Enable PMC material

Author: weiliangjin2021

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `priority` parameter to `web.run()` and related functions to allow vGPU users to set task priority (1-10) in the queue.
 - `EMEFieldMonitor` now supports `interval_space`.
 - `Simulation.precision` option allows to select `"double"` precision for very high-accuracy results. Note that this is very rarely needed, and doubles the simulation computational weight and correpsondingly FlexCredit cost.
+- Added material type `PMCMedium` for perfect magnetic conductor.
 
 ### Changed
 - Switched to an analytical gradient calculation for spatially-varying pole-residue models (`CustomPoleResidue`).

docs/api/mediums.rst

@@ -16,6 +16,7 @@ Spatially uniform
    tidy3d.Medium
    tidy3d.LossyMetalMedium
    tidy3d.PECMedium
+   tidy3d.PMCMedium
    tidy3d.FullyAnisotropicMedium
 
 Spatially varying

tests/test_components/material/test_multi_physics.py

@@ -17,6 +17,7 @@ def test_delegated_attributes_work(dummy_optical):
 
     # delegated names resolve
     assert mp.is_pec is dummy_optical.is_pec
+    assert mp.is_pmc is dummy_optical.is_pmc
     assert mp._eps_plot == dummy_optical._eps_plot
     assert mp.viz_spec == dummy_optical.viz_spec
 
@@ -30,6 +31,9 @@ def test_delegated_attribute_without_optical_raises():
     with pytest.raises(AttributeError, match=r"optical medium is 'None'"):
         _ = mp_no_opt.is_pec
 
+    with pytest.raises(AttributeError, match=r"optical medium is 'None'"):
+        _ = mp_no_opt.is_pmc
+
 
 def test_has_cached_props(dummy_optical):
     mp = td.MultiPhysicsMedium(optical=dummy_optical)

tests/test_components/test_medium.py

@@ -15,12 +15,13 @@
 MEDIUM = td.Medium()
 ANIS_MEDIUM = td.AnisotropicMedium(xx=MEDIUM, yy=MEDIUM, zz=MEDIUM)
 PEC = td.PECMedium()
+PMC = td.PMCMedium()
 PR = td.PoleResidue(poles=[(-1 + 1j, 2 + 2j)])
 SM = td.Sellmeier(coeffs=[(1, 2)])
 LZ = td.Lorentz(coeffs=[(1, 2, 3)])
 DR = td.Drude(coeffs=[(1, 2)])
 DB = td.Debye(coeffs=[(1, 2)])
-MEDIUMS = [MEDIUM, ANIS_MEDIUM, PEC, PR, SM, LZ, DR, DB]
+MEDIUMS = [MEDIUM, ANIS_MEDIUM, PEC, PR, SM, LZ, DR, DB, PMC]
 
 f, AX = plt.subplots()
 
@@ -142,6 +143,10 @@ def test_PEC():
     _ = td.Structure(geometry=td.Box(size=(1, 1, 1)), medium=td.PEC)
 
 
+def test_PMC():
+    _ = td.Structure(geometry=td.Box(size=(1, 1, 1)), medium=td.PMC)
+
+
 def test_lossy_metal():
     # frequency_range shouldn't be None
     with pytest.raises(pydantic.ValidationError):
@@ -406,6 +411,8 @@ def test_n_cfl():
     assert material.n_cfl == 2
     # PEC
     assert PEC.n_cfl == 1
+    # PMC
+    assert PMC.n_cfl == 1
     # anisotropic
     material = td.AnisotropicMedium(xx=MEDIUM, yy=td.Medium(permittivity=4), zz=MEDIUM)
     assert material.n_cfl == 1

tests/test_components/test_time_modulation.py

@@ -215,6 +215,10 @@ def test_unsupported_modulated_medium_types():
     with pytest.raises(pydantic.ValidationError):
         td.PECMedium(modulation_spec=modulation_spec)
 
+    # PMC cannot be modulated
+    with pytest.raises(pydantic.ValidationError):
+        td.PMCMedium(modulation_spec=modulation_spec)
+
     # For Anisotropic medium, one should modulate the components, not the whole medium
     with pytest.raises(pydantic.ValidationError):
         td.AnisotropicMedium(

tests/utils.py

@@ -474,6 +474,10 @@ def make_custom_data(lims, unstructured):
             geometry=td.Box(size=(1, 1, 1), center=(-1, 0, 0)),
             medium=td.AnisotropicMedium(xx=td.PEC, yy=td.Medium(), zz=td.Medium()),
         ),
+        td.Structure(
+            geometry=td.Box(size=(1, 1, 1), center=(-1, 0, 0)),
+            medium=td.AnisotropicMedium(xx=td.PMC, yy=td.Medium(), zz=td.Medium()),
+        ),
         # Test a fully anistropic medium
         td.Structure(
             geometry=td.Box(size=(1, 1, 1), center=(-1, 0, 0)),
@@ -485,6 +489,10 @@ def make_custom_data(lims, unstructured):
             medium=td.PEC,
             name="pec_group",
         ),
+        td.Structure(
+            geometry=td.Box(size=(1, 1, 1), center=(-1, 0, 0)),
+            medium=td.PMC,
+        ),
         td.Structure(
             geometry=td.Cylinder(radius=1.0, length=2.0, center=(1.0, 0.0, -1.0), axis=1),
             medium=td.AnisotropicMedium(

tidy3d/__init__.py

@@ -244,6 +244,7 @@
 from .components.medium import (
     PEC,
     PEC2D,
+    PMC,
     AbstractMedium,
     AnisotropicMedium,
     CustomAnisotropicMedium,
@@ -269,6 +270,7 @@
     PECMedium,
     PerturbationMedium,
     PerturbationPoleResidue,
+    PMCMedium,
     PoleResidue,
     Sellmeier,
     SurfaceImpedanceFitterParam,
@@ -415,6 +417,7 @@ def set_logging_level(level: str) -> None:
     "MU_0",
     "PEC",
     "PEC2D",
+    "PMC",
     "PML",
     "TFSF",
     "Absorber",
@@ -610,6 +613,7 @@ def set_logging_level(level: str) -> None:
     "PECConformal",
     "PECMedium",
     "PMCBoundary",
+    "PMCMedium",
     "PMLParams",
     "PMLTypes",
     "ParameterPerturbation",

tidy3d/components/material/multi_physics.py

@@ -141,6 +141,7 @@ def __getattr__(self, name: str):
             return None
 
         DELEGATED_ATTRIBUTES = {
+            "is_pmc": self.optical,
             "_eps_plot": self.optical,
             "viz_spec": self.optical,
             "eps_diagonal_numerical": self.optical,

tidy3d/components/medium.py

@@ -884,7 +884,7 @@ def _validate_modulation_spec(cls, val, values):
         nonlinear_spec = values.get("nonlinear_spec")
         if val is not None and nonlinear_spec is not None:
             raise ValidationError(
-                f"For medium class {cls}, 'modulation_spec' of class {type(val)} and "
+                f"For medium class {cls.__name__}, 'modulation_spec' of class {type(val)} and "
                 f"'nonlinear_spec' of class {type(nonlinear_spec)} are "
                 "not simultaneously supported."
             )
@@ -1350,6 +1350,11 @@ def is_pec(self):
         """Whether the medium is a PEC."""
         return False
 
+    @cached_property
+    def is_pmc(self):
+        """Whether the medium is a PMC."""
+        return False
+
     def sel_inside(self, bounds: Bound) -> AbstractMedium:
         """Return a new medium that contains the minimal amount data necessary to cover
         a spatial region defined by ``bounds``.
@@ -1740,7 +1745,7 @@ def _validate_modulation_spec(cls, val):
         if val is not None:
             raise ValidationError(
                 f"A 'modulation_spec' of class {type(val)} is not "
-                f"currently supported for medium class {cls}."
+                f"currently supported for medium class {cls.__name__}."
             )
         return val
 
@@ -1767,6 +1772,52 @@ def is_pec(self):
 PEC = PECMedium(name="PEC")
 
 
+# PMC keyword
+class PMCMedium(AbstractMedium):
+    """Perfect magnetic conductor class.
+
+    Note
+    ----
+
+        To avoid confusion from duplicate PMCs, must import ``tidy3d.PMC`` instance directly.
+
+
+
+    """
+
+    @pd.validator("modulation_spec", always=True)
+    def _validate_modulation_spec(cls, val):
+        """Check compatibility with modulation_spec."""
+        if val is not None:
+            raise ValidationError(
+                f"A 'modulation_spec' of class {type(val)} is not "
+                f"currently supported for medium class {cls.__name__}."
+            )
+        return val
+
+    @ensure_freq_in_range
+    def eps_model(self, frequency: float) -> complex:
+        # permittivity of a PMC.
+        return 1.0 + 0j
+
+    @cached_property
+    def n_cfl(self):
+        """This property computes the index of refraction related to CFL condition, so that
+        the FDTD with this medium is stable when the time step size that doesn't take
+        material factor into account is multiplied by ``n_cfl``.
+        """
+        return 1.0
+
+    @cached_property
+    def is_pmc(self):
+        """Whether the medium is a PMC."""
+        return True
+
+
+# PEC builtin instance
+PMC = PMCMedium(name="PMC")
+
+
 class Medium(AbstractMedium):
     """Dispersionless medium. Mediums define the optical properties of the materials within the simulation.
 
@@ -5643,9 +5694,10 @@ def plot(
         return ax
 
 
-IsotropicUniformMediumType = Union[
+IsotropicUniformMediumFor2DType = Union[
     Medium, LossyMetalMedium, PoleResidue, Sellmeier, Lorentz, Debye, Drude, PECMedium
 ]
+IsotropicUniformMediumType = Union[IsotropicUniformMediumFor2DType, PMCMedium]
 IsotropicCustomMediumType = Union[
     CustomPoleResidue,
     CustomSellmeier,
@@ -5719,7 +5771,7 @@ def _validate_modulation_spec(cls, val):
         if val is not None:
             raise ValidationError(
                 f"A 'modulation_spec' of class {type(val)} is not "
-                f"currently supported for medium class {cls}. "
+                f"currently supported for medium class {cls.__name__}. "
                 "Please add modulation to each component."
             )
         return val
@@ -5852,10 +5904,19 @@ def is_pec(self):
         """Whether the medium is a PEC."""
         return any(self.is_comp_pec(i) for i in range(3))
 
+    @cached_property
+    def is_pmc(self):
+        """Whether the medium is a PMC."""
+        return any(self.is_comp_pmc(i) for i in range(3))
+
     def is_comp_pec(self, comp: Axis):
         """Whether the medium is a PEC."""
         return isinstance(self.components[["xx", "yy", "zz"][comp]], PECMedium)
 
+    def is_comp_pmc(self, comp: Axis):
+        """Whether the medium is a PMC."""
+        return isinstance(self.components[["xx", "yy", "zz"][comp]], PMCMedium)
+
     def sel_inside(self, bounds: Bound):
         """Return a new medium that contains the minimal amount data necessary to cover
         a spatial region defined by ``bounds``.
@@ -5945,7 +6006,7 @@ def _validate_modulation_spec(cls, val):
         if val is not None:
             raise ValidationError(
                 f"A 'modulation_spec' of class {type(val)} is not "
-                f"currently supported for medium class {cls}."
+                f"currently supported for medium class {cls.__name__}."
             )
         return val
 
@@ -6970,6 +7031,7 @@ def perturbed_copy(
     Medium,
     AnisotropicMedium,
     PECMedium,
+    PMCMedium,
     PoleResidue,
     Sellmeier,
     Lorentz,
@@ -7004,7 +7066,7 @@ class Medium2D(AbstractMedium):
 
     """
 
-    ss: IsotropicUniformMediumType = pd.Field(
+    ss: IsotropicUniformMediumFor2DType = pd.Field(
         ...,
         title="SS Component",
         description="Medium describing the ss-component of the diagonal permittivity tensor. "
@@ -7015,7 +7077,7 @@ class Medium2D(AbstractMedium):
         discriminator=TYPE_TAG_STR,
     )
 
-    tt: IsotropicUniformMediumType = pd.Field(
+    tt: IsotropicUniformMediumFor2DType = pd.Field(
         ...,
         title="TT Component",
         description="Medium describing the tt-component of the diagonal permittivity tensor. "
@@ -7032,7 +7094,7 @@ def _validate_modulation_spec(cls, val):
         if val is not None:
             raise ValidationError(
                 f"A 'modulation_spec' of class {type(val)} is not "
-                f"currently supported for medium class {cls}."
+                f"currently supported for medium class {cls.__name__}."
             )
         return val
 
@@ -7049,7 +7111,7 @@ def _validate_inplane_pec(cls, val, values):
 
     @classmethod
     def _weighted_avg(
-        cls, meds: list[IsotropicUniformMediumType], weights: list[float]
+        cls, meds: list[IsotropicUniformMediumFor2DType], weights: list[float]
     ) -> Union[PoleResidue, PECMedium]:
         """Average ``meds`` with weights ``weights``."""
         eps_inf = 1
@@ -7103,7 +7165,7 @@ def volumetric_equivalent(
             The 3D material corresponding to this 2D material.
         """
 
-        def get_component(med: MediumType3D, comp: Axis) -> IsotropicUniformMediumType:
+        def get_component(med: MediumType3D, comp: Axis) -> IsotropicUniformMediumFor2DType:
             """Extract the ``comp`` component of ``med``."""
             if isinstance(med, AnisotropicMedium):
                 dim = "xyz"[comp]
@@ -7365,7 +7427,7 @@ def sigma_model(self, freq: float) -> complex:
         return np.mean([self.ss.sigma_model(freq), self.tt.sigma_model(freq)], axis=0)
 
     @property
-    def elements(self) -> dict[str, IsotropicUniformMediumType]:
+    def elements(self) -> dict[str, IsotropicUniformMediumFor2DType]:
         """The diagonal elements of the 2D medium as a dictionary."""
         return {"ss": self.ss, "tt": self.tt}
 

tidy3d/components/mode/mode_solver.py

@@ -1811,6 +1811,8 @@ def _contain_good_conductor(self) -> bool:
         for medium in sim.scene.mediums:
             if medium.is_pec:
                 return True
+            if medium.is_pmc:
+                return True
             if apply_sibc and isinstance(medium, LossyMetalMedium):
                 return True
         return False