Add lossless Green2008 cSi and modify default SiO2 in material_library

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `RectangularWaveguide.plot_field` optionally draws geometry edges over fields. 
 - `RectangularWaveguide` supports layered cladding above and below core.
 - `SubpixelSpec` accepted by `Simulation.subpixel` to select subpixel averaging methods separately for dielectric, metal, and PEC materials. Specifically, added support for conformal mesh methods near PEC structures that can be specified through the field `pec` in the `SubpixelSpec` class. Note: previously, `subpixel=False` was implementing staircasing for every material except PEC. Now, `subpixel=False` implements direct staircasing for all materials. For PEC, the behavior of `subpixel=False` in Tidy3D < 2.7 is now achieved through `subpixel=SubpixelSpec(pec=HeuristicPECStaircasing())`, while `subpixel=True` in Tidy3D < 2.7 is now achieved through `subpixel=SubpixelSpec(pec=Staircasing())`. The default is `subpixel=SubpixelSpec(pec=PECConformal())` for more accurate PEC modelling.
+- Lossless `Green2008` variant for crystalline silicon added to material library.
+
+### Changed
+- Default variant for silicon dioxide in material library switched from `Horiba` to `Palik_Lossless`.
 
 ### Fixed
 - `ModeSolver.plot_field` correctly returning the plot axes.

tests/test_package/test_material_library.py

@@ -1,6 +1,8 @@
 import pytest
 import numpy as np
 import pydantic.v1 as pydantic
+from ..utils import assert_log_level
+from ..utils import log_capture  # noqa: F401
 
 from tidy3d.material_library.material_library import (
     VariantItem,
@@ -14,6 +16,18 @@
 import tidy3d as td
 
 
+def test_warning_default_variant_switching(log_capture):  # noqa: F811
+    """Issue warning for switching default medium variant."""
+
+    # no warning for most materials with no default change
+    _ = td.material_library["cSi"].medium
+    assert_log_level(log_capture, None)
+
+    # issue warning for SiO2
+    _ = td.material_library["SiO2"].medium
+    assert_log_level(log_capture, "WARNING")
+
+
 def test_VariantItem():
     """Test if the variant class is working as expected."""
     _ = VariantItem(

tidy3d/material_library/material_library.py

@@ -6,6 +6,7 @@
 from ..components.medium import PoleResidue, Medium2D, AnisotropicMedium, Sellmeier
 from ..components.base import Tidy3dBaseModel
 from ..components.types import Axis
+from ..log import log
 from ..exceptions import SetupError
 from .material_reference import material_refs, ReferenceData
 from .parametric_materials import Graphene
@@ -99,6 +100,11 @@ def __getitem__(self, variant_name):
     @property
     def medium(self):
         """The default medium."""
+        if self.name == "Silicon Dioxide":
+            log.warning(
+                "Since Tidy3d 2.7, the default variant for silicon dioxide has been switched from "
+                "'Horiba' to 'Palik_Lossless'."
+            )
         return self.variants[self.default].medium
 
 
@@ -1731,6 +1737,22 @@ def medium(self, optical_axis: Axis):
     "main/Si/Green-2008.yml",
 )
 
+cSi_Green2008Lossless = VariantItem(
+    medium=PoleResidue(
+        eps_inf=12.254420790112501,
+        poles=[
+            (
+                (-1286227551710880.2 + 0j),
+                (8.042934900897995e-08 + 0j),
+            ),
+        ],
+        frequency_range=(206753419710997.8, 249827048333333.34),
+    ),
+    reference=[material_refs["Green2008"]],
+    data_url="https://refractiveindex.info/data_csv.php?datafile=database/data-nk/"
+    "main/Si/Green-2008.yml",
+)
+
 cSi_PalikLossy = VariantItem(
     medium=PoleResidue(
         eps_inf=1.0,
@@ -2121,7 +2143,7 @@ def medium(self, optical_axis: Axis):
             Palik_Lossy=SiO2_Palik_Lossy,
             Horiba=SiO2_Horiba,
         ),
-        default="Horiba",
+        default="Palik_Lossless",
     ),
     SiON=MaterialItem(
         name="Silicon Oxynitride",
@@ -2212,6 +2234,7 @@ def medium(self, optical_axis: Axis):
             SalzbergVilla1957=cSi_SalzbergVilla1957,
             Li1993_293K=cSi_Li1993_293K,
             Green2008=cSi_Green2008,
+            Green2008_Lossless=cSi_Green2008Lossless,
         ),
         default="Green2008",
     ),

tidy3d/plugins/dispersion/fit_fast.py

@@ -809,7 +809,12 @@ def make_configs():
                                 best_model.unweighted_rms_error,
                             )
 
-                        return best_model.pole_residue, best_model.rms_error
+                        return (
+                            best_model.pole_residue.updated_copy(
+                                frequency_range=self.frequency_range
+                            ),
+                            best_model.rms_error,
+                        )
 
         # if exited loop, did not reach tolerance (warn)
         progress.update(
@@ -829,7 +834,10 @@ def make_configs():
                 best_model.unweighted_rms_error,
             )
 
-        return best_model.pole_residue, best_model.rms_error
+        return (
+            best_model.pole_residue.updated_copy(frequency_range=self.frequency_range),
+            best_model.rms_error,
+        )
 
     @classmethod
     def constant_loss_tangent_model(