CN-121978831-A - Direct synthesis type optical waveguide design method based on local heat insulation conservation

Abstract

The invention belongs to the technical field of integrated photoelectrons, and particularly relates to a direct synthesis type optical waveguide design method based on local adiabatic conservation. The method comprises the steps of defining and calculating a local adiabatic parameter LAP, setting a global conservation adiabatic target value TAV, directly solving a generating function to synthesize a waveguide profile, and discretizing to generate a physical layout.

Inventors

• Liang Tulu
• QIU JUNYU
• WANG BAIYU
• ZHANG JIARUI
• YAN YIHANG
• ZHOU WENXI
• ZHANG JIN
• Xiao Ziye

Assignees

• 南通大学

Dates

Publication Date

20260505

Application Date

20251211

Claims (6)

1. 1. A direct synthesis type optical waveguide design method based on local heat insulation conservation is characterized by comprising the following steps: Step one, defining and calculating a local adiabatic degree parameter LAP; Step two, setting a global conservation adiabatic degree target value TAV; step three, directly solving a generating function to synthesize a waveguide profile; and fourthly, discretizing to generate a physical layout.
2. 2. The method for designing a direct composite optical waveguide based on local conservation of heat insulation according to claim 1, wherein the first step comprises the steps of: firstly, a physical quantity is defined which describes the difficulty of mode evolution under the geometric parameter W of the waveguide, called LAP, denoted as Γ (W), according to the theory of coupled modes, this parameter being proportional to the mode coupling coefficient and inversely proportional to the square of the difference between the mode propagation constants, expressed in simplified form as: (1); Where C 12 is the mode coupling coefficient, E 1,2 and n eff,1,2 are the electric field and effective refractive index of the two coupled modes, β is the difference in propagation constants, and this parameter Γ (W) is related only to the cross-sectional geometry W of the waveguide and is independent of length.
3. 3. The method of designing a direct composite optical waveguide based on local thermal insulation conservation as claimed in claim 2, wherein in the second step, to ensure the performance of the whole device, a constant local thermal insulation is required, a global conservation thermal insulation target value is set, denoted as Λ 0 , and an ideal thermal insulation waveguide should satisfy at every point along its propagation direction z: (2); Wherein the geometric gradient dW/dz along the length of the waveguide must be inversely proportional to the local degree of difficulty in mode evolution Γ (W) to maintain a constant adiabatic flux Λ 0 .
4. 4. A direct synthesis optical waveguide design method based on local conservation of heat insulation according to claim 3, wherein the core law in step two is deformed to obtain a first order ordinary differential equation about the waveguide profile W (z): (3); Given the boundary condition W (0) =w in , the complete, continuous waveguide width profile function W (z) is directly synthesized in one calculation by standard numerical integration methods, and the end point of the integration is determined by W z, final = W out , thus also yielding the total length z final of the device.
5. 5. The method for designing a direct synthesis optical waveguide based on local conservation of heat insulation according to claim 4, wherein the continuous function W (z) obtained in the third step is subjected to discretization sampling to generate a physical layout in GDSII format for lithography fabrication.
6. 6. Optical waveguide produced on the basis of the method according to any of claims 1-5, characterized in that its geometric profile function W (z) is the only solution of the first order ordinary differential equation for the waveguide profile W (z) under given boundary conditions, such that its internal local adiabatic parameters are strictly conserved along the propagation direction.

Description

Direct synthesis type optical waveguide design method based on local heat insulation conservation Technical Field The invention belongs to the technical field of integrated photoelectrons, and particularly relates to a direct synthesis type optical waveguide design method based on local adiabatic conservation. Background All current methods of adiabatic optical waveguide design, both primary and advanced, can be attributed in nature to iterative optimization of "structure-performance". The logic is as follows: (1) An initial waveguide structure (whether function, empirical, or zonal) is proposed. (2) The performance (e.g., transmission efficiency) of the structure is evaluated by time-consuming full-wave numerical simulations (e.g., FDTD/EME). (3) And adjusting the structural parameters according to the performance evaluation result. (4) Steps 2 and 3 are repeated until an acceptable solution is found. Even the most advanced methods at present, such as identifying a pattern hybridization region and performing finer iterations of the region, still do not skip this "emulation-feedback-tuning" loop. The fundamental limitation of this approach is that: (a) The calculation cost is high, the numerical simulation of the complete device depends on hundreds or thousands of times, and the design period is extremely long. (B) Essentially the "blind-man-like" design process is driven indirectly by a high-level, integrated performance index (overall efficiency) rather than directly guided by underlying, localized physical laws. This results in a designer not being sure whether the resulting solution is truly globally optimal. (C) Path dependency-the final result of the optimization may be related to the choice of initial structure, and certainty and uniqueness cannot be guaranteed. Thus, there is a strong need in the art for a clear and well-defined design method that satisfies the best structure for a particular physical constraint. Disclosure of Invention The present invention aims to completely eliminate the "iterative optimization" design paradigm of the prior art that is computationally expensive, intrinsically blind and path dependent. The method aims to solve the core problem of how to establish a completely new design method for deterministically, non-iteratively and directly generating the optimal waveguide structure at one time based on the first physical principle, so that the design which can be completed by the traditional method can be completed in a few seconds, and the solution is ensured to be physically optimal. The invention discloses a direct synthesis method based on the principle of local conservation of thermal insulation (Conservation of Local Adiabaticity). The core idea of this approach is a perfectly adiabatic waveguide, whose "adiabatic degree" at every point inside should be constant. A local physical parameter is defined that directly quantifies the "degree of adiabatic" and is set to a constant, and then the geometry of the entire waveguide is directly deduced by solving the physical constraint equation. The invention aims to achieve the above purpose, and adopts the following technical scheme that the direct synthesis type optical waveguide design method based on local heat insulation conservation comprises the following steps of defining and calculating local heat insulation parameters (Local Adiabaticity Parameter, LAP), setting a global conservation heat insulation target value (Target Adiabaticity Value, TAV), directly solving a generating function to synthesize a waveguide outline, and discretizing to generate a physical layout. In a further preferred embodiment of the present invention, the first step specifically comprises the steps of first defining a physical quantity, called LAP, denoted Γ (W), capable of describing the degree of difficulty of mode evolution under the geometric parameters W (e.g. width) of the waveguide. According to the coupled mode theory, this parameter is proportional to the mode coupling coefficient and inversely proportional to the square of the difference between the mode propagation constants, which can be expressed in simplified form as: (1) Where C 12 is the mode coupling coefficient, E 1,2 and n eff,1,2 are the electric field and effective refractive index of the two coupled modes, and β is the difference in propagation constants. This parameter Γ (W) is only related to the cross-sectional geometry W of the waveguide and not to the length. We can calculate the Γ (W) function curve over the whole geometrical parameter variation range (from W in to W out) by one-time mode scanning before the design starts Further, as a preferred embodiment of the present invention, a constant local insulation is required to ensure the performance of the whole device (e.g. total loss below-0.01 dB). A global conservation adiabatic target value is set, denoted Λ 0. An ideal adiabatic waveguide should meet at every point along its propagation direction z: (2) This equation