A semiconductor laser and a laser apparatus having the same

Abstract

The application relates to the technical field of semiconductor lasers, and provides a semiconductor laser and a laser device with the semiconductor laser. The semiconductor laser comprises a laser main body and a functional layer arranged on the laser main body; and part or all of the functional layer is configured to be different in refractive index or / and stress along the thickness direction of the functional layer. All or part of the functional layer is configured to be different in refractive index or / and stress, or both of them, along the thickness direction of the functional layer. The difference can be realized by changing the stoichiometric ratio of the material, changing the crystal form of the material, or changing the concentration and distribution of the doped elements, so that the local enhancement of the standing wave and the interface reflection caused by the refractive index mutation in the traditional multilayer film are eliminated, the light field distribution is more uniform, the light absorption hot spots near the cavity surface are reduced, and the COD triggering threshold is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser technology, and particularly relates to a semiconductor laser with sufficient reliability under high power output conditions and a laser device having the semiconductor laser. Background Technology

[0002] Nitride semiconductor lasers cover the ultraviolet to red light wavelength range, featuring wide bandgap, high temperature resistance, high photoelectric efficiency, long lifetime, and small size, and can be directly electrically injected into the laser. They are widely used in laser displays, blue / green light pumping, UV curing, medical detection, and optical storage, and are core components of the optoelectronic industry. The industry is rapidly iterating towards higher power and higher reliability. However, issues such as thermal failure and beam degradation are prominent during device service, with cavity optical catastrophic failure (COD) being a critical bottleneck restricting the development of high-power devices.

[0003] Cavity surface light absorption triggers thermal runaway, instantly causing cavity surface melting and destruction, completely ruining the device's resonant structure. Existing COD-resistant technologies such as passivation coatings, non-absorption windows, and current modulation generally suffer from poor stability, complex processes, weak compatibility, and limited threshold improvement, making it difficult to simultaneously meet the demands of high power, long lifespan, and mass production. Therefore, breakthroughs in novel COD-resistant technologies are urgently needed. Cavity surface coatings, as a mainstream COD-resistant method, can passivate cavity surface dangling bonds and modulate optical properties; examples include alumina (Al2O3) and silicon nitride (SiN). x Single-layer coating can initially improve the damage threshold, and high thermal conductivity coatings such as aluminum nitride (AlN) can also enhance heat dissipation; however, this technology still has problems such as poor film adhesion, heat absorption leading to sudden changes in the optical properties of the film system, easy oxidation and delamination during long-term service, and poor batch process consistency. Existing solutions still cannot effectively solve the COD problem. Summary of the Invention

[0004] The purpose of this invention is to overcome at least one of the shortcomings of the prior art and to provide a semiconductor laser and a laser device having the semiconductor laser, in which the refractive index and / or stress of the functional layer vary or even change continuously along the thickness direction, thereby eliminating light absorption, heat accumulation and stress concentration caused by abrupt interfaces in traditional film systems, thus significantly improving the optical damage threshold of the cavity surface, extending device life and effectively solving the COD problem.

[0005] The present invention provides a semiconductor laser, including a laser body and a functional layer disposed on the laser body; along the thickness direction of the functional layer, some or all of the functional layer are configured to have different refractive indices and / or stresses.

[0006] Optionally, the functional layer includes a first functional layer; along the thickness direction, the stoichiometric ratios of the elements in the first functional layer are different, causing the refractive index of the first functional layer to gradually change along the thickness direction.

[0007] Optionally, along the thickness direction, the crystal morphology of the material in the first functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the first functional layer gradually changes along the thickness direction.

[0008] Optionally, the first functional layer is a passivation film layer attached to the surface of the laser body.

[0009] Optionally, the first functional layer is a gradient film layer, which includes an AlN layer, an AlON intermediate layer and an Al2O3 layer disposed sequentially.

[0010] Optionally, the first functional layer is a gradient film layer, the gradient film layer comprising sequentially disposed SiN x The layers consist of a SiON intermediate layer and a SiO2 layer.

[0011] Optionally, the functional layer further includes a second functional layer, which is stacked with the first functional layer along the thickness direction; Along the thickness direction, the stoichiometry of the elements in the second functional layer is different, causing the refractive index and / or stress of the second functional layer to gradually change along the thickness direction.

[0012] Optionally, along the thickness direction of the second functional layer, the crystal morphology of the material in the second functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the second functional layer gradually changes along the thickness direction.

[0013] Optionally, the second functional layer is a stress-regulating film layer.

[0014] Optionally, the functional layer further includes a third functional layer, wherein the first functional layer, the second functional layer and the third functional layer are stacked along the thickness direction; Along the thickness direction, the stoichiometry of the elements in the third functional layer is different, causing the refractive index and / or stress of the third functional layer to gradually change along the thickness direction.

[0015] And / or, along the thickness direction of the third functional layer, the crystal morphology of the material in the third functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the third functional layer gradually change along the thickness direction.

[0016] Optionally, the third functional layer is a reflectivity adjustment film layer.

[0017] Optionally, the functional layer is a gradient film layer with a continuous gradient without interfaces, and a passivation portion, a stress buffer portion, and a reflectivity adjustment portion are formed sequentially along the thickness direction; Alternatively, the functional layer may include an amorphous layer for passivation and stress adjustment and a reflectivity adjustment film layer for adjusting reflectivity, wherein the amorphous layer and the reflectivity adjustment film layer are stacked, and the amorphous layer and the reflectivity adjustment film layer have different refractive indices and / or stresses.

[0018] The present invention also provides a laser device, including the semiconductor laser described above.

[0019] The present invention provides a semiconductor laser and a laser device having the semiconductor laser, wherein along the thickness direction of the functional layer, all or part of the functional layer is configured to have different refractive indices, different stresses, or both. This can be achieved by changing the stoichiometry of the material, altering its crystal morphology, or altering the concentration and distribution of dopants. This eliminates the local enhancement of standing waves and interface reflections caused by abrupt changes in refractive index in traditional multilayer films, resulting in a more uniform optical field distribution and fewer optical absorption hotspots near the cavity surface. This significantly improves the COD trigger threshold. By creating a gradual stress distribution in the thickness direction of the functional layer (especially transitioning from high-stress to low-stress regions), it can disperse and buffer lattice mismatch stress and thermal stress between different materials or structures. The gradual film layer changes blur the interface effect, preventing stress concentration at the film system interface, reducing the risk of film cracking and delamination, and improving the mechanical stability and long-term reliability of the film system. Cavity surface passivation, stress modulation, and optical matching can be achieved without introducing abrupt interface changes, simplifying the process flow, improving production efficiency and product consistency, enabling nitride semiconductor lasers to operate stably at higher output power levels, and significantly extending device lifespan. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a three-dimensional schematic diagram of a nitride semiconductor laser provided in an embodiment of the present invention; Figure 2 This is a diagram illustrating the refractive index change of the alumina (Al2O3) thin film with a gradient film layer in this invention; Figure 3 This invention illustrates the refractive index change of Al2O3 from its crystalline to its amorphous state. Figure 4 This is a diagram illustrating the refractive index change of AlON formed by continuously adding O2 to an AlN passivation film according to the present invention. Figure 5This invention uses the refractive index variation region as a diagram illustrating the periodic change of refractive index.

[0022] Reference numerals: 10-laser body, 20-functional layer, 21-first functional layer, 22-second functional layer, 23-third functional layer, 30-back cavity membrane. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] It should be noted that the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to direct setup or connection, or indirect setup or connection through centered components or centered structures.

[0025] Furthermore, in embodiments of this invention, terms such as "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" are used to indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, or in a conventional placement or usage state. These terms are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the structures, features, devices, or elements referred to must have a specific orientation or positional relationship, nor that they must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] The various specific technical features and embodiments described in the detailed embodiments can be combined in any suitable manner without contradiction. For example, different implementation methods can be formed by combining different specific technical features / embodiments. In order to avoid unnecessary repetition, the various possible combinations of the various specific technical features / embodiments in this invention will not be described separately.

[0027] In related technologies, a uniform antireflection film is usually deposited on the output cavity surface of a semiconductor laser, or a simple multilayer film composed of two or more materials is deposited. These traditional films have a basically constant refractive index and stress throughout the thickness direction, and there are clear abrupt interfaces between different material layers.

[0028] like Figure 1As shown, an embodiment of the present invention provides a semiconductor laser, including a laser body 10 and a functional layer 20 disposed on the laser body 10; along the thickness direction of the functional layer 20, part or all of the functional layer 20 is configured with different refractive indices and / or stresses. In this embodiment, the functional layer 20 is a front cavity film disposed on the surface (light-emitting surface) of the laser body 10. The semiconductor laser of the present invention, by making the refractive index and / or stress of the functional layer 20 vary or even continuously along the thickness direction, eliminates the light absorption, heat accumulation and stress concentration caused by abrupt interfaces in traditional film systems, thereby significantly improving the optical damage threshold of the cavity surface, extending device life, and effectively solving the COD problem.

[0029] Optionally, the functional layer 20 can be used as a cavity surface film system, including a first functional layer 21. In this embodiment, the first functional layer 21 is attached (deposited) on the light-emitting surface of the laser body 10.

[0030] Specifically, the stoichiometric ratios of the elements in the first functional layer 21 are different along the thickness direction, causing the refractive index of the first functional layer 21 to gradually change along the thickness direction. By using different stoichiometric ratios of the elements in the first functional layer 21 to create differences or gradual changes in the refractive index along the thickness direction, a gradient distribution of optical parameters can be achieved within the same functional layer 20, thereby eliminating abrupt interfaces and stress concentrations in traditional film systems, reducing light absorption, and improving the COD resistance threshold.

[0031] Optionally, along the thickness direction, the crystal morphology or doping control of the material in the first functional layer 21 may differ, resulting in a gradual change in the refractive index and / or stress of the first functional layer 21 along the thickness direction. By varying the crystal morphology or doping control in the first functional layer 21 to achieve a gradual change in the refractive index and / or stress along the thickness direction, a gradient distribution of optical and mechanical properties can also be achieved within the same functional layer 20. This eliminates abrupt interfaces and stress concentrations in traditional film systems, reduces light absorption, and improves the COD resistance threshold.

[0032] In practical applications, the selection of passivation films for nitride laser cavity surfaces considers characteristics such as low absorption, high thermal conductivity, high insulation, and high COD threshold. AlN and SiN are suitable choices. xAl₂O₃ and AlON (Al₂O₃-Al₂O₃) are the mainstream material choices. AlN thin films are generally preferred due to their advantages such as lattice matching with nitride semiconductors, excellent thermal conductivity and high-temperature stability, and high film density. They can effectively passivate defects on the cavity surface of nitride semiconductor lasers, suppress cavity surface oxidation, reduce cavity surface heat dissipation pressure, and enhance the laser cavity surface's resistance to COD. They are widely used in high-power nitride semiconductor lasers. However, AlN thin films have high intrinsic stress and brittleness, making them prone to cracking and detachment. Therefore, to ensure the stability of the AlN passivation film, its deposition thickness must be controlled within 50 nm. In the nitride laser emission surface film system, AlN thin films must be used in conjunction with other optical thin films. Interface effects can easily reduce the mechanical stability of the film system and increase interface state absorption, ultimately accelerating COD at the cavity surface.

[0033] The above problems can be solved by controlling the stoichiometry of materials to achieve abrupt interface film systems. For AlN thin films (x=N / Al), x≈1 (stoichiometry), n (550 nm)∈(2.05, 2.15), n is high and stable, and the film has no light absorption. When x<1, n (550 nm)∈(1.90, 2.05), n is below the standard value, and the light absorption of the film increases due to metal clusters. When x>1, n (550 nm)∈(2.00, 2.10), the density and refractive index decrease, and N can fully passivate the dangling bonds in the film, achieving a non-absorbing film. By depositing stoichiometric AlN thin films on the cavity surface of nitride semiconductors and adjusting the N ratio, N-rich (x>1) AlN films can be obtained, ultimately achieving N control of a single-layer film. The same refractive index control method can be used for all single-layer functional films in the cavity surface film system of nitride semiconductor lasers, not just for passivating functional layers.

[0034] In this embodiment, by making the functional layer 20 have a gradually changing stress in the thickness direction (especially transitioning from a high stress region to a low stress region), it is possible to disperse and buffer the lattice mismatch stress and thermal stress between different materials or different structures, avoid stress concentration at a single interface, reduce the risk of film cracking and delamination, and improve the mechanical stability and long-term reliability of the film system.

[0035] Optionally, the first functional layer 21 is a passivation film layer attached to the surface of the laser body 10.

[0036] Optionally, the first functional layer 21 is a gradient film layer, and the gradient film layer includes an AlN layer, an AlON intermediate layer, and an Al2O3 layer sequentially disposed. By integrating multiple functions such as passivation, stress adjustment, and reflectivity adjustment into a single continuous gradient film (e.g., an AlN→AlON→Al2O3 gradient film layer), and sequentially forming a passivation portion, a stress buffer portion, and a reflectivity adjustment portion along the thickness direction, cavity surface passivation, stress buffering, and optical matching are simultaneously achieved without introducing abrupt interface changes. This simplifies the process flow and improves production efficiency and product consistency.

[0037] Optionally, the first functional layer 21 is a gradient film layer, the gradient film layer comprising sequentially disposed SiN x The layers consist of a SiON intermediate layer and a SiO2 layer.

[0038] In this application, aluminum nitride (AlN) thin films are used as an example for graded films. The refractive index of AlN is closely related to its N / Al atomic ratio. When the N / Al atomic ratio is approximately 1 (i.e., standard stoichiometry), the refractive index of the film at a wavelength of 550 nm is 2.05–2.15, and there is essentially no light absorption. When the N / Al ratio is less than 1 (Al-rich), excess aluminum atoms in the film may form metal clusters, reducing the refractive index to 1.90–2.05, but simultaneously increasing light absorption. When the N / Al ratio is greater than 1 (N-rich), since excess nitrogen exists in the form of nitrogen molecules or interstitial nitrogen, the film density decreases, and the refractive index decreases to 2.00–2.10. Furthermore, under nitrogen-rich conditions, nitrogen can sufficiently passivate the dangling bonds of aluminum, and the film maintains its non-absorption characteristics. During the deposition of the AlN passivation film, the N / Al atomic ratio can be continuously varied along the thickness direction by precisely controlling the ratio of nitrogen flow rate to aluminum source supply rate. For example, a thin initial layer is first deposited at a standard stoichiometric ratio (N / Al≈1) to ensure good lattice matching and extremely low absorption with the nitride semiconductor cavity surface. Then, the nitrogen flow rate is gradually increased to transform the film into a nitrogen-rich state, causing the refractive index to gradually decrease. The entire gradient process is completed within the same thin film, without introducing any abrupt interfaces. This results in a higher refractive index near the semiconductor cavity surface, facilitating a smooth transition of the light field from the semiconductor material to the film layer; and a lower refractive index further away from the cavity surface, enabling better optical matching with subsequent film layers or air. Simultaneously, the absence of abrupt interfaces eliminates light absorption and waste heat generation caused by interface states.

[0039] Taking alumina (Al₂O₃) thin films as an example, graded films can achieve a gradual change in refractive index by adjusting the O / Al atomic ratio. The refractive index of Al₂O₃ with a standard stoichiometric ratio (O / Al = 1.5) is 1.65–1.75; when Al-rich (O / Al < 1.5), the refractive index is 1.55–1.70, but metal cluster absorption may occur; when O-rich (O / Al > 1.5), the refractive index is 1.68–1.85, and oxygen can fully passivate aluminum dangling bonds, achieving no absorption. By continuously changing the oxygen flow rate along the thickness direction, a single-layer Al₂O₃ passivation film with a gradually changing refractive index can be prepared. Silicon nitride (SiN) x Thin films can also achieve similar effects by adjusting the N / Si ratio, which will not be elaborated here. Figure 2 The diagram illustrates the refractive index variation curve of an alumina (Al₂O₃) thin film along its thickness direction in one embodiment of the present invention. (Refer to...) Figure 2 The refractive index of the thin film decreases continuously from the side closer to the semiconductor cavity surface to the side farther away from the cavity surface. This gradual change in refractive index is achieved by continuously changing the stoichiometric ratio (O / Al atomic ratio) of oxygen and aluminum along the thickness direction of the thin film.

[0040] In some embodiments, the crystal morphology of the material constituting the first functional layer 21 is set differently along the thickness direction of the first functional layer 21, thereby causing a gradual change in refractive index and / or stress. Crystal morphologies mainly include crystalline (polycrystalline or single-crystal) and amorphous states. Crystalline films have long-range ordered atomic arrangements and high density, effectively blocking the diffusion of oxygen and water vapor, and exhibiting good passivation effects. However, crystalline films typically have large intrinsic stresses, making them prone to microcracks or even peeling as the film thickness increases. Amorphous films have disordered atomic arrangements and lower density, resulting in relatively weaker ability to block water and oxygen, but they have extremely low internal stress, excellent adhesion and mechanical toughness, making them very suitable as stress-absorbing materials.

[0041] In practical applications, during the deposition of the same material (e.g., Al2O3), the crystal morphology of the thin film can be gradually changed along the thickness direction by controlling parameters such as deposition temperature, plasma power, or ion bombardment energy. For example, in the initial stage of deposition, a higher temperature (e.g., 400℃) or higher ion energy is used to promote crystalline growth, forming a dense layer of crystalline Al2O3 that directly contacts the semiconductor cavity surface, thus fully utilizing its high density and excellent barrier properties. As deposition progresses, the temperature is gradually reduced to near room temperature, causing the film to transform into an amorphous state, obtaining an almost stress-free upper region. This gradual transition from crystalline to amorphous states allows the entire passivation film to possess both dense protection near the interface and low stress characteristics far from the interface, thereby avoiding the problems of easy cracking of a single crystalline film layer and insufficient barrier properties of a single amorphous film layer. Meanwhile, since there is a difference in refractive index between crystalline and amorphous Al2O3 (approximately 1.76–1.78 for crystalline and approximately 1.65–1.75 for amorphous), this gradual change in crystal morphology also brings about a gradual change in refractive index, which is beneficial for optimizing the light field. Figure 3 A schematic diagram illustrating the changes in refractive index and crystal morphology of the Al2O3 thin film along the thickness direction in another embodiment of the present invention is shown. (Refer to...) Figure 3 Along the thickness direction of the film, the crystal morphology of Al2O3 continuously transitions from crystalline to amorphous regions, and the refractive index of the film changes accordingly with this gradual change in crystal morphology. This gradual change in crystal morphology is achieved by controlling the deposition temperature or the ion bombardment energy.

[0042] Optionally, the functional layer 20 further includes a second functional layer 22, which is stacked with the first functional layer 21 along the thickness direction; along the thickness direction, the stoichiometric ratios of the elements in the second functional layer 22 are different, so that the refractive index and / or stress of the second functional layer 22 gradually change along the thickness direction.

[0043] In an optional embodiment of the present invention, the functional layer 20 further includes a second functional layer 22. The second functional layer 22 is stacked with the first functional layer 21 and is located outside the first functional layer 21 (on the side away from the cavity surface of the laser body 10). The second functional layer 22 can be a stress-regulating film layer. The main function of the second functional layer 22 is to regulate the stress distribution of the entire film system; therefore, it can be called a stress-regulating film layer. In traditional multilayer films, large interfacial stresses often arise between different material layers due to differences in lattice constants and coefficients of thermal expansion, leading to film cracking or peeling. The stress-regulating film layer absorbs and buffers these stresses through its low-stress characteristics and appropriate thickness.

[0044] Optionally, the second functional layer 22 may vary in refractive index and / or stress along its thickness direction due to different crystal morphologies or doping control of the materials in the second functional layer 22.

[0045] The second functional layer 22 can also employ the aforementioned stoichiometric gradient, crystal morphology gradient, or doping gradient to achieve a gradient in refractive index and / or stress along its thickness direction. Amorphous materials (such as amorphous Al₂O₃ or amorphous SiN) are particularly preferred. x As the second functional layer 22, the amorphous material has extremely low internal stress and good adhesion, which can effectively counteract any residual stress that may exist in the first functional layer 21 (such as crystalline AlN). Furthermore, if the second functional layer 22 is further designed to gradually change its refractive index from the side closer to the first functional layer 21 to the side farther away, it can also act as an optical transition layer, reducing the optical mismatch between the first functional layer 21 and the subsequent reflectivity adjustment layer. That is, the second functional layer 22 can also have no obvious interface with the first functional layer 21.

[0046] Optionally, the functional layer 20 further includes a third functional layer 23, wherein the first functional layer 21, the second functional layer 22, and the third functional layer 23 are stacked along the thickness direction; the third functional layer 23 may be a reflectivity adjustment film layer, located on the outermost side, in direct contact with air or the encapsulation medium, and its main function is to adjust the reflectivity of the light-emitting cavity surface to achieve the desired anti-reflection effect. For the light-emitting cavity surface of a high-power nitride semiconductor laser, it is typically necessary to reduce the reflectivity to 1% to 20% to improve the laser emission efficiency.

[0047] Along the thickness direction, the stoichiometric ratios of the elements in the third functional layer 23 differ, causing a gradual change in the refractive index and / or stress of the third functional layer 23 along the thickness direction. And / or, along the thickness direction, the crystal morphology or doping control of the materials in the third functional layer 23 differs, causing a gradual change in the refractive index and / or stress of the third functional layer 23. The third functional layer 23 can also achieve a gradual change in refractive index and / or stress by employing gradual changes in stoichiometric ratios, crystal morphology, or doping. Common materials include Al2O3, SiO2, and Ta2O5. Through the design of a gradual refractive index, a better antireflection effect can be obtained over a wider spectral range, while eliminating abrupt interfaces with the second functional layer 22, avoiding interface absorption and stress concentration.

[0048] The crystallographic morphology of a thin film directly affects its density. Crystalline thin films exhibit a periodic and regular atomic arrangement with long-range order, resulting in the highest density and effective barrier against oxygen and water vapor diffusion. However, a drawback is high film stress, which easily leads to cracking and peeling as thickness increases. Amorphous thin films, lacking a periodic structure and long-range order, are essentially stress-free and possess high adhesion and mechanical toughness, making them ideal stress-modulating materials. Therefore, different crystal morphologies of the same thin film material can alter its density, ultimately achieving stress modulation. The stress modulation scheme using changes in the crystallographic morphology of a single functional film can be applied to the aforementioned passivation layers, stress-modulating layers, and reflectivity-modulating layers, and is not limited to single functional layers. Furthermore, changes in the crystallographic morphology of the thin film can further enable refractive index modulation, expanding the dimensions of optical field manipulation.

[0049] Controlling the stoichiometry of thin films can not only change the refractive index but also create films with different microstructures, directly altering the film's density. In the stoichiometry-controlled refractive index scheme for amorphous AlN films, when x≈1 (stoichiometry), the film exhibits advantages such as density, no defects, low stress, uniformity, strong adhesion, and resistance to cracking; when x<1 (Al-rich film), the film exhibits low density; when x>1 (N-rich film), the excess N leads to porosity and reduced density. Combining crystallographic morphology control with monolayer functional films can not only achieve gradual changes in the refractive index of functional films but also obtain low-stress monolayer functional films. This can also be extended to each unit layer in cavity surface film system design, simultaneously achieving low optical absorption and low-stress film systems.

[0050] Doping is a crucial technique for controlling the density of thin films. By altering the lattice structure, defect density, grain boundary behavior, and nucleation growth kinetics, density can be precisely increased or decreased, thereby controlling refractive index, stress, laser damage threshold, and environmental stability. First, when the radius of the dopant ion is close to that of the matrix ion, a solid solution is easily formed, filling lattice interstices, suppressing pores, and increasing density. Second, high-valence doping can compensate for oxygen vacancies, reduce defect channels, hinder gas / water vapor permeation, and increase density. Third, dopant ions segregate at grain boundaries, pinning them, inhibiting grain growth, and forming a fine-grained, dense structure. High-melting-point doping can also hinder atomic diffusion, reducing grain boundary porosity and increasing density. Rare-earth doping can lower the crystallization activation energy, promoting film crystallization and reducing amorphous loose regions. Fourth, doping provides heterogeneous nucleation sites, forming more and smaller grains with tighter packing. Furthermore, it suppresses columnar crystal growth, promotes equiaxed or layered growth, and reduces vertical porosity between columnar crystals.

[0051] Traditional multilayer functional thin films exhibit abrupt refractive index states of different materials and contain interfaces. These interface states increase optical absorption loss, and material changes alter film stress, degrading mechanical properties and potentially causing film peeling. Gradually changing refractive index multilayer thin film designs, lacking abrupt interfaces, avoid optical field loss and waste heat generation at the film interface. They also reduce interfacial lattice mismatch stress, improving film adhesion and anti-aging properties, thus comprehensively improving the stability and lifetime of gallium nitride (GaN) semiconductor lasers. For example, the aforementioned AlN passivation film, by continuously adding O2 to form an AlON interlayer, possesses high thermal conductivity, facilitating rapid heat dissipation from the cavity surface; it also exhibits high optical transmittance across a wide wavelength range, balancing passivation and optical matching; it demonstrates excellent chemical stability and mechanical strength, resists high temperatures and moisture, and exhibits strong film adhesion, making it less prone to cracking and peeling. By further controlling the O and N content in the thin film, Al2O3 thin films can be obtained. This process not only achieves passivation of the cavity surface of the nitride laser by the AlN thin film, but also achieves gradual control of the refractive index (AlN 2.1, AlON 1.9, Al2O3 1.7, for example characteristic values; continuous changes can obtain a film system with more refined N changes). This achieves the goal of fine control of the optical field and effective confinement of the interface states in the gradual film layer, forming a relatively ideal non-absorption film system, thereby effectively avoiding the generation of additional waste heat and improving the thermal stability of the film system.

[0052] Figure 4 This diagram illustrates the refractive index change during the process of forming an AlON interlayer and ultimately transitioning to an Al2O3 thin film from an AlN passivation film through a continuous increase in oxygen flow rate, according to one embodiment of the present invention. (Refer to...) Figure 4 Along the thickness direction of the film, the chemical composition gradually changes from AlN to AlON to Al2O3, and the refractive index changes continuously accordingly, forming a gradient film without abrupt interface.

[0053] Furthermore, AlON films exhibit superior adhesion and mechanical stability, effectively counteracting the stress effect of the AlN passivation layer and efficiently suppressing film peeling. Following this method, Al2O3 films can ultimately be obtained. Using the same cation source, by changing the type of anion, the output cavity film system of high-power nitride semiconductor lasers can be realized, greatly simplifying the production process and achieving true cost reduction and efficiency improvement. For the design of output cavity film systems with different reflectivities, gradual decreases, gradual increases, and continuous gradual decreases followed by continuous gradual increases of N can be achieved. Different reflectivities and light field distributions, as well as flexible stress distribution designs, can also be achieved by varying the design cycle. Compared to equivalent traditional abrupt film system designs, the above schemes have relatively less interface state absorption, relatively smaller stress distribution, and less source material consumption. This scheme can be used for optical films of nitrides and oxides with the same cations. For example, SiN... xSiO2, with its intermediate state being SiON, has a refractive index between its oxide and nitride forms, exhibiting excellent optical properties and mechanical stability. Furthermore, this approach can also be used for thin films with different cations having the same anion, such as Al2O3 and SiO2, co-growing which can achieve SiAlO x Three-element composite film.

[0054] Figure 5 This diagram illustrates a periodic variation in the refractive index of the functional layer along its thickness direction in one embodiment of the present invention. (Refer to...) Figure 5 Along the thickness direction of the functional layer, the refractive index fluctuates according to a preset period, and this periodic change is achieved by continuously adjusting the stoichiometric ratio or crystal morphology.

[0055] In specific applications, the functional layer 20 can adopt a single-layer integrated scheme, that is, the functional layer 20 is a continuously gradient film layer without interfaces, in which a passivation portion, a stress buffer portion, and a reflectivity adjustment portion are formed sequentially along the thickness direction. Specifically, the functional layer 20 is a continuously gradient film layer without interfaces, in which a passivation portion, a stress buffer portion, and a reflectivity adjustment portion are formed sequentially along the thickness direction. The functional layer 20 is only a single physical thin film, but the chemical composition of this film changes continuously along the thickness direction, thus forming the passivation portion, stress buffer portion, and reflectivity adjustment portion sequentially from the cavity surface outwards. In this scheme, the functional layer 20 is a continuously gradient film layer without interfaces. One implementation method is to continuously gradient from aluminum nitride (AlN) to aluminum oxide (Al2O3), passing through an aluminum-oxygen-nitrogen (AlON) transition region. The specific preparation process is as follows: using an aluminum source (such as an aluminum metal target or an aluminum evaporation source) as the same cation source, at the beginning of deposition, the aluminum source and nitrogen source (N2 or NH3) are deposited on the semiconductor cavity surface. AlN exhibits good lattice matching with nitride semiconductors, effectively passivating dangling bonds; this region serves as the passivation layer. After deposition reaches a certain thickness, oxygen (or ozone) is gradually introduced into the reaction chamber while the nitrogen flow rate is correspondingly reduced, causing the oxygen content in the deposited film to gradually increase and the nitrogen content to gradually decrease, thus forming AlON. AlON is a solid solution between AlN and Al2O3, with a refractive index between the two (AlN approximately 2.1, AlON approximately 1.9, Al2O3 approximately 1.7), and the refractive index can be continuously adjusted by regulating the oxygen-nitrogen ratio. Simultaneously, AlON possesses excellent adhesion and mechanical stability, buffering the lattice mismatch stress between AlN and Al2O3; therefore, this region serves as a stress buffer. When the oxygen flow rate is increased sufficiently to completely shut off the nitrogen, the deposited film completely transforms into Al2O3. Al2O3 has a low refractive index and high optical transmittance, making it suitable for use as a reflectivity adjustment layer; by controlling its thickness, the reflectivity of the light-emitting surface can be adjusted to the desired value. This monolayer gradient film contains no abrupt interfaces. Because the chemical composition and refractive index change continuously, light does not encounter abrupt reflection interfaces when passing through the film, significantly weakening the standing wave effect and reducing local light intensity peaks. Simultaneously, since the lattice constant and thermal expansion coefficient also change continuously, stress is dispersed throughout the gradient region and does not concentrate at specific interfaces, resulting in strong film adhesion and resistance to cracking and peeling. Furthermore, the AlON interlayer itself has high thermal conductivity, facilitating rapid heat dissipation from the cavity surface. From a process perspective, the entire deposition process is carried out continuously in the same chamber, requiring only adjustment of the gas flow rate ratio without interruption or replacement of the aluminum source, greatly simplifying the production process and improving batch consistency and yield. Similarly, SiN can also be used. x →SiON→SiO2 gradient system, or composite system of different cations with the same anion (such as Al2O3 and SiO2 co-grown to form SiAlO2).x Composite materials).

[0056] In this embodiment of the invention, a simplified dual-layer integration scheme is also provided. In this scheme, the functional layer 20 includes an amorphous layer for passivation and stress regulation, and a reflectivity regulation film layer for adjusting reflectivity. The amorphous layer and the reflectivity regulation film layer are stacked, and the refractive index and / or stress of the amorphous layer and the reflectivity regulation film layer are different. In this scheme, the functional layer 20 includes an amorphous layer for passivation and stress regulation, and a reflectivity regulation film layer disposed on the amorphous layer for adjusting reflectivity. The amorphous layer and the reflectivity regulation film layer are stacked, and their refractive indices and / or stresses are configured to be different. The amorphous layer is directly deposited on the semiconductor cavity surface, and the material can be selected as amorphous Al2O3 or amorphous SiN. x Alternatively, amorphous AlN can be used. Amorphous materials have extremely low internal stress, good adhesion, and high chemical stability, and can simultaneously passivate the cavity surface (blocking dangling bonds and preventing oxidation) and absorb stress (buffering thermal mismatch stress between subsequent films and the substrate). Amorphous AlN also has very high thermal conductivity (approximately 200 W / (m·K)), which is beneficial for heat dissipation from the cavity surface. The reflectivity adjustment film can be a single layer or multiple layers of conventional dielectric films (such as SiO2, Ta2O5, etc.), and its thickness and refractive index are designed according to the target reflectivity. This two-layer scheme has a simple structure, fewer deposition steps, and is easy to achieve large-scale production.

[0057] like Figure 1 As shown in the figure, an embodiment of the present invention provides a nitride semiconductor laser, including a laser body 10 and a functional layer 20 disposed on the light-emitting cavity surface of the laser body 10. A rear cavity film 30 is disposed on the rear side of the laser body 10, and a front cavity film is disposed on the front side. The front cavity film is the functional layer 20 described in the present invention. The functional layer 20 may include a first functional layer 21 (passivation film layer), a second functional layer 22 (stress-adjusting film layer), and a third functional layer 23 (reflectivity-adjusting film layer). The first functional layer 21, the second functional layer 22, and the third functional layer 23 are stacked sequentially from the inside to the outside. It should be noted that this is only one implementation of the present invention. In other embodiments, the functional layer 20 may be only a single continuous gradient film (in which case passivation, stress adjustment, and reflectivity adjustment functions are integrated in the same film layer), or it may be two layers (e.g., an amorphous layer plus a reflectivity-adjusting layer). Those skilled in the art should understand that the three-layer structure shown in the figures does not constitute a limitation on the scope of protection of the present invention.

[0058] Understandably, the functional layer 20 (whether single-layer or multi-layer) satisfies the following core characteristics: along the thickness direction of the functional layer 20 (i.e., the direction perpendicular to the light-emitting cavity surface and extending outward from the cavity surface), all or part of the functional layer 20 is configured to have different refractive indices, different stresses, or both. The term "different" can refer to segmented or continuous variations along the thickness direction. This can be achieved by changing the stoichiometry of the material, altering its crystal morphology, or altering the concentration and distribution of dopants. This eliminates the local enhancement of standing waves and interface reflections caused by abrupt changes in refractive index in traditional multilayer films, resulting in a more uniform optical field distribution and fewer optical absorption hotspots near the cavity surface. This significantly improves the COD trigger threshold. By applying varying stresses to the functional layer 20 along the thickness direction (especially transitioning from high-stress to low-stress regions), it can disperse and buffer lattice mismatch stresses and thermal stresses between different materials or structures, preventing stress concentration at a single interface, reducing the risk of film cracking and delamination, and improving the mechanical stability and long-term reliability of the film system. By integrating multiple functions such as passivation, stress modulation, and reflectivity modulation into a single continuous gradient film (e.g., AlN→AlON→Al2O3 gradient film), cavity surface passivation, stress buffering, and optical matching are simultaneously achieved without introducing abrupt interfaces. This simplifies the process flow, improves production efficiency and product consistency, and enables nitride semiconductor lasers to operate stably at higher output power levels, significantly extending device lifespan.

[0059] This invention also provides a laser device, including the aforementioned semiconductor laser. This laser device can be, but is not limited to: laser projectors (including laser TVs and digital cinema projectors), laser pump sources (for solid-state lasers or fiber lasers), laser cutting heads (especially blue laser cutting heads for highly reflective materials such as copper and aluminum), lidar (for autonomous driving or surveying), laser medical devices (such as urological lithotripsy lasers and dental treatment instruments), laser curing devices (such as ultraviolet curing devices and 3D printing devices), and laser displays (such as augmented reality and virtual reality optical engines). Due to the use of semiconductor lasers with high COD resistance, these laser devices can stably output high-power lasers for extended periods, significantly improving overall lifespan and reliability.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A semiconductor laser, characterized in that, It includes a laser body and a functional layer disposed on the laser body; Along the thickness direction of the functional layer, some or all of the functional layer are configured to have different refractive indices and / or stresses.

2. A semiconductor laser as described in claim 1, characterized in that, The functional layer includes a first functional layer; Along the thickness direction, the stoichiometry of the elements in the first functional layer is different, causing the refractive index of the first functional layer to gradually change along the thickness direction. And / or, along the thickness direction, the crystal morphology of the material in the first functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the first functional layer gradually change along the thickness direction.

3. A semiconductor laser as described in claim 2, characterized in that, The first functional layer is a passivation film layer attached to the surface of the laser body.

4. A semiconductor laser as described in claim 2, characterized in that, The first functional layer is a gradient film layer, which includes an AlN layer, an AlON intermediate layer and an Al2O3 layer disposed sequentially. Alternatively, the gradient film layer includes sequentially disposed SiN x The layers consist of a SiON intermediate layer and a SiO2 layer.

5. A semiconductor laser as described in claim 2, characterized in that, The functional layer further includes a second functional layer, which is stacked with the first functional layer along the thickness direction; Along the thickness direction, the stoichiometry of the elements in the second functional layer is different, causing the refractive index and / or stress of the second functional layer to gradually change along the thickness direction. And / or, along the thickness direction of the second functional layer, the crystal morphology of the material in the second functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the second functional layer gradually changes along the thickness direction.

6. A semiconductor laser as described in claim 5, characterized in that, The second functional layer is a stress-regulating film layer.

7. A semiconductor laser as described in claim 5, characterized in that, The functional layer further includes a third functional layer, and the first functional layer, the second functional layer and the third functional layer are stacked along the thickness direction; Along the thickness direction, the stoichiometric ratios of the elements in the third functional layer are different, causing the refractive index and / or stress of the third functional layer to gradually change along the thickness direction. And / or, along the thickness direction of the third functional layer, the crystal morphology of the material in the third functional layer is different or the doping is controlled differently, so that the refractive index and / or stress of the third functional layer gradually change along the thickness direction.

8. A semiconductor laser as described in claim 7, characterized in that, The third functional layer is a reflectivity adjustment film layer.

9. A semiconductor laser as described in claim 1, characterized in that, The functional layer is a gradient film layer with a continuous gradient without interface, and a passivation part, a stress buffer part and a reflectivity adjustment part are formed sequentially along the thickness direction; Alternatively, the functional layer may include an amorphous layer for passivation and stress adjustment and a reflectivity adjustment film layer for adjusting reflectivity, wherein the amorphous layer and the reflectivity adjustment film layer are stacked, and the refractive index and / or stress of the amorphous layer and the reflectivity adjustment film layer are different.

10. A laser device, characterized in that, Includes a semiconductor laser as described in any one of claims 1 to 9.

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