CN113311537B - Polymer three-mode multiplexer based on cascade conical coupler - Google Patents

Polymer three-mode multiplexer based on cascade conical coupler Download PDF

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CN113311537B
CN113311537B CN202110690128.5A CN202110690128A CN113311537B CN 113311537 B CN113311537 B CN 113311537B CN 202110690128 A CN202110690128 A CN 202110690128A CN 113311537 B CN113311537 B CN 113311537B
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CN113311537A (en
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尚玉玲
郭文杰
何翔
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Guilin University of Electronic Technology
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/14—Mode converters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers

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Abstract

The invention provides a polymer three-mode multiplexer based on a cascade tapered coupler, which comprises an input straight waveguide, a few-mode tapered waveguide, a single-mode tapered waveguide, an S-shaped bent waveguide and an output straight waveguide, wherein the S-shaped bent waveguide is used for waveguide approaching and separating, and when a basic mode is respectively input from three input straight waveguides and passes through the single-mode tapered waveguide along the S-shaped bent waveguide, the basic mode is respectively transmitted in the few-mode tapered waveguide by a second-order mode, a basic mode and a third-order mode through mode evolution of the few-mode tapered waveguide and the single-mode tapered waveguide, so that the multiplexing of the three modes is realized. The multiplexer has the advantages of high mode conversion efficiency, low extra loss and large bandwidth, and is expected to be applied to a mode division multiplexing system in board-level optical interconnection.

Description

Polymer three-mode multiplexer based on cascade conical coupler
Technical Field
The invention relates to a mode multiplexer, in particular to a polymer three-mode multiplexer based on a cascade taper coupler.
Background
With the increasing demand for large-capacity data transmission of on-board electronic systems, large-capacity and high-performance information transmission between modules becomes one of the key challenges. The Modular Division Multiplexing (MDM) technology can effectively expand the data capacity of a transmission channel, and is a promising method for realizing board-level large-capacity information transmission. The mode multiplexer/demultiplexer is a key component in a mode division multiplexing system. Mode (de) multiplexers based on different structures have been proposed, including asymmetric Y-branches, multimode interference (MMI), Directional Coupling (DC), multimode gratings and adiabatic mode evolution, etc. The cascade-based asymmetric Y-branch waveguide mode multiplexer realizes mode conversion between a basic mode and a high-order mode by controlling the size of a Y-branch arm. These structures require further improvements in the manufacturing process to minimize modal crosstalk and loss. Mode (de) multiplexers based on multi-mode interference can provide a small footprint, a wide bandwidth and low loss, but such designs are complex and their manufacturing tolerances are small. According to the traditional directional coupling principle, the mode multiplexer based on planar directional coupling and non-planar directional coupling can respectively realize the coupling between symmetrical and asymmetrical modes in the vertical direction. However, the mode multiplexer based on the directional coupling or the asymmetric directional coupling needs to operate under an accurate phase matching condition, and thus its performance is sensitive to a size variation. Tapered couplers are a potential choice due to their relaxed manufacturing tolerances and wide operating bandwidth. Many mode (de) multiplexers are currently more suitable for on-chip optical communications. Mode multiplexers applied to board level optical interconnects have not been widely investigated. Multimode polymer waveguides are widely used in the design and fabrication of waveguide devices because they can be directly integrated into conventional PCBs and have loose alignment tolerances to be an excellent transmission medium for board-level optical interconnects. Recently, several polymer mode multiplexers applicable to board-level optical interconnects have been proposed to achieve mode conversion and multiplexing of the fundamental mode and the second-order mode, but they are based on precise dimensional design, including waveguide size and waveguide relative position, and thus have certain complexity and difficulty in device fabrication. A mode multiplexer based on the principle of adiabatic mode evolution is a popular solution because it can provide a certain margin for preparation. More mode conversion and multiplexing are to be investigated for large capacity transport of optical interconnects on board. Therefore, the research on the high-performance polymer mode multiplexer applied to the board-level optical interconnection is of great significance.
Disclosure of Invention
In order to solve the above problems, the present invention provides a polymer three-mode multiplexer based on a cascaded tapered coupler, which includes a first input straight waveguide, a second input straight waveguide, a third input straight waveguide, a first few-modeThe waveguide comprises a tapered waveguide, a second few-mode tapered waveguide, a first single-mode tapered waveguide, a second single-mode tapered waveguide, a first S-shaped curved waveguide, a second S-shaped curved waveguide, a third S-shaped curved waveguide, a fourth S-shaped curved waveguide, a first output straight waveguide, a second output straight waveguide and a third output straight waveguide. The first few-mode tapered waveguide, the second few-mode tapered waveguide, the first single-mode tapered waveguide and the second single-mode tapered waveguide are respectively provided with a small head end and a large head end; the first input straight waveguide width is equal to the first S-shaped curved waveguide width, the first S-shaped curved waveguide width is equal to the first single-mode tapered waveguide big end width, the second S-shaped curved waveguide width is equal to the first single-mode tapered waveguide small end width, the first output straight waveguide width is equal to the second S-shaped curved waveguide width, the second input straight waveguide width is equal to the first few-mode tapered waveguide width small end width, the first few-mode tapered waveguide big end width is equal to the second few-mode tapered waveguide small end width, the second few-mode tapered waveguide big end width is equal to the second output waveguide width, the third input straight waveguide width is equal to the third S-shaped curved waveguide width, the third S-shaped curved waveguide width is equal to the second single-mode tapered waveguide big end width, the second single-mode tapered waveguide small end width is equal to the fourth S-shaped curved waveguide width, the width of the third output waveguide is equal to that of the fourth S-shaped bent waveguide; the first input straight waveguide height, the first S-shaped curved waveguide height, the first single-mode tapered waveguide height, the second S-shaped curved waveguide height, the first output straight waveguide height, the third input straight waveguide height, the third S-shaped curved waveguide height, the second single-mode tapered waveguide height, the fourth S-shaped curved waveguide height and the third output straight waveguide height are equal, the second input straight waveguide height, the first few-mode tapered waveguide height, the second few-mode tapered waveguide height and the second output straight waveguide height are equal, the initial end of the first input waveguide is the first input end of the three-mode multiplexer, the tail end of the first input straight waveguide is connected with the initial end of the first S-shaped curved waveguide, and the tail end of the first S-shaped curved waveguide is connected with the large head end of the first single-mode tapered waveguideThe small end of the first single-mode tapered waveguide is connected with the start end of a second S-shaped curved waveguide, the end of the second S-shaped curved waveguide is connected with the start end of a first output waveguide, the end of the first output waveguide is the first output end of the three-mode multiplexer, the start end of the second input waveguide is the second input end of the three-mode multiplexer, the end of the second input waveguide is connected with the small end of the first few-mode waveguide, the large end of the first few-mode waveguide is connected with the small end of the second few-mode waveguide, the large end of the second few-mode waveguide is connected with the start end of the second output waveguide, the end of the second output waveguide is the second output end of the three-mode multiplexer, and the start end of the third input waveguide is the third input end of the three-mode multiplexer; the end of the third input straight waveguide is connected with the beginning of the third S-shaped curved waveguide, the end of the third S-shaped curved waveguide is connected with the big head end of the second single-mode tapered waveguide, the small head end of the first single-mode tapered waveguide is connected with the beginning of the fourth S-shaped curved waveguide, the end of the fourth S-shaped curved waveguide is connected with the beginning of the third output waveguide, and the end of the third output waveguide is the third output end of the three-mode multiplexer. The first single-mode tapered waveguide is arranged on the right side of the first few-mode tapered waveguide, the distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2-4 mu m, the second single-mode tapered waveguide is arranged on the left side of the second few-mode tapered waveguide, and the distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide is 3-5 mu m; marking the width of the first input straight waveguide, the width of the first S-shaped bent waveguide and the width of the big head end of the first single-mode tapered waveguide as W1aThe width of the small end of the first single-mode tapered waveguide, the width of the second S-shaped curved waveguide and the width of the first output straight waveguide are recorded as W1bThe width of the second input straight waveguide and the width of the small end of the first few-mode tapered waveguide are recorded as W2aThe width of the big end of the first few-mode tapered waveguide is marked as W2bThe width of the small end of the second few-mode tapered waveguide is recorded as W3aSaid second few-mode tapered waveguideThe width of the big end and the width of the second output straight waveguide are marked as W3bThe width of the third input straight waveguide, the width of the third S-shaped bent waveguide and the width of the big end of the second single-mode tapered waveguide are marked as W4aThe width of the small end of the second single-mode tapered waveguide, the width of the fourth S-shaped curved waveguide and the width of the third output straight waveguide are recorded as W4b， W3b> W3a> W2a> W2b> W1a> W1b> W4a> W4bThe height of the first input straight waveguide, the height of the first S-shaped curved waveguide, the height of the first single-mode tapered waveguide, the height of the second S-shaped curved waveguide, the height of the first output straight waveguide, the height of the third input straight waveguide, the height of the third S-shaped curved waveguide, the height of the second single-mode tapered waveguide, the height of the fourth S-shaped curved waveguide and the height of the third output straight waveguide are recorded as H1The height of the second input straight waveguide, the height of the first few-mode tapered waveguide, the height of the second few-mode tapered waveguide and the height of the second output straight waveguide are recorded as H2The mode propagation constants of the first single-mode tapered waveguide small end, the first single-mode tapered waveguide large end and the single-mode tapered waveguide satisfy the following conditions: beta is a1b<β1<β1aWherein, β1Is the mode propagation constant, beta, of the fundamental mode of said first single-mode tapered waveguide1bIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small tip of the first single-mode tapered waveguide1aThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end is the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end, and the mode propagation constants of the second single-mode tapered waveguide big head end and the second single-mode tapered waveguide meet the following conditions: beta is a4b<β2<β4aWherein, β2Is the mode propagation constant, beta, of the fundamental mode of said second single-mode tapered waveguide4bIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the second single-mode tapered waveguide4aIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the big end of the second single-mode tapered waveguide,the mode propagation constants of the first few-mode tapered waveguide large head end and the first few-mode tapered waveguide meet the following conditions: beta is a2a<β3<β2bWherein, β3Is the mode propagation constant, beta, of the fundamental mode of said first few-mode tapered waveguide2aIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the first few-mode tapered waveguide2bThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the first few-mode tapered waveguide is set, and the mode propagation constants of the large head end of the second few-mode tapered waveguide and the second few-mode tapered waveguide meet the following conditions: beta is a3a<β4<β3bWherein, β4Is the mode propagation constant, beta, of the fundamental mode of said second few-mode tapered waveguide3aIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the small end of the second few-mode tapered waveguide, beta3bIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the big head end of the second few-mode tapered waveguide.
The polymer three-mode multiplexer is characterized in that the cladding material at the 1550nm wavelength is EpoClad, the refractive index of the cladding material is 1.5631, the core material is EpoCore, and the refractive index of the core material is 1.5752. The distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2-4 mu m, the distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide is 3-5 mu m, the width of the big head end of the first single-mode tapered waveguide is 9 mu m, the width of the small head end of the first single-mode tapered waveguide is 8 mu m, the width of the small head end of the first few-mode tapered waveguide is 10.5 mu m, the width of the big head end of the first few-mode tapered waveguide is 11.5 mu m, the width of the big head end of the second single-mode tapered waveguide is 4.6 mu m, the width of the small head end of the second single-mode tapered waveguide is 2.6 mu m, the height of the first input straight waveguide, the height of the first S-shaped curved waveguide, the height of the first single-mode tapered waveguide, the height of the second S-shaped curved waveguide, the height of the first output straight waveguide and the height of the third input straight waveguide, the height of the third S-shaped curved waveguide, the height of the second single-mode tapered waveguide, the height of the fourth S-shaped curved waveguide and the height of the third output straight waveguide are 4 mu m, and the height of the second input straight waveguide, the height of the first few-mode tapered waveguide, the height of the second few-mode tapered waveguide and the height of the second output straight waveguide are 8 mu m. The length of the first single-mode tapered waveguide and the length of the first few-mode tapered waveguide are 2.1mm, and the length of the second single-mode tapered waveguide and the length of the second few-mode tapered waveguide are 4.5 mm. The structure enables the parameter configuration of each component in the three-mode multiplexer to realize good performance, and has high mode conversion efficiency, low extra loss and large bandwidth.
Compared with the prior art, the polymer three-mode multiplexer based on the cascade tapered coupler has the advantages that the three-mode multiplexer is formed by the first input straight waveguide, the second input straight waveguide, the third input straight waveguide, the first few-mode tapered waveguide, the second few-mode tapered waveguide, the first single-mode tapered waveguide, the second single-mode tapered waveguide, the first S-shaped curved waveguide, the second S-shaped curved waveguide, the third S-shaped curved waveguide, the fourth S-shaped curved waveguide, the first output straight waveguide, the second output straight waveguide and the third output straight waveguide, and the first few-mode tapered waveguide, the second few-mode tapered waveguide, the first single-mode tapered waveguide and the second single-mode tapered waveguide are respectively provided with a small head end and a large head end; the first input straight waveguide width is equal to the first S-shaped curved waveguide width, the first S-shaped curved waveguide width is equal to the first single-mode tapered waveguide big end width, the second S-shaped curved waveguide width is equal to the first single-mode tapered waveguide small end width, the first output straight waveguide width is equal to the second S-shaped curved waveguide width, the second input straight waveguide width is equal to the first few-mode tapered waveguide small end width, the first few-mode tapered waveguide big end width is equal to the second few-mode tapered waveguide small end width, the second few-mode tapered waveguide big end width is equal to the second output waveguide width, the third input straight waveguide width is equal to the third S-shaped curved waveguide width, the third S-shaped curved waveguide width is equal to the second single-mode tapered waveguide big end width, and the second single-mode tapered waveguide small end width is equal to the fourth S-shaped curved waveguide width, the width of the third output waveguide is equal to that of the fourth S-shaped bent waveguide; the first input straight waveguideThe height, the height of a first S-shaped curved waveguide, the height of a first single-mode tapered waveguide, the height of a second S-shaped curved waveguide, the height of a first output straight waveguide, the height of a third input straight waveguide, the height of a third S-shaped curved waveguide, the height of a second single-mode tapered waveguide, the height of a fourth S-shaped curved waveguide and the height of a third output straight waveguide are equal, the height of a second input straight waveguide, the height of a first few-mode tapered waveguide, the height of a second few-mode tapered waveguide and the height of a second output straight waveguide are equal, the initial end of the first input waveguide is the first input end of the three-mode multiplexer, the tail end of the first input straight waveguide is connected with the initial end of the first S-shaped curved waveguide, the tail end of the first S-shaped curved waveguide is connected with the big head end of the first single-mode tapered waveguide, and the small head end of the first single-mode tapered waveguide is connected with the initial end of the second S-shaped curved waveguide, the tail end of the second S-shaped curved waveguide is connected with the start end of the first output waveguide, the tail end of the first output waveguide is the first output end of the three-mode multiplexer, the start end of the second input waveguide is the second input end of the three-mode multiplexer, the tail end of the second input waveguide is connected with the small end of the first few-mode waveguide, the large end of the first few-mode waveguide is connected with the small end of the second few-mode waveguide, the large end of the second few-mode waveguide is connected with the start end of the second output waveguide, the tail end of the second output waveguide is the second output end of the three-mode multiplexer, and the start end of the third input waveguide is the third input end of the three-mode multiplexer; the tail end of the third input straight waveguide is connected with the starting end of the third S-shaped curved waveguide, the tail end of the third S-shaped curved waveguide is connected with the large head end of the second single-mode tapered waveguide, the small head end of the first single-mode tapered waveguide is connected with the starting end of the fourth S-shaped curved waveguide, the tail end of the fourth S-shaped curved waveguide is connected with the starting end of the third output waveguide, and the tail end of the third output waveguide is the third output end of the three-mode multiplexer. The first single-mode tapered waveguide is arranged on the right side of the first few-mode tapered waveguide, the distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2-4 mu m, and the second single-mode tapered waveguideThe second single-mode tapered waveguide and the second few-mode tapered waveguide are arranged at the left side of the second few-mode tapered waveguide, and the distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide is 3-5 mu m; marking the width of the first input straight waveguide, the width of the first S-shaped bent waveguide and the width of the big head end of the first single-mode tapered waveguide as W1aThe width of the small end of the first single-mode tapered waveguide, the width of the second S-shaped curved waveguide and the width of the first output straight waveguide are recorded as W1bThe width of the second input straight waveguide and the width of the small end of the first few-mode tapered waveguide are recorded as W2aThe width of the large end of the first few-mode tapered waveguide is marked as W2bThe width of the small end of the second few-mode tapered waveguide is recorded as W3aThe width of the big end of the second few-mode tapered waveguide and the width of the second output straight waveguide are marked as W3bThe width of the third input straight waveguide, the width of the third S-shaped bent waveguide and the width of the big end of the second single-mode tapered waveguide are marked as W4aThe width of the small end of the second single-mode tapered waveguide, the width of the fourth S-shaped curved waveguide and the width of the third output straight waveguide are recorded as W4b, W3b> W3a> W2a> W2b> W1a> W1b> W4a> W4bThe height of the first input straight waveguide, the height of the first S-shaped curved waveguide, the height of the first single-mode tapered waveguide, the height of the second S-shaped curved waveguide, the height of the first output straight waveguide, the height of the third input straight waveguide, the height of the third S-shaped curved waveguide, the height of the second single-mode tapered waveguide, the height of the fourth S-shaped curved waveguide and the height of the third output straight waveguide are recorded as H1The height of the second input straight waveguide, the height of the first few-mode tapered waveguide, the height of the second few-mode tapered waveguide and the height of the second output straight waveguide are recorded as H2The mode propagation constants of the first single-mode tapered waveguide small end, the first single-mode tapered waveguide large end and the single-mode tapered waveguide satisfy the following conditions: beta is a1b<β1<β1aWherein, β1Is the mode propagation constant, beta, of the fundamental mode of said first single-mode tapered waveguide1bIs a mode of a fundamental mode in a straight waveguide having a width equal to the width of the small end of the first single-mode tapered waveguideFormula propagation constant, beta1aThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end is the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end, and the mode propagation constants of the second single-mode tapered waveguide big head end and the second single-mode tapered waveguide meet the following conditions: beta is a4b<β2<β4aWherein, β2Is the mode propagation constant, beta, of the fundamental mode of said second single-mode tapered waveguide4bIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the second single-mode tapered waveguide4aThe mode propagation constant of a fundamental mode in the straight waveguide with the width equal to that of the large head end of the second single-mode tapered waveguide is the mode propagation constant of the fundamental mode in the straight waveguide, and the mode propagation constants of the large head end of the first few-mode tapered waveguide and the first few-mode tapered waveguide meet the following conditions: beta is a2a<β3<β2bWherein, β3Is the mode propagation constant, beta, of the fundamental mode of said first few-mode tapered waveguide2aIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the first few-mode tapered waveguide2bThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the first few-mode tapered waveguide is set, and the mode propagation constants of the large head end of the second few-mode tapered waveguide and the second few-mode tapered waveguide meet the following conditions: beta is a beta3a<β4<β3bWherein, β4Is the mode propagation constant, beta, of the fundamental mode of said second few-mode tapered waveguide3aIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the small end of the second few-mode tapered waveguide, beta3bIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the big head end of the second few-mode tapered waveguide.
When a fundamental mode is input from the first input straight waveguide, the mode is coupled through the first single-mode tapered waveguide along the first S-shaped curved waveguide, excited and converted into a second-order mode in the first few-mode tapered waveguide and output along the second few-mode tapered waveguide and the second output straight waveguide, when the fundamental mode is input from the third input straight waveguide, the mode is coupled through the second single-mode tapered waveguide along the third S-shaped curved waveguide, excited and converted into a third-order mode in the second few-mode tapered waveguide and output along the second few-mode tapered waveguide and the second output straight waveguide, and when the fundamental mode is input from the second input straight waveguide, the mode is transmitted along the first few-mode tapered waveguide, the second few-mode tapered waveguide and the second output straight waveguide. Therefore, the mode multiplexer based on the cascade tapered coupler has perfect working characteristics. The mode division multiplexing system has the characteristics of high mode conversion efficiency, low extra loss, large bandwidth and the like, is expected to be applied to a board-level optical interconnection mode division multiplexing system, can realize the transmission of a fundamental mode from a first input straight waveguide to a first few-mode tapered waveguide, then the fundamental mode is converted into a second-order mode through the first single-mode tapered waveguide in a coupling mode, the second few-mode tapered waveguide and a second output straight waveguide, can realize the transmission of the fundamental mode from the second input straight waveguide to the first few-mode tapered waveguide, then the second few-mode tapered waveguide and the second output straight waveguide, and can realize the transmission of the fundamental mode from the third input straight waveguide to the third-order mode through the second single-mode tapered waveguide, then the fundamental mode is converted into a third-order mode through the second single-mode tapered waveguide and the second output straight waveguide in a coupling mode, and the controllability is realized in the actual device preparation process.
Description of the drawings:
fig. 1 is a block diagram of a cascaded tapered coupler based polymer tri-mode multiplexer according to the present invention.
Fig. 2 is a diagram of mode transmission of the cascaded tapered coupler-based polymer triple-mode multiplexer of the present invention when light is input from the first input straight waveguide 1.
Fig. 3 is a diagram of mode transmission of the cascaded tapered coupler-based polymer triple-mode multiplexer of the present invention when light is input from the second input straight waveguide 2.
Fig. 4 is a diagram of mode transmission of the cascaded tapered coupler-based polymer triple-mode multiplexer of the present invention when light is input from the third input straight waveguide 3.
Fig. 5 is a graph showing the relationship between the conversion efficiency between the fundamental mode and the second order mode and the output power of the polymer three-mode multiplexer based on the cascaded tapered coupler according to the present invention.
FIG. 6 is a graph showing the relationship between the conversion efficiency between the fundamental mode and the third order mode and the output power varying with the length of the tapered waveguide in the cascaded tapered coupler-based polymer three-mode multiplexer of the present invention.
Fig. 7 is a graph showing the relationship between the conversion efficiency between the fundamental mode and the second order mode and the extra loss with the operating wavelength of the cascaded tapered coupler-based polymer three-mode multiplexer of the present invention.
Fig. 8 is a graph showing the relationship between the conversion efficiency between the fundamental mode and the third-order mode and the extra loss with the variation of the operating wavelength of the cascaded tapered coupler-based polymer three-mode multiplexer of the present invention.
The specific implementation mode is as follows:
the invention discloses a cascade tapered coupler-based three-mode multiplexer, which is further described by combining the embodiment of the attached drawings.
As shown in fig. 1, a polymer three-mode multiplexer based on a cascaded tapered coupler includes a first input straight waveguide 1, a second input straight waveguide 2, a third input straight waveguide 3, a first output straight waveguide 4, a second output straight waveguide 5, a third output straight waveguide 6, a first S-shaped curved waveguide 7, a second S-shaped curved waveguide 8, a third S-shaped curved waveguide 9, a fourth S-shaped curved waveguide 10, a first single-mode tapered waveguide 11, a second single-mode tapered waveguide 12, a first few-mode tapered waveguide 13, and a second few-mode tapered waveguide 14. The first single-mode tapered waveguide 11, the second single-mode tapered waveguide 12, the first few-mode tapered waveguide 13 and the second few-mode tapered waveguide 14 are respectively provided with a small head end and a large head end; the width 1 of the first input straight waveguide is equal to that of the first S-shaped bent waveguide 7, the width of the first S-shaped bent waveguide 7 is equal to that of the big end of the first single-mode tapered waveguide 11, the width of the second S-shaped bent waveguide 8 is equal to that of the small end of the first single-mode tapered waveguide 11, the width of the first output straight waveguide 4 is equal to that of the second S-shaped bent waveguide 8, the width of the second input straight waveguide 2 is equal to that of the small end of the first few-mode tapered waveguide 13, the width of the big end of the first few-mode tapered waveguide 13 is equal to that of the small end of the second few-mode tapered waveguide 14, and the width of the big end of the second few-mode tapered waveguide 14 is equal to that of the second input small-mode tapered waveguide 14The widths of the output waveguides 5 are equal, the width of the third input straight waveguide 3 is equal to that of the third S-shaped curved waveguide 9, the width of the third S-shaped curved waveguide 9 is equal to that of the large end of the second single-mode tapered waveguide 12, the width of the small end of the second single-mode tapered waveguide 12 is equal to that of the fourth S-shaped curved waveguide 10, and the width of the third output waveguide 6 is equal to that of the fourth S-shaped curved waveguide 10. The height of a first input straight waveguide 1, the height of a first S-shaped curved waveguide 7, the height of a first single-mode tapered waveguide 11, the height of a second S-shaped curved waveguide 8, the height of a first output straight waveguide 4, the height of a third input straight waveguide 3, the height of a third S-shaped curved waveguide 9, the height of a second single-mode tapered waveguide 12, the height of a fourth S-shaped curved waveguide 10 and the height of a third output straight waveguide 6 are equal, the height of a second input straight waveguide 2, the height of a first few-mode tapered waveguide 13, the height of a second few-mode tapered waveguide 14 and the height of a second output straight waveguide 5 are equal, the starting end of the first input waveguide 1 is a first input end of the three-mode multiplexer, the tail end of the first input straight waveguide 1 is connected with the starting end of the first S-shaped curved waveguide 7, the tail end of the first S-shaped curved waveguide 7 is connected with the big end of the first single-mode tapered waveguide 11, the small end of the first single-mode tapered waveguide 11 is connected with the start end of the second S-shaped curved waveguide 8, the end of the second S-shaped curved waveguide 8 is connected with the start end of the first output waveguide 4, the end of the first output waveguide 4 is the first output end of the three-mode multiplexer, the start end of the second input waveguide 2 is the second input end of the three-mode multiplexer, the end of the second input waveguide 2 is connected with the small end of the first few-mode waveguide 13, the large end of the first few-mode waveguide 13 is connected with the small end of the second few-mode waveguide 14, the large end of the second few-mode waveguide 14 is connected with the start end of the second output waveguide 5, the end of the second output waveguide 15 is the second output end of the three-mode multiplexer, and the start end of the third input waveguide 3 is the third input end of the three-mode multiplexer; the tail end of the third input straight waveguide 3 is connected with the start end of a third S-shaped bent waveguide 9, the tail end of the third S-shaped bent waveguide 9 is connected with the large head end of a second single-mode tapered waveguide 12, the small head end of a first single-mode tapered waveguide 11 is connected with the start end of a fourth S-shaped bent waveguide 10, and the tail end of the fourth S-shaped bent waveguide 10 is connected with the start end of a third output waveguide 6The ends are connected and the end of the third output waveguide 6 is the third output end of the three-mode multiplexer. The first single-mode tapered waveguide 11 is arranged on the right side of the first few-mode tapered waveguide 13, the distance between the first single-mode tapered waveguide 11 and the first few-mode tapered waveguide 13 is 2-4 mu m, the second single-mode tapered waveguide 12 is arranged on the left side of the second few-mode tapered waveguide 14, and the distance between the second single-mode tapered waveguide 12 and the second few-mode tapered waveguide 14 is 3-5 mu m; the width of the first input straight waveguide 1, the width of the first S-shaped curved waveguide 7 and the width of the big end of the first single-mode tapered waveguide 11 are denoted as W1aLet W denote the width of the small end of the first single-mode tapered waveguide 11, the width of the second S-bend waveguide 8 and the width of the first output straight waveguide 31bLet W denote the width of the second input straight waveguide 2 and the width of the small end of the first few-mode tapered waveguide 132aThe width of the large end of the first few-mode tapered waveguide 13 is denoted as W2bLet W denote the width of the small end of the second few-mode tapered waveguide 143aLet W denote the width of the large end of the second few-mode tapered waveguide 14 and the width of the second output straight waveguide 53bLet W denote the width of the third input straight waveguide 3, the width of the third S-bend waveguide 9 and the width of the large end of the second single-mode tapered waveguide 124aLet W denote the width of the small end of the second single-mode tapered waveguide 12, the width of the fourth S-bend waveguide 10 and the width of the third output straight waveguide 64b, W3b> W3a> W2a> W2b> W1a> W1b> W4a> W4bThe height of the first input straight waveguide 1, the height of the first S-shaped curved waveguide 7, the height of the first single-mode tapered waveguide 11, the height of the second S-shaped curved waveguide 8, the height of the first output straight waveguide 4, the height of the third input straight waveguide 3, the height of the third S-shaped curved waveguide 9, the height of the second single-mode tapered waveguide 12, the height of the fourth S-shaped curved waveguide 10 and the height of the third output straight waveguide 6 are recorded as H1The height of the second input straight waveguide 2, the height of the first few-mode tapered waveguide 13, the height of the second few-mode tapered waveguide 14 and the height of the second output straight waveguide 5 are recorded as H2The mode propagation constants of the small end of the first single-mode tapered waveguide 11, the large end of the first single-mode tapered waveguide 11 and the single-mode tapered waveguide 11 satisfy the following conditions: beta is a1b<β1<β1aWhich isIn, beta1Is the mode propagation constant, beta, of the fundamental mode of said first single-mode tapered waveguide 111bIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the first single-mode tapered waveguide 111aThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the first single-mode tapered waveguide 11, the mode propagation constant of the small head end of the second single-mode tapered waveguide 12, the large head end of the second single-mode tapered waveguide 12 and the mode propagation constant of the second single-mode tapered waveguide 12 meet the following conditions: beta is a4b<β2<β4aWherein, β2Is the mode propagation constant, beta, of the fundamental mode of said second single-mode tapered waveguide 124bIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the second single-mode tapered waveguide 124aThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the second single-mode tapered waveguide 12 is the mode propagation constant of the fundamental mode in the straight waveguide, and the mode propagation constants of the large head end of the first few-mode tapered waveguide 13 and the first few-mode tapered waveguide 13 meet the following conditions: beta is a2a<β3<β2bWherein, β3Is the mode propagation constant, beta, of the fundamental mode of said first few-mode tapered waveguide 132aIs the mode propagation constant, beta, of the fundamental mode in the straight waveguide with the width equal to the width of the small end of the first few-mode tapered waveguide 132bThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the first few-mode tapered waveguide 13 is the mode propagation constant of the fundamental mode in the straight waveguide, and the mode propagation constants of the large head end of the first few-mode tapered waveguide 13 and the first few-mode tapered waveguide 13 meet the following conditions: beta is a3a<β4<β3bWherein, β4Is the mode propagation constant, beta, of the fundamental mode of said second few-mode tapered waveguide 143aIs the mode propagation constant, beta, of the fundamental mode in the straight waveguide having the same width as the small end of the second few-mode tapered waveguide 143bIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large end of the second few-mode tapered waveguide 14.
In this embodiment, the distance between the first single-mode tapered waveguide 11 and the first few-mode tapered waveguide 13 is 2.5 μm, the distance between the second single-mode tapered waveguide 12 and the second few-mode tapered waveguide 14 is 2.5 μm, the width of the large head end of the first single-mode tapered waveguide 11 is 9 μm, the width of the small head end of the first single-mode tapered waveguide 11 is 8 μm, the width of the small head end of the first few-mode tapered waveguide 13 is 10.5 μm, the width of the large head end of the first few-mode tapered waveguide 13 is 11.5 μm, the width of the large head end of the second single-mode tapered waveguide 12 is 4.6 μm, the width of the small head end of the second single-mode tapered waveguide 12 is 2.6 μm, the height of the first input straight waveguide 1, the height of the first S-shaped curved waveguide 7, the height of the first tapered single-mode waveguide 11, the height of the second S-shaped curved waveguide 8, the height of the first output straight waveguide 4, the height of the third input straight waveguide 3, the height of the third S-shaped curved waveguide 9, the height of the second single-mode tapered waveguide 12, the height of the fourth S-shaped curved waveguide 10 and the height of the third output straight waveguide 6 are 4 mu m, the height of the second input straight waveguide 2, the height of the first few-mode tapered waveguide 13, the height of the second few-mode tapered waveguide 14 and the height of the second output straight waveguide 5 are 8 mu m. The length of the first single-mode tapered waveguide 11 and the length of the first few-mode tapered waveguide 13 are 2.1mm, and the length of the second single-mode tapered waveguide 12 and the length of the second few-mode tapered waveguide 14 are 4.5 mm.
The three-mode transmission diagram of the cascade tapered coupler-based three-mode multiplexer is shown in FIG. 2 under the condition that the working wavelength is 1550 nm. As can be seen from the analysis of fig. 2, when the fundamental mode is input from the first input straight waveguide 1, the mode is coupled along the first S-shaped curved waveguide 7 through the first single-mode tapered waveguide 11, excited and converted into a second-order mode in the first few-mode tapered waveguide 13 and output along the first few-mode tapered waveguide 13, the second few-mode tapered waveguide 14 and the second output straight waveguide 5, when the fundamental mode is input from the third input straight waveguide 2, the mode is coupled along the third S-shaped curved waveguide 8 through the second single-mode tapered waveguide 12, excited and converted into a third-order mode in the second few-mode tapered waveguide 14 and output along the second few-mode tapered waveguide 14 and the second output straight waveguide 5, and when the fundamental mode is input from the second input straight waveguide 2, the mode is output along the first few-mode tapered waveguide 13, the second few-mode tapered waveguide 14 and the second output straight waveguide 5. Therefore, the mode multiplexer based on the cascade tapered coupler has the working characteristics which are perfectly matched with the expected design effect.
According to the polymer three-mode multiplexer based on the cascade tapered coupler, under the working wavelength of 1550nm, the distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2.5 microns, and when a basic mode is input into the input straight waveguide 1 and is coupled and converted into a second-order mode in the first few-mode tapered waveguide 13 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11, the conversion efficiency and the mode power of the tail end of the first output waveguide 4 and the tail end of the second output waveguide 5 are in a conversion relation with the lengths of the first tapered waveguide 11 and the first few-mode tapered waveguide 13, as shown in FIG. 3. In fig. 3, the solid circular connecting line represents the conversion efficiency when the fundamental mode is coupled and converted into the second-order mode in the first few-mode tapered waveguide 13 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 at the input of the input straight waveguide 1 under different tapered waveguide lengths, the right solid triangular connecting line represents the power of the fundamental mode at the end of the second output waveguide 5 converted from the coupling of the fundamental mode from the input straight waveguide 1 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 to the coupling of the second-order mode in the first few-mode tapered waveguide 13 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 under different tapered waveguide lengths, and the left solid triangular connecting line represents the power of the fundamental mode detected at the end of the first output waveguide 4 after the fundamental mode is coupled and converted into the second-order mode in the first few-mode tapered waveguide 13 from the input straight waveguide 1 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 under different tapered waveguide lengths. It can be seen that the conversion efficiency between the fundamental mode and the second order mode is 0.9996, the power of the fundamental mode detected at the end of the output waveguide 1 is-34.28 dB, and the power of the second order mode detected at the end of the output waveguide 12 is-0.14 dB at a tapered waveguide length of 2.1mm, which means that the fundamental mode incident from the input straight waveguide 1 is almost completely converted into the second order mode through the tapered coupling region and transmitted in the less-mode tapered waveguide.
The distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide of the polymer three-mode multiplexer based on the cascaded tapered coupler is 3.5 μm at the working wavelength of 1550nm, and when the fundamental mode is input into the input straight waveguide 3 and is coupled and converted into a third-order mode in the second few-mode tapered waveguide 14 along the third S-bend waveguide 9 and the first single-mode tapered waveguide 12, the conversion efficiency and the mode power of the tail end of the third output waveguide 6 and the tail end of the second output waveguide 5 are in a conversion relation with the lengths of the second tapered waveguide 12 and the second few-mode tapered waveguide 14, as shown in fig. 4. In fig. 4, the "solid circular" connecting line represents the conversion efficiency when the fundamental mode is coupled and converted into the third-order mode in the second few-mode tapered waveguide 14 along the third S-bend waveguide 9 and the second single-mode tapered waveguide 12 at the input of the input straight waveguide 3, the "right solid triangular" connecting line represents the power of the fundamental mode at the end of the second output waveguide 5 converted from the coupling of the input straight waveguide 3 along the third S-bend waveguide 9 and the second single-mode tapered waveguide 12 to the coupling of the second-order mode in the second few-mode tapered waveguide 14 at the different tapered waveguide lengths, and the "left solid triangular" connecting line represents the power of the fundamental mode detected at the end of the third output waveguide 6 after the coupling and conversion of the fundamental mode from the input straight waveguide 3 along the third S-bend waveguide 9 and the second single-mode tapered waveguide 12 to the third-order mode in the second few-mode tapered waveguide 14 at the different tapered waveguide lengths. It can be seen from the figure that the conversion efficiency between the fundamental mode and the third-order mode is 0.9998 at a tapered waveguide length of 4.5mm, the fundamental mode power detected at the end of the output waveguide 1 is-37.35 dB, and the second-order mode power detected at the end of the output waveguide 12 is-0.35 dB, which means that the fundamental mode incident from the input straight waveguide 3 is almost completely converted into the third-order mode through the tapered coupling region and transmitted in the few-mode tapered waveguide.
According to the polymer three-mode multiplexer based on the cascade tapered coupler, the lengths of the first single-mode tapered waveguide 11 and the first few-mode tapered waveguide 13 are 2.1mm, the distance between the first single-mode tapered waveguide 11 and the first few-mode tapered waveguide 13 is 2.5 micrometers, and a graph of the change relationship of the conversion efficiency and the extra loss along with the wavelength when the fundamental mode is input into the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 along the input straight waveguide 1 and is coupled and converted into the second-order mode in the first few-mode tapered waveguide 13 is shown in FIG. 5. In the figure, the solid circular connecting line represents the conversion efficiency of the fundamental mode when the fundamental mode is coupled and converted into the second-order mode in the first few-mode tapered waveguide 13 along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 at the input of the input straight waveguide 1 under different operating wavelengths, the solid triangular connecting line represents the conversion efficiency under different operating wavelengths, the extra loss when the fundamental mode is coupled along the first S-bend waveguide 7 and the first single-mode tapered waveguide 11 at the input of the input straight waveguide 1 to be converted into a second order mode in the first few-mode tapered waveguide 13, as can be seen from the figure, when the working wavelength is 1560nm, the conversion efficiency of the primary mode and the second order mode is 0.9997, in the 1530-1625nm wave band, the conversion efficiency of the primary mode converted into the second-order mode after passing through the conical coupling area is more than 0.91, the extra loss is less than 0.15 dB, in the 1530-1595nm band, the conversion efficiency of the primary mode and the second-order mode is larger than 0.97. The conversion efficiency and the excess loss as a function of wavelength when the fundamental mode is coupled into a third order mode in the second few-mode tapered waveguide 14 along the third S-bend waveguide 9 and the first single-mode tapered waveguide 12 at the input of the input straight waveguide 3 are shown in fig. 6. In the figure, the line of "solid circle" represents the conversion efficiency when the fundamental mode is coupled and converted into the third-order mode in the second few-mode tapered waveguide 14 along the third S-bend waveguide 9 and the first single-mode tapered waveguide 12 at the input of the input straight waveguide 3 at different operating wavelengths, and the line of "upper solid triangle" represents the additional loss when the fundamental mode is coupled and converted into the third-order mode in the second few-mode tapered waveguide 14 along the third S-bend waveguide 9 and the second single-mode tapered waveguide 12 at the input of the input straight waveguide 3 at different operating wavelengths, as shown in the figure, when the operating wavelength is 1560nm, the conversion efficiency of the fundamental mode and the second-order mode is 0.9998, and in the 1530 and 1625nm waveband, the conversion efficiency of the fundamental mode converted into the second-order mode after passing through the tapered coupling region is all greater than 0.97, and the additional loss is all less than 0.55 dB.
It should be noted that the present invention is beneficial to the design of the board-level modular multiplexing system to realize board-level large-capacity information transmission. The method has excellent potential in the technical fields of optical waveguide devices, board-level optical interconnection and optical communication.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed in the present invention should be covered within the protection scope of the present invention.

Claims (3)

1. A polymer three-mode multiplexer based on a cascade taper coupler comprises a first input straight waveguide, a second input straight waveguide and a third input straight waveguideThe waveguide comprises a first few-mode tapered waveguide, a second few-mode tapered waveguide, a first single-mode tapered waveguide, a second single-mode tapered waveguide, a first S-shaped curved waveguide, a second S-shaped curved waveguide, a third S-shaped curved waveguide, a fourth S-shaped curved waveguide, a first output straight waveguide, a second output straight waveguide and a third output straight waveguide, wherein the first single-mode tapered waveguide, the first few-mode tapered waveguide, the second single-mode tapered waveguide and the second few-mode tapered waveguide are respectively provided with a small head end and a large head end; the first input straight waveguide width is equal to the first S-shaped curved waveguide width, the first S-shaped curved waveguide width is equal to the first single-mode tapered big head end width, the second S-shaped curved waveguide width is equal to the first single-mode tapered small head end width, the first output straight waveguide width is equal to the second S-shaped curved waveguide width, the second input straight waveguide width is equal to the first few-mode tapered waveguide width small head width, the first few-mode tapered waveguide big head width is equal to the second few-mode tapered waveguide small head width, the second few-mode tapered waveguide big head width is equal to the second output waveguide width, the third input straight waveguide width is equal to the third S-shaped curved waveguide width, the third S-shaped curved waveguide width is equal to the second single-mode tapered waveguide big head width, and the second single-mode tapered small head width is equal to the fourth S-shaped curved waveguide width, the width of the third output waveguide is equal to that of the fourth S-shaped bent waveguide; the first input straight waveguide height, the first S-shaped curved waveguide height, the first single-mode tapered waveguide height, the second S-shaped curved waveguide height, the first output straight waveguide height, the third input straight waveguide height, the third S-shaped curved waveguide height, the second single-mode tapered waveguide height, the fourth S-shaped curved waveguide height and the third output straight waveguide height are equal, and the second input straight waveguide height, the first few-mode tapered waveguide height, the second few-mode tapered waveguide height and the second output straight waveguide height are equal; the starting end of the first input straight waveguide is the first input end of the three-mode multiplexer, the tail end of the first input straight waveguide is connected with the starting end of the first S-shaped bent waveguide, and the tail end of the first S-shaped bent waveguide is connected with the first single-mode tapered waveguideThe big end is connected, the small end of the first single-mode tapered waveguide is connected with the initial end of the second S-shaped bent waveguide, the tail end of the second S-shaped bent waveguide is connected with the initial end of the first output waveguide, the tail end of the first output waveguide is a first output end of the three-mode multiplexer, the beginning end of the second input waveguide is the second input end of the three-mode multiplexer, the tail end of the second input waveguide is connected with the small end of the first few-mode waveguide, the big head end of the first few-mode waveguide is connected with the small head end of the second few-mode waveguide, the big head end of the second few-mode waveguide is connected with the initial end of the second output waveguide, the tail end of the second output waveguide is a second output end of the three-mode multiplexer, and the starting end of the third input waveguide is a third input end of the three-mode multiplexer; the tail end of the third input straight waveguide is connected with the start end of the third S-shaped curved waveguide, the tail end of the third S-shaped curved waveguide is connected with the large head end of the second single-mode tapered waveguide, the small head end of the first single-mode tapered waveguide is connected with the start end of the fourth S-shaped curved waveguide, the tail end of the fourth S-shaped curved waveguide is connected with the start end of the third output waveguide, and the tail end of the third output waveguide is the third output end of the three-mode multiplexer; the first single-mode tapered waveguide is arranged on the right side of the first few-mode tapered waveguide, the distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2-4 mu m, the length of the first single-mode tapered waveguide is the same as that of the first few-mode tapered waveguide, the second single-mode tapered waveguide is arranged on the left side of the second few-mode tapered waveguide, the distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide is 3-5 mu m, and the length of the second single-mode tapered waveguide is the same as that of the second few-mode tapered waveguide; marking the width of the first input straight waveguide, the width of the first S-shaped bent waveguide and the width of the big head end of the first single-mode tapered waveguide as W1aThe width of the small end of the first single-mode tapered waveguide, the width of the second S-shaped curved waveguide and the width of the first output straight waveguide are recorded as W1bThe width of the second input straight waveguide and the width of the small end of the first few-mode tapered waveguide are recorded as W2aThe method comprises the steps ofThe width of the big end of the first few-mode tapered waveguide is marked as W2bThe width of the small end of the second few-mode tapered waveguide is recorded as W3aThe width of the big end of the second few-mode tapered waveguide and the width of the second output straight waveguide are marked as W3bThe width of the third input straight waveguide, the width of the third S-shaped bent waveguide and the width of the big end of the second single-mode tapered waveguide are marked as W4aThe width of the small end of the second single-mode tapered waveguide, the width of the fourth S-shaped curved waveguide and the width of the third output straight waveguide are recorded as W4b，W3b> W3a> W2a> W2b> W1a> W1b> W4a> W4bThe height of the first input straight waveguide, the height of the first S-shaped curved waveguide, the height of the first single-mode tapered waveguide, the height of the second S-shaped curved waveguide, the height of the first output straight waveguide, the height of the third input straight waveguide, the height of the third S-shaped curved waveguide, the height of the second single-mode tapered waveguide, the height of the fourth S-shaped curved waveguide and the height of the third output straight waveguide are recorded as H1The height of the second input straight waveguide, the height of the first few-mode tapered waveguide, the height of the second few-mode tapered waveguide and the height of the second output straight waveguide are recorded as H2The mode propagation constants of the first single-mode tapered waveguide small end, the first single-mode tapered waveguide large end and the single-mode tapered waveguide satisfy the following conditions: beta is a1b<β1<β1aWherein, β1Is the fundamental mode propagation constant, beta, of said first single-mode tapered waveguide1bIs a propagation constant of a fundamental mode in a straight waveguide having a width equal to the width of the small end of the first single-mode tapered waveguide, beta1aThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end is the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the first single-mode tapered waveguide big head end, and the mode propagation constants of the second single-mode tapered waveguide big head end and the second single-mode tapered waveguide meet the following conditions: beta is a4b<β2<β4aWherein, β2Is the mode propagation constant, beta, of the fundamental mode of said second single-mode tapered waveguide4bIs a straight waveguide with the width equal to that of the small end of the second single-mode tapered waveguideMode propagation constant of fundamental mode, beta4aThe mode propagation constant of a fundamental mode in the straight waveguide with the width equal to that of the large head end of the second single-mode tapered waveguide is set as the mode propagation constant of the fundamental mode in the straight waveguide, and the mode propagation constants of the large head end of the first few-mode tapered waveguide, the small head end of the first few-mode tapered waveguide and the mode propagation constant of the first few-mode tapered waveguide meet the following conditions: beta is a2a<β3<β2bWherein, β3Is the mode propagation constant, beta, of the fundamental mode of said first few-mode tapered waveguide2aIs the mode propagation constant, beta, of the fundamental mode in a straight waveguide having a width equal to the width of the small end of the first few-mode tapered waveguide2bThe mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the large head end of the first few-mode tapered waveguide is set as follows: beta is a3a<β4<β3bWherein, β4Is the mode propagation constant, beta, of the fundamental mode of said second few-mode tapered waveguide3aIs the mode propagation constant, beta, of the fundamental mode in the straight waveguide with the width equal to the width of the small end of the second few-mode tapered waveguide3bIs the mode propagation constant of the fundamental mode in the straight waveguide with the width equal to the width of the big head end of the second few-mode tapered waveguide.
2. The cascaded tapered coupler-based polymer multimode multiplexer according to claim 1, wherein the distance between the first single-mode tapered waveguide and the first few-mode tapered waveguide is 2.5 μm, the distance between the second single-mode tapered waveguide and the second few-mode tapered waveguide is 3.5 μm, the width of the large end of the first single-mode tapered waveguide is 9 μm, the width of the small end of the first single-mode tapered waveguide is 8 μm, the width of the small end of the first few-mode tapered waveguide is 10.5 μm, the width of the large end of the first few-mode tapered waveguide is 11.5 μm, the width of the large end of the second single-mode tapered waveguide is 4.6 μm, the width of the small end of the second single-mode tapered waveguide is 2.6 μm, the height of the first input straight waveguide, the height of the first S-shaped curved waveguide, the height of the first single-mode tapered waveguide, and the height of the second S-shaped curved waveguide, the height of the first output straight waveguide, the height of the third input straight waveguide, the height of the third S-shaped bent waveguide, the height of the second single-mode tapered waveguide, the height of the fourth S-shaped bent waveguide and the height of the third output straight waveguide are 4 mu m, and the height of the second input straight waveguide, the height of the first few-mode tapered waveguide, the height of the second few-mode tapered waveguide and the height of the second output straight waveguide are 8 mu m.
3. The cascaded tapered coupler based polymer multimode multiplexer of claim 1, wherein the polymer multimode multiplexer has a cladding material EpoClad with a refractive index of 1.5631 and a core material EpoCore with a refractive index of 1.5752 at a wavelength of 1550 nm.
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