Electric field monitor for Charge

tests/test_components/test_heat_charge.py

@@ -254,19 +254,22 @@ def monitors():
 
     mesh_mnt = td.VolumeMeshMonitor(size=(1.6, 2, 3), name="mesh_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,
-        mesh_mnt,
+        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
+        mesh_mnt,  # 11
+        electric_field_mnt,  # 12
     ]
 
 
@@ -519,7 +522,10 @@ 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
@@ -679,6 +685,76 @@ 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[12]
+
+    # 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.PointDataArray(
+        [[0.0, 1.0, 0.0], [1.0, 1.0, 1.0], [3.0, 5.0, 1.0], [4.0, 5.0, 3.0], [5.0, 2.0, 1.0]],
+        dims=(
+            "index",
+            "axis",
+        ),
+        name="T",
+    )
+
+    tet_grid = td.TetrahedralGridDataset(
+        points=tet_grid_points,
+        cells=tet_grid_cells,
+        values=tet_grid_values,
+    )
+
+    mnt_data1 = td.SteadyElectricFieldData(monitor=monitor, E=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.IndexedFieldVoltageDataArray(
+        [
+            [[1.0, 1.5], [-1.0, 1.1], [5.1, 0.0]],
+            [[1.0, 1.5], [-1.0, 1.1], [5.1, 0.0]],
+            [[1.0, 1.5], [-1.0, 1.1], [5.1, 0.0]],
+            [[1.0, 1.5], [-1.0, 1.1], [5.1, 0.0]],
+        ],
+        coords={"index": np.arange(4), "axis": np.arange(3), "voltage": [-1, 1]},
+        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, E=tri_grid)
+
+    mnt_data3 = td.SteadyElectricFieldData(monitor=monitor, E=None)
+
+    return (mnt_data1, mnt_data2, mnt_data3)
+
+
 @pytest.fixture(scope="module")
 def simulation_data(
     heat_simulation,
@@ -853,11 +929,52 @@ 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) == 3, "Expected 3 electric field monitor data entries."
+
+    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_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,
+        )
+
+        with pytest.raises(pd.ValidationError):
+            _ = mnt_data.updated_copy(E=tri_grid)
 
 
 def test_grid_spec_validation(grid_specs):

tidy3d/__init__.py

@@ -37,6 +37,7 @@
 )
 from tidy3d.components.tcad.data.types import (
     SteadyCapacitanceData,
+    SteadyElectricFieldData,
     SteadyEnergyBandData,
     SteadyFreeCarrierData,
     SteadyPotentialData,
@@ -53,6 +54,7 @@
 from tidy3d.components.tcad.mesher import VolumeMesher
 from tidy3d.components.tcad.monitors.charge import (
     SteadyCapacitanceMonitor,
+    SteadyElectricFieldMonitor,
     SteadyEnergyBandMonitor,
     SteadyFreeCarrierMonitor,
     SteadyPotentialMonitor,
@@ -136,6 +138,7 @@
     FluxTimeDataArray,
     HeatDataArray,
     IndexedDataArray,
+    IndexedFieldVoltageDataArray,
     IndexedTimeDataArray,
     IndexedVoltageDataArray,
     ModeAmpsDataArray,
@@ -565,6 +568,7 @@ def set_logging_level(level: str) -> None:
     "HuraySurfaceRoughness",
     "IndexPerturbation",
     "IndexedDataArray",
+    "IndexedFieldVoltageDataArray",
     "IndexedTimeDataArray",
     "IndexedVoltageDataArray",
     "InsulatingBC",
@@ -653,6 +657,8 @@ def set_logging_level(level: str) -> None:
     "Staircasing",
     "SteadyCapacitanceData",
     "SteadyCapacitanceMonitor",
+    "SteadyElectricFieldData",
+    "SteadyElectricFieldMonitor",
     "SteadyEnergyBandData",
     "SteadyEnergyBandMonitor",
     "SteadyFreeCarrierData",

tidy3d/components/data/data_array.py

@@ -1175,9 +1175,9 @@ class SteadyVoltageDataArray(DataArray):
 
 
 class PointDataArray(DataArray):
-    """A two-dimensional array that stores coordinates of a collection of points.
+    """A two-dimensional array that stores coordinates/field components for a collection of points.
     Dimension ``index`` denotes the index of a point in the collection, and dimension ``axis``
-    denotes the point's coordinate along that axis.
+    denotes the field component (or point coordinate) in that direction.
 
     Example
     -------
@@ -1188,6 +1188,14 @@ class PointDataArray(DataArray):
     >>> point3 = point_array.sel(index=3)
     >>> # get x coordinates of all points
     >>> x_coords = point_array.sel(axis=0)
+    >>>
+    >>> field_da = PointDataArray(
+    ...     np.random.random((120, 3)), coords=dict(index=np.arange(120), axis=np.arange(3)),
+    ... )
+    >>> # get field of point number 90
+    >>> field_point90 = field_da.sel(index=90)
+    >>> # get z component of all points
+    >>> z_field = field_da.sel(axis=2)
     """
 
     __slots__ = ()
@@ -1265,6 +1273,20 @@ class IndexedTimeDataArray(DataArray):
     _dims = ("index", "t")
 
 
+class IndexedFieldVoltageDataArray(DataArray):
+    """Stores indexed values of vector fields for different voltages. It is typically used
+    in conjuction with a ``PointDataArray`` to store point-associated vector data.
+    Example
+    -------
+    >>> indexed_array = IndexedFieldVoltageDataArray(
+    ...     (1+1j) * np.random.random((4,3,2)), coords=dict(index=np.arange(4), axis=np.arange(3), voltage=[-1, 1])
+    ... )
+    """
+
+    __slots__ = ()
+    _dims = ("index", "axis", "voltage")
+
+
 class SpatialVoltageDataArray(AbstractSpatialDataArray):
     """Spatial distribution with voltage mapping.
 
@@ -1319,11 +1341,18 @@ class PerturbationCoefficientDataArray(DataArray):
     PointDataArray,
     CellDataArray,
     IndexedDataArray,
+    IndexedFieldVoltageDataArray,
     IndexedVoltageDataArray,
     SpatialVoltageDataArray,
     PerturbationCoefficientDataArray,
     IndexedTimeDataArray,
 ]
 DATA_ARRAY_MAP = {data_array.__name__: data_array for data_array in DATA_ARRAY_TYPES}
 
-IndexedDataArrayTypes = Union[IndexedDataArray, IndexedVoltageDataArray, IndexedTimeDataArray]
+IndexedDataArrayTypes = Union[
+    IndexedDataArray,
+    IndexedVoltageDataArray,
+    IndexedTimeDataArray,
+    IndexedFieldVoltageDataArray,
+    PointDataArray,
+]

tidy3d/components/data/unstructured/base.py

@@ -618,6 +618,20 @@ 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(