A method for manufacturing a multi-wavelength pcSEL array for multi-core fiber coupling

Abstract

The application discloses a kind of for multicore optical fiber coupling Multi-wavelength PCSEL array manufacturing method, belong to semiconductor photoelectric technology field, by first wafer direct bonding, realize the hetero-integration of Ⅲ-V PN junction gain structure and silicon-based photonic crystal resonator, avoid the air hole morphology deterioration problem caused by traditional secondary epitaxial growth;Through second metal bonding, realize the efficient heat dissipation integration of laser array and metal heat sink;Device design is carried out using transfer matrix method combined with three-dimensional coupling wave theory, while ensuring calculation accuracy, reduce simulation resource consumption;By adjusting the center distance of double circular air holes in the same square lattice unit of photonic crystal, the wavelength of each laser unit is accurately controlled.The PCSEL array prepared by the application is spatially arranged corresponding to the core layer of multicore optical fiber, and the output fundamental mode Gaussian spot is matched with the multicore optical fiber, which can be directly and efficiently coupled, and is suitable for large-capacity, low-cost wavelength-division and space-division multiplexing optical communication system.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic technology, and in particular to a method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling. Background Technology

[0002] With the explosive growth of data center traffic, the transmission capacity of traditional single-mode optical fiber is gradually approaching its physical limit. Space division multiplexing (SDM) technology, by integrating multiple independent cores into a single optical fiber, can multiply the transmission capacity of optical fibers, becoming one of the core technologies of next-generation optical communication systems. Multi-core optical fibers are the core carrier of SDM technology, with each core layer supporting LP01 fundamental mode transmission. Therefore, a matching multi-channel light source array is required to achieve efficient coupling.

[0003] A PCSEL (Planet-Emitting Solar Laser) is a novel semiconductor laser that uses a two-dimensional photonic crystal as its resonant cavity and achieves vertical laser output through first-order diffraction. Compared to traditional edge-emitting lasers and vertical-cavity surface-emitting lasers (VCSELs), PCSELs offer significant advantages such as high-power single-mode operation, extremely low far-field divergence angle (typically <1°), narrow spectral linewidth, and easy extension of the operating wavelength. In particular, PCSELs can output a Gaussian spot that perfectly matches the LP01 mode of a multi-core fiber, enabling direct coupling without a complex optical coupling system, thus significantly reducing system cost and complexity.

[0004] However, existing multi-wavelength PCSEL array manufacturing technologies still have the following key drawbacks: First, it relies on a complex secondary epitaxial growth process. Traditional PCSELs typically grow epitaxial structures on III-V group substrates, then etch photonic crystal air holes, and finally perform secondary epitaxial growth to cover the air holes. This process is highly susceptible to air hole closure, morphological deformation, and material defects, severely affecting the optical performance of the device and the processing yield, which is usually below 30%.

[0005] Second, the device design efficiency is low. Traditional finite element method (FEM) and finite-difference time-domain method (FDTD) require massive computing resources to simulate large-size PCSEL arrays. The simulation time for a single 98μm×98μm PCSEL element can be as long as several days, which cannot meet the requirements of rapid parameter scanning and optimization for multi-wavelength arrays.

[0006] Third, the implementation of multi-wavelength lasers is complex and has low precision. Existing technologies typically achieve multi-wavelength lasers by changing the lattice constant, air hole radius, or fill factor of the photonic crystal. This requires simultaneous adjustment of multiple structural parameters, resulting in poor wavelength control precision and inconsistencies in threshold gain and far-field characteristics among different units. Summary of the Invention

[0007] The purpose of this invention is to propose a manufacturing method for multi-wavelength PCSEL arrays coupled with multi-core optical fibers, which solves the problems of air hole morphology degradation, large simulation calculation volume, and low multi-wavelength control accuracy caused by secondary epitaxial growth in traditional processes, and realizes low-cost and high-yield manufacturing of multi-wavelength PCSEL arrays directly and efficiently coupled with multi-core optical fibers.

[0008] To achieve the above objectives, the present invention provides a method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling, comprising the following steps: Step S1: Fabricate a silicon-based photonic crystal resonator array. The spatial arrangement, number of units, and size of a single resonator in the silicon-based photonic crystal resonator array correspond one-to-one with the core layer parameters of the target multi-core optical fiber. Step S2: The III-V group wafer with a complete PN junction gain structure epitaxially grown is directly bonded to the silicon-based photonic crystal resonator array for the first time. Step S3: Thinning and mesa etching are performed on the bonded III-V group wafer to form electrically isolated independent laser unit mesa surfaces; Step S4: Prepare coplanar N-electrodes and P-electrodes on the laser unit mesa, and simultaneously or sequentially prepare electrode patterns on the surface of the metal heat sink that correspond one-to-one with the positions of the laser array electrodes. Step S5: Perform a second metal bonding between the laser array with the prepared electrodes and the metal heat sink to complete the core fabrication process before device packaging.

[0009] Preferably, in step S1, the fabrication of the silicon-based photonic crystal resonant cavity array is specifically as follows: using an SOI wafer with a top silicon thickness of 600 nm and a silicon dioxide buried layer thickness of 2 μm as a substrate, defining the photonic crystal pattern by electron beam lithography (EBL), and vertically etching the top silicon thin film by deep reactive ion etching (DRIE) to form a resonant cavity array composed of periodically arranged tetragonal lattice units containing two circular air holes of different radii.

[0010] Preferably, in step S2, the epitaxial structure of the III-V group wafer, from the InP substrate upwards, consists of: an N-contact layer, an N-cladding layer, a multilayer quantum well active region, a P-cladding layer, and a P-contact layer; during bonding, the free surface of the N-contact layer is precisely aligned with the upper surface of the silicon-based photonic crystal resonator to form a direct bonding interface between heteromaterials.

[0011] Preferably, the N-contact layer is made of N-type doped InGaAs material, and the silicon-based photonic crystal layer is made of intrinsic or low-doped single-crystal silicon material, forming a low-temperature direct bonding interface without an intermediate dielectric layer.

[0012] Preferably, in step S3, the specific steps are as follows: a wafer thinning process combining mechanical grinding and chemical etching is used to thin and remove the InP substrate of the III-V group wafer until the complete surface of the P-contact layer is exposed; the device mesa pattern is defined by photolithography using a mask; and an inductively coupled plasma etching (ICP) process is used to vertically etch from the surface of the P-contact layer to the surface of the N-contact layer to form an array channel that penetrates to the depth of the N-contact layer, thereby achieving electrical isolation between adjacent laser units.

[0013] Preferably, in step S4, an insulating layer preparation step is included before electrode preparation: Silicon nitride insulating layers are grown by plasma-enhanced chemical vapor deposition (PECVD) to cover the sidewalls and top surface of all laser unit mesa and the bottom and sidewalls of the array channels. Silicon nitride is selectively etched by photolithography and reactive ion etching (RIE) to expose the electrode contact areas on the top surface of the P-contact layer and the electrode contact areas at the bottom of the array channels. Multilayer metal electrode layers are deposited by electron beam evaporation, and excess metal is removed by a lift-off process to form coplanar N-electrodes and P-electrodes.

[0014] Preferably, in step S1, by adjusting the center-to-center distance between two circular air holes in the same tetragonal lattice unit corresponding to different laser units, each laser unit can generate fundamental mode single-mode laser output of different wavelengths in the target band.

[0015] Preferably, for C-band optical communication applications, the photonic crystal has a lattice constant of 490 nm, the radii of the two circular air holes in the same lattice unit are 87.44 nm and 70.50 nm, respectively, and the air hole fill factor of a single lattice unit is 0.165; the distance between the centers of the two holes is linearly varied in the range of 156.80 nm to 191.10 nm with a fixed step size of 4.90 nm, corresponding to a lasing wavelength interval of about 0.70 nm, which can realize laser output of 7 different wavelengths.

[0016] Preferably, the photonic crystal resonator of each laser unit has a size of 98μm×98μm, and the far-field divergence angle of the fabricated PCSEL unit is ≤1°, outputting a Gaussian spot of the fundamental mode, the mode field distribution of which matches the LP01 fundamental mode transmission characteristics of the multi-core fiber.

[0017] Preferably, before step S1, a device design step based on three-dimensional coupled-wave theory is included, specifically: Determine the target lasing wavelength range, select the corresponding III-V group luminescent material system, and determine the material doping type, doping concentration, and thickness parameters of each layer of the epitaxial structure; Determine the unit cell structure type and air hole filling factor of the silicon-based photonic crystal layer, and calculate its effective refractive index; The waveguide mode equations of the multilayer planar waveguide structure are solved using the transfer matrix method to obtain the electric field distribution of the TE mode perpendicular to the light output direction. Substituting the vertical electric field distribution into the three-dimensional coupled-wave theoretical model, the lasing wavelength, threshold loss, and near-field and far-field distribution of each optical mode are calculated. The distance between the centers of the two air holes is scanned, and a database of the correspondence between the lasing wavelength and the structural parameters is established.

[0018] Therefore, the present invention employs the above-described method for manufacturing multi-wavelength PCSEL arrays for multi-core fiber coupling, which has the following advantages: (1) The core components are of outstanding value: This multi-wavelength photonic crystal surface-emitting laser is based on a two-dimensional photonic crystal resonator and adopts an electric pump excitation method, which is conducive to the direct modulation of radio frequency signals and is expected to become the core light source device of the next generation of data center optical interconnect system; (2) Improved system capacity and efficiency: By directly coupling multi-core optical fiber with multi-wavelength surface-emitting laser array, the transmission capacity of optical communication system can be greatly improved based on wavelength division multiplexing and space division multiplexing technology. The parallel transmission of multiple optical signals can meet the needs of large-scale data transmission. At the same time, the system processing flow is simplified, the dependence of previous photonic crystal surface-emitting lasers on secondary epitaxial growth is reduced, the device yield is improved and the manufacturing cost is reduced, the utilization of optical fiber resources is optimized, the system power consumption efficiency is improved, and lower connection loss is provided. (3) Simple and efficient multi-wavelength control: Only one adjustable degree of freedom (the distance between two cylindrical holes in the photonic crystal structure) is used to change the lasing wavelength of the laser unit, so as to realize a multi-wavelength photonic crystal surface-emitting laser array. The wavelength control method is simple and the optical characteristics of each unit are consistent. (4) High-efficiency and low-power design method: The three-dimensional coupled wave theory significantly reduces the demand for computing resources in the design process while ensuring the accuracy of calculation. At the same time, it can realize the simulation calculation of larger-scale devices, which significantly accelerates the design process of photonic crystal surface-emitting lasers. (5) Significantly enhanced process reliability: The use of bonding technology fundamentally avoids the possible closure of air holes in the secondary epitaxial growth of photonic crystals, ensures the morphological characteristics of air holes, reduces process difficulty, improves device processing yield, and lays a technical foundation for the large-scale production of photonic crystal surface-emitting lasers. (6) Excellent heat dissipation performance: The laser array is directly bonded to a metal heat sink with high thermal conductivity using flip-chip metal bonding technology. The heat dissipation path is short, which effectively reduces the thermal resistance of the device and can support higher power continuous wave operation.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is an overall flowchart of a method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the stacked structure of a single laser unit in a multi-wavelength PCSEL array in an embodiment of the present invention; Figure 3 This is a schematic diagram of the tetragonal lattice unit structure of the silicon-based photonic crystal in an embodiment of the present invention; Figure 4 This is a schematic diagram of the vertical refractive index distribution and TE mode electric field distribution of the laser unit in an embodiment of the present invention; Figure 5 This is the energy band diagram of the photonic crystal unit structure in the embodiment of the present invention; Figure 6 This is a schematic diagram of the overall structure of the silicon-based photonic crystal resonator in an embodiment of the present invention; Figure 7 This is a near-field normalized electric field amplitude intensity distribution diagram of the laser unit in the emission mode D of the present invention. Figure 8 This is a diagram showing the far-field normalized electric field intensity distribution of the laser unit in the emission mode D of this invention embodiment; Figure 9 This is a diagram showing the polarization amplitude intensity distribution of the far-field normalized electric field in the X and Y directions of the laser unit in the emission mode D of this invention. Figure 10 This is a schematic diagram of the wavelength variation of the multi-wavelength PCSEL array in an embodiment of the present invention; Figure 11 This is a schematic diagram of the threshold difference of the multi-wavelength PCSEL array in an embodiment of the present invention; Figure 12 This is a flowchart illustrating the manufacturing process of the multi-wavelength PCSEL array in an embodiment of the present invention. Figure 13 This is a schematic diagram of the direct coupling between a multi-wavelength PCSEL array and a multi-core optical fiber in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] Example like Figure 1-5 As shown in the figure, this embodiment proposes a method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling. The specific implementation steps are as follows: This embodiment provides a method for manufacturing a C-band multi-wavelength PCSEL array for seven-core fiber coupling. The fabricated PCSEL array contains seven independent laser units, with a spatial arrangement identical to that of a standard seven-core fiber. The lasing wavelength range is 1547.85 nm to 1553.03 nm, with a wavelength spacing of approximately 0.70 nm. The overall process flow is as follows: Figure 12 As shown.

[0024] like Figure 2 As shown, in this embodiment of the invention, the single laser unit of the multi-wavelength PCSEL array, in the reverse direction from the light emission direction, consists of: a metal heat sink, coplanar N-electrode and P-electrode, P-contact layer, P-cladding, multilayer quantum well active region, N-cladding, N-contact layer, silicon-based photonic crystal layer, silicon dioxide buried layer, and silicon substrate layer. The laser is emitted perpendicularly from one side of the silicon substrate layer.

[0025] Step 1: Device design based on three-dimensional coupled-wave theory: (1) The target lasing wavelength range is determined to be C-band 1535nm~1560nm. InAlGaAs / InP material system is selected. The parameters of each layer of epitaxial structure are determined: N-contact layer is 200nm thick N-type InGaAs (doping concentration 1×10⁻⁶). 19 cm -3 (Refractive index 3.44), N-cladding is 3000 nm thick N-type InP (doping concentration 1×10⁻⁶). 18 cm -3(Refractive index 3.16), the active region of the multilayer quantum well is a 9-period InAlGaAs quantum well (thickness 6nm) / InAlGaAs barrier (thickness 10nm), and the P-cladding is a 3000nm thick P-type InP (doping concentration 1×10⁻⁶). 18 cm -3 (Refractive index 3.16), the P-contact layer is a 200 nm thick P-type InGaAs (doping concentration 1×10⁻⁶). 19 cm -3 (Refractive index 3.44).

[0026] (2) Determine that the silicon-based photonic crystal adopts a tetragonal lattice double circular air hole structure, such as Figure 3 As shown. The air hole fill factor FF of a single lattice unit is calculated by the following formula: ; In the formula, It is the sum of the areas of two circular air holes within the same tetragonal lattice unit. This represents the area of ​​a single tetragonal lattice unit. In this embodiment, the air hole fill factor is 0.165.

[0027] The average refractive index of a silicon-based photonic crystal layer is calculated by the following formula: ; In the formula, The refractive index of air ( ), The refractive index of single-crystal silicon ( The average refractive index of the silicon-based photonic crystal layer in this embodiment was calculated to be 3.21.

[0028] (3) The waveguide mode equations of the multilayer planar waveguide structure are solved using the transfer matrix method to obtain the electric field distribution of the TE mode perpendicular to the light output direction, such as... Figure 4 As shown. The calculation results show that the optical field confinement factor Γ of the photonic crystal layer... pc =24.57%, the light field confinement factor Γ in the active region act= 7.44%, group refractive index n g =3.31.

[0029] (4) Substitute the vertical electric field distribution into the three-dimensional coupled-wave theory model to calculate the lasing wavelength, threshold loss, and near-field and far-field distribution of each optical mode. The specific calculation process is as follows: First, use the intrinsic mode solver in Lumerical FDTD to solve the guided wave mode (TE mode) of the photonic crystal surface-emitting laser to obtain the field distribution along the light output direction; then import the obtained field distribution into MATLAB and use the three-dimensional coupled-wave theory to calculate the corresponding coupling C. 3D-CWT Matrix; after defining the boundary path of the first Brillouin zone, combine with C3D-CWT The frequency (wavelength) corresponding to each wave vector k can be obtained using MATLAB's built-in matrix eigenvalue solver; finally, the energy band diagram of the photonic crystal unit structure is plotted, as shown below. Figure 5 As shown, from bottom to top, they are defined as four optical modes: A, B, C, and D.

[0030] By scanning the center-to-center spacing parameters of two circular air holes within the same tetragonal lattice unit, a database of the correspondence between lasing wavelength and structural parameters is established, such as... Figure 10 As shown, when the aperture spacing is 156.80 nm, the lasing wavelength is 1553.03 nm; when the aperture spacing is 191.10 nm, the lasing wavelength is 1547.85 nm; with a fixed step size of 4.90 nm, a total of 7 different lasing wavelengths were obtained, with a wavelength interval of approximately 0.70 nm.

[0031] Define the threshold difference between the fundamental modulus D and the second-lowest threshold modulus C as: ; The threshold difference between the fundamental mode D and the first higher-order mode D1 is: ; In the formula, , , These are the threshold loss coefficients for modes C, D, and D1, respectively. The larger the threshold difference, the better the single-mode performance.

[0032] The calculated relationship between the mode threshold difference and the distance between the centers of the two air holes is as follows: Figure 11 As shown, when the spacing is 156.80 nm, the threshold difference between the fundamental mode D and the fundamental mode C is 36.31 cm. -1 The threshold difference between the fundamental mode D and the higher-order mode D1 is 44.10 cm. -1 When the spacing is 191.10 nm, the threshold difference between the fundamental mode D and the fundamental mode C is 3.03 cm. -1 The threshold difference between the fundamental mode D and the higher-order mode D1 is 19.48 cm. -1 This indicates that the laser array has good single-mode operating characteristics across the entire wavelength range.

[0033] The far-field spot distribution of the laser was calculated using the Fraunhofer diffraction method. The far-field complex amplitude of the x-direction polarization component was calculated by the following formula: ; In the formula, The complex amplitude distribution of the electric field perturbation in the x-direction of the near-field plane is shown. The wave number in a vacuum. , Let be the direction cosine in the far-field direction. Square the magnitude of the complex amplitude and multiply by the tilt factor. The far-field intensity distribution can then be obtained. The calculated near-field distribution of the fundamental mode D is as follows: Figure 7 As shown, the far-field distribution is as follows Figure 8 As shown, the polarization distribution in the far-field x and y directions is as follows: Figure 9 As shown.

[0034] Step 2: Fabrication of silicon-based photonic crystal resonator array: An SOI wafer with a top silicon thickness of 600 nm and a silicon dioxide buried layer thickness of 2 μm was used as the substrate (a commercial SOI wafer could be used, or a 2000 nm thick silicon dioxide layer could be obtained on a silicon wafer through thermal oxidation, followed by the growth of a 600 nm thick silicon layer on the silicon dioxide layer via low-pressure chemical vapor deposition). First, the SOI wafer underwent standard RCA cleaning to remove surface organic contaminants and metallic impurities.

[0035] Then, the pattern of a seven-core photonic crystal was defined using electron beam lithography (EBL), with each unit being a square region of 98μm × 98μm, such as... Figure 6 As shown, the interior is composed of periodically arranged tetragonal lattice units with a lattice constant of 490 nm. Each lattice unit contains two circular air holes with different radii, namely 87.44 nm and 70.50 nm. The distance between the centers of the two holes varies linearly from 156.80 nm to 191.10 nm according to the database established in step 1.

[0036] The top silicon film was vertically etched using deep reactive ion etching (DRIE) with an SF6 / C4F8 mixed gas as the etching gas. The etching depth was 600 nm, and the verticality of the etching was better than 89°, forming a silicon-based photonic crystal resonant cavity array. After etching, the photoresist was removed and the wafer was cleaned.

[0037] Step 3: First direct wafer bonding: A complete III-V PN junction gain structure was grown on a 2-inch InP substrate using molecular beam epitaxy (MBE) combined with metal-organic chemical vapor deposition (MOCVD). The structure consists of the following layers from the InP substrate upwards: a 50 nm thick N-type doped InP buffer layer, a 150 nm thick N-type doped InGaAs N-contact layer, a 3000 nm thick N-type doped InP N-cladding, a 9-period InAlGaAs quantum well / barrier active region, a 3000 nm thick P-type doped InP P-cladding, and a 200 nm thick P-type doped InGaAs P-contact layer.

[0038] Chemical mechanical polishing (CMP) was performed on both the grown III-V group wafers and the SOI wafers with prepared photonic crystals to achieve a surface roughness of less than 0.5 nm for both the N-contact layer and the silicon-based photonic crystal layer. Then, both wafers underwent plasma surface activation treatment using an Ar / O2 mixed gas.

[0039] The III-V group wafer was flipped over to precisely align the free surface of the N-contact layer with the upper surface of the silicon-based photonic crystal resonator, with an alignment accuracy better than ±1μm. Low-temperature direct bonding was then performed in a vacuum environment at 250℃ and 5 bar pressure for 2 hours, forming an InGaAs / Si heterobonded interface without an intermediate dielectric layer.

[0040] Step 4: Wafer thinning and mesa etching: A wafer thinning process combining mechanical polishing and chemical etching was used to thin the bonded III-V group wafers. First, the InP substrate thickness was reduced from 500 μm to approximately 50 μm by mechanical polishing. Then, the remaining InP substrate was selectively etched using an etchant solution of HCl:H3PO4 = 3:1 until the complete surface of the P-contact layer was exposed.

[0041] Seven independent square laser unit mesa patterns were defined using photolithography with a mask size of 100μm × 100μm and a unit spacing of 150μm, consistent with the core spacing of a seven-core optical fiber. Inductively coupled plasma etching (ICP) was then used, starting from the P-contact layer and vertically etching down to the N-contact layer surface to a depth of approximately 6.4μm, forming an array channel with a width of 20μm to achieve electrical isolation between adjacent laser units.

[0042] Step 5: Fabrication of insulating layer and electrode: A 300 nm thick silicon nitride insulating layer was grown using plasma-enhanced chemical vapor deposition (PECVD) at a growth temperature of 300 °C, covering the sidewalls and top surface of all laser unit mesa and the bottom and sidewalls of the array channels.

[0043] The electrode contact window pattern is defined by photolithography, and then silicon nitride is selectively etched using reactive ion etching (RIE) to expose only the electrode contact area on the top surface of the P-contact layer and the N-contact layer electrode contact area at the bottom of the array channel.

[0044] Ti / Pt / Au multilayer metal electrode layers with thicknesses of 50 nm, 100 nm, and 300 nm were sequentially deposited using an electron beam evaporation process. The wafer was then immersed in an acetone solution for a lift-off process to remove excess metal layers, forming coplanar N- and P-electrodes.

[0045] Step 6: Second metal bonding and back-end packaging: Oxygen-free copper was used as the metal heat sink material. Ti / Au electrode patterns corresponding to the positions of the laser array electrodes were prepared on the surface of the metal heat sink by photolithography and electron beam evaporation processes, with thicknesses of 50 nm and 500 nm, respectively.

[0046] The laser array with prepared electrodes was inverted to ensure precise alignment between the coplanar N-electrode, P-electrode, and the electrode pattern on the metal heat sink, with an alignment accuracy better than ±2 μm. Au-Au metal thermocompression bonding was then performed at 200℃ and 3 bar pressure for 30 minutes.

[0047] Finally, the devices are diced, glued, wire-bonded, and hermetically sealed to complete the fabrication of the multi-wavelength PCSEL array.

[0048] A schematic diagram of the direct coupling between the multi-wavelength PCSEL array and the seven-core optical fiber prepared in this embodiment is shown below. Figure 13 As shown, taking a seven-core optical fiber as an example, each core has a diameter of 100μm, and the spacing between any two cores is 150μm. Since the laser's emission area is 98μm × 98μm and its divergence angle is approximately 0.8°, calculations show that when the distance between the multi-core optical fiber and the multi-wavelength surface-emitting laser array is less than 0.23mm, the spot diameter is smaller than the fiber core, resulting in the highest coupling efficiency. When the distance is less than 5.96mm, the laser unit can couple independently to each core without mutual interference, ensuring effective coupling of the laser to each fiber core. Furthermore, the laser beam (Gaussian spot) perfectly matches the fiber optic LP01 transmission mode, thus achieving high-efficiency coupling.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, the present invention is also applicable to other optical communication bands such as O-band and L-band, only requiring corresponding adjustments to the III-V group material system and photonic crystal structure parameters; the present invention is also applicable to multi-core optical fibers with other core numbers such as 3 cores and 19 cores, only requiring adjustments to the spatial arrangement and number of units of the laser array.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling, characterized in that, Includes the following steps: Step S1: Fabricate a silicon-based photonic crystal resonator array. The spatial arrangement, number of units, and size of a single resonator in the silicon-based photonic crystal resonator array correspond one-to-one with the core layer parameters of the target multi-core optical fiber. Step S2: The III-V group wafer with a complete PN junction gain structure epitaxially grown is directly bonded to the silicon-based photonic crystal resonator array for the first time. Step S3: Thinning and mesa etching are performed on the bonded III-V group wafer to form electrically isolated independent laser unit mesa surfaces; Step S4: Prepare coplanar N-electrodes and P-electrodes on the laser unit mesa, and simultaneously or sequentially prepare electrode patterns on the surface of the metal heat sink that correspond one-to-one with the positions of the laser array electrodes. Step S5: Perform a second metal bonding between the laser array with the prepared electrodes and the metal heat sink to complete the core fabrication process before device packaging.

2. The method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: In step S1, the fabrication of the silicon-based photonic crystal resonant cavity array is specifically as follows: using an SOI wafer with a top silicon thickness of 600 nm and a silicon dioxide buried layer thickness of 2 μm as the substrate, the photonic crystal pattern is defined by electron beam lithography (EBL), and the top silicon thin film is vertically etched by deep reactive ion etching (DRIE) to form a resonant cavity array composed of periodically arranged tetragonal lattice units containing two circular air holes of different radii.

3. The method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: In step S2, the epitaxial structure of the III-V group wafer, from the InP substrate upwards, consists of: N-contact layer, N-cladding layer, multilayer quantum well active region, P-cladding layer, and P-contact layer. During bonding, the free surface of the N-contact layer is precisely aligned with the upper surface of the silicon-based photonic crystal resonator to form a direct bonding interface between heteromaterials.

4. The method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 3, characterized in that: The N-contact layer uses N-type doped InGaAs material, and the silicon-based photonic crystal layer uses intrinsic or low-doped single-crystal silicon material, forming a low-temperature direct bonding interface without an intermediate dielectric layer.

5. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: In step S3, the specific steps are as follows: a wafer thinning process combining mechanical grinding and chemical etching is used to thin and remove the InP substrate of the III-V group wafer until the complete surface of the P-contact layer is exposed; the device mesa pattern is defined by photolithography using a mask; and an inductively coupled plasma etching (ICP) process is used to vertically etch from the surface of the P-contact layer to the surface of the N-contact layer to form an array channel that penetrates to the N-contact layer, thereby achieving electrical isolation between adjacent laser units.

6. The method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: In step S4, an insulating layer preparation step is also included before electrode preparation: Silicon nitride insulating layers are grown by plasma-enhanced chemical vapor deposition (PECVD) to cover the sidewalls and top surface of all laser unit mesa and the bottom and sidewalls of the array channels. Silicon nitride is selectively etched by photolithography and reactive ion etching (RIE) to expose the electrode contact areas on the top surface of the P-contact layer and the electrode contact areas at the bottom of the array channels. Multilayer metal electrode layers are deposited by electron beam evaporation, and excess metal is removed by a lift-off process to form coplanar N-electrodes and P-electrodes.

7. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: In step S1, by adjusting the center-to-center distance between two circular air holes in the same tetragonal lattice unit corresponding to different laser units, each laser unit can generate fundamental mode single-mode laser output of different wavelengths in the target band.

8. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 7, characterized in that: For C-band optical communication applications, the photonic crystal has a lattice constant of 490 nm. The radii of the two circular air holes in the same lattice unit are 87.44 nm and 70.50 nm, respectively, and the air hole fill factor of a single lattice unit is 0.

165. The distance between the centers of the two holes is linearly varied in the range of 156.80 nm to 191.10 nm with a fixed step size of 4.90 nm, corresponding to a lasing wavelength interval of about 0.70 nm, which can realize laser output of 7 different wavelengths.

9. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: Each laser unit has a photonic crystal resonator size of 98μm×98μm. The fabricated PCSEL unit has a far-field divergence angle of ≤1° and outputs a Gaussian beam of the fundamental mode. Its mode field distribution matches the LP01 fundamental mode transmission characteristics of the multi-core fiber.

10. A method for manufacturing a multi-wavelength PCSEL array for multi-core fiber coupling according to claim 1, characterized in that: Before step S1, there are also device design steps based on three-dimensional coupled-wave theory, specifically: Determine the target lasing wavelength range, select the corresponding III-V group luminescent material system, and determine the material doping type, doping concentration, and thickness parameters of each layer of the epitaxial structure; Determine the unit cell structure type and air hole filling factor of the silicon-based photonic crystal layer, and calculate its effective refractive index; The waveguide mode equations of the multilayer planar waveguide structure are solved using the transfer matrix method to obtain the electric field distribution of the TE mode perpendicular to the light output direction. Substituting the vertical electric field distribution into the three-dimensional coupled-wave theoretical model, the lasing wavelength, threshold loss, and near-field and far-field distribution of each optical mode are calculated. The distance between the centers of the two air holes is scanned, and a database of the correspondence between the lasing wavelength and the structural parameters is established.

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