A design method for on-chip cross optical waveguides and the on-chip cross optical waveguides

Abstract

This invention relates to the field of integrated photonics technology, and particularly to a design method and an on-chip cross-waveguide. The method includes: crossing two straight waveguides to form a cross-waveguide with a crossing angle of less than 90 degrees; performing a preliminary design on the crossing region of the cross-waveguide to ensure that the initial structural parameters of the crossing region are less than 4 micrometers by 4 micrometers; using a particle swarm optimization algorithm to optimize the initial structural parameters of the crossing region to change the material refractive index distribution within the crossing region, obtaining the material refractive index distribution within the crossing region that maximizes the light transmittance of the cross-waveguide and satisfies the vertical and horizontal symmetry of the structure, and using the corresponding structural parameters of the crossing region as the target structural parameters; and redesigning the crossing region of the cross-waveguide using the target structural parameters to solve the problems of large area occupied by the cross-waveguide, complex design of small-angle cross-waveguides, and high difficulty in three-dimensional fabrication.

Description

Technical Field

[0001] This invention relates to the field of integrated photonics technology, and in particular to a design method for an on-chip cross-waveguide and an on-chip cross-waveguide. Background Technology

[0002] With the rapid development of information technology, photonic integrated chips are becoming a crucial supporting technology for next-generation optical communication, optical computing, and optical sensing due to their significant advantages in high-speed data transmission, low-power computing, and high integration. Compared to traditional electronic chips, photonic integrated chips utilize optical signals for information transmission and processing, effectively reducing energy consumption while increasing data transmission rates and bandwidth. Therefore, the design of highly integrated and high-efficiency photonic devices is key to driving the development of photonic integrated chips, among which high-density interconnect technology of optical waveguides is particularly important.

[0003] Within photonic integrated chips, different functional units require signal transmission via optical waveguides. In complex optical path designs, multiple optical signal channels often need to intersect to achieve a more compact layout and more efficient optical path design. Therefore, intersecting optical waveguides, as a core structure, play a crucial role in on-chip optical interconnects. An ideal intersecting optical waveguide needs to possess a compact size, high transmittance, and broadband characteristics to meet the demands of high-density photonic integration. However, existing intersecting optical waveguide designs still have many limitations, making it difficult to simultaneously achieve high integration density and manufacturing feasibility.

[0004] Currently, common cross-shaped waveguide structures mainly include the cross-shaped scheme. This scheme typically uses two straight waveguides that cross directly through an intermediate extension, or optimizes the structure of the cross region through reverse design. Specifically, the simplest method is to directly cross the two straight waveguides and design the parameters of the resulting "cross" structure, which usually requires a 10-micron by 10-micron structural region. The advantages of this method are its simple design, mature fabrication technology, and ability to achieve low loss and broadband characteristics. However, because the cross angle of this structure is 90 degrees, it occupies a large area, which is not conducive to high-density integration. In addition, although the cross-shaped waveguide with a cross region structure optimized by reverse design is slightly smaller, with an area of ​​approximately 4 microns by 4 microns, the cross angle is still 90 degrees, making it difficult to achieve high-density integration.

[0005] To reduce the footprint of intersecting optical waveguides and improve the integration density of photonic integrated chips, some design schemes attempt to achieve a more compact layout by reducing the intersection angle. However, under small intersection angle conditions, the mode matching problem of optical signals becomes more complex, easily introducing additional mode coupling effects and affecting the overall performance of the device. Therefore, in some application scenarios, three-dimensional optical path interconnect integrated chip solutions have also been proposed to utilize different waveguide layers (such as a silicon-silicon dioxide-silicon "sandwich" structure) or photonic crystal structures to achieve spatial optical signal separation, thereby avoiding the need for waveguide intersections. However, the fabrication of three-dimensional optical waveguides involves complex stacked structures, resulting in high manufacturing costs and extremely high requirements for process precision, making it difficult to popularize in large-scale production.

[0006] In summary, existing cross-waveguide technologies have the following main shortcomings:

[0007] 1. Large footprint: Traditional cross-shaped waveguides have a large intersection angle, which limits the feasibility of high-density integration.

[0008] 2. Small-angle crossover design is complex: When the crossover angle is small, the mode matching and coupling problems between waveguides become more significant, affecting the stability of the device.

[0009] 3. High difficulty in three-dimensional processing: Although three-dimensional optical path design can avoid waveguide crossing, its manufacturing process is complex and costly, making it difficult to meet the needs of large-scale manufacturing. Summary of the Invention

[0010] The purpose of this invention is to provide a design method and an on-chip cross optical waveguide, which can solve the problems of large area occupation, complex small-angle cross design, and high difficulty in three-dimensional processing of existing cross optical waveguides.

[0011] To address the aforementioned technical problems, embodiments of the present invention provide a design method for an on-chip cross optical waveguide, comprising the following steps:

[0012] Two straight waveguides are crossed to form a cross-optical waveguide with an angle of less than 90 degrees;

[0013] A preliminary design is carried out for the intersection region of the cross-optical waveguides, so that the initial structural parameters of the intersection region are less than 4 micrometers by 4 micrometers;

[0014] The particle swarm optimization algorithm is used to optimize the initial structural parameters of the intersection region to change the material refractive index distribution in the intersection region. The algorithm obtains the material refractive index distribution in the intersection region when the light transmittance of the intersection waveguide is maximized and the structure of the intersection region satisfies the vertical and horizontal symmetry. The corresponding structural parameters of the intersection region are then used as the target structural parameters of the intersection region.

[0015] The cross region of the cross optical waveguide is redesigned based on the target structural parameters.

[0016] Optionally, the objective function of the particle swarm optimization algorithm is established with the goal of maximizing the light transmittance of the cross-optical waveguide;

[0017] The target structural parameters are obtained through the following steps:

[0018] S1. Initialize the particle swarm: In the initially designed intersection area, several initial particles are randomly generated. Each particle represents a possible material refractive distribution, and each material refractive distribution corresponds to a structural parameter.

[0019] S2. Calculate light transmittance: Calculate the light transmittance of the cross waveguide under each material refractive distribution, and evaluate the optimization degree according to the objective function;

[0020] S3. Update particle velocity and position: Adjust the position of each particle according to its local optimum and the global optimum of the entire particle swarm, so as to converge toward the optimum.

[0021] S4. Iterative optimization: Repeat steps S2 and S3 until the convergence condition is met and the optimal solution is obtained. The convergence condition is that the transmittance reaches a preset percentage or the number of iterations reaches a preset number.

[0022] S5. Obtain the target structure parameters based on the optimal solution.

[0023] Optionally, the cross angle of the cross optical waveguide is 20°.

[0024] Optionally, the initial structural parameters of the intersection region are 2 micrometers by 2 micrometers.

[0025] Optionally, the target structural parameters are 2 micrometers × 1.45 micrometers.

[0026] Optionally, the redesign of the intersection region of the cross-optical waveguides based on the target structural parameters includes:

[0027] Replace the nanoscale feature regions within the intersection of the target structural parameters with rectangular units, and fix the length of the rectangular units at 2 micrometers, while allowing the width to vary in the range of 20 nanometers to 30 nanometers.

[0028] Among them, the nanoscale feature region is the region with a line width of less than 10 nanometers within the intersection area.

[0029] Optionally, when the wavelength of the cross-optical waveguide is 1550 nanometers, the preset percentage is 95%.

[0030] An embodiment of the present invention also provides an on-chip cross optical waveguide, which is designed by the on-chip cross optical waveguide design method described above.

[0031] The on-chip cross-waveguide design method provided by this invention has at least the following beneficial effects:

[0032] By intersecting two straight waveguides to form a cross-angle optical waveguide with an angle less than 90 degrees, and by initially designing the cross-region of the cross-waveguide, the initial structural parameters of the cross-region are made smaller than 4 micrometers by 4 micrometers. This achieves a small-angle cross-angle design, maintains a compact device size, and helps improve the overall integration of photonic integrated chips. Then, the structural parameters of the cross-region are optimized using a particle swarm optimization algorithm to change the material refractive index distribution within the cross-region. The algorithm obtains the material refractive index distribution within the cross-waveguide when the light transmittance is maximized and the structure of the cross-region satisfies the vertical and horizontal symmetry requirements. The corresponding structural parameters of the cross-region are then used as the final target structural parameters for the cross-region. Based on this, the design of the cross-region of the cross-waveguide is completed, optimizing the optical field distribution of the cross-region. This reduces mode mismatch effects, improves the transmission stability of optical signals, and eliminates the need for additional three-dimensional processing steps, thus reducing manufacturing complexity and cost. Attached Figure Description

[0033] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.

[0034] Figure 1 This is a flowchart of a design method for an on-chip cross optical waveguide according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a structure for reverse engineering using a particle swarm optimization algorithm according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the transmittance of a cross waveguide designed in reverse using a particle swarm optimization algorithm, according to an embodiment of the present invention.

[0037] Figure 4 This is a simplified cross-waveguide structure schematic diagram according to an embodiment of the present invention;

[0038] Figure 5 This is a simplified cross-waveguide transmittance diagram provided according to an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0040] There is an urgent need for a new cross-waveguide design method to achieve compact integration under small-angle crossover conditions, while maintaining good optical transmission performance, and improving the integration level and manufacturing feasibility of photonic chips.

[0041] Therefore, this invention aims to solve the integration limitations of existing cross-waveguides in small-angle crossover situations. Specifically, this invention achieves efficient crossover of two waveguides within a small angle range by optimizing the waveguide structure and the design of the crossover region, while maintaining a compact device size, which helps to improve the overall integration of photonic integrated chips. Simultaneously, it is compatible with existing photonic integrated manufacturing processes, eliminating the need for additional three-dimensional processing steps, thereby reducing manufacturing complexity and cost. Furthermore, this method is applicable to various on-chip photonic platforms, such as silicon photonics and silicon nitride photonics, and can be widely used in optical communication, optical computing, and other fields.

[0042] Compared to traditional large-angle cross-waveguide solutions, the method of this invention can provide higher integration while ensuring optical transmission performance, providing a new solution for high-density photonic integration.

[0043] One embodiment of the present invention relates to a design method for an on-chip cross optical waveguide. The implementation details of the design method for the on-chip cross optical waveguide in this embodiment are described in detail below. The following implementation details are provided for ease of understanding and are not necessary for implementing this solution.

[0044] The specific flow of the on-chip cross optical waveguide design method in this embodiment can be described as follows: Figure 1 As shown, it includes:

[0045] Step 101: Cross the two straight waveguides to form a cross optical waveguide with a cross angle of less than 90 degrees.

[0046] In one example, the cross angle of the cross waveguides is set to 20 degrees to achieve a compact device layout while taking into account the mode matching and transmission stability of the optical signal.

[0047] Step 102: Perform preliminary design of the cross region of the cross optical waveguide, so that the initial structural parameters of the cross region are less than 4 micrometers by 4 micrometers.

[0048] In one example, a 2-micron by 2-micron reverse design region is introduced within the cross region as the cross region of the cross optical waveguide.

[0049] Step 103: The particle swarm optimization algorithm is used to optimize the initial structural parameters of the intersection region to change the material refractive index distribution in the intersection region. The material refractive index distribution in the intersection region is obtained when the light transmittance of the cross optical waveguide is maximized and the structure of the intersection region satisfies the vertical and horizontal symmetry. The corresponding structural parameters of the intersection region are then used as the target structural parameters of the intersection region.

[0050] In this implementation, after determining the angle of the cross waveguides (20 degrees) and the size of the reverse design region (2 μm × 2 μm), this embodiment improves the optical field distribution in the cross region, reduces mode mismatch effects, and enhances overall optical transmission efficiency by precisely optimizing the structural parameters of this region. Specifically, a reverse design based on the particle swarm optimization algorithm is adopted, that is, the particle swarm optimization algorithm is used to reverse design this region to optimize its structural parameters, enabling the cross waveguides to maintain good optical transmission performance even at small-angle crossovers.

[0051] Basic Principles: Reverse engineering is a computational method based on objective function optimization, often used in optical device design for structural optimization to meet specific optical performance requirements. Particle swarm optimization (PSO) is a biomimetic optimization algorithm that simulates the behavior of flocks of birds or schools of fish searching for optimal food sources. Through information sharing and adaptive adjustment among particles, it achieves the optimal search for the objective function. In optics, this algorithm is mainly applied to the optimization of required structural parameters, and is particularly suitable for high-dimensional nonlinear problems such as light field manipulation and mode matching. In the design method of this invention, PSO is used to adjust the refractive index distribution of the material within the reverse engineering region, minimizing scattering and mode mismatch of the optical signal in the crossing region and successfully completing the waveguide crossing process, thereby optimizing transmittance.

[0052] Objective function setting: Particle swarm optimization requires defining an objective function so that the algorithm can continuously optimize structural parameters to meet performance requirements. In this embodiment, the objective function of the particle swarm optimization algorithm is established with the goal of maximizing the light transmittance of the cross-waveguide, and is set as follows: ,in, The transmittance of the cross-waveguide is defined as the transmittance of the cross-waveguide at a target wavelength (e.g., 1550 nm) that reaches or approaches 95%. Therefore, the goal of the particle swarm optimization algorithm is to find the optimal structural parameters that maximize the value of this objective function.

[0053] The particle swarm optimization process (i.e., the process of obtaining the target structure parameters) is as follows:

[0054] S1. Initialize the particle swarm: In the initially designed intersection region (e.g., in a 2 µm × 2 µm reverse design region), randomly generate several initial particles. Each particle represents a possible material refraction distribution, and each distribution is set to be vertically symmetrical about the x-direction to ensure that the generated structure can satisfy simultaneous forward and reverse transmission; where each material refraction distribution corresponds to a structural parameter.

[0055] S2. Calculate the light transmittance: Use the three-dimensional full-wave electromagnetic solution method (the finite-difference time-domain method is used in this embodiment) to calculate the light transmittance of the cross waveguide under the refractive distribution of each material, and evaluate its optimization degree according to the objective function;

[0056] S3. Update particle velocity and position: Adjust the position of each particle according to its own historical optimal solution (local optimum) and the global optimal solution of the entire particle swarm, so as to converge toward the optimal solution (i.e. the highest cross waveguide transmittance).

[0057] S4. Iterative optimization: Repeat steps S2 and S3 until the convergence condition is met and the optimal solution is obtained. The convergence condition is that the transmittance reaches a preset percentage or the number of iterations reaches a preset number. The preset percentage can be 95%.

[0058] S5. Optimization Results: After iterative optimization using the particle swarm optimization algorithm, the resulting cross-region structure satisfies vertical symmetry, with structural parameters of 2 µm × 1.45 µm, and the structure is as follows: Figure 2 As shown, this significantly reduces the size of the intersection region while ensuring that the transmittance of the intersection waveguide reaches 94%. (See [reference]) Figure 3 .

[0059] Step 104: Redesign the cross region of the cross optical waveguide based on the target structural parameters.

[0060] In one example, after reverse engineering using a particle swarm optimization algorithm, although a cross-waveguide structure with high transmittance was obtained, the feature size in some optimized regions may be too small, for example, less than 10 nm, making it difficult to manufacture precisely using existing micro / nano fabrication processes (such as photolithography or electron beam lithography). Therefore, while ensuring that the outer contour remains unchanged, this invention further optimizes the fabrication feasibility of the optimized structure, i.e., simplifies the structure. In the actual manufacturing process of micro / nano optical devices, process capabilities are usually limited by the following factors: minimum manufacturable feature size (too small a spacing may lead to processing defects, such as pattern collapse or reduced resolution), and manufacturing cost (extremely fine structures require longer processing time, increasing manufacturing cost and difficulty). Therefore, this embodiment simplifies the structure based on optimization, so that the final design is compatible with standard complementary metal-oxide-semiconductor (CMOS) compatible photolithography or electron beam lithography processes.

[0061] In this implementation, to improve fabrication feasibility while maintaining optimized performance, this embodiment uses rectangular units instead of the complex small structures within the optimized region. Keeping the outer contour unchanged (i.e., the structural dimensions remain 2 µm × 1.45 µm), the optimized complex nanoscale feature regions (linewidths less than 10 nm) are replaced with easily fabricated rectangular units. The length is fixed at 2 µm, while the width varies within the range of 20 nm - 30 nm to accommodate different refractive index distributions and fabrication accuracy requirements. The simplified cross-waveguide structure is shown below. Figure 4 As shown, the transmittance of the simplified cross-waveguide is as follows: Figure 5 As shown, this corresponds to rectangular widths of 20 nm and 30 nm. For an incident wavelength of 1550 nm, this improves the bandwidth while simultaneously achieving both process standards and high transmittance, avoiding processing defects caused by excessively small structures and improving the repeatability of large-scale manufacturing.

[0062] As can be seen, this invention proposes a design and implementation method for an efficient on-chip cross-optical waveguide to address the technical problem. It can achieve efficient transmission of optical signals within a small angle range, providing a more optimized solution for high-density photonic integration.

[0063] Specifically, this invention achieves a high-efficiency on-chip cross-waveguide scheme by optimizing the cross-waveguide design, combining it with particle swarm optimization (PSO) for reverse design, and simplifying the structure based on the optimization to adapt to existing micro-nano fabrication processes. This method improves the integration density of photonic integrated chips, making the optical path design more compact, while optimizing the optical field distribution in the cross region and improving the transmission stability of optical signals. The structural simplification strategy avoids ultra-small feature sizes, ensuring that the design is compatible with standard photolithography or electron beam lithography processes, reducing manufacturing costs, and improving CMOS fabrication consistency. Furthermore, this invention requires no additional three-dimensional fabrication steps and is applicable to mainstream photonic integration platforms such as silicon photonics and silicon nitride, providing a highly efficient and reliable new solution for the design and fabrication of high-density photonic chips.

[0064] The steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of this invention. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, without changing the core design of the algorithm and process, are also within the protection scope of this invention.

[0065] Another embodiment of the present invention relates to an on-chip cross optical waveguide, which is designed by the on-chip cross optical waveguide design method described in the above embodiments.

[0066] It is not difficult to see that this embodiment is a waveguide component embodiment corresponding to the above method embodiments, and this embodiment can be implemented in conjunction with the above method embodiments. The relevant technical details and effects mentioned in the above embodiments are still valid in this embodiment, and will not be repeated here to reduce repetition. Accordingly, the relevant technical details mentioned in this embodiment can also be applied to the above embodiments.

[0067] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of the embodiments of the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the embodiments of the present invention; therefore, the scope of protection of the embodiments of the present invention should be determined by the scope defined in the claims.

Claims

1. A design method for an on-chip cross-shaped optical waveguide, characterized in that, The method includes: Two straight waveguides are crossed to form a cross-optical waveguide with an angle of less than 90 degrees; A preliminary design is carried out for the intersection region of the cross-optical waveguides, so that the initial structural parameters of the intersection region are less than 4 micrometers by 4 micrometers; The particle swarm optimization algorithm is used to optimize the initial structural parameters of the intersection region to change the material refractive index distribution in the intersection region. The algorithm obtains the material refractive index distribution in the intersection region when the light transmittance of the intersection waveguide is maximized and the structure of the intersection region satisfies the vertical and horizontal symmetry. The corresponding structural parameters of the intersection region are then used as the target structural parameters of the intersection region. The cross region of the cross optical waveguide is redesigned based on the target structural parameters; The objective function of the particle swarm optimization algorithm is established with the goal of maximizing the light transmittance of the cross-optical waveguide. The target structural parameters are obtained through the following steps: S1. Initialize the particle swarm: In the initially designed intersection area, several initial particles are randomly generated. Each particle represents a possible material refractive distribution, and each material refractive distribution corresponds to a structural parameter. S2. Calculate light transmittance: Calculate the light transmittance of the cross waveguide under each material refractive distribution, and evaluate the optimization degree according to the objective function; S3. Update particle velocity and position: Adjust the position of each particle according to its local optimum and the global optimum of the entire particle swarm, so as to converge toward the optimum. S4. Iterative optimization: Repeat steps S2 and S3 until the convergence condition is met and the optimal solution is obtained. The convergence condition is that the transmittance reaches a preset percentage or the number of iterations reaches a preset number. S5. Obtain the target structure parameters based on the optimal solution; The redesign of the cross region of the cross optical waveguide based on the target structural parameters includes: Replace the nanoscale feature regions within the intersection of the target structural parameters with rectangular units, and fix the length of the rectangular units at 2 micrometers, while allowing the width to vary in the range of 20 nanometers to 30 nanometers. Among them, the nanoscale feature region is the region with a line width of less than 10 nanometers within the intersection region, the initial structural parameters of the intersection region are 2 micrometers by 2 micrometers, and the target structural parameters are 2 micrometers by 1.45 micrometers.

2. The design method for on-chip cross-optical waveguides according to claim 1, characterized in that, The cross angle of the cross optical waveguide is 20°.

3. The design method for on-chip cross-optical waveguides according to claim 1, characterized in that, When the wavelength of the cross-optical waveguide is 1550 nanometers, the preset percentage is 95%.

4. An on-chip cross-waveguide, characterized in that, The on-chip cross-waveguide is designed using the design method for on-chip cross-waveguides as described in any one of claims 1 to 3.

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