Adding support for current density monitor

tests/test_components/test_heat_charge.py

@@ -256,6 +256,10 @@ def monitors():
 
     electric_field_mnt = td.SteadyElectricFieldMonitor(size=(1.6, 2, 3), name="electric_field_test")
 
+    current_density_mnt = td.SteadyCurrentDensityMonitor(
+        size=(1.6, 2, 3), name="electric_field_mnt"
+    )
+
     return [
         temp_mnt1,  # 0
         temp_mnt2,  # 1
@@ -270,6 +274,7 @@ def monitors():
         energy_band_mnt1,  # 10
         mesh_mnt,  # 11
         electric_field_mnt,  # 12
+        current_density_mnt,  # 13
     ]
 
 
@@ -755,6 +760,19 @@ def electric_field_monitor_data(monitors):
     return (mnt_data1, mnt_data2, mnt_data3)
 
 
+@pytest.fixture(scope="module")
+def current_density_monitor_data(monitors, electric_field_monitor_data):
+    """Creates different current density monitor data."""
+    monitor = monitors[13]
+    e_data1, e_data2, e_data3 = electric_field_monitor_data
+
+    mnt_data1 = td.SteadyCurrentDensityData(monitor=monitor, J=e_data1.E)
+    mnt_data2 = td.SteadyCurrentDensityData(monitor=monitor, J=e_data2.E)
+    mnt_data3 = td.SteadyCurrentDensityData(monitor=monitor, J=e_data3.E)
+
+    return (mnt_data1, mnt_data2, mnt_data3)
+
+
 @pytest.fixture(scope="module")
 def simulation_data(
     heat_simulation,
@@ -929,52 +947,68 @@ def test_monitor_crosses_medium(mediums, structures, heat_simulation, conduction
 
 
 def test_heat_charge_mnt_data(
-    temperature_monitor_data, voltage_monitor_data, electric_field_monitor_data
+    temperature_monitor_data,
+    voltage_monitor_data,
+    electric_field_monitor_data,
+    current_density_monitor_data,
 ):
     """Tests whether different heat-charge monitor data can be created."""
     assert len(temperature_monitor_data) == 4, "Expected 4 temperature monitor data entries."
     assert len(voltage_monitor_data) == 4, "Expected 4 voltage monitor data entries."
     assert len(electric_field_monitor_data) == 3, "Expected 3 electric field monitor data entries."
+    assert len(current_density_monitor_data) == 3, (
+        "Expected 3 current density monitor data entries."
+    )
+
+    for var, mnt_data_lists in [
+        ("E", electric_field_monitor_data),
+        ("J", current_density_monitor_data),
+    ]:
+        for mnt_data in mnt_data_lists:
+            assert var in mnt_data.field_components.keys()
+
+            symm_data = mnt_data.symmetry_expanded_copy
+            if var == "E":
+                assert symm_data.E == mnt_data.E
+            elif var == "J":
+                assert symm_data.J == mnt_data.J
+
+            names = mnt_data.field_name("abs^2")
+            assert names == var + "²"
+            names = mnt_data.field_name()
+            assert names == var
+
+            # make sure an error is raised if we don't use a field data array
+            # TriangularGridDataset
+            tri_grid_points = td.PointDataArray(
+                [[0.0, 0.0], [1.0, 0.0], [0.0, 1.0], [1.0, 1.0]],
+                dims=("index", "axis"),
+            )
 
-    for mnt_data in electric_field_monitor_data:
-        assert "E" in mnt_data.field_components.keys()
-
-        symm_data = mnt_data.symmetry_expanded_copy
-        assert symm_data.E == mnt_data.E
-
-        names = mnt_data.field_name("abs^2")
-        assert names == "E²"
-        names = mnt_data.field_name()
-        assert names == "E"
-
-        # make sure an error is raised if we don't use a field data array
-        # TriangularGridDataset
-        tri_grid_points = td.PointDataArray(
-            [[0.0, 0.0], [1.0, 0.0], [0.0, 1.0], [1.0, 1.0]],
-            dims=("index", "axis"),
-        )
-
-        tri_grid_cells = td.CellDataArray(
-            [[0, 1, 2], [1, 2, 3]],
-            dims=("cell_index", "vertex_index"),
-        )
+            tri_grid_cells = td.CellDataArray(
+                [[0, 1, 2], [1, 2, 3]],
+                dims=("cell_index", "vertex_index"),
+            )
 
-        tri_grid_values = td.IndexedDataArray(
-            [1.0, 2.0, 3.0, 4.0],
-            dims=("index",),
-            name="T",
-        )
+            tri_grid_values = td.IndexedDataArray(
+                [1.0, 2.0, 3.0, 4.0],
+                dims=("index",),
+                name="T",
+            )
 
-        tri_grid = td.TriangularGridDataset(
-            normal_axis=1,
-            normal_pos=0,
-            points=tri_grid_points,
-            cells=tri_grid_cells,
-            values=tri_grid_values,
-        )
+            tri_grid = td.TriangularGridDataset(
+                normal_axis=1,
+                normal_pos=0,
+                points=tri_grid_points,
+                cells=tri_grid_cells,
+                values=tri_grid_values,
+            )
 
-        with pytest.raises(pd.ValidationError):
-            _ = mnt_data.updated_copy(E=tri_grid)
+            with pytest.raises(pd.ValidationError):
+                if var == "E":
+                    _ = mnt_data.updated_copy(E=tri_grid)
+                elif var == "J":
+                    _ = mnt_data.updated_copy(J=tri_grid)
 
 
 def test_grid_spec_validation(grid_specs):

tidy3d/__init__.py

@@ -37,6 +37,7 @@
 )
 from tidy3d.components.tcad.data.types import (
     SteadyCapacitanceData,
+    SteadyCurrentDensityData,
     SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyFreeCarrierData,
@@ -54,6 +55,7 @@
 from tidy3d.components.tcad.mesher import VolumeMesher
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyCurrentDensityMonitor,
     SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
@@ -659,6 +661,8 @@ def set_logging_level(level: str) -> None:
     "Staircasing",
     "SteadyCapacitanceData",
     "SteadyCapacitanceMonitor",
+    "SteadyCurrentDensityData",
+    "SteadyCurrentDensityMonitor",
     "SteadyElectricFieldData",
     "SteadyElectricFieldMonitor",
     "SteadyEnergyBandData",

tidy3d/components/tcad/data/monitor_data/charge.py

@@ -20,6 +20,7 @@
 from tidy3d.components.tcad.data.monitor_data.abstract import HeatChargeMonitorData
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyCurrentDensityMonitor,
     SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
@@ -467,7 +468,7 @@ def symmetry_expanded_copy(self) -> SteadyCapacitanceData:
 
 class SteadyElectricFieldData(HeatChargeMonitorData):
     """
-    Stores electric field :math:`\\vec{E}` from a charge simulation.
+    Stores electric field :math:`\\vec{E}` from a Charge/Conduction simulation.
 
     Notes
     -----
@@ -478,7 +479,7 @@ class SteadyElectricFieldData(HeatChargeMonitorData):
     monitor: SteadyElectricFieldMonitor = pd.Field(
         ...,
         title="Electric field monitor",
-        description="Electric field data associated with a Charge simulation.",
+        description="Electric field data associated with a Charge/Conduction simulation.",
     )
 
     E: UnstructuredFieldType = pd.Field(
@@ -542,3 +543,78 @@ def field_name(self, val: str = "") -> str:
             return "E²"
         else:
             return "E"
+
+
+class SteadyCurrentDensityData(HeatChargeMonitorData):
+    """
+    Stores current density :math:`\\vec{J}` from a Charge/Conduction simulation. It is given in
+    units of :math:`A/\\mu m^2`
+    """
+
+    monitor: SteadyCurrentDensityMonitor = pd.Field(
+        ...,
+        title="Current density monitor",
+        description="Current density data associated with a Charge/Conduction simulation.",
+    )
+
+    J: UnstructuredFieldType = pd.Field(
+        None,
+        title="Current density",
+        description=r"Contains the computed current density in :math:`A/\\mu m^2`.",
+        discriminator=TYPE_TAG_STR,
+    )
+
+    @property
+    def field_components(self) -> dict[str, UnstructuredFieldType]:
+        """Maps the field components to their associated data."""
+        return {"J": self.J}
+
+    @pd.root_validator(skip_on_failure=True)
+    def warn_no_data(cls, values):
+        """Warn if no data provided."""
+
+        mnt = values.get("monitor")
+        J = values.get("J")
+
+        if J is None:
+            log.warning(
+                f"No data is available for monitor '{mnt.name}'. This is typically caused by "
+                "monitor not intersecting any solid medium."
+            )
+
+        return values
+
+    @pd.root_validator(skip_on_failure=True)
+    def check_correct_data_type(cls, values):
+        """Issue error if incorrect data type is used"""
+
+        mnt = values.get("monitor")
+        J = values.get("J")
+
+        if isinstance(J, TetrahedralGridDataset) or isinstance(J, TriangularGridDataset):
+            AcceptedTypes = (IndexedFieldVoltageDataArray, PointDataArray)
+            if not isinstance(J.values, AcceptedTypes):
+                raise ValueError(
+                    f"In the data associated with monitor {mnt}, must contain a field. This can be "
+                    "defined with IndexedFieldVoltageDataArray or PointDataArray."
+                )
+
+        return values
+
+    @property
+    def symmetry_expanded_copy(self) -> SteadyCurrentDensityData:
+        """Return copy of self with symmetry applied."""
+
+        new_J = self._symmetry_expanded_copy(property=self.J)
+
+        return self.updated_copy(
+            J=new_J,
+            symmetry=(0, 0, 0),
+        )
+
+    def field_name(self, val: str = "") -> str:
+        """Gets the name of the fields to be plotted."""
+        if val == "abs^2":
+            return "J²"
+        else:
+            return "J"

tidy3d/components/tcad/data/types.py

@@ -6,6 +6,7 @@
 
 from tidy3d.components.tcad.data.monitor_data.charge import (
     SteadyCapacitanceData,
+    SteadyCurrentDensityData,
     SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyFreeCarrierData,
@@ -20,4 +21,5 @@
     SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyCapacitanceData,
+    SteadyCurrentDensityData,
 ]

tidy3d/components/tcad/monitors/charge.py

@@ -84,7 +84,7 @@ class SteadyCapacitanceMonitor(HeatChargeMonitor):
 
 class SteadyElectricFieldMonitor(HeatChargeMonitor):
     """
-    Electric field monitor for Charge simulations.
+    Electric field monitor for Charge/Conduction simulations.
 
     Example
     -------
@@ -99,3 +99,22 @@ class SteadyElectricFieldMonitor(HeatChargeMonitor):
         title="Unstructured Grid",
         description="Return data on the original unstructured grid.",
     )
+
+
+class SteadyCurrentDensityMonitor(HeatChargeMonitor):
+    """
+    Current density monitor for Charge/Conduction simulations.
+
+    Example
+    -------
+    >>> import tidy3d as td
+    >>> current_density_monitor_z0 = td.SteadyCurrentDensityMonitor(
+    ... center=(0, 0.14, 0), size=(0.6, 0.3, 0), name="current_density_z0",
+    ... )
+    """
+
+    unstructured: Literal[True] = pd.Field(
+        True,
+        title="Unstructured Grid",
+        description="Return data on the original unstructured grid.",
+    )

tidy3d/components/tcad/simulation/heat_charge.py

@@ -49,6 +49,7 @@
 )
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyCurrentDensityMonitor,
     SteadyFreeCarrierMonitor,
     SteadyPotentialMonitor,
 )
@@ -546,6 +547,7 @@ def check_charge_simulation(cls, values):
             SteadyPotentialMonitor,
             SteadyFreeCarrierMonitor,
             SteadyCapacitanceMonitor,
+            SteadyCurrentDensityMonitor,
         )
 
         simulation_types = cls._check_simulation_types(values=values)
@@ -568,7 +570,7 @@ def check_charge_simulation(cls, values):
             if not any(isinstance(mnt, ChargeMonitorType) for mnt in monitors):
                 raise SetupError(
                     "Charge simulations require the definition of, at least, one of these monitors: "
-                    "'[SteadyPotentialMonitor, SteadyFreeCarrierMonitor, SteadyCapacitanceMonitor]' "
+                    "'[SteadyPotentialMonitor, SteadyFreeCarrierMonitor, SteadyCapacitanceMonitor, SteadyCurrentDensityMonitor]' "
                     "but none have been defined."
                 )
 

tidy3d/components/tcad/types.py

@@ -13,6 +13,7 @@
 from tidy3d.components.tcad.mobility import CaugheyThomasMobility, ConstantMobilityModel
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyCurrentDensityMonitor,
     SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
@@ -37,6 +38,7 @@
     SteadyEnergyBandMonitor,
     SteadyElectricFieldMonitor,
     SteadyCapacitanceMonitor,
+    SteadyCurrentDensityMonitor,
 ]
 HeatChargeSourceType = Union[HeatSource, HeatFromElectricSource, UniformHeatSource]
 HeatChargeBCType = Union[