Added optika.materials.AbstractLayer.n() method.

optika/materials/_layers.py

@@ -28,6 +28,20 @@ class AbstractLayer(
     of homogeneous layers.
     """
 
+    @abc.abstractmethod
+    def n(
+        self,
+        wavelength: u.Quantity | na.AbstractScalar,
+    ) -> na.AbstractScalar:
+        """
+        The index of refraction on the left side of the layer.
+
+        Parameters
+        ----------
+        wavelength
+            The wavelength of the incident light in vacuum
+        """
+
     @property
     @abc.abstractmethod
     def thickness(self) -> u.Quantity | na.AbstractScalar:
@@ -179,7 +193,7 @@ def n(
         wavelength: u.Quantity | na.AbstractScalar,
     ) -> float | na.AbstractScalar:
         """
-        The complex index of refraction of this layer.
+        The complex index of refraction of this entire layer.
         """
         if self.chemical is None:
             return 1
@@ -384,6 +398,12 @@ class LayerSequence(AbstractLayerSequence):
     layers: Sequence[AbstractLayer] = dataclasses.MISSING
     """A sequence of layers."""
 
+    def n(
+        self,
+        wavelength: u.Quantity | na.AbstractScalar,
+    ) -> na.AbstractScalar:
+        return self.layers[0].n(wavelength)
+
     @property
     def thickness(self) -> u.Quantity | na.AbstractScalar:
         result = 0 * u.nm
@@ -508,6 +528,12 @@ class PeriodicLayerSequence(AbstractLayerSequence):
     num_periods: int = dataclasses.MISSING
     """The number of times to repeat the layer sequence."""
 
+    def n(
+        self,
+        wavelength: u.Quantity | na.AbstractScalar,
+    ) -> na.AbstractScalar:
+        return self.layers[0].n(wavelength)
+
     @property
     def thickness(self) -> u.Quantity | na.AbstractScalar:
         return self.num_periods * LayerSequence(self.layers).thickness

optika/materials/_tests/test_layers.py

@@ -11,6 +11,16 @@ class AbstractTestAbstractLayer(
     optika._tests.test_mixins.AbstractTestPrintable,
 ):
 
+    @pytest.mark.parametrize("wavelength", [100 * u.AA])
+    def test_n(
+        self,
+        a: optika.materials.AbstractLayer,
+        wavelength: u.Quantity | na.AbstractScalar,
+    ):
+        result = a.n(wavelength)
+        assert np.all(np.real(result) >= 0)
+        assert np.all(np.imag(result) >= 0)
+
     def test_thickness(
         self,
         a: optika.materials.AbstractLayer,