Direct synthesis type optical waveguide design method based on local adiabatic degree conservation
By directly synthesizing optical waveguide structures using the principle of local adiabatic conservation, the problems of high computational cost and strong path dependence in existing technologies are solved, enabling fast and deterministic optimal design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANTONG UNIV
- Filing Date
- 2025-12-11
- Publication Date
- 2026-05-05
AI Technical Summary
Existing optical waveguide design methods are computationally expensive, path-dependent, have long design cycles, and cannot guarantee optimality, nor can they be directly guided by local physical laws.
By adopting the principle of local adiabatic conservation, and by defining local adiabatic parameters and setting global conservation target values, the differential equations of waveguide geometry are directly solved to generate the optical waveguide structure.
It achieves the completion of designs that would take days using traditional methods within seconds, ensuring that the design results are physically optimal, significantly improving design efficiency and providing high certainty of results.
Smart Images
Figure CN121978831A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of integrated optoelectronics technology, specifically relating to a direct synthesis optical waveguide design method based on local adiabatic conservation. Background Technology
[0002] All current design methods for thermally adiabatic optical waveguides, whether basic or advanced, can essentially be reduced to iterative optimization of the "structure-performance" relationship. The logic is:
[0003] (1) Propose an initial waveguide structure (whether based on function, experience or partitioning).
[0004] (2) Evaluate the performance (e.g., transmission efficiency) of the structure by time-consuming full-wave numerical simulation (e.g., FDTD / EME).
[0005] (3) Adjust the structural parameters based on the performance evaluation results.
[0006] (4) Repeat steps 2 and 3 until an acceptable solution is found.
[0007] Even the most advanced methods, such as identifying hybrid regions and performing finer iterations on them, still fall within this "simulation-feedback-adjustment" cycle. The fundamental limitation of this approach lies in:
[0008] (a) High computational cost: It relies on hundreds or thousands of numerical simulations of the complete device, resulting in an extremely long design cycle.
[0009] (b) Essentially, it is a “blind men and the elephant” situation: the design process is indirectly driven by high-level, integral performance metrics (overall efficiency) rather than directly guided by low-level, local physical laws. This makes it impossible for designers to be certain whether the solution obtained is truly globally optimal.
[0010] (c) Path dependence: The final result of optimization may be related to the choice of the initial structure, and determinism and uniqueness cannot be guaranteed.
[0011] Therefore, there is an urgent need in this field for a clear and explicit design methodology that can achieve the best structure that meets specific physical constraints. Summary of the Invention
[0012] This invention aims to completely abolish the computationally expensive, inherently blind, and path-dependent "iterative optimization" design paradigm in existing technologies. The core problem this invention addresses is: how to establish a new deterministic, non-iterative, one-time direct generation of optimal waveguide structures based on first physics principles, thereby completing a design that would take days using traditional methods within seconds, and guaranteeing that the solution is physically optimal.
[0013] This invention discloses a direct synthesis method based on the principle of local adiabaticity conservation. The core idea of this method is that in a perfectly adiabatic waveguide, the degree of adiabaticity at every point within it should be constant. A local physical parameter that can directly quantify this degree of adiabaticity is defined and set as a constant. Then, the geometry of the entire waveguide is directly derived by solving this physical constraint equation.
[0014] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a direct synthesis optical waveguide design method based on local adiabaticity conservation, comprising the following steps: Step 1: Define and calculate the "Local Adiabaticity Parameter (LAP)"; Step 2: Set the globally conserved "Target Adiabaticity Value (TAV)"; Step 3: Directly solve the generating function to synthesize the waveguide profile; Step 4: Discretize to generate the physical layout.
[0015] As a further preferred embodiment of the present invention, step one specifically includes the following steps: First, define a physical quantity that can describe the difficulty of mode evolution under waveguide geometric parameters W (such as width), called LAP, denoted as Γ(W). According to coupled-mode theory, this parameter is proportional to the mode coupling coefficient and inversely proportional to the square of the difference in mode propagation constants, and its simplified form can be expressed as:
[0016] (1)
[0017] Among them, C 12 It is the mode coupling coefficient, E 1,2 and n eff,1,2 Γ(W) represents the electric field and effective refractive index of the two coupled modes, and ∆β is the difference in propagation constants. This parameter Γ(W) depends only on the cross-sectional geometry W of the waveguide and is independent of its length. We can calculate this parameter over the entire range of geometric parameters (from W) using a single mode scan before design begins. in To W out The Γ(W) function curve
[0018] Furthermore, as a preferred embodiment of the present invention, to ensure the performance of the entire device (e.g., total loss below -0.01dB), a constant local adiabatic strength is required. A globally conserved adiabatic strength target value is set, denoted as Λ0. An ideal adiabatic waveguide, at every point along its propagation direction z, should satisfy:
[0019] (2)
[0020] This equation is the core physical law of this invention. It shows that the geometric gradient rate dW / dz along the waveguide length must be inversely proportional to the local mode evolution difficulty Γ(W) in order to maintain a constant adiabatic flux Λ0.
[0021] Furthermore, as a preferred embodiment of the present invention, by transforming the core law in step two, we obtain a first-order ordinary differential equation concerning the waveguide profile W(z):
[0022] (3)
[0023] This is an equation that can be solved directly. Given the boundary conditions (W(0) = W... in Using standard numerical integration methods (such as the Runge-Kutta method), we can directly synthesize a complete and continuous waveguide width profile function W(z) in a single calculation. The endpoint of the integration is W... z, final = W out This determines the total length z of the device, and thus also gives the total length z of the device. final .
[0024] As a further preferred technical solution of the present invention, the continuous function W(z) obtained in step three is discretized and sampled to generate a physical layout in formats such as GDSII for photolithography manufacturing.
[0025] This invention also protects an optical waveguide generated using the aforementioned "direct synthesis method". Its structural feature is that its geometric profile function W(z) is the unique solution to the first-order ordinary differential equation of the waveguide profile W(z) under given boundary conditions, ensuring that its internal "local adiabatic parameter" is strictly conserved along the propagation direction.
[0026] The direct synthesis optical waveguide design method based on local adiabatic conservation described in this invention has the following technical advantages compared with existing technologies:
[0027] (1) Revolution in design paradigm: This invention replaces "nondeterministic iterative optimization" with "deterministic direct synthesis", which is a fundamental leap in design thinking. The design process changes from "black box trial and error" to "white box creation", opening up a brand-new deterministic design path based on physical laws for the field of photonic device design.
[0028] (2) Ultimate improvement in design efficiency: By eliminating all time-consuming full-wave simulation iterations, design time is reduced from days or hours to seconds or minutes (only the time for mode scanning and solving differential equations). This makes rapid prototyping and global exploration of complex devices possible.
[0029] (3) Guarantee of physical optimality: The design results are directly derived from the strict satisfaction of the adiabatic physical conditions, ensuring its optimality on the Pareto front of "efficiency-size", without worrying about getting trapped in local optima.
[0030] (4) Profound physical insights: This method not only provides a structure, but also reveals why the structure is optimal. The Γ(W) function itself is a quantitative characterization of the physical bottleneck of the device, providing designers with unprecedented profound physical insights. Attached Figure Description
[0031] Figure 1 This is a function curve of the local adiabatic parameter Γ(W) calculated in step one of the embodiments of the present invention as a function of waveguide width W;
[0032] Figure 2 The image shows the optimal waveguide width profile W(z) function directly synthesized by solving the differential equation in step three of this embodiment of the invention. Detailed Implementation
[0033] The present invention will be further explained in detail below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the following examples are only used to explain the present invention and are not intended to limit the present invention.
[0034] A direct synthesis optical waveguide design method based on local adiabatic conservation includes the following steps:
[0035] Step 1: Define and calculate the "Local Adiabaticity Parameter (LAP)".
[0036] First, we define a physical quantity, called LAP, denoted as Γ(W), that describes the difficulty of mode evolution under waveguide geometric parameters W (such as width). According to coupled-mode theory, this parameter is proportional to the mode coupling coefficient and inversely proportional to the square of the difference in mode propagation constants. Its simplified form can be expressed as:
[0037] (1)
[0038] Among them, C 12 It is the mode coupling coefficient, E 1,2 and n eff,1,2 Γ(W) represents the electric field and effective refractive index of the two coupled modes, and ∆β is the difference in propagation constants. This parameter Γ(W) depends only on the cross-sectional geometry W of the waveguide and is independent of its length. It can be calculated over the entire range of geometric parameters (from W) through a single mode scan before design begins. in To W out The Γ(W) function curve of ).
[0039] Step 2: Set the global conservation target adiabaticity value (TAV).
[0040] To ensure the overall performance of the device (e.g., total loss below -0.01 dB), a constant local adiabatic temperature is required. A globally conserved adiabatic temperature target value, denoted as Λ0, is set. An ideal adiabatic waveguide, at every point along its propagation direction z, should satisfy:
[0041] (2)
[0042] This equation is the core physical law of this invention. It shows that the geometric gradient rate dW / dz along the waveguide length must be inversely proportional to the local mode evolution difficulty Γ(W) in order to maintain a constant adiabatic flux Λ0.
[0043] Step 3: Directly solve for the generating function and synthesize the waveguide profile.
[0044] Transforming the core law in step two, we obtain a first-order ordinary differential equation for the waveguide profile W(z):
[0045] (3)
[0046] This is an equation that can be solved directly. Given the boundary conditions (W(0) = W... in Using standard numerical integration methods (such as the Runge-Kutta method), a complete and continuous waveguide width profile function W(z) can be directly synthesized in a single calculation. The endpoint of the integration is W... z, final = W out This determines the total length z of the device, and thus also gives the total length z of the device. final .
[0047] Step 4: Discretize to generate physical layout.
[0048] The continuous function W(z) obtained in step three is discretized and sampled to generate physical layouts in formats such as GDSII for photolithography.
[0049] This invention also protects an optical waveguide generated using the above-mentioned "direct synthesis method". Its fundamental structural feature is that its geometric profile function W(z) is the unique solution of a specific differential equation (3) under given boundary conditions, which makes its internal "local adiabatic parameter" strictly conserved along the propagation direction.
[0050] In practical implementation, taking the design of a TE0-TE1 mode converter (with a width gradually changing from 1.18 μm to 1.70 μm) identical to the aforementioned case as an example, we will demonstrate the revolutionary path of this invention:
[0051] (1) Calculation of LAP function (step one):
[0052] No iterations are performed. The first step, and the only one requiring electromagnetic field calculations, is a one-time mode analysis. The waveguide width W is scanned from 1.18 μm to 1.70 μm, and the n values for the TE0 and TE1 modes are calculated for each W cross-section. eff The field distribution was determined, and the local adiabatic parameter Γ(W) was calculated using the formula. The resulting Γ(W) curve is shown below. Figure 1 As shown, a large peak appears near W≈ 1.45 μm due to mode anti-crossover.
[0053] (2) Set up TAV (Step 2):
[0054] Based on the system's requirement for total losses (e.g., <-40dB), a suitable global conserved adiabatic target value Λ0 is selected through theoretical calculation or experience. This is a single scalar value.
[0055] (3) Directly synthesize the contour (step three):
[0056] Now, we solve the differential equation (3) using W(0) = 1.18 μm as the initial condition. We then use the ode45 solver in MATLAB (code provided later) to numerically integrate the equation. The integration process will automatically generate the W(z) curve (e.g., ...). Figure 2 Because the denominator is extremely large in the peak region of Γ(W) (W ≈ 1.45 μm), resulting in a very small dW / dz, the integrated W(z) curve naturally and inevitably becomes extremely flat in this region. Integration stops when the value of W(z) reaches 1.70 μm, at which point z = 20.7377 μm is the shortest total length required for the device. The entire process takes less than a minute.
[0057] (4) Generate the layout (step four):
[0058] The obtained continuous curve W(z) is sampled and converted into a polygonal GDSII file, which can then be used for chip fabrication.
[0059] Ultimately, without any simulation or iteration of the complete device, the physically optimal device structure was synthesized deterministically in a single step. This is fundamentally different from existing technologies in terms of methodology and possesses undeniable, groundbreaking innovation.
[0060] The specific implementation schemes described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific implementation schemes of the present invention and are not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.
Claims
1. A direct synthesis optical waveguide design method based on local adiabatic conservation, characterized in that, Includes the following steps: Step 1: Define and calculate the local adiabatic parameter LAP; Step 2: Set the target value for globally conserved adiabatic heat (TAV); Step 3: Directly solve for the generating function and synthesize the waveguide profile; Step 4: Discretize to generate physical layout.
2. The direct synthesis optical waveguide design method based on local adiabatic conservation as described in claim 1, characterized in that, Step one specifically includes the following steps: First, we define a physical quantity, called LAP, denoted as Γ(W), that describes the difficulty of mode evolution under waveguide geometry parameter W. According to coupled-mode theory, this parameter is proportional to the mode coupling coefficient and inversely proportional to the square of the difference in mode propagation constants. Its simplified form is expressed as: （1）； Among them, C 12 It is the mode coupling coefficient, E 1,2 and n eff,1,2 Γ(W) represents the electric field and effective refractive index of the two coupled modes, and ∆β is the difference in propagation constants. This parameter Γ(W) depends only on the cross-sectional geometry W of the waveguide and is independent of its length.
3. The direct synthesis optical waveguide design method based on local adiabatic conservation according to claim 2, characterized in that, In step two, to ensure the performance of the entire device, a constant local adiabatic temperature is required. A globally conserved adiabatic temperature target value is set, denoted as Λ0. An ideal adiabatic waveguide should satisfy the following at every point along its propagation direction z: (2); Among them, the geometric gradient rate dW / dz along the waveguide length direction must be inversely proportional to the local mode evolution difficulty Γ(W) in order to maintain a constant adiabatic flux Λ0.
4. The direct synthesis optical waveguide design method based on local adiabatic conservation according to claim 3, characterized in that, Transforming the core law in step two, we obtain a first-order ordinary differential equation for the waveguide profile W(z): （3）； Given the boundary condition W(0) = W in The complete and continuous waveguide width profile function W(z) is directly synthesized in a single calculation using standard numerical integration methods; the endpoint of the integration is W. z, final = W out This determines the total length z of the device, and thus also gives the total length z of the device. final .
5. The direct synthesis optical waveguide design method based on local adiabatic conservation according to claim 4, characterized in that, The continuous function W(z) obtained in step three is discretized and sampled to generate a physical layout in GDSII format for photolithography.
6. An optical waveguide generated by the method according to any one of claims 1-5, characterized in that, Its geometric profile function W(z) is the unique solution of the first-order ordinary differential equation of the waveguide profile W(z) under given boundary conditions, which makes the local adiabatic parameter inside it strictly conserved along the propagation direction.