vertical-cavity surface-emitting lasers (DBRs), the upper and lower DBRs are divided into alternating N-type and P-type mirror regions. This dual-sided multi-tunnel junction configuration enables simultaneous coordinated control of the lateral carrier distribution from both the top and bottom directions, maximizing the utilization of the high conductivity of the N-type material and comprehensively optimizing the lateral current expansion capability of the entire device structure. This structure is particularly suitable for large-aperture VCSEL devices, maintaining a uniform current distribution and a Gaussian-like far-field optical field distribution even under high injection current conditions, while significantly reducing the thermal effects of the device and improving its reliability and stability under high-power operating conditions.

[0019] The vertical cavity surface-emitting laser disclosed in this application further includes an oxide layer disposed in or near the active region, the oxide layer being used to define a light-emitting aperture.

[0020] According to the vertical cavity surface-emitting laser of this application, by setting an oxide layer and using it to define the emission aperture, the injection current path is effectively limited.

[0021] In the vertical cavity surface-emitting laser disclosed in this application, the shape of the light-emitting aperture is circular, N-sided, or irregular, where N is an integer greater than or equal to 3.

[0022] According to the vertical cavity surface-emitting laser of this application, by designing the shape of the emission aperture in various ways (circular, triangular, square, pentagonal, hexagonal or irregular shape), the VCSEL can select different emission aperture geometries according to specific application requirements. Different shaped emission apertures affect the distribution of transverse modes and polarization characteristics in the resonant cavity. For example, polygonal or non-circular emission apertures can break the mode degeneracy caused by circular symmetry, which is beneficial to the selection and stability of specific transverse modes and further optimizes the uniformity and symmetry of the far-field optical field distribution.

[0023] In the vertical-cavity surface-emitting laser disclosed in this application, the vertical-cavity surface-emitting laser is a single-junction vertical-cavity surface-emitting laser or a multi-junction vertical-cavity surface-emitting laser.

[0024] In the vertical-cavity surface-emitting laser disclosed in this application, the emission wavelength of the vertical-cavity surface-emitting laser is 350nm to 530nm, and the material system of the vertical-cavity surface-emitting laser is gallium nitride-based; or, the emission wavelength of the vertical-cavity surface-emitting laser is 500nm to 1000nm, and the material system of the vertical-cavity surface-emitting laser is gallium arsenide-based; or the emission wavelength of the vertical-cavity surface-emitting laser is 1000nm to 1600nm, and the material system of the vertical-cavity surface-emitting laser is indium phosphide-based. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a traditional vertical-cavity surface-emitting laser.

[0026] Figure 2 A far-field image of a conventional vertical-cavity surface-emitting laser (VCSEL) captured by a camera;

[0027] Figure 3 To and Figure 2 The corresponding light intensity distribution diagram in the horizontal direction of the far-field light field;

[0028] Figure 4 To and Figure 2 The corresponding light intensity distribution in the vertical direction of the far-field light field;

[0029] Figure 5 This is a schematic diagram of the structure of the first embodiment of the vertical cavity surface-emitting laser involved in this application;

[0030] Figure 6 A far-field spot image of a first embodiment of a vertical-cavity surface-emitting laser, captured by a camera.

[0031] Figure 7 To and Figure 6 The corresponding light intensity distribution diagram in the horizontal direction of the far-field light field;

[0032] Figure 8 To and Figure 6 The corresponding light intensity distribution in the vertical direction of the far-field light field;

[0033] Figure 9 This is a schematic diagram of the structure of a second embodiment of the vertical cavity surface-emitting laser involved in this application;

[0034] Figure 10 This is a schematic diagram of the third embodiment of the vertical-cavity surface-emitting laser involved in this application;

[0035] Figure 11 This is a schematic diagram of the fourth embodiment of the vertical-cavity surface-emitting laser involved in this application.

[0036] Figure 12-14This is a schematic diagram of the fifth embodiment of the vertical cavity surface-emitting laser involved in this application. Detailed Implementation

[0037] The present application will be further described below with reference to specific embodiments and accompanying drawings. It is to be understood that the illustrative embodiments of this disclosure are merely for explaining the present application and not for limiting it. Furthermore, for ease of description, the accompanying drawings show only the parts relevant to the present application, and not all of the structures or processes.

[0038] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0039] Unless the context otherwise specifies, the terms “contains,” “has,” and “includes” are synonyms. The phrase “A / B” means “A or B.” The phrase “A and / or B” means “(A and B) or (A or B).”

[0040] It should be understood that although terms such as "first," "second," etc., may be used herein to describe various components, units, or data, these components, units, or data should not be limited by these terms. These terms are used merely to distinguish one feature from another. For example, without departing from the scope of the exemplary embodiments, a first feature may be referred to as a second feature, and similarly, a second feature may be referred to as a first feature.

[0041] It should be understood that although directional terms such as "up," "down," "left," and "right" may be used here to describe the positional relationship between the various components, these directional terms are only for the convenience of understanding and are not intended to limit the scope of protection of this application.

[0042] It should be noted that in this specification, similar reference numerals and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0044] Figure 1 This is a schematic diagram of a traditional vertical-cavity surface-emitting laser. (Example:) Figure 1 As shown, a conventional vertical-cavity surface-emitting laser (VCSEL) includes: a substrate 10, a first distributed Bragg reflector (DBR) 20 disposed on the substrate 10, an active region 30 disposed on the first DBR 20, and a second DBR 40 disposed on the active region 30. In a conventional VCSEL, the first DBR 20 is an N-type DBR (N-DBR), and the second DBR 40 is a P-type DBR (P-DBR). It also includes an oxide layer 50 disposed between the active region 30 and the second DBR 40 to define an emission aperture, and a contact layer 60 disposed on the second DBR 40 for electrical connection. It should be noted that... Figure 1 The intermediate contact layer 60 is a P-type contact layer (Pcontact), and the N-type contact layer (N contact) located at the bottom of the substrate 10 is omitted in the figure.

[0045] In a traditional VCSEL structure, the second DBR at the top is a P-DBR. Since the mobility of holes is much lower than that of electrons, the lateral resistance of the P-DBR layer is relatively high. When current is injected from the top P-type contact layer, it tends to flow along the path of least resistance—the edge of the oxide layer—as it passes through the emission aperture defined by the oxide layer. This results in current concentration at the edge of the emission aperture, known as the "current crowding effect." This non-uniform current injection leads to uneven lateral distribution of carrier concentration and optical gain in the active region. Specifically, the gain is high at the edges and low at the center, affecting the competition of transverse modes within the resonant cavity. Higher-order transverse modes (typically with a ring-shaped optical field distribution) dominate the competition, while the fundamental transverse mode is suppressed. Ultimately, this results in a ring-shaped near-field optical field distribution, and a saddle-shaped (or ring-shaped, donut-shaped) far-field optical field distribution, characterized by weaker light intensity at the center and stronger light intensity at the edges.

[0046] Figure 2 This is a far-field image of a conventional vertical-cavity surface-emitting laser (VCSEL) captured by a camera. Figure 3 To and Figure 2 The corresponding light intensity distribution diagram in the horizontal direction of the far-field light field. Figure 4 To and Figure 2 The corresponding light intensity distribution in the vertical direction of the far-field light field. Figure 3 and Figure 4The horizontal axis represents distance in terms of camera pixels. Figure 3 and Figure 4 The vertical axis represents the gray value, which indicates the light intensity. Specifically, it refers to the digital quantization value converted by the camera from the intensity of the received light signal. The value directly corresponds to the relative brightness or photon accumulation of a pixel. For example... Figure 2-4 As shown, the far-field optical field of a traditional VCSEL exhibits a saddle shape, dark at the center and bright at the edges. It should be noted that, in this application, the horizontal and vertical directions refer to the horizontal and vertical directions of the plane of the paper in the attached figures.

[0047] Figure 5 This is a schematic diagram of the first embodiment of the vertical-cavity surface-emitting laser (VCSEL) according to this application. Compared with conventional VCSELs, the VCSEL according to this application further includes at least one tunnel junction, such as... Figure 5 As shown, a tunnel junction 70 is disposed between the second DBR40 and the active region 30, wherein the first DBR20 and the second DBR40 are both N-DBRs, and the contact layer 60 above the second DBR40 is an N-type contact layer.

[0048] The substrate 10 can be made of materials such as gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP), depending on the target emission wavelength of the VCSEL. For example, for VCSELs with emission wavelengths of 350 nm to 530 nm, the substrate 10 is preferably made of GaN; for VCSELs with emission wavelengths of 500 nm to 1000 nm, the substrate 10 is preferably made of GaAs; and for VCSELs with emission wavelengths of 1000 nm to 1600 nm, the substrate 10 is preferably made of InP.

[0049] A DBR consists of alternating stacked high-refractive-index layers and low-refractive-index layers. The materials of the high-refractive-index layers and low-refractive-index layers can be any combination of DBR materials known in the art suitable for VCSELs, such as AlGaAs / GaAs, AlAs / GaAs, AlGaInP / InP, etc. The number of stacking periods of the DBR can be set according to the desired reflectivity, for example, it can include 20 to 40 pairs of alternating high-refractive-index layers and low-refractive-index layers.

[0050] The active region 30 is disposed on the first DBR 20, and may include one or more quantum well layers, such as InGaAs / GaAs quantum wells, InGaAsP / InP quantum wells, or InGaN / GaN quantum wells. The composition and structure of the active region 30 can be selected and designed according to the target emission wavelength, and its specific structure is well known to those skilled in the art and will not be described in detail here.

[0051] The VCSEL of this application may further include an oxide layer 50 disposed within or near the active region 30, the oxide layer 50 defining the light-emitting aperture. The oxide layer 50 may be formed by a selective oxidation process, for example, by wet oxidation of an AlAs layer or a high-Al content AlGaAs layer to form an AlOx oxide layer. The oxide layer 50 is disposed around the periphery of the light-emitting aperture, forming a current-limiting aperture so that the injected current enters the active region 30 only through the light-emitting aperture region. The shape of the light-emitting aperture may be circular, N-sided (such as triangular, square, pentagonal, hexagonal, etc.), or irregular.

[0052] The tunnel junction 70 is disposed between the active region 30 and the second DBR 40. The tunnel junction 70 includes a heavily p-type doped layer and a heavily n-type doped layer, which are stacked sequentially. The thickness of the tunnel junction 70 can be 10 nm to 100 nm, preferably 20 nm to 50 nm. The material system of the tunnel junction 70 should match the material system of the active region 30. For example, for a GaN-based VCSEL, the tunnel junction 70 can be a GaInN tunnel junction; for a GaAs-based VCSEL, the tunnel junction 70 can be an (Al)GaAs tunnel junction; and for an InP-based VCSEL, the tunnel junction 70 can be an InGa(Al)As tunnel junction.

[0053] In this embodiment, since a tunnel junction 70 is provided between the active region 30 and the second DBR 40, the second DBR 40 in the conventional VCSEL structure can be converted from a P-DBR to an N-DBR. When current is injected from the top contact layer 60, since the second DBR 40 is an N-type DBR, the electron mobility in the N-type DBR is much higher than the hole mobility in the conventional P-DBR. Therefore, the current can diffuse more uniformly in the lateral direction, which can change the current density distribution injected into the active region 30 from the edge-concentrated type in the conventional structure to a uniform type, thereby forming a Gaussian far-field optical field distribution.

[0054] Figure 6 This is a far-field image of a first embodiment of a vertical-cavity surface-emitting laser, captured by a camera. Figure 7 To and Figure 6 The corresponding light intensity distribution diagram in the horizontal direction of the far-field light field. Figure 8 To and Figure 6 The corresponding intensity distribution of the far-field light field in the vertical direction. For example... Figure 6-8 As shown, the far-field light field of the VCSEL in the first embodiment exhibits a Gaussian-like far-field light field distribution with a brighter center and darker edges.

[0055] By adjusting the distance between the tunnel junction 70 and the active region 30, the lateral distribution of charge carriers can be controlled, thereby enabling the far-field optical field distribution of the vertical-cavity surface-emitting laser to exhibit a Gaussian-like distribution. Specifically, by adjusting the distance d between the tunnel junction 70 and the active region 30, the thickness of the P-DBR transition to N-DBR in the second DBR can be determined, thus controlling the degree of lateral carrier diffusion. A larger distance d results in a smaller N-DBR thickness in the second DBR, less lateral carrier diffusion before reaching the active region 30, and a more non-uniform current density distribution injected into the active region 30. Conversely, a smaller distance d results in a larger N-DBR thickness in the second DBR, more complete lateral carrier diffusion before reaching the active region 30, and a more uniform current density distribution injected into the active region 30. Therefore, by precisely controlling the distance d, the current density distribution injected into the active region 30 can be gradually transformed from the edge-concentrated type (resulting in a saddle-shaped far-field optical field distribution) in the traditional VCSEL structure to a uniform type (resulting in a Gaussian-like far-field optical field distribution). In other words, it is possible to achieve... Figure 2-4 The saddle-shaped far-field light field distribution shown is... Figure 6-8 By selecting an appropriate far-field optical field distribution from the Gaussian-like far-field distributions shown, it is possible to match the requirements of different optical system designs.

[0056] The following section further explains the principle that adjusting the distance between the tunnel junction 70 and the active region 30 can make the far-field optical field distribution of the VCSEL exhibit a Gaussian distribution.

[0057] By combining the "transverse Ohm's law" and the "law of conservation of charge" in circularly symmetric geometry, a two-dimensional Laplace operator for voltage in cylindrical coordinates can be obtained:

[0058] .

[0059] Where V(r) is the transverse voltage distribution, 𝜌 𝐷𝐵𝑅 Let be the resistivity of the material above the active region, r be the radius, and J(r) be the externally injected current density (the current density injected vertically downwards from the contact layer to the active layer). In traditional VCSEL designs (where the second DBR is a P-DBR structure), the extremely low hole mobility leads to 𝜌 P-D𝐵𝑅 The voltage gradient is extremely large, forcing the VCSEL element to generate a very large voltage gradient around the light-emitting aperture in order to drive sufficient total current. This causes J(r) to be severely concentrated at the edge of the light-emitting aperture, forming a saddle-shaped distribution. In this application, a tunnel junction is used to convert at least a portion of the second DBR into an N-DBR. The high electron mobility of the N-type material at the tunnel junction interface... N-D𝐵𝑅 With 𝜌 P-D𝐵𝑅 Compared to this, it has been reduced by 1 to 2 orders of magnitude (k). N-D𝐵𝑅 ≪𝜌 P-D𝐵𝑅Therefore, the transverse voltage gradient on the left side of the equation is significantly flat, forcing the current density to spread towards a uniform distribution, thus forming a Gaussian distribution (fundamental mode LP). 01 ).

[0060] Further refer to the following transverse mode rate equations:

[0061] ,

[0062] Wherein, the rate of change of carrier density at a certain location r in the active region with time is (φ(r,t) / φ), which is equal to "injection" minus "recombination" plus "diffusion"; J(r) is the externally injected current density; φ 𝑛 For carrier lifetime; 𝑣 𝑔 The group velocity of light in the medium; 𝑔 𝑚 (𝑟) represents the gain of this mode; 𝑣 𝑔 ⋅𝑔 represents the rate at which photons are amplified, 𝑆 𝑚 (Ψ) represents the total photon density of the m-th transverse mode; |Ψ 𝑚 (𝑟)| 2 The light field intensity distribution (normalized) for the m-th transverse mode; 𝐷 𝑛 It is the carrier diffusion coefficient; 𝛻 ⊥ 2 It is a two-dimensional Laplace operator.

[0063] In traditional VCSEL designs, J(r) is severely crowded at the edge of the emission aperture, resulting in extremely high carrier injection rates at the edge. This preferentially satisfies higher-order modes (such as LP). 11 The gain requirement (where the peak energy of the light field is precisely at the edge) leads to the dominance of higher-order modes, resulting in a saddle-shaped distribution in the far field. In this application, J(r) is optimized into a centrally concentrated Gaussian distribution, which allows the injection gain to be precisely supplied to the fundamental mode (LP). 01 Its optical field energy is concentrated at the center (r=0). This cuts off the energy source of higher-order modes in the rate equation, suppresses competition of higher-order modes, and thus achieves a single-peak Gaussian distribution that maintains high beam quality in the far field.

[0064] Figure 9 This is a schematic diagram of a second embodiment of the vertical-cavity surface-emitting laser involved in this application. Figure 9 As shown, in the VCSEL of the second embodiment, the first DBR20 is an N-DBR, and the tunnel junction 70 is disposed within the second DBR40, dividing the second DBR40 into a P-type reflector region 42 located below the tunnel junction 70 and an N-type reflector region 41 located above the tunnel junction 70.

[0065] The difference from the first embodiment is that in the second embodiment, the tunnel junction 70 is not disposed between the active region 30 and the second DBR 40, but is embedded inside the second DBR 40. Specifically, the second DBR 40 is divided into two parts by the tunnel junction 70: a P-type reflector region 42 located below the tunnel junction 70 (i.e., closer to the active region 30) and an N-type reflector region 41 located above the tunnel junction 70 (i.e., away from the active region 30).

[0066] In the second embodiment, the distance d between the tunnel junction 70 and the active region 30 is the thickness of the P-type mirror region 42. By adjusting the position of the tunnel junction 70 in the second DBR 40 (i.e., adjusting the stacking period number or the thickness of each layer of the P-type mirror region 42), the distance d between the tunnel junction 70 and the active region 30 can be changed, thereby regulating the lateral distribution state of the charge carriers and thus controlling the far-field optical field distribution of the VCSEL.

[0067] Figure 10 This is a schematic diagram of the third embodiment of the vertical-cavity surface-emitting laser involved in this application. Figure 10 As shown, in the VCSEL of the third embodiment, the second DBR40 is an N-DBR, and the tunnel junction 70 is disposed within the first DBR20, dividing the first DBR20 into an N-type reflector region 22 located below the tunnel junction 70 and a P-type reflector region 21 located above the tunnel junction 70.

[0068] The difference from the second embodiment is that in the third embodiment, the tunnel junction 70 is not disposed within the second DBR 40, but within the first DBR 20. Specifically, the first DBR 20 is divided into two parts by the tunnel junction 70: an N-type mirror region 22 located below the tunnel junction 70 (i.e., near the substrate 10) and a P-type mirror region 21 located above the tunnel junction 70 (i.e., near the active region 30). The second DBR 40 is an N-type DBR.

[0069] In the third embodiment, the tunnel junction 70 is placed inside the bottom first DBR 20, so that the top second DBR 40 is entirely an N-type DBR. The current injected from the top can achieve sufficient lateral diffusion in the N-type second DBR 40. Moreover, the P-type reflector region 21 is only located above the tunnel junction 70 and has a relatively small number of logarithms, thus contributing less to the series resistance of the device.

[0070] Figure 11 This is a schematic diagram of the fourth embodiment of the vertical-cavity surface-emitting laser involved in this application. Figure 11As shown, in the VCSEL of the fourth embodiment, the first DBR 20 is an N-type DBR, and multiple tunnel junctions 70a and 70b are disposed in the second DBR 40, dividing the second DBR 40 into mutually spaced P-type reflector regions 42, N-type reflector regions 41 and P-type reflector regions 42.

[0071] The difference from the second embodiment is that the fourth embodiment has multiple tunnel knots. Figure 11 The diagram schematically shows two tunnel junctions 70a and 70b, but this application is not limited to this; the number of tunnel junctions can be two or more. Multiple tunnel junctions 70a and 70b are arranged sequentially and at intervals along the vertical direction within the second DBR40, dividing the second DBR40 into alternating P-type mirror regions 42, N-type mirror regions 41, and P-type mirror regions 42. Those skilled in the art will understand that when the number of tunnel junctions is N, the second DBR40 is divided into N+1 mirror regions, with N-type mirror regions 41 and P-type mirror regions 42 alternating. The second DBR40, from bottom to top (i.e., from the side closer to the active region 30 to the side farther from the active region 30), consists of a P-type mirror region, a tunnel junction, an N-type mirror region, another tunnel junction, a P-type mirror region, and so on.

[0072] In the fourth embodiment, by setting multiple tunnel junctions, multi-level control of the lateral distribution of charge carriers can be achieved. As the current passes through each tunnel junction sequentially, lateral diffusion is achieved in each N-type mirror region. Through the cascade tunneling effect of each tunnel junction, the lateral distribution of charge carriers is optimized step by step, ultimately resulting in a more uniform current density distribution injected into the active region 30. Furthermore, the cascade arrangement of multiple tunnel junctions can further reduce the series resistance of the device through the cascade tunneling effect.

[0073] Figure 12-14 This is a schematic diagram of the fifth embodiment of the vertical-cavity surface-emitting laser involved in this application. Figure 12-14 As shown, in the VCSEL of the fifth embodiment, multiple tunnel junctions are respectively disposed in the first DBR20 and the second DBR40, dividing the first DBR20 and the second DBR40 into mutually spaced N-type reflector regions and P-type reflector regions.

[0074] The difference from the fourth embodiment is that in the fifth embodiment, multiple tunnel junctions are not only disposed within the second DBR40, but also within the first DBR20. Specifically, in Figure 12 In the second DBR40, a tunnel junction 70a is provided, dividing the second DBR40 into alternating N-type mirror regions 41 and P-type mirror regions 42. Similarly, a tunnel junction 70b is provided in the first DBR20, dividing the first DBR20 into alternating N-type mirror regions 22 and P-type mirror regions 21. Figure 13In the first DBR 20, two tunnel junctions 70a and 70b are provided, dividing the second DBR 40 into alternating N-type mirror regions 41, P-type mirror regions 42, and N-type mirror regions 41. A tunnel junction 70c is provided in the first DBR 20, dividing the first DBR 20 into alternating N-type mirror regions 22 and P-type mirror regions 21. Figure 14 In the first DBR20, a tunnel junction 70a is provided, which divides the second DBR40 into alternating N-type mirror area 41 and P-type mirror area 42. Two tunnel junctions 70b and 70c are provided in the first DBR20, which divides the first DBR20 into alternating N-type mirror area 22, P-type mirror area 21 and N-type mirror area 22.

[0075] In the fifth embodiment, by incorporating multiple tunnel junctions in both the first DBR 20 and the second DBR 40, the lateral distribution of charge carriers is simultaneously controlled from both the top and bottom directions. At the top, after current is injected from the top electrode, it undergoes lateral diffusion in each N-type mirror region of the second DBR 40; at the bottom, current also undergoes lateral diffusion as it passes through each tunnel junction of the first DBR 20. This dual-sided multi-tunnel junction configuration maximizes the high conductivity of the N-type material, thereby comprehensively optimizing the lateral current diffusion capability throughout the entire device structure.

[0076] This application introduces at least one tunnel junction in a VCSEL and precisely controls the distance between it and the active region. By utilizing the physical properties that electron mobility is much higher than hole mobility and the lateral resistance of the N-type layer is significantly lower than that of the P-type layer, the injected current can be fully and uniformly diffused in the lateral direction, thereby effectively suppressing the current crowding effect caused by the low hole mobility in the traditional structure. The uniform current density distribution promotes the uniformity of the lateral gain distribution, making the fundamental transverse mode dominant in mode competition and effectively suppressing higher-order transverse modes. This significantly transforms the far-field optical field distribution from the saddle-shaped (ring-shaped) distribution of the traditional structure to a Gaussian-like distribution, which can greatly improve beam quality and optical system coupling efficiency.

[0077] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Where there is no conflict, the embodiments and features described in the embodiments of this application can be combined with each other. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, include: Substrate; A first distributed Bragg reflector disposed on the substrate; The active region is set on the first distributed Bragg reflector; A second distributed Bragg reflector is disposed on the active region; as well as At least one tunnel knot; Specifically, by adjusting the distance between the tunnel junction and the active region, the lateral distribution of charge carriers is controlled, thereby causing the far-field optical field distribution of the vertical cavity surface-emitting laser to exhibit a Gaussian-like distribution.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first distributed Bragg reflector and the second distributed Bragg reflector are type N distributed Bragg reflectors; The tunnel junction is positioned between the second distributed Bragg reflector and the active region.

3. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first distributed Bragg reflector is an N-type distributed Bragg reflector; The tunnel junction is disposed within the second distributed Bragg reflector, dividing the second distributed Bragg reflector into a P-type reflector region located below the tunnel junction and an N-type reflector region located above the tunnel junction.

4. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The second distributed Bragg reflector is an N-type distributed Bragg reflector; The tunnel junction is disposed within the first distributed Bragg reflector, dividing the first distributed Bragg reflector into an N-type reflector region located below the tunnel junction and a P-type reflector region located above the tunnel junction.

5. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The first distributed Bragg reflector is an N-type distributed Bragg reflector; The tunnel structure consists of multiple tunnels, which are set inside the second distributed Bragg reflector, dividing the second distributed Bragg reflector into mutually spaced N-type reflector regions and P-type reflector regions.

6. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The tunnel structure consists of multiple tunnels, which are respectively set inside the first distributed Bragg reflector and the second distributed Bragg reflector, dividing the first distributed Bragg reflector and the second distributed Bragg reflector into mutually spaced N-type reflector regions and P-type reflector regions.

7. The vertical-cavity surface-emitting laser according to any one of claims 1-6, characterized in that, Also includes: An oxide layer disposed in or near the active region, the oxide layer defining a light-emitting aperture.

8. The vertical-cavity surface-emitting laser according to claim 7, characterized in that, The shape of the light-emitting hole is circular, N-sided, or irregular, where N is an integer greater than or equal to 3.

9. The vertical-cavity surface-emitting laser according to any one of claims 1-6, characterized in that, The vertical cavity surface-emitting laser is a single-junction vertical cavity surface-emitting laser or a multi-junction vertical cavity surface-emitting laser.

10. The vertical-cavity surface-emitting laser according to any one of claims 1-6, characterized in that, The vertical-cavity surface-emitting laser (VCSEL) emits light in the range of 350 nm to 530 nm, and its material system is gallium nitride-based; or... The vertical-cavity surface-emitting laser has an emission wavelength of 500 nm to 1000 nm, and the material system of the vertical-cavity surface-emitting laser is gallium arsenide-based; or The vertical cavity surface-emitting laser has an emission wavelength of 1000nm to 1600nm, and the material system of the vertical cavity surface-emitting laser is indium phosphide-based.

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