Vertical cavity surface emitting laser array light source and preparation method thereof

Abstract

The invention provides a vertical cavity surface emitting laser array light source and a preparation method thereof, and the preparation method comprises the steps: carrying out the vapor deposition of a metal organic alkyl precursor and an inorganic vapor phase precursor to obtain a substrate layer, and introducing a metal organic complex precursor and ammonia gas to deposit an ammoniation layer; coating and exposing the ammoniated layer, introducing a first oxide precursor, depositing to form a first refraction layer, introducing a second oxide precursor, depositing to form a second refraction layer on the first refraction layer, and repeatedly stacking the first refraction layer and the second refraction layer to obtain an intermediate substrate with an anti-Bragg grating structure; a silicon nitride layer is deposited on an intermediate base material, etching is carried out on the silicon nitride layer, finally, a lens layer is packaged to obtain a vertical cavity surface emitting laser, and the vertical cavity surface emitting laser is divided into a plurality of laser units to form the vertical cavity surface emitting laser array light source. Therefore, the power of a single laser unit and the stability and the consistency of the array light source are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and particularly relates to a vertical cavity surface emitting laser array light source and a preparation method thereof. Background Art

[0002] A vertical cavity surface emitting laser (VCSEL) array light source is a laser device manufactured by semiconductor processes. Its laser cavity is constructed along the direction perpendicular to the substrate, and the laser light is emitted vertically from the device surface. By integrating multiple VCSEL units, an array light source can be formed to achieve large-area, high-brightness, and uniformly distributed laser output, meeting the application requirements in high-power or specific scenarios. The preparation of VCSEL mainly relies on semiconductor materials, which have direct bandgap characteristics and can efficiently achieve electroluminescence. The electronic structure of semiconductor materials is suitable for generating stimulated emission, thereby realizing laser gain.

[0003] However, in the related art, the output power of a single VCSEL is usually low. Although the overall optical power can be increased through an array structure, it is still difficult to improve the power of a single unit, especially in high-power application scenarios. At the same time, the array structure of VCSEL makes it difficult to control the output power and wavelength consistency between different laser units. The error between different laser units will cause a significant decrease in the light field uniformity of the overall system, thereby affecting the application effect and reducing the stability and consistency of the array light source. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a vertical cavity surface emitting laser array light source and a preparation method thereof, aiming to solve the problem of poor heat insulation effect.

[0005] To solve the above technical problem, the present invention is implemented as follows. The present invention provides a preparation method for a vertical cavity surface emitting laser array light source, and the steps include: S1. A metal organic alkyl precursor and an inorganic gas phase precursor are used to obtain a base layer through chemical vapor deposition, and then a metal organic complex precursor and ammonia are introduced to deposit an ammoniated layer on the base layer; S2. Coating and exposure are performed on the ammoniated layer according to a preset pattern, and then a first oxide precursor is introduced to deposit a first refractive layer on the preset pattern. Then, a second oxide precursor is introduced to deposit a second refractive layer on the first refractive layer. The first refractive layer and the second refractive layer are repeatedly stacked until a preset number of layers is reached to obtain an intermediate substrate with an anti-Bragg grating structure, wherein the refractive index of the first refractive layer is different from that of the second refractive layer; S3. Heat the intermediate substrate to a preset decomposition temperature, then introduce a silicon source gas and ammonia gas to deposit a silicon nitride layer on the intermediate substrate. Etch the silicon nitride layer according to a preset pattern to obtain an etched pattern. Finally, after encapsulating the lens layer, a vertical cavity surface emitting laser is obtained. The vertical cavity surface emitting laser is divided into multiple laser units to form a vertical cavity surface emitting laser array light source.

[0006] In some embodiments of the present invention, step S1 includes: S1.1. Place the substrate in a chemical vapor deposition reactor and heat it to 630 - 650 °C. Introduce a metal organic alkyl precursor and an inorganic gas phase precursor, adjust the internal pressure to 10 - 20 Torr, and the deposition time is 30 - 40 minutes to obtain a base layer; S1.2. Lower the temperature to 250 - 300 °C, then introduce a metal organic complex precursor and ammonia for cyclic deposition. The cyclic time is 20 - 30 minutes, and stop when the preset number of cycles is reached to obtain an ammoniated layer deposited on the base layer.

[0007] In some embodiments of the present invention, in step S1, the metal organic alkyl precursor includes at least one of trimethylgallium, trimethylindium, and trimethylaluminum; the inorganic gas phase precursor includes at least one of arsine, phosphine, and stibine; the metal organic complex precursor includes at least one of titanium tetraisopropoxide, titanium tetra-n-butoxide, and tetrakis(dimethylamino)titanium; the substrate includes at least one of gallium arsenide, indium phosphide, and silicon.

[0008] In some embodiments of the present invention, in step S1.2, the operation of single deposition in cyclic deposition includes: First, introduce the metal organic complex precursor, and set the time to 5 seconds; Then introduce an inert gas to remove impurities, and set the time to 8 seconds; Then introduce ammonia, and set the time to 3 seconds; Finally, introduce an inert gas, and set the time to 8 seconds to complete a single deposition.

[0009] In some embodiments of the present invention, in step S2, the first oxide precursor includes at least one of tetraethoxytitanium, tetrakis(isopropoxy)titanium, and tetrakis(n-butoxy)titanium; the second oxide precursor includes at least one of tetraethoxysilane, tetrakis(isopropoxy)silane, and tetrakis(n-butoxy)silane.

[0010] In some embodiments of the present invention, step S2 includes: S2.1. Spin-coat the positive photoresist evenly on the surface of the ammoniated layer, control the thickness within 150 - 200 nm, heat it to 90 - 100 °C, and the heating time is 1 - 2 minutes; S2.2. Use an electron beam lithography device or an ultraviolet lithography device to perform exposure according to a pre-pattern, soak in a developer for 30 seconds, then rinse with deionized water and dry to obtain a prefabricated substrate. Among them, the working voltage of the electron beam lithography device is 20 - 30 kV, and the exposure wavelength of the ultraviolet lithography device is 365 nm; S2.3. Place the exposed prefabricated substrate in a chemical vapor deposition reactor, heat it to 350 - 450 °C, and introduce a first oxide precursor to form a first refractive layer; S2.4. Maintain the temperature and introduce a second oxide precursor to form a second refractive layer; S2.5. Repeat steps S2.3 and S2.4 until the preset number of layers is reached to obtain an intermediate substrate with an anti-Bragg grating structure.

[0011] In some embodiments of the present invention, in step S2, the thicknesses of the first refractive layer and the second refractive layer are 1 / 4 of the preset working wavelength.

[0012] In some embodiments of the present invention, in step S3, the silicon source gas includes at least one of silane, dichlorosilane, and disilane, and the volume ratio of the silicon source gas to the ammonia gas is 1:(4 - 5).

[0013] In some embodiments of the present invention, step S3 includes: S3.1. Place the intermediate substrate in an inert atmosphere for preheating, raise the temperature to 500 - 600 °C, and adjust the internal pressure to 200 - 300 mTorr; S3.2. Maintain the temperature and pressure, introduce the silicon source gas and ammonia gas, and the deposition time is 10 - 20 minutes to form a silicon nitride layer; S3.3. Pour the photosensitive composite solution into a lens mold, apply a pressure of 0.1 - 0.2 MPa and hold for 3 - 5 minutes, place it in an ultraviolet light curing device, and irradiate with ultraviolet light with an irradiation intensity of 10 - 15 mW / cm² and a wavelength of 365 nm for 60 - 90 seconds to obtain a lens layer, and bond the lens layer and the silicon nitride layer to obtain a vertical cavity surface emitting laser; S3.4. Spin-coat a positive photoresist on the vertical cavity surface emitting laser, control the thickness to be 150 - 200 nm, bake at 90 - 100 °C for 1 - 2 minutes, use an electron beam lithography device or an ultraviolet lithography device to perform exposure according to a pre-pattern, soak in a developer for 30 seconds, then rinse with deionized water and dry; S3.5. Then place it in an inductively coupled plasma device for etching, adjust the power to 150 W, set the radio frequency power to 50 W, adjust the pressure to 5 - 10 mTorr, introduce a mixed gas of trifluoromethane and oxygen, and the etching time is 40 - 60 seconds to form an isolation zone for the laser unit; S3.6. Deposit an adhesion layer on the surface of the isolation strip first, and then deposit a gold layer to form an electrode layer. Perform exposure and etching operations on the electrode layer according to a preset electrode pattern to obtain an exposed cutting pattern; S3.7. Cut the vertical cavity surface emitting laser according to the cutting pattern, and obtain a vertical cavity surface emitting laser array light source after packaging.

[0014] The present invention provides a vertical cavity surface emitting laser array light source, which is made by the preparation method of a vertical cavity surface emitting laser array light source as described above. The vertical cavity surface emitting laser array light source includes a substrate layer, an anti-Bragg grating structure and a lens layer; wherein, The substrate layer is used to provide mechanical support and a lattice matching environment; The anti-Bragg grating structure is used to form a mirror structure of the vertical cavity; The lens layer is used to shape and collimate the emitted light beam.

[0015] Compared with the prior art, the beneficial effects of a vertical cavity surface emitting laser array light source and its preparation method in the present invention are as follows: By repeatedly depositing the first refractive layer and the second refractive layer with different refractive indexes in step S2, an anti-Bragg grating structure with high reflectivity and high cavity quality factor is constructed. The high reflectivity can reduce the loss of light energy in the cavity, improve the photon storage effect, thereby reducing the threshold current and enhancing the stimulated emission efficiency, and finally significantly improving the output power of a single vertical cavity surface emitting laser unit. Using metal-organic alkyl precursors and inorganic gas-phase precursors to deposit the substrate layer in step S1 and performing exposure and deposition according to a preset pattern in step S2 can greatly ensure the thickness and material uniformity of each layer. The thickness and interface quality directly determine the performance of the mirror, thus playing a key role in enhancing the optical field in the laser cavity, and further facilitating higher-power lasing. In step S3, by depositing a silicon nitride layer on the intermediate substrate and combining with etching a preset pattern, this step not only further forms good optical and electrical isolation, but also improves the vertical and horizontal confinement of the optical field, helps to effectively guide and enhance the laser output, and enables a single laser unit to obtain higher conversion efficiency and output power.

[0016] Vapor deposition has extremely high repeatability and uniformity, ensuring that the physical properties such as thickness and refractive index of each layer in each batch of devices are almost identical. This high uniformity guarantees that the optical cavities and anti-Bragg grating properties of each vertical-cavity surface-emitting laser (VCSEL) unit in the entire array are consistent, thereby significantly improving the overall stability and consistency of the array. The layered anti-Bragg grating structure and subsequent deposition of the silicon nitride layer are optimized to improve the interface quality of the laser cavity. A high-quality interface can effectively suppress scattering and non-radiative recombination processes caused by material defects, thus ensuring a higher stimulated emission efficiency of the laser within the cavity, reducing the phenomenon of hot spots and non-uniform emission, and further improving the long-term stable operation performance of the device. Preset pattern control and etching processes can precisely define the size and shape of each VCSEL unit, reducing device-to-device variations caused by inconsistent microstructures. This precise microstructure control ensures the uniformity of key performance parameters such as laser output power, beam shape, and threshold current across the entire array, enhancing the batch production consistency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flowchart of a method for preparing a vertical-cavity surface-emitting laser array light source according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present 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 only used to explain the present invention and are not used to limit the present invention.

[0019] Please refer to Figure 1 , the present invention provides a method for preparing a vertical-cavity surface-emitting laser array light source, the steps including: S1. Obtain a base layer by vapor deposition of a metalorganic alkyl precursor and an inorganic gas-phase precursor, and then introduce a metalorganic complex precursor and ammonia to deposit an ammoniated layer on the base layer.

[0020] In step S1, the metalorganic alkyl precursor includes at least one of trimethylgallium, trimethylindium, and trimethylaluminum, the inorganic gas-phase precursor includes at least one of arsine, phosphine, and stibine, the metalorganic complex precursor includes at least one of titanium tetraisopropoxide, titanium tetra-n-butoxide, and tetrakis(dimethylamino)titanium, and the substrate includes at least one of gallium arsenide, indium phosphide, and silicon.

[0021] Step S1 includes: S1.1. Place the substrate in a chemical vapor deposition reactor and heat it to 630 - 650 °C. Introduce a metalorganic alkyl precursor and an inorganic gas-phase precursor, adjust the internal pressure to 10 - 20 Torr, and set the deposition time to 30 - 40 minutes to obtain a base layer. The thickness of the base layer can be 2 - 3 μm.

[0022] In the chemical vapor deposition reactor, the substrate is heated to 630 - 650 °C. This high-temperature environment promotes the decomposition of the metalorganic alkyl precursor to release active metal atoms, which combine with the components generated by the decomposition of the inorganic gas-phase precursor to form a corresponding compound thin film. At high temperatures, the organic ligands of the metalorganic precursor detach, and the inorganic gas-phase precursor decomposes to produce active arsenic. The two recombine on the substrate surface to form a high-quality, crystal-complete base layer, while methane is generated as a by-product. High-purity, low-defect thin film deposition can be achieved through high-temperature reactions, which provides ideal lattice matching and interface flatness for the deposition of subsequent functional layers. By precisely controlling the temperature and pressure, the base layer can be uniformly grown over a large area, ensuring the consistency and repeatability of the internal structure of the device. This layer provides an ideal crystal substrate and interface flatness for the device, which is crucial for the growth and performance of subsequent deposition layers. By selecting different metalorganic alkyl precursors and inorganic precursors, the composition and properties of the generated thin film can be regulated to meet the requirements of different devices (such as adjusting the carrier concentration, bandgap width, etc.).

[0023] S1.2. Lower the temperature to 250 - 300 °C, then introduce a metalorganic complex precursor and ammonia for cyclic deposition. The cyclic deposition time is 20 - 30 minutes. Stop when the preset number of cycles is reached to obtain an ammoniated layer deposited on the base layer. The thickness of the ammoniated layer can be 20 - 30 nm.

[0024] In the S1.2 stage, after the temperature of the base layer is lowered to 250 - 300 °C, a metalorganic complex precursor and ammonia are introduced for cyclic deposition. At a lower temperature, the metalorganic complex precursor adsorbs on the substrate surface. Subsequently, ammonia is introduced, and nitrogen reacts with metal ions to form a metal nitride thin film. At the same time, the organic ligands detach and volatilize as by-products in the form of isopropanol, etc. The deposited nitride layer usually has good chemical stability and heat resistance, and can act as a buffer layer between subsequent functional layers, improving interface adhesion, reducing interface defects, and suppressing adverse diffusion phenomena. The metal nitride layer has high thermal conductivity and moderate electrical conductivity, which helps to effectively dissipate heat in the device. At the same time, in some designs, it can also act as an electrode function. This layer plays a role in interface buffering, enhancing adhesion, and improving thermoelectric properties, which is conducive to the stability and efficient operation of the subsequent device structure. Depositing the nitride layer at a low temperature of 250 - 300 °C helps to avoid damaging the crystal structure of the base layer deposited at high temperature, thus ensuring the overall crystal quality and optical performance of the device.

[0025] In step S1.2, the operations of a single deposition in the cyclic deposition include: First, introduce the metal-organic complex precursor for 5 seconds. Then, introduce an inert gas to remove impurities for 8 seconds. Next, introduce ammonia for 3 seconds. Finally, introduce an inert gas for 8 seconds to complete a single deposition.

[0026] By first introducing the metal-organic complex precursor for 5 seconds, it is allowed to fully adsorb on the substrate surface to ensure that the reaction is limited to the coverage of a single monolayer of molecules. Then, by introducing an inert gas for cleaning, it is ensured that unreacted precursors or excess molecules are completely removed, thereby avoiding gas-phase reactions and non-uniform deposition in the next step. Next, introduce ammonia (for 3 seconds) so that the metal-organic complex adsorbed on the surface reacts with the nitrogen source to form the target nitride film. Finally, by again introducing an inert gas for cleaning (for 8 seconds), the volatile by-products generated by the reaction are completely removed to ensure the purity and continuity of the thin film layer. Each single deposition cycle has strict and controllable reaction steps and times. By repeating the cycles multiple times, atomic-level thickness control can be achieved, ensuring that the deposited layer is uniform and defect-free. This method avoids the problems of over-deposition or thickness non-uniformity that may occur in traditional continuous deposition and is one of the key technologies for realizing precise control of thin films. Operating at a relatively low temperature of 250 - 300 °C reduces the risk of thermal damage, helps maintain the crystal quality and interface integrity of the base layer, and is also suitable for the integration of subsequent multi-layer structures.

[0027] S2. Coating and exposure are performed on the ammoniated layer according to a preset pattern. Then, introduce the first oxide precursor to deposit and form the first refractive layer on the preset pattern. Next, introduce the second oxide precursor to deposit and form the second refractive layer on the first refractive layer. Repeat the stacking of the first refractive layer and the second refractive layer until the preset number of layers is reached to obtain an intermediate substrate with an anti-Bragg grating structure, where the refractive index of the first refractive layer is different from that of the second refractive layer. In step S2, the first oxide precursor includes at least one of tetraethoxy titanium, tetra(isopropoxy) titanium, and tetra(n-butoxy) titanium, and the second oxide precursor includes at least one of tetraethoxysilane, tetra(isopropoxy) silane, and tetra(n-butoxy) silane. In step S2, the thicknesses of the first refractive layer and the second refractive layer are 1 / 4 of the preset working wavelength.

[0028] Step S2 includes: S2.1. Spin coat a positive photoresist evenly on the surface of the ammoniated layer, control the thickness within 150 - 200 nm, heat up to 90 - 100 °C, and the heating time is 1 - 2 minutes. The positive photoresist includes at least one of Shipley S1813 positive photoresist, AZ5214E positive photoresist, and SPR - 220 positive photoresist. The specific referents of the above positive photoresists are known to those skilled in the art and will not be elaborated here.

[0029] The positive photoresist used here is not an active chemical that participates in a chemical reaction to form a fixed dielectric layer, but a photosensitive polymer. Its main function is to change solubility after exposure to form an exposed pattern that conforms to a preset pattern for subsequent deposition. Among them, the preset pattern is set according to actual usage needs, such as a regularly or irregularly spaced pattern arranged in an array, such as circles, rectangles, triangles, etc. The pre - baking process is beneficial to solvent volatilization and film stability, and at the same time improves the corrosion resistance of the photoresist. Ensure that the thickness of the photoresist layer is uniform and the surface is flat, providing a good foundation for subsequent precise pattern exposure. After pre - baking, the thermal stability of the film is improved and it is not easily damaged by subsequent processing, thus ensuring the accuracy of pattern size and position.

[0030] S2.2. Use an electron beam lithography device or an ultraviolet lithography device to perform exposure according to a pre - designed pattern, soak in a developer for 30 seconds, then rinse with deionized water and dry to obtain a pre - fabricated substrate. Among them, the working voltage of the electron beam lithography device is 20 - 30 kV, and the exposure wavelength of the ultraviolet lithography device is 365 nm. The developer includes at least one of tetramethylammonium hydroxide solution, MF - 319 developer, and AZ726 developer.

[0031] During the exposure process, after the photoresist receives an electron beam or ultraviolet light, its chemical bonds break or cross - link, changing the chemical solubility of the irradiated area. The developer has a selective difference in the dissolution rate of the irradiated and non - irradiated areas, thus realizing the fine separation and manifestation of the pattern. The pre - designed pattern (used to define the subsequent deposition area) is accurately transferred to the photoresist; ensuring that subsequent deposition occurs only in the preset area, providing an accurate template for the subsequent formation of an alternately stacked dielectric layer.

[0032] S2.3. Place the exposed pre - fabricated substrate in a chemical vapor deposition reactor, heat it to 350 - 450 °C, and introduce a first oxide precursor to form a first refractive layer.

[0033] The first oxide precursor can be selected from at least one of titanium tetraethoxide, titanium tetraisopropoxide, or titanium tetrabutoxide. At a temperature of 350 - 450 °C, these precursors generate a titanium oxide thin film with a high refractive index through a pyrolysis reaction. The generated titanium oxide thin film has a high refractive index, forming an obvious optical refractive index contrast with the subsequent low refractive index layer as the first refractive layer. The deposition parameters are strictly controlled so that the optical thickness of this layer reaches 1 / 4 of the designed wavelength, thereby forming ideal interference conditions in the multi-layer alternation. It is deposited only within the preset pattern area to ensure regional positioning and overall structural consistency.

[0034] S2.4. Maintain the temperature and introduce the second oxide precursor to form the second refractive layer.

[0035] The second oxide precursor can be selected from at least one of tetraethoxysilane, tetraisopropoxysilane, or tetrabutoxysilane. At the same temperature, these precursors generate a low refractive index silicon dioxide thin film through a pyrolysis reaction. Similarly, the role of the pattern template ensures that the silicon dioxide layer is deposited on the previous titanium oxide layer, and the thickness is precisely controlled to the design requirement (1 / 4 of the working wavelength).

[0036] The generated silicon dioxide thin film has a low refractive index, forming an obvious interfacial refractive index difference with titanium oxide, which constitutes a necessary condition for the anti-Bragg grating structure; when the titanium oxide and silicon dioxide layers are stacked alternately, the 1 / 4 wavelength design of each layer makes the phase differences of the reflected light at each interface add up to achieve the optimal reflection effect; ensuring the interfacial quality between layers during multi-layer stacking is beneficial to long-term stable optical performance.

[0037] S2.5. Repeat steps S2.3 and S2.4 until the preset number of layers is reached to obtain an intermediate substrate with an anti-Bragg grating structure. The preset number of layers can be 12 - 24 layers.

[0038] Each pair of refractive layers consists of a high refractive index titanium oxide layer and a low refractive index silicon dioxide layer. Through multiple laminations, using the principle of optical interference, a high reflectivity effect is achieved at the designed wavelength, and its central working principle is the anti-Bragg effect. The intermediate substrate formed after repeated stacking has a very high reflectivity, which can form an effective resonant cavity in a vertical cavity laser and reduce the laser threshold; the precise control of the thickness of each layer ensures that the phases of the reflected light at each interface are consistent at the target wavelength, and constructive interference achieves the best reflection effect; the multi-layer dielectric film structure not only provides an optical reflection function but also has good mechanical stability and thermal stability, laying a solid foundation for the preparation of downstream devices.

[0039] S3. Heat the intermediate substrate to a preset decomposition temperature, then introduce a silicon source gas and ammonia gas, deposit a silicon nitride layer on the intermediate substrate, etch according to a preset pattern on the silicon nitride layer to obtain an etched pattern, and finally obtain a vertical cavity surface emitting laser after encapsulating the lens layer. After dividing the vertical cavity surface emitting laser into multiple laser units, a vertical cavity surface emitting laser array light source is formed. In step S3, the silicon source gas includes at least one of silane, dichlorosilane, and disilane, and the volume ratio of the silicon source gas to ammonia gas is 1:(4 - 5). The preset pattern can be the same as or different from the preset pattern in step S2.

[0040] Step S3 includes: S3.1. Place the intermediate substrate in an inert atmosphere for preheating, heat it to 500 - 600 °C, and adjust the internal pressure to 200 - 300 mTorr.

[0041] During the preheating process, the substrate temperature reaches the critical temperature required for the thermal decomposition of the silicon source precursor, which creates suitable reaction conditions for the subsequent deposition of the silicon nitride layer. In addition, using a low pressure helps to improve gas transport and reaction uniformity, ensures that the surface of the intermediate substrate is pollution-free and reaches a stable state, provides a stable temperature platform for the high-uniformity and high-quality deposition of the silicon nitride layer, and prevents film defects or non-uniform deposition caused by insufficient temperature.

[0042] S3.2. Maintain the temperature and pressure, introduce the silicon source gas and ammonia gas, and the deposition time is 10 - 20 minutes to form a silicon nitride layer. The thickness of the silicon nitride layer can be 100 - 200 nm.

[0043] At 500 - 600 °C, silane reacts with ammonia gas to form a silicon nitride thin film, and hydrogen is generated as a by-product at the same time. At high temperatures, the silicon source precursor decomposes and reacts with the nitrogen in ammonia gas to form a dense and uniform thin film. Silicon nitride has high chemical stability, mechanical strength, and excellent dielectric properties. A silicon nitride layer with good optical and mechanical properties is obtained, providing a stable film base for the subsequent pattern etching. This layer also plays roles of isolation, protection, and optical regulation, and is an important part of the overall performance of the device.

[0044] S3.3. Pour the photosensitive composite solution into the lens mold, apply a pressure of 0.1 - 0.2 MPa and maintain it for 3 - 5 minutes. Place it in an ultraviolet curing device and irradiate it with ultraviolet light with an irradiation intensity of 10 - 15 mW / cm² and a wavelength of 365 nm for 60 - 90 seconds to obtain a lens layer. Bond the lens layer and the silicon nitride layer to obtain a vertical cavity surface emitting laser. The photosensitive composite solution includes a photosensitive polymer matrix, functional nanoparticles, and a photosensitizer. Among them, the photosensitive polymer matrix includes at least one of polymethyl methacrylate and polystyrene, the functional nanoparticles include at least one of silicon dioxide, alumina, and zinc oxide, and the photosensitizer includes at least one of 2-hydroxy-2-methyl-1-phenylpropanone, 2,2-dimethyl-1-phenyl-1-hydroxyethanone, and phenyl bis(2,4,6-trimethylphenyl) phosphate. In the composite solution, the photosensitive polymer matrix serves as an optically transparent matrix and transforms into a solid film with high mechanical strength and a smooth surface after solvent evaporation and ultraviolet curing; the incorporation of silicon dioxide nanoparticles adjusts the refractive index of the film and helps to form a microprism structure, further improving the beam shaping and collimation effects. The formed aspherical lens encapsulation layer not only protects the internal structure of the device and reduces interference from the external environment, but also can effectively shape and collimate the emitted beam, improving the optical performance of the laser. The bonding with the crude product ensures the mechanical stability of the overall structure and the reliability of long-term operation.

[0045] In one embodiment, the following calculation equation is used to calculate the simulation shape coordinate system to determine the specific shape setting of the lens layer. The calculation equation is: Where, is the phase delay, which describes the optical path difference that should be introduced at the point (x, y) on the lens layer to achieve the target wavefront correction effect. The unit is radian (rad). It is obtained by calculation according to the actual curvature of the laser output wavefront and the design target (such as a plane wave or an ideal focusing state). is the wave number, which is related to the working wavelength λ and is defined as = 2π / λ, and the unit is , which is determined by the working wavelength. The working wavelength of the vertical cavity surface emitting laser array light source can be 800 - 1000 nm. (x, y) is the lens surface coordinate, which represents the position of any point on the lens layer and determines the phase delay at that point. The unit is expressed in μm or mm, depending on the device size, and is determined according to the lens design size and the predetermined free-form surface shape. and are the coordinate offsets, which reflect the position offset of the central reference point in the (x, y) coordinate system. Their settings are related to the central alignment of the entire phase compensation distribution. The unit is μm and is determined according to the optical alignment requirements and the design simulation data. For example, it can be 0 - 50 μm. is the focal length, representing the distance of target focusing or collimation in the design, i.e., the reference length of the optical path. The unit is expressed in μm or mm, and the appropriate value can be, for example, between 50 µm and 300 µm.

[0046] In an actual laser system, the incident light wavefront is often not an ideal plane wave and will be distorted or inhomogeneous due to various factors. This requires corresponding optical compensation to correct these non-idealities. Due to the emission characteristics of the light source itself or the phase errors introduced by optical components (such as anti-Bragg gratings, substrates, etc.), there are often local phase deviations and curvature changes in the incident light wavefront. This distortion will cause problems such as beam divergence and focus shift during the propagation of the laser beam. By designing the free-form surface of the lens surface (i.e., the spatial variation of the thickness), an appropriate phase delay can be introduced to cancel the inhomogeneity of the incident wavefront, making the output wavefront flatter or achieving a predetermined curvature. This is a crucial step in ensuring that the output beam has ideal collimation, focusing, or uniform characteristics. The uncompensated distorted wavefront will reduce the beam quality, resulting in spot deformation, scattered foci, and uneven energy distribution, thus affecting the overall application effect of the laser (such as its use in laser processing, communication, and imaging). By precisely controlling the thickness variation of the lens surface to correct the entire output wavefront, the beam quality of the laser can be significantly improved, the power concentration and transmission efficiency can be enhanced, while unnecessary energy losses and interference noise can be reduced.

[0047] In many high-performance laser applications, such as vertical-cavity surface-emitting laser arrays, it is required that the output beam has an extremely low divergence angle and high focusing ability in the far field. This requires the output wavefront to strictly meet the design requirements. Adjusting the lens surface to generate a phase modulation opposite to the distortion of the incident wavefront, so that the local phases of all wavefronts are synchronized and corrected after passing through the lens, achieving an ideal collimation or focusing effect, which is crucial for realizing high-quality laser beam output.

[0048] Therefore, the phase delay calculated by the formula is directly corresponding to the physical optical path difference required for each point. Designing the free-form surface of the lens surface is to introduce fine phase compensation at the micro scale, thereby regulating the entire output wavefront to achieve the expected optical effect. This is why it is necessary to compensate for the non-ideal shape of the incident light wavefront to ensure that the beam output by the final laser meets high requirements in terms of energy concentration, uniformity, and focusing performance.

[0049] The phase delay calculated by the formula is proportional to the physical optical path difference required for each (x, y) point. To compensate for the non-ideal shape of the incident light wavefront, the lens surface needs to be designed with corresponding thickness variations. In the S3.5 mold processing stage, using the one obtained from this formula, The value can be converted into the physical thickness t(x, y) (the relationship between the thickness variation and the phase delay is , where n is the refractive index of the lens material). This thickness distribution is the target shape of the freeform surface. By designing the freeform surface of the lens layer, the wavefront of the incident laser is compensated to an ideal wavefront (such as a plane wave or specific focusing characteristics) after passing through the lens. The parameter in the formula directly determines the focusing effect after compensation - a larger value generally corresponds to a weaker optical focus, while a smaller strengthens the focus. In the preparation of the S3.5 lens layer, a prefabricated lens mold is used, and its inner surface has been machined according to the freeform surface shape calculated by the above formula. The key to this step is to obtain the target thickness t(x, y) at each (x, y) point using the above formula and fabricate the matching inner surface of the mold. Pour the photosensitive composite solution into the mold, and under the external pressure (0.1 - 0.2 MPa) and ultraviolet light curing conditions, cure the solution into a lens layer with the same shape as the mold. The cured lens layer has a thickness distribution that matches the freeform surface design, and this distribution enables the laser wavefront after passing through the lens to achieve the predetermined collimation or focusing characteristics after corresponding compensation.

[0050] S3.4. Spin-coat a positive photoresist on the vertical-cavity surface-emitting laser, control the thickness at 150 - 200 nm, bake it at 90 - 100 °C for 1 - 2 minutes, use an electron beam lithography device or an ultraviolet lithography device to expose it according to the pre-pattern, soak it in the developer for 30 seconds, and then rinse it with deionized water and dry it.

[0051] During the photolithography exposure process, chemical changes occur in the photoresist in the light-receiving area, and only the preset pattern area remains after development. The preset pattern is accurately transferred to the photoresist, providing a high-resolution template for the subsequent etching. Ensure that the size and position of the pattern meet the design requirements, so as to achieve the generation of precise structures in the subsequent etching.

[0052] S3.4. Then place it in an inductively coupled plasma device for etching, adjust the power to 150 W, set the radio frequency power to 50 W, adjust the pressure to 5 - 10 mTorr, introduce a mixed gas of trifluoromethane and oxygen, and the etching time is 40 - 60 seconds to form the isolation band of the laser unit.

[0053] In the low-pressure plasma, the fluorine ions formed by the decomposition of trifluoromethane chemically react with silicon nitride to generate volatile silicon fluoride; at the same time, the bombardment of ions has a physical etching effect. The added oxygen helps to control the etching rate and improve the etching surface quality. The radio frequency power provides a vertical acceleration electric field to ensure etching anisotropy, making the etching profile clear and the sidewalls vertical.

[0054] S3.6. First deposit an adhesion layer on the surface of the isolation strip, and then deposit a gold layer to form an electrode layer. Perform exposure and etching operations on the electrode layer according to a preset electrode pattern to obtain an exposed cutting pattern. The adhesion layer can be chromium or titanium with a thickness of 10 nm. The thickness of the gold layer is 100 - 200 nm.

[0055] Use a thin chromium or titanium adhesion layer to ensure firm adhesion between the gold layer and the underlying material, so that the electrode pattern remains stable and uniform during the etching process. The deposited thickness of the gold layer (100 - 200 nm) ensures sufficient conductivity. At the same time, in the design, through photolithography pattern definition, the electrodes are only arranged in the non-optical emission area (isolation strip) or the edge area, thus avoiding blocking the core light-transmitting area. The exposed area of the electrode pattern on the isolation strip provides a clear boundary for the subsequent cutting step, enabling precise cutting along the preset cutting line during the laser scribing process without damaging the key electrode structure. The precise electrode pattern and isolation layer design contribute to uniform current injection in each laser unit, thereby reducing the output power and wavelength deviation caused by uneven current distribution and enhancing the consistency and stability of the entire array.

[0056] In one embodiment, indium tin oxide is deposited on the isolation strip as an electrode. Indium tin oxide has high optical transparency and good conductivity, enabling it to not only conduct electricity effectively but also maintain the light transmittance in the laser emission area. In the electrode area of the laser unit, even with the indium tin oxide layer covering, it will not significantly hinder the propagation of light, thus ensuring current injection without affecting the optical output of the laser. Using indium tin oxide as the electrode material can achieve low-resistance conduction, which helps to evenly distribute the injected current. Uniform current injection can reduce the threshold and output power differences between units caused by uneven current, thereby improving the overall consistency and stability of the entire laser array. The indium tin oxide layer can form a high-resolution pattern through standard photolithography and etching processes. Its processing technology is mature and can accurately deposit and process the required electrode pattern within the preset isolation strip area. Through precise patterning, the indium tin oxide electrode can be accurately positioned in the non-optical emission area or the isolation strip area, ensuring separation of the electrode from the core area of the laser and avoiding unnecessary light loss caused by metal blockage. Indium tin oxide is a transparent conductive material widely used in display technology and optoelectronic devices, with strong compatibility and easy integration with other semiconductor processes. During packaging and overall integration, the indium tin oxide layer can be smoothly integrated with other optical regulation and circuit layers, facilitating large-scale array production and performing well in terms of thermal management and mechanical stability.

[0057] S3.7. Cut the vertical cavity surface emitting laser according to the cutting pattern, and obtain a vertical cavity surface emitting laser array light source after encapsulation. Use a laser scribing system for cutting, and the laser power is 10 - 20W. Then use epoxy resin or ceramic housing for encapsulation, and the specific operation is known to those skilled in the art and will not be elaborated here.

[0058] The laser scribing precisely cuts along the pre-defined isolation band pattern, which can effectively isolate the laser units and avoid abnormal electrical or thermal coupling between units caused by uneven cutting. The laser power is set within 10 - 20W, making the cutting process efficient and without causing thermal damage to nearby electrodes or optical structures. After cutting, through overall encapsulation, the laser units are arranged into a uniform array, maintaining the integrity of the original device structure. The encapsulation simultaneously provides heat dissipation, mechanical protection, and electrical interconnection, ensuring that the entire array outputs stably and has consistent performance during long-term operation. Optimization of edge treatment and overall thermal management during the cutting and encapsulation stages helps reduce stress generated by the device edges or cutting, thereby maintaining the consistency of the output power and wavelength of each unit in the array.

[0059] In one embodiment, ultrasonically clean the vertical cavity surface emitting laser array light source (using deionized water and organic solvents), remove the residual contaminants on the surface, and dry it in pure air. Then arrange it evenly on a dedicated carrier board to ensure uniform heat conduction between units.

[0060] Then place the vertical cavity surface emitting laser array light source in an inert gas (high-purity nitrogen or argon) atmosphere and slowly heat it to 400°C - 450°C. This temperature range is sufficient to activate atomic migration inside the material, helping to eliminate thermal stress and reduce lattice defects, while not causing thermal degradation of other sensitive layers in the device. The heating rate is controlled within about 5°C / min to ensure uniform temperature rise of the entire vertical cavity surface emitting laser array light source. Keep it at the target temperature for 30 - 60 minutes to fully release the stress inside the vertical cavity surface emitting laser array light source and make each laser unit reach a thermal equilibrium state. When cooling, also cool it slowly to room temperature at a controlled rate (5°C / min) to ensure that there is no local rapid temperature change in the device that causes the re-generation of thermal stress.

[0061] Uniform heating and slow cooling enable the various layers of materials inside the vertical cavity surface emitting laser array light source (such as crystal, dielectric layer, nitride layer, and encapsulation lens layer) to reach overall thermal equilibrium, eliminating the stress distribution differences caused by local temperature non-uniformity. Annealing treatment can promote the rearrangement of atoms inside the semiconductor material, repair some lattice defects, improve the crystal quality of the laser unit, and thus improve the consistency of output performance. Since temperature equalization and annealing can reduce the micro-stress inside the as-fabricated product and reduce the phase drift caused by thermal effects in the optical path, the emitted light wavefront can maintain a more ideal shape, improving the beam shaping effect and collimation of the entire vertical cavity surface emitting laser array light source. After all laser units undergo unified annealing treatment, their various optoelectronic parameters (such as threshold current, output power, and operating wavelength) will be more consistent, which is beneficial to the stability of the overall performance of the array.

[0062] In one embodiment, to accurately measure and correct the output energy of each laser unit or segmented area, ensure that the output energy of each laser unit is equal, and reduce the non-linear energy distribution problem caused by edge effects when multiple light sources are superimposed. The following steps are carried out: Use a high-precision optical detection instrument (such as a CCD camera or a power meter) to measure the near-field or far-field spot of the output of the prepared laser array. Measure the light intensity distribution of each laser unit or preset segmented area . Using the measured light intensity data, apply the energy mapping algorithm to obtain the actual output energy of each preset area Compare with the target equilibrium energy to obtain the energy compensation mapping function: where, is the ideal light intensity designed or simulated (usually taking the output power at the center of the array or the average value of the entire area), with the unit of watt per square meter (W / m²). is the light intensity of each segmented area obtained after actual measurement (W / m²). M(x, y) is the mapping function, dimensionless, reflecting the proportion that needs to be compensated.

[0063] When depositing the silicon nitride layer in the S3.2 stage, its thickness will directly affect the local gain and optical characteristics inside the laser cavity. The thickness of the silicon nitride layer determines the optical path of the light wave propagation inside the cavity. Since the laser cavity design of the VCSEL laser strictly depends on the optical path matching between layers (such as ensuring a certain phase accumulation to form a resonant cavity), a slight thickness change will cause an optical path difference, thus affecting the coherent superposition and mode selection of the light wave inside the cavity. The thickness change will cause different local cavity lengths, change the resonant frequency and mode of the laser, making some areas easily reach the laser threshold while some areas have insufficient gain, resulting in inconsistent output power and wavelength.

[0064] In a VCSEL, the optical coupling between the active region and the cavity structure is very sensitive. The thickness variation of the silicon nitride layer will affect the light distribution and the electric field strength distribution in the laser cavity, and further affect the local effective gain. In regions with a relatively large local thickness, the light field may be over-diffused, reducing the laser resonance efficiency, while in thinner regions, the light field may be too concentrated, thus changing the local gain conditions. The silicon nitride layer not only exists as a structural layer, but its thickness variation may also change the local effective refractive index distribution, and further affect the interference conditions in the cavity. In VCSELs, the thickness of each layer is often required to be precisely controlled to the nanometer level to ensure high reflectivity and optimized mode matching at a specific wavelength. Thickness deviation will lead to poor interference effects. The lens packaging and subsequent free-form surface design rely on the precise thickness of the previous layers to determine the shape of the output light wavefront. If the thickness variation of the silicon nitride layer is large, it will cause the wavefront of the entire laser cavity to be in a non-ideal state, and further reduce the collimation and focusing quality of the output beam. In a laser array, the cavity structures of each laser unit must be highly consistent. As an important part of the cavity, the uneven thickness of the silicon nitride layer will cause differences in modes and gains between different laser units, thus affecting the output consistency and stability of the overall array.

[0065] Therefore, according to the distribution result of M(x, y), the thickness of the silicon nitride layer is adjusted by feedback.

[0066] For low-energy regions (M(x, y) > 1), the thickness of the silicon nitride layer is increased to improve the local optical gain. If the current deposition thickness is 100 nm, the deposition thickness is increased by 2 - 3 nm (for example, increased by 2.5 nm), which is equivalent to increasing the gain compensation by approximately 2.5% to 3%. For high-energy regions (M(x, y) < 1), the thickness of the silicon nitride layer is reduced by about 2 - 3 nm (such as reduced by 2.5 nm). After a preliminary adjustment, the light intensity measurement is repeated again until the distribution of M(x, y) approaches 1 (that is, the output energy of all regions is equal and the deviation is less than 5%).

[0067] By the energy mapping method, the output energy of each segment or each laser unit is regulated to be approximately the same, ensuring that the overall array output meets the design standard in terms of light intensity. When the light fields of multiple laser units are superimposed, energy balance can effectively eliminate the light intensity irregularities caused by edge effects and local non-uniformity, improving the uniformity and stability of the entire beam. The feedback regulation process makes each unit controlled during the production process, reducing the manufacturing differences of the devices, thus overall improving the performance consistency and reliability of the vertical cavity surface emitting laser array.

[0068] The present invention provides a vertical cavity surface emitting laser array light source, which is fabricated by a method for fabricating a vertical cavity surface emitting laser array light source. The vertical cavity surface emitting laser array light source includes a base layer, an anti-Bragg grating structure, and a lens layer; wherein, The base layer is used to provide mechanical support and a lattice matching environment; The anti-Bragg grating structure is used to form a mirror structure for the vertical cavity; The lens layer is used to shape and collimate the emitted light beam.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a vertical cavity surface emitting laser array light source, characterized in that the steps Including: S1. Deposit a base layer by chemical vapor deposition (CVD) using a metal-organic alkyl precursor and an inorganic gas-phase precursor, then introduce a metal-organic complex precursor and ammonia gas to deposit an ammoniated layer on the base layer. S2. Spin-coat and expose the ammoniated layer according to a preset pattern, then introduce a first oxide precursor to deposit a first refractive layer on the preset pattern, and then introduce a second oxide precursor to deposit a second refractive layer on the first refractive layer. Repeat stacking the first refractive layer and the second refractive layer until the preset number of layers is reached to obtain an intermediate substrate with an inverse Bragg grating structure, where the refractive index of the first refractive layer is different from that of the second refractive layer. S3. Heat the intermediate substrate to a preset decomposition temperature, then introduce a silicon source gas and ammonia gas to deposit a silicon nitride layer on the intermediate substrate. Etch the silicon nitride layer according to a preset pattern to obtain an etched pattern. Finally, encapsulate the lens layer to obtain a vertical-cavity surface-emitting laser (VCSEL), and divide the VCSEL into multiple laser units to form a VCSEL array light source.

2. The manufacturing method of a vertical cavity surface emitting laser array light source according to claim 1, characterized in that Step S1 includes: S1.

1. Place the substrate in a CVD reactor and heat it to 630 - 650 °C. Introduce the metal-organic alkyl precursor and the inorganic gas-phase precursor, adjust the internal pressure to 10 - 20 Torr, and set the deposition time to 30 - 40 minutes to obtain the base layer. S1.

2. Lower the temperature to 250 - 300 °C, then introduce the metal-organic complex precursor and ammonia gas for cyclic deposition. Set the cycle time to 20 - 30 minutes and stop when the preset number of cycles is reached to obtain the ammoniated layer deposited on the base layer.

3. The preparation method of a vertical cavity surface emitting laser array light source according to claim 2, characterized in that, In step S1, the metal-organic alkyl precursor includes at least one of trimethylgallium, trimethylindium, and trimethylaluminum; the inorganic gas-phase precursor includes at least one of arsine, phosphine, and stibine; the metal-organic complex precursor includes at least one of titanium tetraisopropoxide, titanium tetra-n-butoxide, and tetrakis(dimethylamino)titanium; and the substrate includes at least one of gallium arsenide, indium phosphide, and silicon.

4. The preparation method of a vertical cavity surface emitting laser array light source according to claim 2, characterized in that, In step S1.2, the operation of a single deposition in the cyclic deposition includes: First, introduce the metal-organic complex precursor for 5 seconds. Then, introduce an inert gas to purge impurities for 8 seconds. Then, introduce ammonia gas for 3 seconds. Finally, introduce an inert gas for 8 seconds to complete a single deposition.

5. The preparation method of a vertical cavity surface emitting laser array light source according to claim 1, characterized in that, In step S2, the first oxide precursor includes at least one of tetraethoxytitanium, tetrakis(isopropoxy)titanium, and tetrakis(n-butoxy)titanium; the second oxide precursor includes at least one of tetraethoxysilane, tetrakis(isopropoxy)silane, and tetrakis(n-butoxy)silane.

6. The manufacturing method of a vertical cavity surface emitting laser array light source according to claim 5, characterized in that, Step S2 includes: S2.

1. Spin-coat positive photoresist uniformly on the surface of the ammoniated layer, control the thickness within 150 - 200 nm, heat it to 90 - 100 °C, and set the heating time to 1 - 2 minutes. S2.

2. Use an electron beam lithography device or an ultraviolet lithography device to perform exposure according to a pre-pattern, soak in a developer solution for 30 seconds, then rinse with deionized water and dry to obtain a prefabricated substrate. Among them, the working voltage of the electron beam lithography device is 20 - 30 kV, and the exposure wavelength of the ultraviolet lithography device is 365 nm; S2.

3. Place the exposed prefabricated substrate in a chemical vapor deposition reactor, heat it to 350 - 450 °C, and introduce a first oxide precursor to form a first refractive layer; S2.

4. Maintain the temperature and introduce a second oxide precursor to form a second refractive layer; S2.

5. Repeat steps S2.3 and S2.4 until the preset number of layers is reached to obtain an intermediate substrate with an anti-Bragg grating structure.

7. The preparation method of a vertical cavity surface emitting laser array light source according to claim 1, characterized in that In step S2, the thickness of the first refractive layer and the second refractive layer is 1 / 4 of the preset working wavelength.

8. The preparation method of a vertical cavity surface emitting laser array light source according to claim 1, characterized in that, In step S3, the silicon source gas includes at least one of silane, dichlorosilane, and disilane, and the volume ratio of the silicon source gas to the ammonia gas is 1:(4 - 5).

9. The manufacturing method of a vertical cavity surface emitting laser array light source according to claim 1 or 8, characterized in that Step S3 includes: S3.

1. Place the intermediate substrate in an inert atmosphere for preheating, raise the temperature to 500 - 600 °C, and adjust the internal pressure to 200 - 300 mTorr; S3.

2. Maintain the temperature and pressure, introduce the silicon source gas and ammonia gas, and the deposition time is 10 - 20 minutes to form a silicon nitride layer; S3.

3. Pour the photosensitive composite solution into a lens mold, apply a pressure of 0.1 - 0.2 MPa and hold for 3 - 5 minutes, place it in an ultraviolet curing device, and irradiate with ultraviolet light with an irradiation intensity of 10 - 15 mW / cm² and a wavelength of 365 nm for 60 - 90 seconds to obtain a lens layer, and bond the lens layer and the silicon nitride layer to obtain a vertical cavity surface emitting laser; S3.

4. Spin-coat a positive photoresist on the vertical cavity surface emitting laser, control the thickness to 150 - 200 nm, bake at 90 - 100 °C for 1 - 2 minutes, use an electron beam lithography device or an ultraviolet lithography device to perform exposure according to a pre-pattern, soak in a developer solution for 30 seconds, then rinse with deionized water and dry; S3.

5. Then place it in an inductively coupled plasma device for etching, adjust the power to 150 W, set the radio frequency power to 50 W, adjust the pressure to 5 - 10 mTorr, introduce a mixed gas of trifluoromethane and oxygen, and the etching time is 40 - 60 seconds to form an isolation band for the laser unit; S3.

6. First deposit an adhesion layer on the surface of the isolation band, then deposit a gold layer to form an electrode layer, and perform exposure and etching operations on the electrode layer according to a preset electrode pattern to obtain an exposed cutting pattern; S3.

7. Cut the vertical cavity surface emitting laser according to the cutting pattern, and after encapsulation, obtain a vertical cavity surface emitting laser array light source.

10. A vertical cavity surface emitting laser array light source, characterized in that, Prepared by the method for preparing a vertical cavity surface emitting laser array light source according to any one of claims 1 - 9, the vertical cavity surface emitting laser array light source includes a base layer, an anti-Bragg grating structure, and a lens layer; wherein, The base layer is used to provide mechanical support and a lattice matching environment; The anti-Bragg grating structure is used to form the mirror structure of the vertical cavity; The lens layer is used to shape and collimate the emitted light beam.

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