Set minimum PML layers to 6

CHANGELOG.md

@@ -18,7 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - `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
+- Calling `.values` on `DataArray` no longer raises a `DeprecationWarning` during automatic differentiation.
+- Minimum number of PML layers set to 6.
 
 ### Fixed
 - Regression in local field projection leading to incorrect results for `far_field_approx=True`.

tidy3d/components/boundary.py

@@ -260,10 +260,11 @@ class PMLParams(AbsorberParams):
 class AbsorberSpec(BoundaryEdge):
     """Specifies the generic absorber properties along a single dimension."""
 
-    num_layers: pd.NonNegativeInt = pd.Field(
+    num_layers: int = pd.Field(
         ...,
         title="Number of Layers",
         description="Number of layers of standard PML.",
+        gt=5,
     )
     parameters: AbsorberParams = pd.Field(
         ...,
@@ -376,10 +377,11 @@ class PML(AbsorberSpec):
 
     """
 
-    num_layers: pd.NonNegativeInt = pd.Field(
+    num_layers: int = pd.Field(
         12,
         title="Number of Layers",
         description="Number of layers of standard PML.",
+        gt=5,
     )
 
     parameters: PMLParams = pd.Field(
@@ -413,8 +415,11 @@ class StablePML(AbsorberSpec):
         * `Introduction to perfectly matched layer (PML) tutorial <https://www.flexcompute.com/fdtd101/Lecture-6-Introduction-to-perfectly-matched-layer/>`__
     """
 
-    num_layers: pd.NonNegativeInt = pd.Field(
-        40, title="Number of Layers", description="Number of layers of 'stable' PML."
+    num_layers: int = pd.Field(
+        40,
+        title="Number of Layers",
+        description="Number of layers of 'stable' PML.",
+        gt=5,
     )
 
     parameters: PMLParams = pd.Field(
@@ -463,10 +468,11 @@ class Absorber(AbsorberSpec):
         * `How to troubleshoot a diverged FDTD simulation <../../notebooks/DivergedFDTDSimulation.html>`_
     """
 
-    num_layers: pd.NonNegativeInt = pd.Field(
+    num_layers: int = pd.Field(
         40,
         title="Number of Layers",
         description="Number of layers of absorber to add to + and - boundaries.",
+        gt=5,
     )
 
     parameters: AbsorberParams = pd.Field(