Electric field monitor for Charge

tests/test_components/test_heat_charge.py

@@ -252,18 +252,21 @@ def monitors():
 
     energy_band_mnt1 = td.SteadyEnergyBandMonitor(size=(1.6, 2, 3), name="bandgap_test")
 
+    electric_field_mnt = td.SteadyElectricFieldMonitor(size=(1.6, 2, 3), name="electric_field_test")
+
     return [
-        temp_mnt1,
-        temp_mnt2,
-        temp_mnt3,
-        temp_mnt4,
-        volt_mnt1,
-        volt_mnt2,
-        volt_mnt3,
-        volt_mnt4,
-        capacitance_mnt1,
-        free_carrier_mnt1,
-        energy_band_mnt1,
+        temp_mnt1,  # 0
+        temp_mnt2,  # 1
+        temp_mnt3,  # 2
+        temp_mnt4,  # 3
+        volt_mnt1,  # 4
+        volt_mnt2,  # 5
+        volt_mnt3,  # 6
+        volt_mnt4,  # 7
+        capacitance_mnt1,  # 8
+        free_carrier_mnt1,  # 9
+        energy_band_mnt1,  # 10
+        electric_field_mnt,  # 11
     ]
 
 
@@ -516,7 +519,10 @@ def temperature_monitor_data(monitors):
 @pytest.fixture(scope="module")
 def voltage_monitor_data(monitors):
     """Creates different voltage monitor data."""
-    _, _, _, _, volt_mnt1, volt_mnt2, volt_mnt3, volt_mnt4, _, _, _ = monitors
+    volt_mnt1 = monitors[4]
+    volt_mnt2 = monitors[5]
+    volt_mnt3 = monitors[6]
+    volt_mnt4 = monitors[7]
 
     # SpatialDataArray
     nx, ny, nz = 9, 6, 5
@@ -642,6 +648,84 @@ def energy_band_monitor_data(monitors):
     return (eb_data1,)
 
 
+@pytest.fixture(scope="module")
+def electric_field_monitor_data(monitors):
+    """Creates different electric field monitor data."""
+    monitor = monitors[11]
+
+    # TetrahedralGridDataset
+    tet_grid_points = td.PointDataArray(
+        [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [1.0, 1.0, 0.0], [0.0, 0.0, 1.0]],
+        dims=("index", "axis"),
+    )
+
+    tet_grid_cells = td.CellDataArray(
+        [[0, 1, 2, 4], [1, 2, 3, 4]],
+        dims=("cell_index", "vertex_index"),
+    )
+
+    tet_grid_values = td.IndexedDataArray(
+        [1.0, 2.0, 3.0, 4.0, 5.0],
+        dims=("index",),
+        name="T",
+    )
+
+    tet_grid = td.TetrahedralGridDataset(
+        points=tet_grid_points,
+        cells=tet_grid_cells,
+        values=tet_grid_values,
+    )
+
+    mnt_data1 = td.SteadyElectricFieldData(monitor=monitor, Ex=tet_grid, Ey=tet_grid, Ez=tet_grid)
+
+    # 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_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,
+    )
+
+    mnt_data2 = td.SteadyElectricFieldData(monitor=monitor, Ex=tri_grid, Ey=tri_grid, Ez=tri_grid)
+
+    mnt_data3 = td.SteadyElectricFieldData(monitor=monitor, Ex=None, Ey=None, Ez=None)
+
+    data_v = td.IndexedVoltageDataArray(
+        [[0.0, 1.5], [1.5, 2], [2.5, 3.0], [3.5, -4.0]],
+        coords={"index": np.arange(4), "voltage": [-1, 1]},
+        name="test",
+    )
+    tri_grid_v = td.TriangularGridDataset(
+        normal_axis=1,
+        normal_pos=0,
+        points=tri_grid_points,
+        cells=tri_grid_cells,
+        values=data_v,
+    )
+    mnt_data4 = td.SteadyElectricFieldData(
+        monitor=monitor, Ex=tri_grid_v, Ey=tri_grid_v, Ez=tri_grid_v
+    )
+
+    return (mnt_data1, mnt_data2, mnt_data3, mnt_data4)
+
+
 @pytest.fixture(scope="module")
 def simulation_data(
     heat_simulation,
@@ -797,11 +881,27 @@ def test_monitor_crosses_medium(mediums, structures, heat_simulation, conduction
 
 
 def test_heat_charge_mnt_data(
-    temperature_monitor_data, voltage_monitor_data, capacitance_monitor_data
+    temperature_monitor_data, voltage_monitor_data, electric_field_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) == 4, "Expected 4 electric field monitor data entries."
+
+    for mnt_data in electric_field_monitor_data:
+        assert "Ex" in mnt_data.field_components.keys()
+        assert "Ey" in mnt_data.field_components.keys()
+        assert "Ez" in mnt_data.field_components.keys()
+
+        symm_data = mnt_data.symmetry_expanded_copy
+        assert symm_data.Ex == mnt_data.Ex
+        assert symm_data.Ey == mnt_data.Ey
+        assert symm_data.Ez == mnt_data.Ez
+
+        names = mnt_data.field_name("abs^2")
+        assert names == "Ex², Ey², Ez²"
+        names = mnt_data.field_name()
+        assert names == "Ex, Ey, Ez"
 
 
 def test_grid_spec_validation(grid_specs):

tidy3d/__init__.py

@@ -35,6 +35,7 @@
 )
 from tidy3d.components.tcad.data.types import (
     SteadyCapacitanceData,
+    SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyFreeCarrierData,
     SteadyPotentialData,
@@ -50,6 +51,7 @@
 )
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
     SteadyPotentialMonitor,
@@ -651,6 +653,8 @@ def set_logging_level(level: str) -> None:
     "Staircasing",
     "SteadyCapacitanceData",
     "SteadyCapacitanceMonitor",
+    "SteadyElectricFieldData",
+    "SteadyElectricFieldMonitor",
     "SteadyEnergyBandData",
     "SteadyEnergyBandMonitor",
     "SteadyFreeCarrierData",

tidy3d/components/data/unstructured/base.py

@@ -566,6 +566,20 @@ def to_vtu(self, fname: str):
         writer.SetInputData(self._vtk_obj)
         writer.Write()
 
+    @classmethod
+    @requires_vtk
+    def _cell_to_point_data(
+        cls,
+        vtk_obj,
+    ):
+        """Get point data values from a VTK object."""
+
+        cellDataToPointData = vtk["mod"].vtkCellDataToPointData()
+        cellDataToPointData.SetInputData(vtk_obj)
+        cellDataToPointData.Update()
+
+        return cellDataToPointData.GetOutput()
+
     @classmethod
     @requires_vtk
     def _get_values_from_vtk(

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

@@ -18,6 +18,7 @@
 from tidy3d.components.tcad.data.monitor_data.abstract import HeatChargeMonitorData
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
     SteadyPotentialMonitor,
@@ -460,3 +461,85 @@ def symmetry_expanded_copy(self) -> SteadyCapacitanceData:
             electron_capacitance=new_electron_capacitance,
             symmetry=(0, 0, 0),
         )
+
+
+class SteadyElectricFieldData(HeatChargeMonitorData):
+    """
+    Stores electric field :math:`\\vec{E}` from a charge simulation.
+
+    Notes
+    -----
+        The electric field is computed as the negative gradient of the electric potential :math:`\\vec{E} = -\\nabla \\psi`.
+        It is given in units of :math:`V/\\mu m` (Volts per micrometer).
+    """
+
+    monitor: SteadyElectricFieldMonitor = pd.Field(
+        ...,
+        title="Electric field monitor",
+        description="Electric field data associated with a Charge simulation.",
+    )
+
+    Ex: UnstructuredFieldType = pd.Field(
+        None,
+        title="x component of the electric field",
+        description=r"Contains the computed x component of the electric field in :math:`V/\\mu m`.",
+        discriminator=TYPE_TAG_STR,
+    )
+
+    Ey: UnstructuredFieldType = pd.Field(
+        None,
+        title="y component of the electric field",
+        description=r"Contains the computed y component of the electric field in :math:`V/\\mu m`.",
+        discriminator=TYPE_TAG_STR,
+    )
+
+    Ez: UnstructuredFieldType = pd.Field(
+        None,
+        title="z component of the electric field",
+        description=r"Contains the computed z component of the electric field in :math:`V/\\mu m`.",
+        discriminator=TYPE_TAG_STR,
+    )
+
+    @property
+    def field_components(self) -> dict[str, UnstructuredFieldType]:
+        """Maps the field components to their associated data."""
+        return {"Ex": self.Ex, "Ey": self.Ey, "Ez": self.Ez}
+
+    @pd.root_validator(skip_on_failure=True)
+    def warn_no_data(cls, values):
+        """Warn if no data provided."""
+
+        mnt = values.get("monitor")
+        Ex = values.get("Ex")
+        Ey = values.get("Ey")
+        Ez = values.get("Ez")
+
+        if Ex is None or Ey is None or Ez 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
+
+    @property
+    def symmetry_expanded_copy(self) -> SteadyElectricFieldData:
+        """Return copy of self with symmetry applied."""
+
+        new_Ex = self._symmetry_expanded_copy(property=self.Ex)
+        new_Ey = self._symmetry_expanded_copy(property=self.Ey)
+        new_Ez = self._symmetry_expanded_copy(property=self.Ez)
+
+        return self.updated_copy(
+            Ex=new_Ex,
+            Ey=new_Ey,
+            Ez=new_Ez,
+            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 "Ex², Ey², Ez²"
+        else:
+            return "Ex, Ey, Ez"

tidy3d/components/tcad/data/types.py

@@ -6,6 +6,7 @@
 
 from tidy3d.components.tcad.data.monitor_data.charge import (
     SteadyCapacitanceData,
+    SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyFreeCarrierData,
     SteadyPotentialData,
@@ -16,6 +17,7 @@
     TemperatureData,
     SteadyPotentialData,
     SteadyFreeCarrierData,
+    SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyCapacitanceData,
 ]

tidy3d/components/tcad/monitors/charge.py

@@ -80,3 +80,22 @@ class SteadyCapacitanceMonitor(HeatChargeMonitor):
         title="Unstructured Grid",
         description="Return data on the original unstructured grid.",
     )
+
+
+class SteadyElectricFieldMonitor(HeatChargeMonitor):
+    """
+    Electric field monitor for Charge simulations.
+
+    Example
+    -------
+    >>> import tidy3d as td
+    >>> electric_field_monitor_z0 = td.SteadyElectricFieldMonitor(
+    ... center=(0, 0.14, 0), size=(0.6, 0.3, 0), name="electric_field_z0",
+    ... )
+    """
+
+    unstructured: Literal[True] = pd.Field(
+        True,
+        title="Unstructured Grid",
+        description="Return data on the original unstructured grid.",
+    )

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,
+    SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
     SteadyPotentialMonitor,
@@ -34,6 +35,7 @@
     SteadyPotentialMonitor,
     SteadyFreeCarrierMonitor,
     SteadyEnergyBandMonitor,
+    SteadyElectricFieldMonitor,
     SteadyCapacitanceMonitor,
 ]
 HeatChargeSourceType = Union[HeatSource, HeatFromElectricSource, UniformHeatSource]