Design method and device and equipment of adiabatic coupling waveguide section of adiabatic coupler
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHONGXING PHOTONICS TECH CO LTD
- Filing Date
- 2020-08-19
- Publication Date
- 2026-06-02
Smart Images
Figure CN114077773B_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present invention relate to, but are not limited to, the field of silicon-based photonic integrated chip technology, and particularly to a method, apparatus, device, and computer-readable storage medium for designing an adiabatic coupling waveguide segment of an adiabatic coupler. Background Technology
[0002] "Adiabatic" refers to the phenomenon that when the parameters of a waveguide (or potential well) change slowly, the light field (wave function) that was originally in a certain mode (such as an eigenstate) remains in the corresponding mode (such as an eigenstate) after the change ends.
[0003] A thermally adiabatic coupler (ADC) is a structure in silicon-based photonic integrated circuits that can replace 2×2 multimode interference couplers or ordinary directional couplers, characterized by low loss and wide-range wavelength flatness. An adiabatic coupler can be divided into an input section, an adiabatic section, and an output section. The two waveguides in the input section are designed with one wide and one narrow, and are relatively far apart, with virtually no coupling; their function is only to determine the waveguide width and facilitate bending. The two waveguides in the output section are symmetrically separated, requiring only a sufficiently large waveguide bending radius to avoid loss. The adiabatic section constitutes the majority of the coupler's length.
[0004] However, due to the need to ensure process stability, the minimum spacing of the coupling waveguides in the thermal coupler cannot be too small. For example, when the minimum spacing of the coupling waveguides is above 300nm, the mass production performance of the thermal coupler is relatively consistent. As the spacing between the coupling waveguides increases, the coupling efficiency decreases, requiring a slower width change in the adiabatic section, resulting in a longer thermal coupler. If a linear parameter variation method is used to design the thermal coupler, the required length will be excessive, making it difficult to place in silicon-based photonic integrated chips. Therefore, a better design method is needed to reduce the length of the thermal coupler. Summary of the Invention
[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.
[0006] This invention provides a design method, apparatus, device, and computer-readable storage medium for the thermally insulated waveguide section of an thermally insulated coupler, which can reduce the length of the thermally insulated coupler while ensuring that the thermally insulated waveguide section meets the thermal insulation requirements.
[0007] In a first aspect, embodiments of the present invention provide a method for designing the adiabatic coupling waveguide section of an adiabatic coupler, comprising:
[0008] The initial parameters of the thermally coupled waveguide segment are obtained, and the initial model of the thermally coupled waveguide segment is determined based on the initial parameters. The initial model includes a first coupled waveguide and a second coupled waveguide, and a gap is provided between the first coupled waveguide and the second coupled waveguide.
[0009] The thermally coupled waveguide segment is divided into N small segments with equal gap widths, and the coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment is calculated, where N is a positive integer.
[0010] Obtain parameter curves, which correspond to the variation of the gap width with the length of the thermally coupled waveguide segment;
[0011] Obtain the length intervals of the N segments corresponding to the parameter curves, and combine the length intervals with the coupling efficiency to calculate the transmission efficiency of the current thermally coupled waveguide segment;
[0012] Modify the shape of the parameter curve to update the transmission efficiency of the thermally coupled waveguide segment.
[0013] In a second aspect, embodiments of the present invention also provide a processing apparatus, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the thermally coupled waveguide segment design method described in the first aspect above.
[0014] Thirdly, embodiments of the present invention also provide a computing device, including the processing apparatus described in the second aspect above.
[0015] Fourthly, embodiments of the present invention also provide a computer-readable storage medium storing computer-executable instructions for executing the thermally coupled waveguide segment design method described above.
[0016] This invention includes the following steps: obtaining initial parameters of an adiabatic coupled waveguide segment; determining an initial model of the adiabatic coupled waveguide segment based on the initial parameters; the initial model including a first coupled waveguide and a second coupled waveguide, with a gap between the first and second coupled waveguides; dividing the adiabatic coupled waveguide segment into N small segments with equal gap width intervals; calculating the coupling efficiency of the eigenmodes of each waveguide between each cross-section of the adiabatic coupled waveguide segment, where N is a positive integer; obtaining parameter curves, the parameter curves corresponding to the change in gap width with the length of the adiabatic coupled waveguide segment; obtaining the length intervals of the N small segments corresponding to the parameter curves; combining the length intervals with the coupling efficiency to calculate the transmission efficiency of the current adiabatic coupled waveguide segment; and modifying the shape of the parameter curves to update the transmission efficiency of the adiabatic coupled waveguide segment. According to the solution provided in the embodiments of the present invention, the thermally coupled waveguide segment corresponding to the parameter curve is divided into N small segments with equal gap widths. The coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment is calculated, and the length intervals of the N small segments corresponding to the parameter curve are obtained. The length intervals are combined with the coupling efficiency to calculate the transmission efficiency of the current thermally coupled waveguide segment. The shape of the thermally coupled waveguide segment is adjusted by modifying the shape of the parameter curve, thereby updating the transmission efficiency of the thermally coupled waveguide segment. Throughout the design process, a nonlinear parameter variation method is used to adjust the shape of the parameter curve. Therefore, compared to the related art which uses a linear parameter variation method to design the thermally coupled waveguide segment, the solution of the embodiments of the present invention can reduce the length of the thermally coupled waveguide segment while meeting the thermal insulation requirements, thereby reducing the length of the thermally coupled coupler.
[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description
[0018] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.
[0019] Figure 1 This is a schematic diagram of an adiabatic coupler that requires design according to an embodiment of the present invention;
[0020] Figure 2 This is a flowchart of a design method for the thermally adiabatic waveguide section of an thermally adiabatic coupler provided in one embodiment of the present invention;
[0021] Figure 3 This is a flowchart of a design method for the thermally adiabatic waveguide section of an thermally adiabatic coupler provided in another embodiment of the present invention;
[0022] Figure 4 This is a schematic diagram of a table method for obtaining a first mapping relationship provided in an embodiment of the present invention;
[0023] Figure 5 This is a flowchart of a design method for the thermally adiabatic waveguide section of an thermally adiabatic coupler provided in another embodiment of the present invention;
[0024] Figure 6 This is a cross-sectional view of the initial model and auxiliary model provided in one embodiment of the present invention;
[0025] Figure 7 This is a schematic diagram of an adiabatic coupled waveguide segment that requires design, provided in another embodiment of the present invention;
[0026] Figure 8 This is a schematic diagram of an optimized parameter curve provided in one embodiment of the present invention;
[0027] Figure 9 This is a graph showing the splitting ratio test results of a 3dB linear thermally adiabatic coupler with a thermally adiabatic coupling waveguide section length of 300μm.
[0028] Figure 10 The image shows the splitting ratio test results of a 3dB thermally adiabatic coupler with a waveguide section length of 250μm optimized using the design method of this invention. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0030] It should be noted that although a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0031] The thermally adiabatic coupler can be divided into an input section 100, a thermally adiabatic coupling waveguide section 200, and an output section 300, such as... Figure 1As shown, the two waveguides of the input segment 100 are designed with one wide and one narrow, and the two waveguides are far apart and have basically no coupling. They only serve to determine the waveguide width and bend closer together. The two waveguides of the output segment 300 are symmetrically separated, and only the waveguide bending radius needs to be large enough to avoid loss. The thermally adiabatic coupling waveguide segment 200 occupies the main part of the thermally adiabatic coupler. The thermally adiabatic coupling waveguide segment 200 includes a first coupling waveguide 210 and a second coupling waveguide 220 that are close to each other, and a gap 230 is provided between the first coupling waveguide 210 and the second coupling waveguide 220.
[0032] To ensure the stability of the manufacturing process, the minimum gap between the two coupled waveguides in the thermally coupled waveguide section of the thermally coupled coupler cannot be too small. For example, the performance of the thermally coupled coupler is relatively stable when the minimum gap between the two coupled waveguides is above 300 nm. When the gap between the two coupled waveguides increases, the coupling efficiency decreases, which requires a slower width change in the thermally coupled waveguide section to maintain the insulation requirements. This results in a longer thermally coupled coupler. If a linear parameter variation method is used to design the thermally coupled coupler, the required length will be too long, making it difficult to place in silicon-based photonic integrated chips.
[0033] To address the aforementioned technical problems, this invention provides a design method, apparatus, device, and computer-readable storage medium for an adiabatic coupler's adiabatic coupling waveguide segment. First, initial parameters of the adiabatic coupling waveguide segment are obtained. An initial model of the adiabatic coupling waveguide segment is determined based on these initial parameters. The initial model includes a first coupling waveguide and a second coupling waveguide, with a gap between them. Next, the adiabatic coupling waveguide segment corresponding to the parameter curve is divided into N small segments with equal gap widths. The coupling efficiency of each waveguide eigenmode between each cross-section of the adiabatic coupling waveguide segment is calculated. The length intervals of the N small segments corresponding to the parameter curve are obtained. The length intervals are combined with the coupling efficiency to calculate the current transmission efficiency of the adiabatic coupling waveguide segment. The shape of the adiabatic coupling waveguide segment is adjusted by modifying the shape of the parameter curve, thereby updating the transmission efficiency of the adiabatic coupling waveguide segment. Throughout the design process, a nonlinear parameter variation method was used to adjust the shape of the parameter curve. Therefore, compared with the linear parameter variation method used in related technologies to design the thermally coupled waveguide section, the solution of this invention can reduce the length of the thermally coupled waveguide section while meeting the thermal insulation requirements, thereby reducing the length of the thermally coupled coupler.
[0034] The embodiments of the present invention will be further described below with reference to the accompanying drawings.
[0035] like Figure 2 As shown, Figure 2This is a flowchart of a design method for an adiabatic coupling waveguide segment of an adiabatic coupler provided in an embodiment of the present invention. The design method includes, but is not limited to, steps S100, S200, S300, S400 and S500.
[0036] Step S100: Obtain the initial parameters of the thermally coupled waveguide segment, and determine the initial model of the thermally coupled waveguide segment based on the initial parameters. The initial model includes a first coupled waveguide and a second coupled waveguide, with a gap between the first coupled waveguide and the second coupled waveguide.
[0037] In one embodiment, the initial parameters of the thermally coupled waveguide segment include a first starting width and a first ending width of the first coupled waveguide, a second starting width and a second ending width of the second coupled waveguide, and a third starting width and a third ending width of the gap. Therefore, once the initial parameters of the thermally coupled waveguide segment are determined, the initial shape of the thermally coupled waveguide segment, i.e., the initial model, can be determined. Specifically, the first ending width of the first coupled waveguide and the second ending width of the second coupled waveguide are equal.
[0038] In one embodiment, the initial parameters of the thermally coupled waveguide segment can be determined based on the modal effective refractive index at the beginning of the segment, the minimum gap width limitation imposed by the manufacturing process on the end of the segment, and the beam splitting design target of the thermal coupler.
[0039] Step S200: Divide the thermally coupled waveguide segment into N small segments with equal gap widths, and calculate the coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment, where N is a positive integer.
[0040] In one embodiment, the thermally coupled waveguide segment is divided into N smaller segments with equal gap widths, wherein the width variation between each segment is Δg, and N = |W end -W start | / Δg,W end It is the starting width of the gap (i.e., the third starting width), W start The width at the end of the gap (i.e., the width at the third end) is the minimum width. When the width variation Δg is small, each segment can be considered to have a nearly constant width. After dividing the adiabatic coupled waveguide segment into N segments with equal gap widths, the coupling efficiency of each waveguide eigenmode between each cross-section of the adiabatic coupled waveguide segment can be calculated.
[0041] In one embodiment, numerical simulation can be performed using eigenmode expansion (EME) to calculate the waveguide eigenmodes of each segment and the coupling efficiency between the waveguide eigenmodes of two adjacent segments. This allows the coupling efficiency of each waveguide eigenmode between each cross section of the adiabatic coupled waveguide segment to be obtained, which facilitates subsequent steps in calculating the transmission efficiency.
[0042] Step S300: Obtain the parameter curve, which corresponds to the change in the gap width as the length of the thermally coupled waveguide segment changes.
[0043] In one embodiment, the parametric curve can be implemented in different ways, such as a circular arc splicing curve or a Bézier curve. The appropriate choice can be made according to the actual application. This embodiment does not make any specific limitation in this regard.
[0044] It is worth noting that the parameter curve corresponds to the change in gap width with the length of the thermally coupled waveguide segment. Therefore, the parameter curve can be considered to correspond to the edge shape of the first coupled waveguide in the gap, or the edge shape of the second coupled waveguide in the gap. Since the thermally coupled waveguide segment in the thermal coupler is symmetrical, the parameter curve corresponding to the edge shape of the first coupled waveguide in the gap and the parameter curve corresponding to the edge shape of the second coupled waveguide in the gap can be considered to be mirror images of each other. Therefore, once one parameter curve is determined, the other parameter curve can be obtained accordingly.
[0045] Step S400: Obtain the length intervals of N small segments corresponding to the parameter curves, combine the length intervals with the coupling efficiency, and calculate the transmission efficiency of the current adiabatic coupled waveguide segment.
[0046] In one embodiment, since the parameter curve corresponds to the edge shape of the coupled waveguide in the gap, and the N segments are obtained by dividing the thermally coupled waveguide segment into equal gap width intervals, the length intervals of the N segments corresponding to the parameter curve can be obtained, and the length intervals can be combined with the coupling efficiency to calculate the transmission efficiency of the current thermally coupled waveguide segment.
[0047] It is worth noting that since the parameter curve corresponds to the edge shape of the coupled waveguide in the gap, it can be considered that the parameter curve lies in a length-width coordinate system established according to the length direction of the thermally coupled waveguide segment and the width direction of the gap. Therefore, there are different ways to obtain the length intervals of N segments corresponding to the parameter curve. For example, the length intervals of N segments corresponding to the parameter curve can be obtained based on the coordinate system in which the parameter curve is located and combined with the coordinate information of the parameter curve in that coordinate system. Alternatively, the widths of the gaps before and after each segment can be interpolated to the parameter curve as independent variables to obtain two length positions corresponding to the widths of the gaps before and after, and the difference between the two length positions is the length interval of the current segment corresponding to the parameter curve.
[0048] In one embodiment, after obtaining the length intervals of N segments corresponding to the parametric curves, the length intervals can be assigned to each segment corresponding to the pre-calculated waveguide eigenmodes to determine the phase information of each waveguide eigenmode. For example, the front width W of each segment can be... i and the width W i+1 By interpolating this value as the independent variable into the parametric curve, the width W of each segment can be obtained. i Corresponding length position L i , and the width W i+1 Corresponding length position L i+1 The length interval of each segment is ΔL. i =L i+1 -L i (i = 1, 2, ..., N). Next, the length interval of each segment is ΔL. i By substituting the values into the pre-calculated waveguide eigenmodes of each segment, the phase information of the corresponding waveguide eigenmode can be determined. Then, by combining this phase information with the coupling efficiency of each waveguide eigenmode between each cross section to form a complete transmission matrix, the transmission efficiency of the current adiabatic coupled waveguide segment can be quickly obtained.
[0049] Step S500: Modify the shape of the parameter curve and update the transmission efficiency of the thermally coupled waveguide segment.
[0050] In one embodiment, since the parameter curve obtained in step S300 is not necessarily the optimal parameter curve, it is necessary to modify the shape of the parameter curve in order to update the transmission efficiency of the thermally coupled waveguide segment so that the transmission efficiency of the thermally coupled waveguide segment corresponding to the parameter curve can meet the design requirements.
[0051] In one embodiment, since the shape of the parameter curve is modified, the shape of the thermally coupled waveguide segment will also change accordingly. Therefore, the transmission efficiency of the thermally coupled waveguide segment needs to be updated accordingly in order to determine whether the transmission efficiency of the thermally coupled waveguide segment corresponding to the modified parameter curve meets the design requirements.
[0052] In one embodiment, when it is necessary to update the transmission efficiency of the thermally coupled waveguide segment, the length interval of each segment corresponding to the modified parameter curve is first obtained. Then, the length interval is assigned to each segment corresponding to the pre-calculated waveguide eigenmode to determine the phase information of each waveguide eigenmode. Finally, the coupling efficiency of each waveguide eigenmode between each cross section is combined to form a complete transmission matrix, thereby updating the transmission efficiency of the thermally coupled waveguide segment.
[0053] In one embodiment, by employing an adiabatic coupled waveguide segment design method including the aforementioned steps S100, S200, S300, S400, and S500, the adiabatic coupled waveguide segment corresponding to the parameter curve is divided into N small segments with equal gap widths during the design process. The coupling efficiency of each waveguide eigenmode between each cross-section of the adiabatic coupled waveguide segment is calculated, and the length intervals of the N small segments corresponding to the parameter curve are obtained. The length intervals are combined with the coupling efficiency to calculate the transmission efficiency of the current adiabatic coupled waveguide segment. The shape of the adiabatic coupled waveguide segment is adjusted by modifying the shape of the parameter curve, thereby updating the transmission efficiency of the adiabatic coupled waveguide segment. Throughout the design process, a nonlinear parameter variation method is used to adjust the shape of the parameter curve. Therefore, compared to the linear parameter variation method used in related technologies for designing adiabatic coupled waveguide segments, this embodiment can reduce the length of the adiabatic coupled waveguide segment while meeting the insulation requirements, thereby reducing the length of the adiabatic coupler.
[0054] Additionally, in one embodiment, reference is made to Figure 3 The initial model for determining the adiabatic coupled waveguide segment based on initial parameters in step S100 may include, but is not limited to, the following steps:
[0055] Step S110: Obtain a first mapping relationship based on the change relationship between the first starting width and the first ending width and the change relationship between the third starting width and the third ending width, or obtain a second mapping relationship based on the change relationship between the second starting width and the second ending width and the change relationship between the third starting width and the third ending width;
[0056] Step S120: Obtain the initial model of the thermally coupled waveguide segment based on the first mapping relationship or the second mapping relationship.
[0057] In one embodiment, determining the initial model of the thermally coupled waveguide segment requires first determining the relationship between the widths of the first and second coupled waveguides and their lengths, as well as the relationship between the width of the gap and the length of the thermally coupled waveguide segment. Specifically, it requires determining the relationship between the widths from the first starting point to the first ending point (w1(z), the widths from the second starting point to the second ending point (w2(z), and the widths from the third starting point to the third ending point (g(z))). Here, w1 is the width of the first coupled waveguide, w2 is the width of the second coupled waveguide, g is the width of the gap, and z is the length of the thermally coupled waveguide segment. Because the thermally coupled waveguide segment is symmetrical, w1(z) and w2(z) can be set to change in opposite directions simultaneously until they become identical. That is, the sum of w1(z) and w2(z) will remain constant. Therefore, in the specific design process, only one of w1(z) and w2(z) needs to be determined, thus reducing design time and improving design efficiency.
[0058] In one embodiment, intrinsic mode expansion can be used to design the adiabatic coupled waveguide segment. Since intrinsic mode expansion is relatively quick for length-scanning simulation of the structure of each segment of a given waveguide cross-section, a first mapping relationship w1(g) can be obtained first based on w1(z) and g(z), or a second mapping relationship w2(g) can be obtained first based on w2(z) and g(z). Then, an initial model of the adiabatic coupled waveguide segment can be obtained based on w1(g) or w2(g). Once w1(g) or w2(g) is determined, the shape of each waveguide cross-section that the optical signal passes through when propagating in the adiabatic coupled waveguide segment is determined (the width g of each gap corresponds to two specific waveguide widths w1 and w2). Therefore, the initial model of the adiabatic coupled waveguide segment can be determined. Then, in subsequent steps, the adiabatic coupled waveguide segment that meets the design requirements can be obtained by optimizing g(z).
[0059] In one embodiment, the first mapping relationship w1(g) or the second mapping relationship w2(g) can be obtained through linear parameter variation, or w1(g) or w2(g) can be obtained through nonlinear parameter variation. This embodiment does not specifically limit the method. For example, when obtaining w1(g) through nonlinear parameter variation, the following method can be used: Figure 4 The table shown illustrates the method for obtaining w1(g). The specific method is as follows: First, the parameters showing the variation of the width w1 of the first coupled waveguide with the width g of the gap are plotted as follows... Figure 4 The table shown is in the form of... Figure 4In the table shown, the row coordinates represent the scan of waveguide width variations, and the column coordinates represent the scan of gap width variations. Unfilled grid points represent w1-g parameters, while filled grid points represent the adiabatic length coefficients required for variations between two w1-g parameters. For each pair of adjacent w1-g parameters (including diagonally adjacent ones), the two waveguide cross-sections are integrated using an odd-even mode overlap integral to obtain two corresponding coupling efficiencies. These coupling efficiencies characterize the adiabatic length coefficients required for adiabatic variations between the two w1-g parameters. Therefore, by finding the shortest path in the table where the adiabatic length coefficients between the starting and ending grid point parameters of the adiabatic coupled waveguide segment are summed, the first mapping relationship w1(g) can be obtained. Figure 4 As shown, the grid points corresponding to w1[0] and g[0] are the starting grid points of the adiabatic coupled waveguide segment, and the grid points corresponding to w1[3] and g[3] are the ending grid points of the adiabatic coupled waveguide segment. Therefore, Figure 4 The dashed path in the diagram represents the first mapping relationship w1(g) with linear change, while the solid path represents the path with the minimum total adiabatic length coefficient with nonlinear change from the starting grid point parameter to the ending grid point parameter. At this time, based on the grid points filled with values that the solid path passes through, the total adiabatic length coefficient of the minimum path can be obtained as 1+1+2+1=5, that is, the first mapping relationship w1(g) with the shortest total adiabatic length can be obtained.
[0060] Additionally, in one embodiment, reference is made to Figure 5 The acquisition of the parameter curve in step S300 may include, but is not limited to, the following steps:
[0061] Step S310: Establish a length-width coordinate system corresponding to the length direction of the thermally coupled waveguide segment and the width direction of the gap;
[0062] Step S320: Randomly generate a parametric curve in the length-width coordinate system. The parametric curve is within the set length range and gap width range, and includes curve control points.
[0063] In one embodiment, the coordinates of the control points of the parametric curve are randomly generated, so the shape of the parametric curve is also random. Alternatively, a default parametric curve can be automatically generated by the system based on a preset length range and a preset gap width range. After generating the parametric curve, since this parametric curve is not necessarily the optimal one, its shape can be changed by adjusting the coordinates of the control points. Because the coordinates of the control points are a 2D array, they can be easily adjusted. For example, the coordinate values of the control points can be manually adjusted, or they can be adjusted by setting a system algorithm, such as automatically traversing the curve by setting a step size for value changes.
[0064] In another embodiment, modifying the shape of the parameter curve in step S500 may include, but is not limited to, the following steps:
[0065] The shape of the parametric curve can be modified by changing the coordinates of its control points.
[0066] In one embodiment, the shape of the parametric curve is modified by adjusting the coordinates of the curve control points. When the shape of the parametric curve changes, the shape of the corresponding thermally coupled waveguide segment also changes. In related technologies, when the shape of the thermally coupled waveguide segment changes, it is necessary to re-simulate and calculate the structure of the thermally coupled waveguide segment. However, in this embodiment, since the starting width and ending width of the thermally coupled waveguide segment remain unchanged (the first starting width and first ending width of the first coupled waveguide, the second starting width and second ending width of the second coupled waveguide, and the third starting width and third ending width of the gap all remain unchanged), the shape of the parametric curve is controlled by the curve control points. There is no need to rebuild the formula and coefficients of the parametric curve. The change in the shape of the parametric curve only affects the length interval of each of the N segments. Since the waveguide eigenmode of each segment and the coupling efficiency between the waveguide eigenmodes of two adjacent segments have already been calculated in step S400, it is only necessary to assign the length interval of each segment that has changed due to the change in the shape of the parametric curve to the already calculated waveguide eigenmode to quickly update the transmission efficiency of the thermally coupled waveguide segment.
[0067] In another embodiment, the thermally coupled waveguide section design method further includes, but is not limited to, the following steps:
[0068] The shape of the parameter curve is continuously modified until the transmission efficiency of the adiabatic coupled waveguide section meets the preset conditions, thus obtaining the corresponding optimal parameter curve.
[0069] In one embodiment, by continuously modifying the shape of the parameter curve and simulating the transmission efficiency of the thermally coupled waveguide segment corresponding to the shape of the parameter curve, until the transmission efficiency meets the preset conditions, the corresponding parameter curve is the preferred parameter curve, and the shape of the thermally coupled waveguide segment corresponding to the preferred parameter curve is the optimal shape.
[0070] In one embodiment, the preset condition can be that the transmission efficiency is greater than a certain preset threshold. The transmission efficiency of the adiabatic coupled waveguide segment meets the preset condition, which means that the mode loss of the adiabatic coupled waveguide segment is very low, and the odd and even modes of the adiabatic coupled waveguide segment remain adiabatic.
[0071] In another embodiment, continuously modifying the shape of the parameter curve may include, but is not limited to, the following steps:
[0072] The shape of the parametric curve is optimized by modifying the coordinates of the control points of the curve using an optimization algorithm.
[0073] In one embodiment, to improve the optimization speed, the parameter curve can be modified and optimized using an optimization algorithm, such as particle swarm optimization (PSO) or a neural network algorithm.
[0074] It is worth noting that Particle Swarm Optimization (PSO) is a population-based search process where each individual, called a particle, is defined as a potential solution to the problem in a multidimensional search space. Each particle stores its historical best position, the best positions of all particles, and its velocity. In each generation, the information from the particles is combined to adjust the velocity components in each dimension, which are then used to calculate the new particle position. Particles continuously change their states in the multidimensional search space until they reach equilibrium or an optimal state, or until computational limitations are exceeded.
[0075] In one embodiment, when the particle swarm optimization algorithm is used to optimize the parameter curve, the coordinates of the curve control points are first used as random initialization particles to initialize the population and velocity. Then, the individual extreme value and the population extreme value are found by calculating the transmission efficiency of the corresponding adiabatic coupled waveguide segment. The velocity and position of the individual are continuously updated until the termination condition is met, and the coordinates of the curve control points corresponding to the transmission efficiency of the optimal adiabatic coupled waveguide segment are obtained, thereby determining the corresponding parameter curve and the shape of the adiabatic coupled waveguide segment.
[0076] In one embodiment, when using a neural network algorithm to optimize the parameter curve, the initial parameters of the thermally coupled waveguide segment—namely, the first starting width and first ending width of the first coupled waveguide, the second starting width and second ending width of the second coupled waveguide, and the third starting width and third ending width of the gap—are first input into a trained neural network algorithm to obtain the parameter curve corresponding to the optimal transmission efficiency of the thermally coupled waveguide segment. The training of the neural network model requires constructing a training set, which includes the initial parameters of multiple thermally coupled waveguide segments and their corresponding parameter curves for optimal transmission efficiency.
[0077] The aforementioned particle swarm optimization algorithm and neural network algorithm are known techniques to those skilled in the art, and will not be elaborated upon here.
[0078] In another embodiment, the thermally coupled waveguide section design method further includes, but is not limited to, the following steps:
[0079] An auxiliary model is obtained based on the initial model, and both the initial model and the auxiliary model correspond to the parameter curves.
[0080] In one embodiment, to address the issue of processing tolerance during the production process, reference is made to... Figure 6 The corresponding auxiliary model can be obtained by changing the height of the waveguide. Since both the initial model and the auxiliary model correspond to the parameter curve, when modifying the parameter curve, it is necessary not only for the transmission efficiency of the adiabatic coupled waveguide section in the initial model to meet the preset conditions (i.e., the adiabatic conditions), but also for the transmission efficiency of the adiabatic coupled waveguide section in the auxiliary model to meet the preset conditions. Therefore, the robustness of the design can be improved.
[0081] In one embodiment, an auxiliary model can be obtained based on the initial model by changing the heights of the two waveguides in the thermally coupled waveguide section, or by changing the height of the bottom planar waveguide, or by decreasing or increasing the width of the two waveguides in the thermally coupled waveguide section by a fixed value compared to a predetermined value, to simulate the waveguide physical shape deviations that may occur during chip fabrication. It is worth noting that the number of auxiliary models can be one or more, and can be appropriately selected according to the actual application; this embodiment does not impose a specific limitation on this.
[0082] In one embodiment, the initial model and the auxiliary model are of equal length, and therefore can be simultaneously and consistently divided into N small segments with equal gap widths. Then, the coupling efficiency of each waveguide eigenmode between each cross-section of the initial model and the auxiliary model is calculated. After calculating the coupling efficiency of each waveguide eigenmode between each cross-section of the initial model and the auxiliary model, the following steps are performed for both the initial model and the auxiliary model: obtain the length intervals of the N small segments corresponding to the parameter curves, combine the length intervals with the coupling efficiency, and calculate the transmission efficiency of the current adiabatic coupled waveguide segment. Therefore, the transmission efficiency of the adiabatic coupled waveguide segment corresponding to the initial model and the adiabatic coupled waveguide segment corresponding to the auxiliary model can be obtained.
[0083] In one embodiment, after obtaining the transmission efficiency of the adiabatic coupled waveguide segment corresponding to the initial model and the transmission efficiency of the adiabatic coupled waveguide segment corresponding to the auxiliary model, the shape of the parameter curve can be modified to synchronously update the transmission efficiency of the initial model and the auxiliary model. Only when the transmission efficiency of the initial model and the auxiliary model both meet the design requirements is the corresponding parameter curve the optimal parameter curve.
[0084] In another embodiment, the thermally coupled waveguide section design method further includes, but is not limited to, the following steps:
[0085] The shape of the parameter curve is continuously modified until the transmission efficiency of both the initial model and the auxiliary model meets the preset conditions, thus obtaining the corresponding optimal parameter curve.
[0086] In one embodiment, by continuously modifying the shape of the parameter curve and simulating the transmission efficiency of the initial model and auxiliary model corresponding to the shape of the parameter curve, until the transmission efficiency of the initial model and auxiliary model both meet the preset conditions, the corresponding parameter curve is the preferred parameter curve.
[0087] In one embodiment, since adjusting the parameter curve requires simultaneously satisfying the transmission efficiency of both the initial model and the auxiliary model, and the auxiliary model is an error model of the initial model, different weights can be applied to the transmission efficiency of the initial model and the auxiliary model respectively to obtain a weighted average of the transmission efficiency, which is then recorded as the average transmission efficiency. Therefore, by continuously adjusting the coordinates of the control points of the parameter curve and optimizing its shape, until the average transmission efficiency meets a preset condition, such as reaching or exceeding a preset efficiency threshold, the corresponding optimal parameter curve can be obtained, thereby achieving a thermally coupled waveguide section that meets the design requirements.
[0088] To more clearly illustrate the processing flow of the thermally coupled waveguide segment design method in the above embodiments, a specific example is provided below.
[0089] Example 1:
[0090] A waveguide structure with a core layer height of 220nm and a planar waveguide height of 150nm is designed as follows: Figure 1 The thermally adiabatic waveguide section of the 3dB beam splitter shown has a length of L = 250 μm.
[0091] The entire design process can be divided into six steps: Steps one to three are used to determine the model parameters of the thermally coupled waveguide section; Step four is used to establish the thermally coupled waveguide section model; Step five is used to match the thermally coupled waveguide section model with the parameter curves; and Step six is used to optimize the parameter curves.
[0092] In this example, the thermally adiabatic waveguide section of the 3dB beam splitter thermally adiabatic coupler is as follows: Figure 7 As shown, there are three main parameters: waveguide width w (w1 and w2), gap width g, and waveguide length z. Therefore, the relationship between w and g can be determined first, and then the relationship between g and z can be determined to fully determine the parameters of the thermally coupled waveguide segment.
[0093] Step 1: Determine the first starting width w1(0) and the first ending width w1(L) of the first coupled waveguide, the second starting width w2(0) and the second ending width w2(L) of the second coupled waveguide, and the third starting width g(0) and the third ending width g(L) of the gap, where L is the length of the thermally coupled waveguide segment (i.e. the length of the first coupled waveguide and the second coupled waveguide).
[0094] Since the thermal coupler is a 3dB splitter, w1(L) and w2(L) are equal, i.e., w1(L) = w2(L) = (w1(0) + w2(0)) / 2. g(0) requires that the effective refractive index of the odd and even modes be equal to the effective refractive index of the single waveguide itself (i.e., the two waveguides are not coupled). In addition, g(L) is limited by the consistency of the manufacturing process. Therefore, g(L) is the minimum acceptable gap width.
[0095] Step 2: Determine the relationship between the waveguide width and the gap width from the starting end to the ending end, w1(g) or w2(g).
[0096] Where w1(g) and w2(g) can be linear changes, or they can adopt a linear variation, such as... Figure 4 The table shown illustrates the method for obtaining the waveguide width, which will not be elaborated upon here. Once the relationship between the waveguide width and the gap width from the starting end to the ending end, w1(g) or w2(g), is determined, the initial model of the thermally coupled waveguide segment can be obtained.
[0097] Step 3: Considering manufacturing tolerances, based on the initial model, generate two auxiliary models with different waveguide heights by changing the heights of the two waveguides in the adiabatic coupled waveguide segment, such as... Figure 6 As shown, three simulation structures of the thermally coupled waveguide section are obtained.
[0098] Step 4: Simultaneously divide the three simulation structures into N small segments with equal gap width Δg, and calculate the waveguide eigenmodes of each segment and the coupling efficiency between the waveguide eigenmodes of adjacent segments using eigenmode expansion. It is worth noting that when dividing the initial model, it is also necessary to divide the two auxiliary models simultaneously at the same location; therefore, the coupling efficiency of the three simulation structures can be calculated simultaneously.
[0099] Step 5: Obtain the parameter curves within a preset length range and a preset gap width range in the gz coordinate system, as well as the curve control points used to control the shape of the parameter curves. These parameter curves correspond to changes in gz. Based on the start and end gap values of the N segments, obtain the length interval Δz of the N segments corresponding to the adjusted parameter curves through interpolation. Then, assign this length interval Δz to each segment corresponding to the pre-calculated waveguide eigenmode to obtain the corresponding phase information. Next, based on the phase information and coupling efficiency corresponding to the length interval Δz, the transmission efficiency of the three simulation structures can be obtained, thus allowing for faster updates to the even and odd mode transmission efficiencies of these three simulation structures.
[0100] Step Six: The transmission efficiencies of the three simulation structures are weighted differently to obtain a weighted average, which is then recorded as the average transmission efficiency. By changing the coordinates of the curve control points to adjust the shape of the parameter curve, the average transmission efficiency of the simulation structure corresponding to different parameter curves (i.e., g(z)) can be calculated relatively quickly. Based on this average transmission efficiency, the parameter curve is modified until the corresponding average transmission efficiency is better than the preset efficiency threshold required by the design. For example, if the average transmission efficiency reaches or exceeds the preset efficiency threshold, the corresponding optimal parameter curve can be obtained. Figure 8 As shown, Figure 8 This represents the optimized parametric curve (i.e., g(z)). It's worth noting that when changing the coordinates of the curve's control points to adjust the shape of the parametric curve, particle swarm optimization algorithms or neural network models can be used to find the optimal control points or optimize the parametric curve until the evaluation function is better than the target optimized parameters.
[0101] like Figure 9 and Figure 10 As shown, Figure 9 The image shows the splitting ratio test results for a 3dB linear thermally adiabatic coupler with a thermally adiabatic coupling waveguide section length of 300μm. Figure 10 The image shows the splitting ratio test results for a 3dB thermally adiabatic coupler with an optimized adiabatic waveguide section length of 250μm, obtained using the method described in this example. (Comparison) Figure 9 and Figure 10 The test results show that even though the length of the thermally coupled waveguide segment in the 3dB linear thermally adiabatic coupler is 300μm, it still does not meet the thermal insulation requirements. However, the 3dB thermally adiabatic coupler optimized using the thermally coupled waveguide segment design method in this example has a thermally coupled waveguide segment length of only 250μm, but the spectral ratio is close to 3dB, thus exhibiting better thermal insulation performance. Therefore, using the thermally coupled waveguide segment design method in this example allows for the reduction of the length of the thermally coupled waveguide segment while still meeting the thermal insulation requirements, thereby reducing the overall length of the thermally adiabatic coupler.
[0102] In addition, one embodiment of the present invention provides a processing apparatus, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor.
[0103] The processor and memory can be connected via a bus or other means.
[0104] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.
[0105] The non-transient software program and instructions required to implement the thermally coupled waveguide segment design method of the above embodiments are stored in memory. When executed by a processor, the thermally coupled waveguide segment design method of the above embodiments is executed, for example, the method described above is executed. Figure 2 Method steps S100 to S500 Figure 3 Method steps S110 to S120, Figure 5 Method steps S310 to S320.
[0106] In addition, one embodiment of the present invention provides a computing device, which includes the processing unit as described in the above embodiment. The computing device can be a local computing device such as a personal computer, tablet, or mobile phone, or a cloud computing device such as a cloud server, local area network server, or cloud host.
[0107] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.
[0108] Furthermore, one embodiment of the present invention provides a computer-readable storage medium storing computer-executable instructions that are executed by a processor or controller, for example, by a processor in the above-described processing device embodiment, causing the processor to perform the thermally coupled waveguide segment design method described above, for example, performing the above-described... Figure 2 Method steps S100 to S500 Figure 3 Method steps S110 to S120, Figure 5 Method steps S310 to S320.
[0109] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.
[0110] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.
Claims
1. A method for designing the adiabatic coupling waveguide section of an adiabatic coupler, comprising: The initial parameters of the thermally coupled waveguide segment are obtained, and the initial model of the thermally coupled waveguide segment is determined based on the initial parameters. The initial model includes a first coupled waveguide and a second coupled waveguide, and a gap is provided between the first coupled waveguide and the second coupled waveguide. The thermally coupled waveguide segment is divided into N small segments with equal gap widths, and the coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment is calculated, where N is a positive integer. Obtain parameter curves, which correspond to the variation of the gap width with the length of the thermally coupled waveguide segment; Obtain the length intervals of the N segments corresponding to the parameter curves, and combine the length intervals with the coupling efficiency to calculate the transmission efficiency of the current thermally coupled waveguide segment; Modify the shape of the parameter curve to update the transmission efficiency of the thermally coupled waveguide segment; The step of dividing the thermally coupled waveguide segment into N smaller segments with equal gap width intervals means dividing the thermally coupled waveguide segment into N smaller segments along its extension direction, using the consistency of the gap width variation between the first and second coupled waveguides in the thermally coupled waveguide segment as the dividing criterion.
2. The design method for the thermally coupled waveguide section according to claim 1, characterized in that, The initial parameters include the first starting width and the first ending width of the first coupled waveguide, the second starting width and the second ending width of the second coupled waveguide, and the third starting width and the third ending width of the gap; Determining the initial model of the adiabatic coupled waveguide segment based on the initial parameters includes: A first mapping relationship can be obtained based on the relationship between the first starting width and the first ending width and the relationship between the third starting width and the third ending width; or a second mapping relationship can be obtained based on the relationship between the second starting width and the second ending width and the third starting width and the third ending width. The initial model of the thermally coupled waveguide segment is obtained based on the first mapping relationship or the second mapping relationship.
3. The design method for the thermally coupled waveguide section according to claim 1, characterized in that, The calculation of the coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment includes: The coupling efficiency of each waveguide eigenmode between each cross section of the adiabatic coupled waveguide segment is obtained by calculating the waveguide eigenmode of each segment and the coupling efficiency between the waveguide eigenmodes of two adjacent segments through eigenmode expansion.
4. The design method for an adiabatic coupled waveguide section according to claim 1, characterized in that, The acquisition of parameter curves includes: Establish a length-width coordinate system corresponding to the length direction of the thermally coupled waveguide segment and the width direction of the gap; A parametric curve is randomly generated in the length-width coordinate system. The parametric curve is within a set length range and gap width range, and includes curve control points.
5. The design method for an adiabatic coupled waveguide section according to claim 1, characterized in that, The step of obtaining the length intervals of the N segments corresponding to the parameter curve includes: The width of the front and rear gaps of each segment is used as an independent variable to interpolate to the parameter curve, resulting in two length positions corresponding to the width of the front and rear gaps. The difference between the two length positions is the length interval of the current segment corresponding to the parameter curve.
6. The design method for an adiabatic coupled waveguide section according to claim 1 or 5, characterized in that, The step of combining the length interval with the coupling efficiency to calculate the transmission efficiency of the current thermally coupled waveguide segment includes: The length interval is assigned to each of the small segments corresponding to each pre-calculated waveguide eigenmode to determine the phase information of each waveguide eigenmode. The coupling efficiency of each waveguide eigenmode between the cross sections is combined to form a complete transmission matrix, thereby obtaining the transmission efficiency of the current adiabatic coupled waveguide segment.
7. The design method for an adiabatic coupled waveguide section according to claim 1, characterized in that, Updating the transmission efficiency of the thermally coupled waveguide segment includes: Obtain the length interval of each segment corresponding to the modified parameter curve, assign the length interval to each segment corresponding to each pre-calculated waveguide eigenmode to determine the phase information of each waveguide eigenmode, combine the coupling efficiency of each waveguide eigenmode between each cross section to form a complete transmission matrix, and update the transmission efficiency of the adiabatic coupled waveguide segment.
8. The design method for the thermally coupled waveguide section according to claim 4, characterized in that, Modifying the shape of the parameter curve includes: The shape of the parametric curve is modified by changing the coordinates of the curve control points.
9. The design method for an adiabatic coupled waveguide section according to claim 4, characterized in that, Also includes: The shape of the parameter curve is continuously modified until the transmission efficiency of the thermally coupled waveguide segment meets the preset conditions, thereby obtaining the corresponding optimal parameter curve.
10. The design method for an adiabatic coupled waveguide section according to claim 9, characterized in that, The continuous modification of the shape of the parameter curve includes: The shape of the parametric curve is optimized by modifying the coordinates of the control points of the curve using an optimization algorithm.
11. The design method for an adiabatic coupled waveguide section according to claim 1, characterized in that, It also includes, An auxiliary model is obtained based on the initial model, and both the initial model and the auxiliary model correspond to the parameter curve. The step of dividing the thermally coupled waveguide segment into N small segments with equal gap widths and calculating the coupling efficiency of each waveguide eigenmode between each cross section of the thermally coupled waveguide segment includes: The initial model and the auxiliary model are divided into N segments with equal gap widths, and the coupling efficiency of each waveguide eigenmode between each cross section of the initial model and the auxiliary model is calculated.
12. The design method for an adiabatic coupled waveguide section according to claim 11, characterized in that, Modifying the shape of the parameter curve and updating the transmission efficiency of the thermally coupled waveguide segment includes: Modify the shape of the parameter curve to update the transmission efficiency of the initial model and the auxiliary model.
13. The design method for an adiabatic coupled waveguide section according to claim 12, characterized in that, Also includes: The shape of the parameter curve is continuously modified until the transmission efficiency of both the initial model and the auxiliary model meets the preset conditions, thereby obtaining the corresponding optimal parameter curve.
14. A processing apparatus, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, when the processor executes the computer program, it implements the thermally coupled waveguide segment design method as described in any one of claims 1 to 13.
15. A computing device, characterized in that, It includes the processing apparatus as described in claim 14.
16. A computer-readable storage medium storing computer-executable instructions for performing the thermally coupled waveguide segment design method according to any one of claims 1 to 13.