Merge pull request #1919 from flexcompute/qiming/error_bloch

added validator to error out Bloch boundaries in along 0-dim in 2D simulations

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - `PolySlab` now raises error when differentiating and dilation causes damage to the polygon.
+- Validator `boundaries_for_zero_dims` to raise error when Bloch boundaries are used along 0-sized dims.
 
 ### Fixed
 - `DataArray` interpolation failure due to incorrect ordering of coordinates when interpolating with autograd tracers.

tidy3d/components/simulation.py

@@ -2410,7 +2410,7 @@ def tfsf_with_symmetry(cls, val, values):
     @pydantic.validator("boundary_spec", always=True)
     @skip_if_fields_missing(["size", "symmetry"])
     def boundaries_for_zero_dims(cls, val, values):
-        """Error if absorbing boundaries, unmatching pec/pmc, or symmetry is used along a zero dimension."""
+        """Error if absorbing boundaries, bloch boundaries, unmatching pec/pmc, or symmetry is used along a zero dimension."""
         boundaries = val.to_list
         size = values.get("size")
         symmetry = values.get("symmetry")
@@ -2420,6 +2420,7 @@ def boundaries_for_zero_dims(cls, val, values):
             if size_dim == 0:
                 axis = axis_names[dim]
                 num_absorbing_bdries = sum(isinstance(bnd, AbsorberSpec) for bnd in boundary)
+                num_bloch_bdries = sum(isinstance(bnd, BlochBoundary) for bnd in boundary)
 
                 if num_absorbing_bdries > 0:
                     raise SetupError(
@@ -2428,6 +2429,14 @@ def boundaries_for_zero_dims(cls, val, values):
                         f"Use either 'Periodic' or 'BlochBoundary' along {axis}."
                     )
 
+                if num_bloch_bdries > 0:
+                    raise SetupError(
+                        f"The simulation has zero size along the {axis} axis, "
+                        "using a Bloch boundary along such an axis is not supported because of "
+                        "the Bloch vector definition in units of '2 * pi / (size along dimension)'. Use a small "
+                        "but nonzero size along the dimension instead."
+                    )
+
                 if symmetry_dim != 0:
                     raise SetupError(
                         f"The simulation has zero size along the {axis} axis, so "