fix field data flux

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Bug in PolySlab intersection if slab bounds are `inf` on one side.
 - Better error message when trying to transform a geometry with infinite bounds.
 - `JaxSimulation.epsilon` properly handles `input_structures`.
+- `FieldData.flux` in adjoint plugin properly returns `JaxDataArray` containing frequency coordinate `f` instead of summing over values.
 
 ## [2.6.3] - 2024-04-02
 

tests/test_plugins/test_adjoint.py

@@ -29,7 +29,11 @@
 from tidy3d.plugins.adjoint.components.simulation import JaxSimulation, JaxInfo, RUN_TIME_FACTOR
 from tidy3d.plugins.adjoint.components.simulation import MAX_NUM_INPUT_STRUCTURES
 from tidy3d.plugins.adjoint.components.data.sim_data import JaxSimulationData
-from tidy3d.plugins.adjoint.components.data.monitor_data import JaxModeData, JaxDiffractionData
+from tidy3d.plugins.adjoint.components.data.monitor_data import (
+    JaxModeData,
+    JaxDiffractionData,
+    JaxFieldData,
+)
 from tidy3d.plugins.adjoint.components.data.data_array import JaxDataArray, JAX_DATA_ARRAY_TAG
 from tidy3d.plugins.adjoint.components.data.dataset import JaxPermittivityDataset
 from tidy3d.plugins.adjoint.web import run, run_async
@@ -1797,3 +1801,16 @@ def test_sidewall_angle_validator(log_capture, sidewall_angle, log_expected):
 
     with AssertLogLevel(log_capture, log_expected, contains_str="sidewall"):
         jax_polyslab1.updated_copy(sidewall_angle=sidewall_angle)
+
+
+def test_package_flux():
+    """Test handling of packaging flux data for single and multi-freq."""
+
+    value = 1.0
+    da_single = JaxDataArray(values=[value], coords=dict(f=[1.0]))
+    res_single = JaxFieldData.package_flux_results(None, da_single)
+    assert res_single == value
+
+    da_multi = JaxDataArray(values=[1.0, 2.0], coords=dict(f=[1.0, 2.0]))
+    res_multi = JaxFieldData.package_flux_results(None, da_multi)
+    assert res_multi == da_multi

tidy3d/plugins/adjoint/components/data/monitor_data.py

@@ -160,12 +160,18 @@ def package_colocate_results(self, centered_fields: Dict[str, ScalarFieldDataArr
         """How to package the dictionary of fields computed via self.colocate()."""
         return self.updated_copy(**centered_fields)
 
-    def package_flux_results(self, flux_values: JaxDataArray) -> float:
+    def package_flux_results(self, flux_values: JaxDataArray) -> Union[float, JaxDataArray]:
         """How to package the dictionary of fields computed via self.colocate()."""
-        flux_data = flux_values
-        if isinstance(flux_data, JaxDataArray):
-            return jnp.sum(flux_data.values)
-        return jnp.sum(flux_data)
+
+        freqs = flux_values.coords.get("f")
+
+        # handle single frequency case separately for backwards compatibility
+        # return a float of the only value
+        if freqs is not None and len(freqs) == 1:
+            return jnp.sum(flux_values.values)
+
+        # for multi-frequency, return a JaxDataArray
+        return flux_values
 
     @property
     def intensity(self) -> ScalarFieldDataArray: