Method for defining mode mixing area

Abstract

The invention belongs to the technical field of integrated photoelectronics, and particularly relates to a method for defining a mode mixing region. The method comprises the following steps: S1, setting and scanning structural parameters; s2, calculating the effective refractive index of the target mode; s3, calculating an effective refractive index difference curve; s4, determining modal mixing points; s5, judging the refractive index difference change direction; s6, determining the boundary of the rapid change side; s7, determining the boundary of the other side; and S8, defining a mixing region. The invention has the following advantages: the invention provides a boundary judgment method based on the change trend of physical quantity (effective refractive index difference); according to the method, the manual subjective limit is eliminated, and the repeatability of the design process is enhanced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of integrated optoelectronics, and particularly relates to a method for defining a mode hybridization region. BACKGROUND

[0002] In integrated photonic devices, different guided modes often cause modal anti-crossing or strong coupling behavior due to structural changes, forming a so-called "hybridization region". Such a region has a significant impact on the transmission characteristics of the optical field, the modal purity, the device insertion loss, and the operating bandwidth. In the design of high-performance photonic devices (such as mode converters, multimode interferometers, and adiabatic waveguides), it is necessary to accurately identify and avoid such regions to ensure the controllability and robustness of modal evolution.

[0003] However, most existing methods rely on empirical interpretation or artificially set width windows, lacking a universal, repeatable, and physically based region definition mechanism. This is reflected in the papers D. Dai, Y. Tang, and J. E. Bowers, "Mode conversion in tapered submicron silicon ridge optical waveguides," Opt. Express, vol. 20, no. 12, pp. 13425-13439, May 2012, and T. L. Liang, X. Cheng, J. Shi, G. Wu, K. Xu, W. Rong, L. Lin, and W. Shao, "Analysis and design of compact adiabatic mode converters based on adiabatic mode evolutions," J. Lightwave Technol., vol. 41, no. 19, pp. 6356-6361, Oct. 2023. This becomes a key technical bottleneck that limits further performance improvement in automated optimization and intelligent design processes.

[0004] Therefore, it is crucial to develop a mode hybridization region definition method with clear physical definition and programmable implementation to improve the quality and efficiency of photonic device design. SUMMARY

[0005] The purpose of the present application is to provide a method for defining a mode hybridization region, which automatically calculates the physical boundaries of the region using modal coupling characteristics to accurately identify and avoid modal behavior.

[0006] The application is to realize the above-mentioned application purposes, and the technical solutions adopted are as follows: A mode mixing area definition method, comprising the following steps:

[0007] S1, structure parameter setting and scanning: setting the structure scanning parameters of the waveguide, selecting the variation range and step length of the waveguide width W; S2, calculating the effective refractive index of the target mode: performing eigenmode solving on the selected mode to the TE m and TM n modes, to obtain the effective refractive index under each width W and

[0008] S3, calculating the effective refractive index difference curve: calculating the effective refractive index difference of the two modes for all scanning points;

[0009]

[0010] S4, determining the mode mixing point: finding the waveguide width corresponding to the minimum value of Δn eff (W), denoted as the mode mixing point W hi ; at this point, the mode coupling is the strongest;

[0011] S5, judging the refractive index difference change direction: comparing the change rates of Δn eff (W) on the two sides of W hi and W hi , judging which side changes more drastically;

[0012] S6, determining the boundary of the fast change side: setting the maximum Δn max in the fast direction as Δn half , then the half growth value is:

[0013]

[0014] calculating the corresponding structure parameter W B of Δn half , as the boundary point of the fast direction;

[0015] S7, determining the boundary of the other side: based on the symmetry assumption, setting the other boundary as:

[0016] W sym = 2W hi -W B (3)

[0017] S8, defining the mixing area: the mode mixing area is finally defined as

[0018] W ∈ [min(W B ,W sym ), max(W B ,W sym )] (4)

[0019] Further, as a preferred technical solution of the present application, W∈[W min ,W max ] in S1, and the step is 0.005 μm-0.05 μm.

[0020] The present application also provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the mode mixing region definition method when executing the program.

[0021] The present application also provides a computer readable storage medium, which stores a computer program, wherein the computer program is executable on a processor to implement the steps of the mode mixing region definition method.

[0022] The mode mixing region definition method has the following technical effects compared with the prior art:

[0023] (1) a boundary judgment method based on the variation trend of physical quantity (effective refractive index difference) is provided;

[0024] (2) artificial subjective limits are eliminated, and the repeatability of the design process is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Fig. 1 is a schematic view of the cross section of a double-layer heat insulation mode converter in an embodiment of the present application;

[0026] Figure 2 Fig. 3 is a schematic view of the effective refractive index difference curve in an embodiment of the present application;

[0027] In the figure, the reference numerals are as follows: 1, first silicon core; 2, second silicon core; 3, cladding layer. DETAILED DESCRIPTION

[0028] The present application will be further explained in detail below with reference to the accompanying drawings, so that those skilled in the art can have a deeper understanding of the present application and can implement it. However, the following examples are only used to explain the present application, and do not limit the present application.

[0029] The "mode mixing region" refers to a parameter interval in which the effective refractive indices of two or more guided modes are very close to each other, and strong modal coupling occurs, during the variation of the waveguide structure parameters. In this interval, the energy exchange between modes is significant, and has a great influence on the device performance, which must be identified and controlled.

[0030] The method takes the waveguide width W as the independent variable, and identifies and defines the mode mixing region by analyzing the variation trend of the effective refractive index difference between different guided modes with W.

[0031] In practical implementation, to verify the effectiveness of the mode mixing region delineation method proposed in this invention, a typical photonic device—a double-layer adiabatic mode converter—is used as an example for detailed explanation and analysis. Taking a double-layer adiabatic mode converter as an example, as follows... Figure 1 As shown. The structure includes a first silicon core 1, a second silicon core 2, and a cladding layer 3, wherein the cladding layer 3 is made of SiO2 with a refractive index n. SiO2 =1.445, width is W bottom =9μm, thickness h0 =1250nm. The refractive index of both the first silicon core 1 and the second silicon core 2 is n. Si =3.455. The thickness of the first silicon core 1 is h1 = 200nm, and the width is w = 2W. side +W0. The second silicon core 2 has a thickness of h2 = 200 nm and a width of W0 = 1 μm, where W side The width of the side rib is denoted as W. The incident beam wavelength is set to 1.55 μm. This embodiment focuses on the control of the lateral structure of the first silicon core 1, with the specific scanning variable being the rib width W. side To explore its impact on modal coupling characteristics.

[0032] The TE2 and TM1 modes were selected as the target mode pair for analysis. These two modes have different polarization directions and lateral distribution characteristics, and strong coupling can occur when the waveguide structure parameters fall into a specific mixing region, which may lead to inter-mode energy interference. However, as long as the initial waveguide width and the terminal waveguide width are both outside the defined mode mixing region, the excitation of non-target modes can be effectively avoided, and efficient conversion between the TE2 and TM1 modes can be achieved.

[0033] This invention employs a method for defining a mixed-mode region, comprising the following steps:

[0034] S1. Structural Parameter Setting and Scanning: Set the waveguide structural scanning parameters, selecting the variation range and step size of the waveguide width W; adjust the waveguide width W... side The scan is performed within the range of [0.2, 1.2] μm with a step size of 0.01 μm;

[0035] S2. Calculate the effective refractive index of the target mode: For the selected mode pair TE m With TM n Perform eigenmode solving to obtain the effective refraction at various widths W. and The effective refractive indices of the TE2 and TM1 modes were calculated using FDTD.

[0036] S3. Calculate the effective refractive index difference curve: For all scan points, calculate the effective refractive index difference between the two modes;

[0037]

[0038] The effective refractive index difference curve is calculated by formula (1) as shown in Figure 2

[0039] S4, determine the mode mixing point: find the waveguide width corresponding to the minimum value of Δn eff (W), denoted as the mode mixing point W hi ; at this point, the mode coupling is the strongest; as shown in Figure 2 , at W side =0.6 μm, the refractive index difference between the two is the smallest, Δn eff =0.06, and it is determined that the mixing point W h1 =0.6 μm, at which the mode coupling is the strongest;

[0040] S5, determine the change direction of the refractive index difference: compare the change rates of Δn eff (W) on both sides of W hi W hi , and determine which side changes more drastically; in the direction of reducing W side , Δn eff increases to a maximum of 0.38, so this side is the side of drastic change;

[0041] S6, determine the boundary of the rapidly changing side: set the maximum Δn max in the rapid direction, then the half-increase value is:

[0042]

[0043] Calculate the structure parameter W half corresponding to Δn B , which is the boundary point of the rapid direction;

[0044] The intermediate refractive index difference Δn half is calculated by formula (2) as follows: 0.06+(0.38-0.06) / 2=0.22, and the waveguide width corresponding to this value is W B =0.2 μm;

[0045] S7, determine the other boundary: based on the symmetry assumption, set the other boundary as:

[0046] W sym =2W hi -W B (3)

[0047] The symmetric boundary is determined by formula (3) as W sym =2×0.6-0.2=1.0 μm;

[0048] S8, define the mixing region: the mode mixing region is finally defined as ​

[0049] W∈[min(W B ,W sym ),max(W B ,W sym )](4) Through formula (4), the finally defined mixed region is: W side ∈[0.2,1.0]μm.

[0050] Through the method of the application, in the coupling problem of TE2-TM1 mode pair, the mixed region boundary is clearly defined, thereby providing a reliable reference for subsequent adiabatic device design: as long as the initial and end width of the device does not fall into the interval [0.2μm, 1.0μm], the coupling interference caused by mode mixing can be avoided, and stable and efficient mode conversion is achieved.

[0051] The specific embodiments described above further illustrate the purposes, technical solutions and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and is not intended to limit the scope of the application. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the application shall fall within the scope of the application.

Claims

1. A method of defining a mode mixing region, characterized by, The method comprises the following steps: S1, structure parameter setting and scanning: setting the structure scanning parameters of the waveguide, selecting the variation range and step of the waveguide width W; S2, calculate the effective refractive index of the target mode: for the selected mode pair TE m vs. TM n Perform eigenmode solving to obtain the effective refractive index of each width W and S3, calculating the effective refractive index difference curve: for all scanning points, calculating the effective refractive index difference of the two modes; S4, determine the modal mixing point: find Δn eff The waveguide width corresponding to the minimum of Δn(W) is denoted as the modal mixing point W hi At this point, the modal coupling is the strongest; S5, judge the refractive index difference change direction: compare Δn eff (W) in W < W hi and W > W hi The rate of change on both sides, determine which side changes more sharply; S6, determine the boundary of the side of rapid change: set the maximum Δn in the rapid direction max Then the half growth value is: Compute Δn half Corresponding structure parameter W B is the fast direction boundary point; S7, determining the other side boundary: based on the symmetry assumption, setting the other side boundary as: W sym = 2W hi - W B (3) S8, defining the mixing region: the pattern mixing region is finally defined as W e [min(W B ,W sym ),max(W B ,W sym )] (4).

2. The method of claim 1, wherein S1 W ∈ [W min ,W max ] with a step size of 0.005 μm to 0.05 μm.

3. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor implements the steps of the mode mixing area determination method according to any one of claims 1 to 2 when executing the program.

4. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program implements the steps of the mode mixing area determination method according to any one of claims 1 to 2 when executed by the processor.

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