CN-121978835-A - Design method of integrated multimode bent optical waveguide and integrated multimode bent optical waveguide

CN121978835ACN 121978835 ACN121978835 ACN 121978835ACN-121978835-A

Abstract

The invention discloses a design method of an integrated multimode bent optical waveguide and the integrated multimode bent optical waveguide, and belongs to the technical field of integrated optics. Aiming at the problem that the traditional multimode bent waveguide is difficult to achieve low loss and low crosstalk under the compact size, the invention constructs the waveguide model formed by cascading a plurality of sections of variable-width generalized Euler spiral curve elements. And (3) performing double-degree-of-freedom cooperative regulation and control on the curvature radius and the waveguide width of each section of curve element by using an iterative optimization algorithm based on mode field analysis, and obtaining the optimal geometric parameters with the aim of minimizing the full-mode loss. The waveguide structure breaks through the limitation of the traditional fixed width design, realizes low-loss and low-crosstalk transmission of multimode signals under the condition of extremely small bending radius, remarkably improves the tolerance of devices to manufacturing process deviation, and is suitable for high-density on-chip optical interconnection systems.

Inventors

JIANG RONGJIN
ZHANG LINGXIAO
Hu Luxing

Assignees

杭州太消科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (10)

1. A method of designing an integrated multimode bent optical waveguide, comprising the steps of: The method comprises the steps of constructing a structural model of a curved optical waveguide to be designed, wherein the structural model describes the geometric boundary of the waveguide by adopting a variable width free form curve, the variable width free form curve is composed of a plurality of sections of curve elements which are sequentially cascaded, and each section of curve element is configured to have curvature radius parameters and waveguide width parameters which are independently changed along with the path length; Determining all working modes transmitted by the bent optical waveguide, and defining all-mode loss evaluation indexes for all the working modes; Calculating the full-mode loss of the structural model under the current geometric parameters based on mode field analysis, and carrying out iterative optimization on the geometric parameters of each section of curve element by taking the full-mode loss as a target that the full-mode loss meets a preset threshold value until an optimal geometric parameter sequence is obtained; and generating a layout structure of the integrated multimode bent optical waveguide according to the optimal geometric parameter sequence.
2. The design method as set forth in claim 1, wherein the curve element is a broad width generalized euler spiral curve element; The curvature radius parameter which is changed independently along with the path length is expressed in that the curvature of the curve element is changed linearly along with the path length; The waveguide width parameter which is independently changed along with the path length is expressed in that the width of the curve element is linearly changed along with the path length.
3. The method of designing according to claim 2, wherein the geometric parameters of each of the curve elements include a start point radius of curvature, an end point radius of curvature, a start point width, an end point width, a curve element angle, and a curve element length; In the iterative optimization process, the curve element length is set to a fixed value, and at least one of the start point curvature radius, the end point curvature radius, the start point width, and the end point width is used as an adjustable optimization variable.
4. The design method of claim 1, wherein the full mode loss evaluation index includes full mode mismatch loss and full mode radiation loss; the full mode mismatch loss is defined as the maximum value of the mode mismatch loss of each order mode in all the working modes; the full mode radiation loss is defined as the maximum of radiation losses for each order mode of the all modes of operation.
5. The design method according to claim 4, wherein the iterative optimization process employs a directional-range binary search algorithm; The algorithm builds a merit function, wherein the merit function is configured as a logic function and is used for judging whether the current full-mode mismatch loss and the full-mode radiation loss are respectively lower than a set mismatch loss threshold and a set radiation loss threshold, and if the conditions are met, judging that the current geometric parameters are effective and continuously searching for a better solution or stopping iteration.
6. The design method of claim 1, further introducing a mode polarization ratio as a constraint in the iterative optimization process; And calculating the mode polarization ratio of each working mode under the current geometric parameter, and accepting the optimization result under the geometric parameter only when the mode polarization ratio meets the preset polarization purity requirement so as to inhibit modal hybridization.
7. The design method according to claim 1, wherein in the structural model, the width of the input port and the width of the output port of the curved optical waveguide connected with the external straight waveguide are equal; and the iterative optimization is to perform segment-by-segment optimization on the multiple segments of curve elements which are sequentially cascaded, wherein the end geometric parameter of the upper segment of curve element is used as a constraint condition of the start geometric parameter of the lower segment of curve element so as to maintain the continuity of the waveguide boundary.
8. The method of designing according to claim 1, wherein the material of the curved optical waveguide comprises one of silicon, silicon nitride, silicon dioxide, indium phosphide, gallium arsenide, silicon carbide, lithium niobate, or a polymer material; The structural form of the bent optical waveguide comprises a strip waveguide, a ridge waveguide or a multilayer waveguide.
9. An integrated multimode bent optical waveguide, characterized in that it is produced by the design method according to any one of claims 1 to 8; the geometric structure of the bent optical waveguide consists of a plurality of sections of cascaded wide-width generalized Euler spiral curve elements, the curvature radius and the waveguide width of each section of curve element continuously change along with an optical transmission path, and the whole bending angle range of the bent optical waveguide is 0-360 degrees.
10. The integrated multimode bent optical waveguide of claim 9, wherein said bent optical waveguide is configured to support at least three spatial mode transmissions; In a preset working wavelength range, the transmission loss of the bent optical waveguide to all supported space modes and the intermodal crosstalk between any two space modes are lower than preset indexes, and the bent optical waveguide has process tolerance for tolerating the manufacturing deviation of the waveguide width in the preset range.

Description

Design method of integrated multimode bent optical waveguide and integrated multimode bent optical waveguide Technical Field The invention belongs to the technical field of integrated optics, and particularly relates to a design method for an integrated multimode bent optical waveguide and the integrated multimode bent optical waveguide. Background With the explosive growth of large data and communication demands, conventional single-mode transmission systems face capacity bottlenecks. The mode multiplexing (Mode Division Multiplexing, MDM) technique, which uses multiple orthogonal modes in an optical waveguide as independent channels to transmit information in parallel, has become a key technique for improving communication capacity and on-chip interconnect bandwidth density. In MDM integrated photonic systems, curved optical waveguides are essential connection elements for achieving a compact layout with a turning optical path. However, the design of multimode bent optical waveguides faces serious challenges in that higher order modes are more prone to radiation leakage at the bends and that changes in phase matching conditions between different modes are highly prone to cause intermodal coupling (crosstalk), resulting in compromised signal integrity. The existing solutions mainly comprise: 1. The traditional arc or fixed curve design is simple in structure, but due to abrupt curvature or insufficient design freedom, radiation loss and intermodal crosstalk are difficult to simultaneously restrain under small-radius bending. 2. Auxiliary structures such as mode converters are added between the straight waveguide and the curved waveguide, or structures such as sub-wavelength gratings, side-wall mirrors, etc. are used. These methods tend to result in increased device size, complex fabrication processes (e.g., requiring high precision lithography), and may introduce additional scattering losses. 3. Conventional Free-Form Curve (FFC) designs, while introducing graded curvature, are mostly based on fixed waveguide widths or simple mathematical models (e.g., B-splines, standard euler spirals), still suffer from significantly limited design freedom when dealing with complex boundary conditions for multimode transmission, and lack efficient optimization algorithms for All-mode (All-modes) performance, resulting in high optimization costs or difficult convergence. Therefore, there is a need for a new multi-mode curved optical waveguide structure design that efficiently balances low loss, low crosstalk, compact size, and process tolerance with a large degree of design freedom. Disclosure of Invention The embodiment of the invention provides a design method of an integrated multimode bent optical waveguide and the integrated multimode bent optical waveguide, aiming at the problems that the existing multimode bent optical waveguide technology is limited by a fixed waveguide width or a single curvature change model, so that the design freedom degree is insufficient, the compact bending radius cannot be realized, the low loss and the low inter-mode crosstalk of all transmission modes are considered, and the technology is sensitive to manufacturing process errors. The core technology of the invention mainly adopts a free form curve formed by cascading a plurality of variable-width generalized Euler spiral curve elements to construct a waveguide model, and carries out double-degree-of-freedom iterative optimization on the curvature radius of each section of curve element and the waveguide width by a directed range binary search algorithm based on mode field analysis, thereby realizing low-loss and low-crosstalk transmission in a full working mode. In a first aspect, the present invention provides a method of designing an integrated multimode curved optical waveguide, the method comprising the steps of: Constructing a structural model of the curved optical waveguide to be designed, wherein the structural model describes the geometric boundary of the waveguide by adopting a variable width free form curve, the variable width free form curve consists of a plurality of sections of curve elements which are sequentially cascaded, and each section of curve element is configured to have curvature radius parameters and waveguide width parameters which are independently changed along with the path length; Determining all working modes transmitted by the bent optical waveguide, and defining all-mode loss evaluation indexes for all the working modes; calculating the full-mode loss of the structural model under the current geometric parameters based on the mode field analysis, and carrying out iterative optimization on the geometric parameters of each section of curve element by taking the full-mode loss as a target and taking the full-mode loss as a target until an optimal geometric parameter sequence is obtained; and generating a layout structure of the integrated multimode bent optical waveguide according to the optimal geometric pa