Add ContourPath averaging option to dielectric subpixel

Author: weiliangjin2021

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - `fill` and `fill_structures` argument in `td.Simulation.plot_structures()` and `td.Simulation.plot()` respectively to disable fill and plot outlines of structures only.
+- New subpixel averaging option `ContourPathAveraging` applied to dielectric material boundaries.
+
 ### Fixed
 - Compatibility with `xarray>=2025.03`.
 

docs/api/subpixel_averaging.rst

@@ -20,5 +20,6 @@ Types of Subpixel Averaging Methods
    tidy3d.VolumetricAveraging
    tidy3d.HeuristicPECStaircasing
    tidy3d.PolarizedAveraging
+   tidy3d.ContourPathAveraging
    tidy3d.PECConformal
    tidy3d.SurfaceImpedance

tidy3d/__init__.py

@@ -333,6 +333,7 @@
 
 # subpixel
 from .components.subpixel_spec import (
+    ContourPathAveraging,
     HeuristicPECStaircasing,
     PECConformal,
     PolarizedAveraging,
@@ -627,6 +628,7 @@ def set_logging_level(level: str) -> None:
     "Staircasing",
     "VolumetricAveraging",
     "PolarizedAveraging",
+    "ContourPathAveraging",
     "HeuristicPECStaircasing",
     "PECConformal",
     "SurfaceImpedance",

tidy3d/components/subpixel_spec.py

@@ -39,7 +39,8 @@ class Staircasing(AbstractSubpixelAveragingMethod):
 
 
 class PolarizedAveraging(AbstractSubpixelAveragingMethod):
-    """Apply a polarized subpixel averaging method to dielectric boundaries.
+    """Apply a polarized subpixel averaging method to dielectric boundaries, which
+    is a phenomenological approximation of :class:`.ContourPathAveraging`.
 
     Note
     ----
@@ -51,7 +52,20 @@ class PolarizedAveraging(AbstractSubpixelAveragingMethod):
     """
 
 
-DielectricSubpixelType = Union[Staircasing, PolarizedAveraging]
+class ContourPathAveraging(AbstractSubpixelAveragingMethod):
+    """Apply a contour-path subpixel averaging method to dielectric boundaries.
+
+    Note
+    ----
+    The algorithm is based on:
+
+        A. Mohammadi, H. Nadgaran and M. Agio, "Contour-path effective
+        permittivities for the two-dimensional finite-difference
+        time-domain method", Optics express, 13(25), 10367-10381 (2005).
+    """
+
+
+DielectricSubpixelType = Union[Staircasing, PolarizedAveraging, ContourPathAveraging]
 
 
 class VolumetricAveraging(AbstractSubpixelAveragingMethod):