Heterogeneous integrated coupling structure based on semiconductor laser and preparation method thereof
By designing a double-layer tapered waveguide structure and a vertical coupling method, the problem of efficient coupling between a 780 nm semiconductor laser and a silicon nitride optical waveguide was solved, achieving efficient on-chip heterogeneous integration, improving coupling efficiency, and making it suitable for applications such as cold atom devices and quantum computing.
Patent Information
- Application Number
- CN202511951458.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies struggle to achieve efficient coupling between 780nm semiconductor lasers and silicon nitride or lithium niobate optical waveguides, especially in applications such as cold atom devices and quantum computing, where transmission losses are high and alignment accuracy requirements are stringent, making efficient optical field coupling difficult.
A heterogeneous integrated coupling structure based on semiconductor lasers is designed, employing a double-layer tapered waveguide structure. By placing silicon nitride tapered waveguides and silicon nitride single-mode waveguides on the chip and achieving optical interconnection through vertical coupling, and combining tapered waveguide design with specific size and material, significant laser absorption during the coupling process is avoided.
This improved the mode matching and coupling efficiency between the laser and the silicon nitride chip, achieving efficient on-chip heterogeneous integration and enhancing the coupling efficiency of the 780 nm laser.
Smart Images
Figure CN121863182A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optoelectronic integrated device technology, specifically to a heterogeneous integrated coupling structure based on a semiconductor laser and its fabrication method. Background Technology
[0002] Optoelectronic heterogeneous integration technology combines III-V compound semiconductor materials (such as indium phosphide and gallium arsenide) with low-loss transmission and large-scale manufacturing advantages of silicon-based passive photonic platforms (such as silicon, silicon nitride, and lithium niobate insulators) to construct high-performance, highly integrated photonic chips. The technique of bonding diced dies to a whole wafer is called die-to-wafer bonding (D2W), a heterogeneous / hybrid integration method that bonds dies from different materials, devices, or chips to other wafers or substrates. For example, dies formed by dicing epitaxial wafers can be bonded and integrated onto a silicon wafer fabricated with a silicon nitride optical waveguide system. In this integration scheme, it is crucial to couple optical signals from active optoelectronic devices (such as semiconductor lasers) made of III-V semiconductors to the passive waveguide with low loss. Common coupling structures include end-face coupling, grating coupling, and adiabatic tapered coupling.
[0003] Currently, the main technical solutions for heterogeneous integration of semiconductor lasers onto silicon nitride optical waveguide platforms include silicon epitaxial growth, micro-transfer printing, and on-chip bonding heterogeneous integration. Silicon epitaxial growth is a true monolithic integration technology, where all devices are fabricated on the same substrate, offering the highest integration density and lowest manufacturing cost potential. Furthermore, photolithography defines all devices, minimizing alignment errors. However, due to the significant differences in lattice constants and thermal expansion coefficients between silicon and group III-V materials, direct growth generates numerous crystal defects such as dislocations, severely impacting laser performance and lifespan. Micro-transfer printing can pick up and place a large number of cores at once, offering high efficiency and high tolerance for the material and morphology of the target substrate. However, its alignment accuracy is significantly lower than photolithography alignment, making it difficult to guarantee process stability. On-chip bonding heterogeneous integration achieves high alignment accuracy, high coupling efficiency, and high integration density, but the process is complex, development is difficult, and issues such as thermal mismatch exist.
[0004] The primary application areas of current optoelectronic heterogeneous / hybrid integration technology are optical modules and optical interconnects. This is due to the enormous demand generated by data centers and artificial intelligence in recent years, and the foreseeable future technological needs and market size are relatively clear. Therefore, optoelectronic heterogeneous / hybrid integration technology is rapidly developing in the O-band (center wavelength 1310 nm) and C-band (center wavelength 1550 nm) optical communication to meet the needs of these applications. In fact, there is also a demand for optoelectronic heterogeneous / hybrid integration in other optical bands, not limited to optical communication, but also in sensing, navigation, biological and medical applications. Among these, 780 nm lasers are crucial in cold atom devices and technologies. Currently, integrated devices and systems based on cold atoms are developing rapidly, mainly targeting applications such as atomic sensing and measurement, and quantum computing. Integrating 780 nm semiconductor lasers and optical waveguide systems on a chip, thereby pushing rubidium cold atom systems towards chip-level integration, is a very important research direction. Currently, the coupling scheme for monolithic integration of 780nm semiconductor lasers with passive waveguides on a chip mainly uses end-face coupling. This scheme requires precise alignment between the active layer of the laser and the core layer of the passive waveguide, with very high alignment accuracy requirements, making it difficult to achieve a coupling efficiency higher than 50%. Research on adiabatic tapered coupling of 780nm semiconductor lasers with silicon nitride or lithium niobate is limited. This is because commonly used silicon materials exhibit significant interband absorption at 780nm, resulting in excessive transmission loss. Furthermore, silicon nitride and lithium niobate have significantly different refractive indices from III-V group materials, making it difficult for adiabatic tapered coupling to achieve effective refractive index matching and efficient optical field coupling. Summary of the Invention
[0005] Based on the shortcomings of existing technologies, the purpose of this invention is to provide a heterogeneous integrated coupling structure based on semiconductor lasers and its fabrication method.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a heterogeneous integrated coupling structure based on a semiconductor laser, comprising a chip and a laser; The chip is provided with bonding grooves, silicon nitride tapered waveguides and silicon nitride single-mode waveguides, and the wide end of the silicon nitride tapered waveguide is connected to the silicon nitride single-mode straight waveguide; The laser includes a contact layer, a ridge waveguide, a first tapered waveguide, and a second tapered waveguide. The contact layer is bonded to the bonding groove. The ridge waveguide is disposed on the contact layer. The wide end of the first tapered waveguide is connected to the ridge waveguide of the laser. The wide end of the second tapered waveguide is connected to the ridge waveguide of the laser. The first tapered waveguide is located on the second tapered waveguide. The second tapered waveguide and the silicon nitride tapered waveguide are optically interconnected in a vertical coupling manner.
[0007] In a second aspect, the present invention provides a method for preparing the above-mentioned heterogeneous integrated coupling structure, comprising the following steps: S1. Deposit a silicon dioxide layer on the silicon layer; S2. Deposit a silicon nitride substrate on a silicon dioxide layer, and etch the silicon nitride substrate to form a bonding groove, a silicon nitride tapered waveguide, and a silicon nitride single-mode waveguide, wherein the surface roughness of the bonding groove is not greater than 0.5 nm. S3. Remove part of the contact layer of the laser core and bond the contact layer of the laser core to the bonding groove; S4. Remove the substrate of the laser core, and then etch the laser core after removing the substrate to form the ridge waveguide, the first tapered waveguide and the second tapered waveguide of the laser, thereby obtaining the heterogeneous integrated coupling structure.
[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention designs a double-layer tapered waveguide structure consisting of a first tapered waveguide and a second tapered waveguide. By placing silicon nitride tapered waveguides and silicon nitride single-mode waveguides on the chip and optically interconnecting the second tapered waveguide with the silicon nitride tapered waveguide in a vertical coupling manner, it can effectively solve the problem of mode compatibility between existing lasers and silicon nitride chips, realize efficient on-chip coupling of heterogeneous laser integration, and improve the coupling efficiency of heterogeneous integrated coupling structures. Attached Figure Description
[0009] Figure 1 A three-dimensional view of the heterogeneous integrated coupling structure based on a semiconductor laser provided by the present invention; Figure 2 This is a front view of the heterogeneous integrated coupling structure provided by the present invention; Figure 3 This is a top view of the heterogeneous integrated coupling structure provided by the present invention; Figure 4 A schematic diagram of the layered structure of a laser with the contact layer removed, provided by the present invention; Figure 5 This is a flowchart illustrating the fabrication process of the heterogeneous integrated coupling structure provided by the present invention. Figure 6 The simulated optical field distribution diagram of the heterogeneous integrated coupling structure provided by the present invention. Detailed Implementation
[0010] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.
[0011] In the open-ended description of the technical features in this invention, there are both closed-ended technical solutions composed of the listed features and open-ended technical solutions.
[0012] It should be understood that, unless otherwise specified, the numerical ranges involved in this invention are considered continuous, including the minimum and maximum values of the range, and every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the maximum and minimum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed in this invention should be understood to include any or all of the subranges to which they are included.
[0013] In the first aspect of the invention, please refer to Figures 1-4 The present invention provides a heterogeneous integrated coupling structure based on a semiconductor laser 2, comprising a chip 1 and a laser 2; Chip 1 is provided with bonding groove 11, silicon nitride tapered waveguide 12 and silicon nitride single-mode waveguide, and the wide end of silicon nitride tapered waveguide 12 is connected to silicon nitride single-mode straight waveguide 13; Laser 2 includes a contact layer 21, a ridge waveguide 22, a first tapered waveguide 23, and a second tapered waveguide 24. The contact layer 21 is bonded to the bonding groove 11. The ridge waveguide 22 is disposed on the contact layer 21. The wide end of the first tapered waveguide 23 is connected to the ridge waveguide 22 of laser 2. The wide end of the second tapered waveguide 24 is connected to the ridge waveguide 22 of laser 2. The first tapered waveguide 23 is located on the second tapered waveguide 24. The second tapered waveguide 24 is optically interconnected with the silicon nitride tapered waveguide 12 in a vertical coupling manner.
[0014] This invention achieves efficient on-chip coupling of heterogeneous integration of laser 2; when the heterogeneous integration coupling structure based on semiconductor laser is working, the laser is emitted from the first waveguide layer C, the active layer D and the second waveguide layer E of the ridge waveguide 22, then passes through the first tapered waveguide 23, is coupled from the first tapered waveguide 23 to the second tapered waveguide 24, and then is coupled from the second tapered waveguide 24 to the silicon nitride tapered waveguide 12, and finally output from the silicon nitride single-mode straight waveguide 13 connected to the silicon nitride tapered waveguide 12.
[0015] Compared with the existing end-face coupling structure of 780nm laser 2, the coupling efficiency of the heterogeneous integrated coupling structure based on semiconductor laser 2 in this invention is greatly improved.
[0016] In this invention, the width refers to... Figures 1-3 The dimension in the width direction of the heterogeneous integrated coupling structure, wherein the length refers to the length in the width direction. Figures 1-3The dimensions along the length of the heterogeneous integrated coupling structure, where thickness and depth refer to the dimensions along the length of the structure. Figures 1-3 The thickness dimension of the heterogeneous integrated coupling structure.
[0017] In some embodiments, chip 1 includes a silicon layer 16, a silicon dioxide layer 15, and a silicon nitride layer 14 disposed sequentially along its thickness direction, a bonding groove 11 disposed on the silicon nitride layer 14, and a silicon nitride tapered waveguide 12 and a silicon nitride single-mode waveguide disposed on the silicon dioxide layer 15.
[0018] In some embodiments, the thickness of the silicon dioxide layer 15 is 5~20 μm, and the thickness of the silicon nitride layer 14 is 100~500 nm.
[0019] For example, the thickness of the silicon dioxide layer 15 can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or any two of these values; the thickness of the silicon nitride layer 14 can be 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 370nm, 400nm, 420nm, 450nm, 480nm, 500nm or any two of these values.
[0020] In some embodiments, the depth of the bonding groove 11 is 50~300nm.
[0021] For example, the depth of the bonding groove 11 can be 50nm, 80nm, 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, 280nm, 300nm, or a range of any two sets of values.
[0022] In some embodiments, the distance between the outer wall of the contact layer 21 and the inner wall of the bonding groove 11 can be 1~10μm.
[0023] For example, the distance between the outer wall of the contact layer 21 and the inner wall of the bonding groove 11 can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any two of these values.
[0024] In some embodiments, the thickness of the silicon nitride tapered waveguide 12 is 100~500nm, and the thickness of the silicon nitride single-mode straight waveguide 13 is 100~500nm.
[0025] For example, the thickness of the silicon nitride tapered waveguide 12 can be 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 370nm, 400nm, 420nm, 450nm, 480nm, 500nm, or any two of these values. The thickness of the silicon nitride single-mode straight waveguide 13 can be 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 370nm, 400nm, 420nm, 450nm, 480nm, 500nm, or any two of these values.
[0026] In some embodiments, the width of the silicon nitride tapered waveguide 12 decreases linearly from its wide end to its narrow end, with the wide end width of the silicon nitride tapered waveguide 12 being 0.5~2μm, the narrow end width of the silicon nitride tapered waveguide 12 being 100~500nm, and the length of the silicon nitride tapered waveguide 12 being 30~200μm.
[0027] For example, the wide end width of the silicon nitride tapered waveguide 12 can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, or a range of any two sets of values.
[0028] The narrow end width of the silicon nitride tapered waveguide 12 can be 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 370nm, 400nm, 420nm, 450nm, 480nm, 500nm, or any combination of two such values. The length of the silicon nitride tapered waveguide 12 can be 30μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, or any combination of two such values.
[0029] In some embodiments, the width of the wide end of the silicon nitride tapered waveguide 12 is equal to the width of the silicon nitride single-mode straight waveguide 13.
[0030] In some embodiments, the coupling gap between the second tapered waveguide 24 and the silicon nitride tapered waveguide 12 in the thickness direction of the heterogeneous integrated coupling structure is 10~100nm.
[0031] For example, in the thickness direction of the heterogeneous integrated coupling structure, the coupling gap between the second tapered waveguide 24 and the silicon nitride tapered waveguide 12 can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm or any two of these values.
[0032] In some embodiments, the coupling gap is filled with benzocyclobutene resin.
[0033] In some embodiments, the spacing between the silicon nitride tapered waveguide 12 and the bonding groove 11 is 5~30μm.
[0034] For example, the spacing between the silicon nitride tapered waveguide 12 and the bonding groove 11 can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm or any two of these values.
[0035] In some embodiments, the width of the ridge waveguide 22 is 0.5~2μm, the width of the wide end of the first tapered waveguide 23 is equal to the width of the ridge waveguide 22, and the width of the wide end of the second tapered waveguide 24 is equal to the width of the ridge waveguide 22.
[0036] For example, the width of the ridge waveguide 22 can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, or a range of any two sets of values.
[0037] In some embodiments, the length of the second tapered waveguide 24 is greater than the length of the first tapered waveguide 23, and the length ratio between the second tapered waveguide 24 and the first tapered waveguide 23 is 1.2 to 2.
[0038] For example, the length ratio between the second tapered waveguide 24 and the first tapered waveguide 23 can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any two of these values.
[0039] In some embodiments, the contact layer 21 does not contact the second tapered waveguide 24, and the ratio between the area of the second tapered waveguide 24 and the area of the contact layer 21 on a plane perpendicular to the thickness direction of the heterogeneous integrated coupling structure is not greater than 0.1.
[0040] The inventors discovered that the contact layer 21 does not contact the second tapered waveguide 24, meaning the contact layer 21 does not extend into the gap between the second tapered waveguide 24 and the silicon nitride tapered waveguide 12. This prevents the laser from being absorbed by the contact layer 21, which exists in the coupling gap, when it couples downward from the second tapered waveguide 24 structure to the silicon nitride tapered waveguide 12. This improves the coupling efficiency of the heterogeneous integrated coupling structure described in this invention. Furthermore, on a plane perpendicular to the thickness direction of the heterogeneous integrated coupling structure, the ratio between the area of the second tapered waveguide 24 and the area of the contact layer 21 is not greater than 0.1, which can effectively ensure the bonding quality of the contact layer 21.
[0041] In some embodiments, the width of the first tapered waveguide 23 decreases linearly from its wide end to its narrow end, the width of the wide end of the first tapered waveguide 23 is 0.5~2μm, the width of the narrow end of the first tapered waveguide 23 is 10~100nm, and the length of the first tapered waveguide 23 is 20~100μm.
[0042] For example, the width of the wide end of the first tapered waveguide 23 can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, or any two sets of values therein. The width of the narrow end of the first tapered waveguide 23 can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any two sets of values therein. The length of the first tapered waveguide 23 can be 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, or any two sets of values therein.
[0043] In some embodiments, the width of the second tapered waveguide 24 decreases linearly from its wide end to its narrow end, the width of the second tapered waveguide 24 is 0.5~2μm, the width of the second tapered waveguide 24 is 10~100nm, and the length of the second tapered waveguide 24 is 30~200μm.
[0044] For example, the wide end width of the second tapered waveguide 24 can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, or any two sets of values therein. The narrow end width of the second tapered waveguide 24 can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any two sets of values therein. The length of the second tapered waveguide 24 can be 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, or a range consisting of any two sets of values.
[0045] By rationally designing the dimensions of the silicon nitride tapered waveguide 12, the silicon nitride single-mode waveguide, the first tapered waveguide 23, and the second tapered waveguide 24, this invention can effectively avoid the problem of significant absorption of 780nm laser by the contact layer 21 (especially the contact layer 21 made of gallium arsenide), improve the three-dimensional alignment accuracy between the laser 2 and the silicon nitride tapered waveguide 12 on the chip 1, and achieve efficient coupling of the 780nm laser 2 using the tapered coupling structure.
[0046] In some embodiments, the contact layer 21 is made of gallium arsenide and has a thickness of 50~300nm.
[0047] The total thickness of the ridge waveguide is 725~3820nm.
[0048] For example, the thickness of the contact layer 21 can be 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 300nm, or any two of these values. The total thickness of the ridge waveguide can be 725nm, 800nm, 850nm, 900nm, 1000nm, 1200nm, 1500nm, 1800nm, 2000nm, 2200nm, 2500nm, 2800nm, 3000nm, 3200nm, 3500nm, 3800nm, 3820nm, or any two of these values.
[0049] In some embodiments, the ridge waveguide 22 includes a first gradient layer A, a first cladding layer B, a first waveguide layer C, an active layer D, a second waveguide layer E, a second cladding layer F, a second gradient layer G, and a buffer layer H arranged sequentially along its thickness direction, with the first gradient layer A of the ridge waveguide 22 disposed on the contact layer 21. The first tapered waveguide 23 includes a first waveguide layer C, an active layer D, a second waveguide layer E, a second cladding layer F, a second gradient layer G, and a buffer layer H arranged sequentially along its thickness direction; The second tapered waveguide 24 includes a first gradient layer A and a first cladding layer B arranged sequentially along its thickness direction; The first waveguide layer C of the first tapered waveguide 23 is in contact with the first cladding layer B of the second tapered waveguide 24.
[0050] In some embodiments, the first gradient layer A is made of gallium indium phosphide, and the thickness of the first gradient layer A is 10~100nm.
[0051] The first cladding layer B is made of aluminum indium phosphide, and its thickness is 200~1000nm.
[0052] The first waveguide layer C is made of gallium indium phosphide, and its thickness is 50~300nm.
[0053] The active layer D is made of gallium arsenide phosphide, and the thickness of the active layer D is 5~20nm.
[0054] The second waveguide layer E is made of gallium indium phosphide, and its thickness is 50~300nm.
[0055] The second cladding layer F is made of aluminum indium phosphide, and its thickness is 200~1000nm.
[0056] The second gradient layer G is made of gallium indium phosphide, and its thickness is 10~100nm.
[0057] The buffer layer H is made of gallium arsenide, and the thickness of the buffer layer H is 200~1000nm.
[0058] For example, the thickness of the first gradient layer A can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any two sets of values therein; the thickness of the first cladding layer B can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or any two sets of values therein; and the thickness of the first waveguide layer C... The thickness can be 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 300nm, or any two of these values. The thickness of the active layer D can be 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, or any other value. The thickness of the second waveguide layer E can be any range consisting of two sets of values: 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 300nm, or any two sets of values. The thickness of the second cladding layer F can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or... The thickness of the second gradient layer G can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any two sets of values within the range of any given two sets of values. The thickness of the buffer layer H can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or any two sets of values within the range of any given two sets of values. In a second aspect, the present invention provides a method for preparing the above-mentioned heterogeneous integrated coupling structure, comprising the following steps: S1. Deposit a silicon dioxide layer 15 on the silicon layer 16; S2. A silicon nitride substrate is deposited on the silicon dioxide layer 15, and the silicon nitride substrate is etched to form a bonding groove 11, a silicon nitride tapered waveguide 12 and a silicon nitride single-mode waveguide, and the surface roughness of the bonding groove 11 is not greater than 0.5 nm. S3. Remove part of the contact layer 21 of the laser core and bond the contact layer 21 of the laser core to the bonding groove 11. S4. Remove the substrate I of the laser core, and then etch the laser core after removing the substrate to form the ridge waveguide 22, the first tapered waveguide 23 and the second tapered waveguide 24 of the laser 2, thereby obtaining the heterogeneous integrated coupling structure.
[0059] The inventors discovered that the contact layer 21 of the laser 2 has significant absorption of 780nm wavelength laser light. Before the bonding step, the present invention removes the contact layer 21 located below the predetermined second tapered waveguide 24 to prevent the laser light from being absorbed by the contact layer 21 existing in the coupling gap when it is coupled downward from the structure of the second tapered waveguide 24 to the silicon nitride waveguide. Furthermore, on the plane perpendicular to the thickness direction of the heterogeneous integrated coupling structure, the area of the removed contact layer 21 region is no more than one-tenth of the area of the entire laser core, so it will not affect the bonding quality of the laser 2.
[0060] In some embodiments, the deposition method in steps S1 and S2 may include chemical vapor deposition.
[0061] In some implementations, the bonding method in step S3 includes the D2W heterogeneous / hybrid bonding method.
[0062] In some embodiments, in step S4, the substrate of the laser core is removed by at least one of mechanical grinding thinning, chemical mechanical polishing, and wet etching.
[0063] In some implementations, step S4 may be followed by: S5. Use BCB adhesive for planarization. S6. Electron beam lithography is performed using electron-sensitive ARP photoresist to expose and develop the P-electrode window pattern. Reactive ion etching is used to etch the corresponding area of BCB adhesive to expose the corresponding area of contact layer 21. The photoresist is removed by inductively coupled plasma technology. Electron beam lithography is performed on the ARP photoresist to expose and develop the pattern of the P-electrode and its lead-out pads (the pattern covers the window of contact layer 21 and extends above the BCB adhesive to form pads). Metal is deposited by electron beam evaporation to form the P-electrode on the contact layer 21 and BCB adhesive. The photoresist is stripped using acetone. S7. Electron beam lithography is performed on the buffer layer H of the ridge waveguide 22 using electron-sensitive ARP photoresist to expose and develop the N electrode window pattern. Reactive ion etching is used to etch the corresponding area of BCB adhesive to expose the corresponding area of the buffer layer H. The photoresist is removed by inductively coupled plasma technology. Electron beam lithography is performed on the ARP photoresist to expose and develop the pattern of the N electrode and its lead-out pads (the pattern covers the window of the buffer layer H and extends above the BCB adhesive to form pads). Metal is deposited by electron beam evaporation to form the N electrode on the exposed buffer layer H and BCB adhesive. The photoresist is stripped with acetone to complete the fabrication of the device.
[0064] In some embodiments, the metal in step S6 includes at least one of gold, platinum, and titanium.
[0065] In some embodiments, the metal in step S7 includes at least one of gold, germanium, and nickel.
[0066] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0067] Example 1 This embodiment provides an example of a heterogeneous integrated coupling structure based on a semiconductor laser 2 and its fabrication method. The heterogeneous integrated coupling structure based on the semiconductor laser 2 includes a chip 1 and a laser 2. The chip 1 is provided with a bonding groove 11, a silicon nitride tapered waveguide 12, and a silicon nitride single-mode waveguide. The wide end of the silicon nitride tapered waveguide 12 is connected to the silicon nitride single-mode straight waveguide 13. The laser 2 includes a contact layer 21, a ridge waveguide 22, a first tapered waveguide 23, and a second tapered waveguide 24. The contact layer 21 is bonded to the bonding groove 11. The ridge waveguide 22 is disposed on the contact layer 21. The wide end of the first tapered waveguide 23 is connected to the ridge waveguide 22 of the laser 2. The wide end of the second tapered waveguide 24 is connected to the ridge waveguide 22 of the laser 2. The first tapered waveguide 23 is located on the second tapered waveguide 24. The second tapered waveguide 24 and the silicon nitride tapered waveguide 12 are optically interconnected in a vertical coupling manner.
[0068] Chip 1 includes a silicon layer 16, a silicon dioxide layer 15 and a silicon nitride layer 14 arranged sequentially along its thickness direction. A bonding groove 11 is disposed on the silicon nitride layer 14, and a silicon nitride tapered waveguide 12 and a silicon nitride single-mode waveguide are both disposed on the silicon dioxide layer 15.
[0069] The silicon dioxide layer 15 has a thickness of 10 μm, and the silicon nitride layer 14 has a thickness of 300 nm.
[0070] The thickness of silicon nitride tapered waveguide 12 is 300 nm, and the thickness of silicon nitride single-mode straight waveguide 13 is 300 nm.
[0071] The width of the silicon nitride tapered waveguide 12 decreases linearly from its wide end to its narrow end. The width of the wide end of the silicon nitride tapered waveguide 12 is 1 μm, the width of the narrow end of the silicon nitride tapered waveguide 12 is 300 nm, the length of the silicon nitride tapered waveguide 12 is 80 μm, and the width of the wide end of the silicon nitride tapered waveguide 12 is equal to the width of the silicon nitride single-mode straight waveguide 13.
[0072] The bonding groove 11 has a depth of 150 nm, a length of 1926 μm, and a width of 506 μm.
[0073] The distance between the outer wall of the contact layer 21 and the inner wall of the bonding groove 11 can be 3 μm.
[0074] In the thickness direction of the heterogeneous integrated coupling structure, there is a coupling gap between the second tapered waveguide 24 and the silicon nitride tapered waveguide 12. The size of the coupling gap is 50 nm, and the coupling gap is filled with benzocyclobutene resin (BCB).
[0075] The spacing between the silicon nitride tapered waveguide 12 and the bonding groove 11 is 17 μm.
[0076] The ridge waveguide 22 has a width of 1 μm and a length of 1900 μm. The width of the wide end of the first tapered waveguide 23 is equal to the width of the ridge waveguide 22, and the width of the wide end of the second tapered waveguide 24 is equal to the width of the ridge waveguide 22.
[0077] The width of the first tapered waveguide 23 decreases linearly from its wide end to its narrow end. The width of the wide end of the first tapered waveguide 23 is 1 μm, the width of the narrow end of the first tapered waveguide 23 is 50 nm, and the length of the first tapered waveguide 23 is 50 μm.
[0078] The width of the second tapered waveguide 24 decreases linearly from its wide end to its narrow end. The width of the wide end of the second tapered waveguide 24 is 1 μm, the width of the narrow end of the second tapered waveguide 24 is 50 nm, and the length of the second tapered waveguide 24 is 80 μm.
[0079] The contact layer 21 is made of gallium arsenide, with a thickness of 200 nm, a length of 1920 μm, and a width of 500 μm. The contact layer 21 is not in contact with the second tapered waveguide 24. On a plane perpendicular to the thickness direction of the heterogeneous integrated coupling structure, the ratio between the area of the second tapered waveguide 24 and the area of the contact layer 21 is less than 0.1.
[0080] The ridge waveguide 22 has a length of 1900 μm and includes a first gradient layer A, a first cladding layer B, a first waveguide layer C, an active layer D, a second waveguide layer E, a second cladding layer F, a second gradient layer G, and a buffer layer H arranged sequentially along its thickness direction. The first gradient layer A of the ridge waveguide 22 is disposed on the contact layer 21. The first tapered waveguide 23 includes a first waveguide layer C, an active layer D, a second waveguide layer E, a second cladding layer F, a second gradient layer G, and a buffer layer H arranged sequentially along its thickness direction. The second tapered waveguide 24 includes a first gradient layer A and a first cladding layer B arranged sequentially along its thickness direction. The first waveguide layer C of the first tapered waveguide 23 and the first gradient layer G of the second tapered waveguide 24 are connected in series. The first gradient layer A is made of gallium indium phosphide (GaInP) and has a thickness of 50 nm; the first cladding layer B is made of aluminum indium phosphide (AIP) and has a thickness of 500 nm; the first waveguide layer C is made of GaInP and has a thickness of 150 nm; the active layer D is made of gallium arsenide (GaAsP) and has a thickness of 9 nm; the second waveguide layer E is made of GaInP and has a thickness of 150 nm; the second cladding layer F is made of AIP and has a thickness of 600 nm; the second gradient layer G is made of GaInP and has a thickness of 50 nm; and the buffer layer H is made of gallium arsenide (GaAsP) and has a thickness of 500 nm.
[0081] like Figure 5 As shown in the figure, this embodiment also provides a method for fabricating a heterogeneous integrated coupling structure and device, including the following steps: S1. A silicon dioxide layer 15 is deposited on the silicon layer 16 by chemical vapor deposition. S2. A silicon nitride substrate is deposited on the silicon dioxide layer 15 by chemical vapor deposition. The silicon nitride substrate is etched to form a bonding groove 11, a silicon nitride tapered waveguide 12 and a silicon nitride single-mode waveguide, and the surface roughness of the bonding groove 11 is not greater than 0.5 nm. S3. Prepare a laser core with a length of 2000μm and a width of 500μm. The laser core consists of a contact layer J, a first gradient layer A, a first cladding layer B, a first waveguide layer C, an active layer D, a second waveguide layer E, a second cladding layer F, a second gradient layer G, a buffer layer H, and a substrate I arranged sequentially along its thickness direction. The contact layer 21 has a thickness of 200nm, the first gradient layer A has a thickness of 50nm, the first cladding layer B has a thickness of 500nm, the first waveguide layer C has a thickness of 150nm, the active layer D has a thickness of 9nm, the second waveguide layer E has a thickness of 150nm, the second cladding layer F has a thickness of 600nm, the second gradient layer G has a thickness of 50nm, and the buffer layer H has a thickness of 500nm. A portion of the contact layer 21 of the laser core is removed, and the etching area has an etching depth of 200 nm, a width of 500 μm, and a length of 80 μm. After etching, the bonding surface of the laser core has a length of 1920 μm and a width of 500 μm, and the contact layer 21 of the laser core is bonded to the bonding groove 11. S4. The substrate I of the laser core is removed by mechanical grinding, chemical mechanical polishing and wet etching. Then, the laser core with the substrate removed is laser etched to form the ridge waveguide 22, the first tapered waveguide 23 and the second tapered waveguide 24 of the laser 2, thereby obtaining the heterogeneous integrated coupling structure. S5. Use BCB adhesive to planarize the heterogeneous integrated coupling structure. S6. Electron beam lithography is performed using electron-sensitive ARP photoresist to expose and develop the P-electrode window pattern. Reactive ion etching is used to etch the corresponding area of BCB adhesive to expose the corresponding area of contact layer 21. The photoresist is removed by inductively coupled plasma technology. Electron beam lithography is performed on the ARP photoresist to expose and develop the pattern of the P-electrode and its lead-out pads (the pattern covers the window of contact layer 21 and extends above the BCB adhesive to form pads). Titanium, platinum and gold are deposited sequentially using electron beam evaporation to form the P-electrode composed of sequentially arranged titanium, platinum and gold layers on the contact layer 21 and BCB adhesive. The photoresist is stripped using acetone. S7. Electron beam lithography is performed on the buffer layer H of the ridge waveguide 22 using thermally stable negative photoresist to expose and develop the N electrode window pattern. Reactive ion etching is used to etch the corresponding area of BCB resist to expose the corresponding area of the buffer layer H. The photoresist is removed by inductively coupled plasma technology. Electron beam lithography is performed on the ARP photoresist to expose and develop the pattern of the N electrode and its lead-out pads (the pattern covers the window of the buffer layer H and extends above the BCB resist to form pads). Nickel, germanium and gold are deposited sequentially by electron beam evaporation to form the N electrode, which consists of a nickel layer, a germanium layer and a gold layer arranged sequentially, on the exposed buffer layer H and BCB resist. The photoresist is stripped with acetone to complete the fabrication of the device.
[0082] The above-mentioned device was simulated and tested. The simulated optical field distribution of the device is shown in the figure below. Figure 6 As shown in the figure. Simulation tests revealed that the coupling efficiency of the device reached 96.9%, indicating that the heterogeneous integrated coupling structure provided by this invention has excellent coupling efficiency.
[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. 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 be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A heterogeneous integrated coupling structure based on a semiconductor laser, characterized in that, Including chips and lasers; The chip is provided with bonding grooves, silicon nitride tapered waveguides and silicon nitride single-mode waveguides, and the wide end of the silicon nitride tapered waveguide is connected to the silicon nitride single-mode straight waveguide; The laser includes a contact layer, a ridge waveguide, a first tapered waveguide, and a second tapered waveguide. The contact layer is bonded to the bonding groove. The ridge waveguide is disposed on the contact layer. The wide end of the first tapered waveguide is connected to the ridge waveguide of the laser. The wide end of the second tapered waveguide is connected to the ridge waveguide of the laser. The first tapered waveguide is located on the second tapered waveguide. The second tapered waveguide and the silicon nitride tapered waveguide are optically interconnected in a vertical coupling manner.
2. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The chip includes a silicon layer, a silicon dioxide layer, and a silicon nitride layer arranged sequentially along its thickness direction. The bonding groove is disposed on the silicon nitride layer, and the silicon nitride tapered waveguide and the silicon nitride single-mode waveguide are both disposed on the silicon dioxide layer.
3. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The width of the silicon nitride tapered waveguide decreases linearly from its wide end to its narrow end. The width of the wide end of the silicon nitride tapered waveguide is 0.5~2μm, the width of the narrow end of the silicon nitride tapered waveguide is 100~500nm, and the length of the silicon nitride tapered waveguide is 30~200μm.
4. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, In the thickness direction of the heterogeneous integrated coupling structure, the coupling gap between the second tapered waveguide and the silicon nitride tapered waveguide is 10~100nm.
5. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The distance between the silicon nitride tapered waveguide and the bonding groove is 5~30μm.
6. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The length of the second tapered waveguide is greater than the length of the first tapered waveguide, and the length ratio between the second tapered waveguide and the first tapered waveguide is 1.2 to 2.
7. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The contact layer does not contact the second tapered waveguide, and on a plane perpendicular to the thickness direction of the heterogeneous integrated coupling structure, the ratio between the area of the second tapered waveguide and the area of the contact layer is not greater than 0.
1.
8. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The width of the first tapered waveguide decreases linearly from its wide end to its narrow end. The width of the wide end of the first tapered waveguide is 0.5~2μm, the width of the narrow end of the first tapered waveguide is 10~100nm, and the length of the first tapered waveguide is 20~100μm.
9. The heterogeneous integrated coupling structure based on a semiconductor laser as described in claim 1, characterized in that, The width of the second tapered waveguide decreases linearly from its wide end to its narrow end. The width of the wide end of the second tapered waveguide is 0.5~2μm, the width of the narrow end of the second tapered waveguide is 10~100nm, and the length of the second tapered waveguide is 30~200μm.
10. The method for fabricating the heterogeneous integrated coupling structure according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Deposit a silicon dioxide layer on the silicon layer; S2. Deposit a silicon nitride substrate on a silicon dioxide layer, and etch the silicon nitride substrate to form a bonding groove, a silicon nitride tapered waveguide, and a silicon nitride single-mode waveguide, wherein the surface roughness of the bonding groove is not greater than 0.5 nm. S3. Remove part of the contact layer of the laser core and bond the contact layer of the laser core to the bonding groove; S4. Remove the substrate of the laser core, and then etch the laser core after removing the substrate to form the ridge waveguide, the first tapered waveguide and the second tapered waveguide of the laser, thereby obtaining the heterogeneous integrated coupling structure.