Fix bug in EME simulations with bends

Author: caseyflex

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed shaping of `CustomMedium` gradients when permittivity data includes a frequency dimension with multiple entries.
 - Bug in contains check for `LumpedElement`, which should allow the case of a `LumpedElement` touching the simulation boundaries.
 - Bug when generating a grid with snapping points near the simulation boundaries.
+- Solver error for EME simulations with bends, introduced when support for 2D EME simulations was added.
 
 ### Changed
 - Relaxed bounds checking of path integrals during `WavePort` validation.

tests/test_components/test_monitor.py

@@ -309,7 +309,7 @@ def test_mode_bend_radius():
             size=(5, 0, 1),
             freqs=np.linspace(1e14, 2e14, 100),
             name="test",
-            mode_spec=td.ModeSpec(num_modes=1, bend_radius=1, bend_axis=1),
+            mode_spec=td.ModeSpec(num_modes=1, bend_radius=1, bend_axis=2),
         )
         _ = td.Simulation(
             size=(2, 2, 2),

tests/test_plugins/test_mode_solver.py

@@ -1131,13 +1131,29 @@ def test_modes_eme_sim(mock_remote_api, local):
 
 def test_mode_small_bend_radius_fail():
     """Test that small bend radius fails."""
-
+    simulation = td.Simulation(
+        size=SIM_SIZE,
+        grid_spec=td.GridSpec(wavelength=1.0),
+        structures=[WAVEGUIDE],
+        run_time=1e-12,
+        symmetry=(1, 0, -1),
+        boundary_spec=td.BoundarySpec.all_sides(boundary=td.Periodic()),
+        sources=[SRC],
+    )
     with pytest.raises(ValueError):
         ms = ModeSolver(
             plane=PLANE,
             freqs=np.linspace(1e14, 2e14, 100),
             mode_spec=td.ModeSpec(num_modes=1, bend_radius=1, bend_axis=0),
+            simulation=simulation,
         )
+    # should work for infinite mode plane
+    ms = ModeSolver(
+        plane=td.Box(center=(0, 0, 0), size=(td.inf, 0, td.inf)),
+        freqs=np.linspace(1e14, 2e14, 100),
+        mode_spec=td.ModeSpec(num_modes=1, bend_radius=10000, bend_axis=0),
+        simulation=simulation,
+    )
 
 
 def make_high_order_mode_solver(sign, dim=3):

tidy3d/components/mode/mode_solver.py

@@ -56,7 +56,6 @@
 from tidy3d.components.validators import (
     validate_freqs_min,
     validate_freqs_not_empty,
-    validate_mode_plane_radius,
 )
 from tidy3d.components.viz import make_ax, plot_params_pml
 from tidy3d.constants import C_0
@@ -211,8 +210,11 @@ def plane_in_sim_bounds(cls, val, values):
         return val
 
     def _post_init_validators(self) -> None:
-        validate_mode_plane_radius(
-            mode_spec=self.mode_spec, plane=self.plane, msg_prefix="Mode solver"
+        self._validate_mode_plane_radius(
+            mode_spec=self.mode_spec,
+            plane=self.plane,
+            sim_geom=self.simulation.geometry,
+            msg_prefix="Mode solver",
         )
         self._warn_thick_pml(simulation=self.simulation, plane=self.plane, mode_spec=self.mode_spec)
 
@@ -239,6 +241,35 @@ def _warn_thick_pml(
                     "or smaller 'num_pml'."
                 )
 
+    @staticmethod
+    def _mode_plane(plane: Box, sim_geom: Box) -> Box:
+        """Intersect the mode plane with the sim geometry to get the effective
+        mode plane."""
+        mode_plane_bnds = plane.bounds_intersection(plane.bounds, sim_geom.bounds)
+        return Box.from_bounds(*mode_plane_bnds)
+
+    @classmethod
+    def _validate_mode_plane_radius(
+        cls, mode_spec: ModeSpec, plane: Box, sim_geom: Box, msg_prefix: str = ""
+    ):
+        """Validate that the radius of a mode spec with a bend is not smaller than half the size of
+        the plane along the radial direction."""
+
+        if not mode_spec.bend_radius:
+            return
+
+        mode_plane = cls._mode_plane(plane=plane, sim_geom=sim_geom)
+
+        # radial axis is the plane axis that is not the bend axis
+        _, plane_axs = mode_plane.pop_axis([0, 1, 2], mode_plane.size.index(0.0))
+        radial_ax = plane_axs[(mode_spec.bend_axis + 1) % 2]
+
+        if np.abs(mode_spec.bend_radius) < mode_plane.size[radial_ax] / 2:
+            raise ValueError(
+                f"{msg_prefix} bend radius is smaller than half the mode plane size "
+                "along the radial axis, which can produce wrong results."
+            )
+
     @cached_property
     def normal_axis(self) -> Axis:
         """Axis normal to the mode plane."""

tidy3d/components/mode/simulation.py

@@ -21,7 +21,6 @@
 )
 from tidy3d.components.source.field import ModeSource
 from tidy3d.components.types import TYPE_TAG_STR, Ax, Direction, EMField, FreqArray
-from tidy3d.components.validators import validate_mode_plane_radius
 from tidy3d.constants import C_0
 from tidy3d.exceptions import SetupError, ValidationError
 from tidy3d.log import log
@@ -228,8 +227,11 @@ def boundaries_for_zero_dims(cls, val, values):
 
     def _post_init_validators(self) -> None:
         """Call validators taking `self` that get run after init."""
-        validate_mode_plane_radius(
-            mode_spec=self.mode_spec, plane=self.plane, msg_prefix="'ModeSimulation'"
+        ModeSolver._validate_mode_plane_radius(
+            mode_spec=self.mode_spec,
+            plane=self.plane,
+            sim_geom=self.geometry,
+            msg_prefix="'ModeSimulation'",
         )
         _ = self._mode_solver
         _ = self.grid

tidy3d/components/simulation.py

@@ -118,7 +118,6 @@
     assert_objects_contained_in_sim_bounds,
     assert_objects_in_sim_bounds,
     validate_mode_objects_symmetry,
-    validate_mode_plane_radius,
 )
 from .viz import (
     PlotParams,
@@ -3729,18 +3728,22 @@ def _warn_mode_object_pml(self) -> None:
 
     def _validate_mode_object_bends(self) -> None:
         """Error if any mode sources or monitors with bends have a radius that is too small."""
+        from .mode.mode_solver import ModeSolver
+
         for imnt, monitor in enumerate(self.monitors):
             if isinstance(monitor, AbstractModeMonitor):
-                validate_mode_plane_radius(
+                ModeSolver._validate_mode_plane_radius(
                     mode_spec=monitor.mode_spec,
                     plane=monitor.geometry,
+                    sim_geom=self.geometry,
                     msg_prefix=f"Monitor at 'monitors[{imnt}]' ",
                 )
         for isrc, source in enumerate(self.sources):
             if isinstance(source, ModeSource):
-                validate_mode_plane_radius(
+                ModeSolver._validate_mode_plane_radius(
                     mode_spec=source.mode_spec,
                     plane=source.geometry,
+                    sim_geom=self.geometry,
                     msg_prefix=f"Source at 'sources[{isrc}]' ",
                 )
 

tidy3d/components/validators.py

@@ -15,7 +15,6 @@
 from .base import DATA_ARRAY_MAP, skip_if_fields_missing
 from .data.dataset import Dataset, FieldDataset
 from .geometry.base import Box
-from .mode_spec import ModeSpec
 
 """ Explanation of pydantic validators:
 
@@ -464,24 +463,6 @@ def freqs_not_empty(cls, val):
     return freqs_not_empty
 
 
-def validate_mode_plane_radius(mode_spec: ModeSpec, plane: Box, msg_prefix: str = ""):
-    """Validate that the radius of a mode spec with a bend is not smaller than half the size of
-    the plane along the radial direction."""
-
-    if not mode_spec.bend_radius:
-        return
-
-    # radial axis is the plane axis that is not the bend axis
-    _, plane_axs = plane.pop_axis([0, 1, 2], plane.size.index(0.0))
-    radial_ax = plane_axs[(mode_spec.bend_axis + 1) % 2]
-
-    if np.abs(mode_spec.bend_radius) < plane.size[radial_ax] / 2:
-        raise ValueError(
-            f"{msg_prefix} bend radius is smaller than half the mode plane size "
-            "along the radial axis, which can produce wrong results."
-        )
-
-
 def _warn_unsupported_traced_argument(name: str):
     @pydantic.validator(name, always=True, allow_reuse=True)
     def _warn_traced_arg(cls, val, values):