Use default td.ModeSpec in mode monitors

CHANGELOG.md

@@ -37,6 +37,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Enabled the user to set the `ModeMonitor.colocate` field and changed to `True` by default (fields were actually already returned colocated even though this field was `False` previously).
 - More robust mode solver at radio frequencies.
 - Disallow very small polygons when subdividing 2D structures.
+- `CustomMedium` design regions require far less data when performing inverse design by reducing adjoint field monitor size for dims with one pixel.
+- Calling `.values` on `DataArray` no longer raises a `DeprecationWarning` during automatic differentiation.
+- `ModeMonitor` and `ModeSolverMonitor` now use the default `td.ModeSpec()` when `mode_spec` is not provided.
 
 ### Fixed
 - Significant speedup for field projection computations.

tests/test_components/test_monitor.py

@@ -337,16 +337,16 @@ def test_monitor():
     m5 = td.ModeMonitor(
         size=(1, 1, 0), center=center, mode_spec=td.ModeSpec(), freqs=FREQS, name="test_mon"
     )
-    m6 = td.ModeSolverMonitor(
+    m6 = td.ModeMonitor(size=(1, 1, 0), center=center, freqs=FREQS, name="test_mon")
+    m7 = td.ModeSolverMonitor(
         size=(1, 1, 0),
         center=center,
-        mode_spec=td.ModeSpec(),
         freqs=FREQS,
         name="test_mon",
         direction="-",
     )
-    m7 = td.PermittivityMonitor(size=size, center=center, freqs=FREQS, name="perm")
-    m8 = td.DirectivityMonitor(
+    m8 = td.PermittivityMonitor(size=size, center=center, freqs=FREQS, name="perm")
+    m9 = td.DirectivityMonitor(
         size=size,
         center=center,
         theta=thetas,
@@ -355,12 +355,11 @@ def test_monitor():
         freqs=FREQS,
         name="directivity",
     )
+    m10 = td.PermittivityMonitor(size=size, center=center, freqs=FREQS, name="perm")
 
     tmesh = np.linspace(0, 1, 10)
 
-    for m in [m1, m2, m3, m4, m5, m6, m7, m8]:
-        # m.plot(y=2)
-        # plt.close()
+    for m in [m1, m2, m3, m4, m5, m6, m7, m8, m9, m10]:
         m.storage_size(num_cells=100, tmesh=tmesh)
 
     for m in [m2, m4]:

tidy3d/components/monitor.py

@@ -285,7 +285,7 @@ class AbstractModeMonitor(PlanarMonitor, FreqMonitor):
     """:class:`Monitor` that records mode-related data."""
 
     mode_spec: ModeSpec = pydantic.Field(
-        ...,
+        default_factory=ModeSpec,
         title="Mode Specification",
         description="Parameters to feed to mode solver which determine modes measured by monitor.",
     )