From 3e51130ba72280b2d2b41ef79cfceac8ced398ef Mon Sep 17 00:00:00 2001
From: Roy Smart <roytsmart@gmail.com>
Date: Sun, 17 Mar 2024 23:57:01 -0600
Subject: [PATCH] Added
 `esis.flights.f1.optics.gratings.materials.multilayer_fit()` factory
 function.

---
 .../optics/gratings/materials/_materials.py   | 129 ++++++++++++++++++
 .../gratings/materials/_materials_test.py     |   5 +
 2 files changed, 134 insertions(+)

diff --git a/esis/flights/f1/optics/gratings/materials/_materials.py b/esis/flights/f1/optics/gratings/materials/_materials.py
index 3d28e1a..cc60fc4 100644
--- a/esis/flights/f1/optics/gratings/materials/_materials.py
+++ b/esis/flights/f1/optics/gratings/materials/_materials.py
@@ -10,6 +10,7 @@
     "multilayer_design",
     "multilayer_witness_measured",
     "multilayer_witness_fit",
+    "multilayer_fit",
 ]
 
 
@@ -432,3 +433,131 @@ def _func(x: np.ndarray):
     )
 
     return _multilayer(*fit.x)
+
+
+def multilayer_fit() -> optika.materials.MultilayerMirror:
+    """
+    A multilayer coating determined by modifying :func:`multilayer_witness_fit`
+    to have a glass substrate with the appropriate roughness.
+
+    Examples
+    --------
+
+    Plot the theoretical reflectivity of this multilayer stack vs. the
+    theoretical reflectivity of :func:`multilayer_witness_fit`.
+
+    .. jupyter-execute::
+
+        import numpy as np
+        import matplotlib.pyplot as plt
+        import astropy.units as u
+        import named_arrays as na
+        import optika
+        from esis.flights.f1.optics import gratings
+
+        # Define a grid of wavelength samples
+        wavelength = na.geomspace(100, 1000, axis="wavelength", num=1001) * u.AA
+
+        # Define a grid of incidence angles
+        angle = 4 * u.deg
+
+        # Define the light rays incident on the multilayer stack
+        rays = optika.rays.RayVectorArray(
+            wavelength=wavelength,
+            direction=na.Cartesian3dVectorArray(
+                x=np.sin(angle),
+                y=0,
+                z=np.cos(angle),
+            ),
+        )
+
+        # Initialize the multilayer stacks
+        multilayer_witness_fit = gratings.materials.multilayer_witness_fit()
+        multilayer_fit = gratings.materials.multilayer_fit()
+
+        # Define the vector normal to the multilayer stack
+        normal = na.Cartesian3dVectorArray(0, 0, -1)
+
+        # Compute the reflectivity of the multilayer for the given incident rays
+        reflectivity_witness = multilayer_witness_fit.efficiency(rays, normal)
+        reflectivity_fit = multilayer_fit.efficiency(rays, normal)
+
+        # Plot the reflectivities as a function of wavelength
+        fig, ax = plt.subplots(constrained_layout=True)
+        na.plt.plot(
+            wavelength,
+            reflectivity_witness,
+            ax=ax,
+            axis="wavelength",
+            label="witness fit",
+        );
+        na.plt.plot(
+            wavelength,
+            reflectivity_fit,
+            ax=ax,
+            axis="wavelength",
+            label="grating fit",
+        );
+        ax.set_xlabel(f"wavelength ({wavelength.unit:latex_inline})");
+        ax.set_ylabel("reflectivity");
+        ax.legend();
+
+    |
+
+    Plot the reflectivity of this multilayer stack as a function of incidence angle.
+
+    .. jupyter-execute::
+
+        import numpy as np
+        import matplotlib.pyplot as plt
+        import astropy.units as u
+        import named_arrays as na
+        import optika
+        from esis.flights.f1.optics import gratings
+
+        # Define a grid of wavelength samples
+        wavelength = na.geomspace(100, 1000, axis="wavelength", num=1001) * u.AA
+
+        # Define a grid of incidence angles
+        angle = na.linspace(0, 20, axis="angle", num=3) * u.deg
+
+        # Define the light rays incident on the multilayer stack
+        rays = optika.rays.RayVectorArray(
+            wavelength=wavelength,
+            direction=na.Cartesian3dVectorArray(
+                x=np.sin(angle),
+                y=0,
+                z=np.cos(angle),
+            ),
+        )
+
+        # Initialize the multilayer stack
+        multilayer = gratings.materials.multilayer_fit()
+
+        # Compute the reflectivity of the multilayer for the given incident rays
+        reflectivity = multilayer.efficiency(
+            rays=rays,
+            normal=na.Cartesian3dVectorArray(0, 0, -1),
+        )
+
+        # Plot the reflectivity of the multilayer as a function of wavelength
+        fig, ax = plt.subplots(constrained_layout=True)
+        na.plt.plot(
+            wavelength,
+            reflectivity,
+            ax=ax,
+            axis="wavelength",
+            label=angle,
+        );
+        ax.set_xlabel(f"wavelength ({wavelength.unit:latex_inline})");
+        ax.set_ylabel("reflectivity");
+        ax.legend();
+    """
+    result = multilayer_design()
+    witness = multilayer_witness_fit()
+
+    result.layers = witness.layers
+
+    result.substrate.interface.width = 0.5 * u.nm
+
+    return result
diff --git a/esis/flights/f1/optics/gratings/materials/_materials_test.py b/esis/flights/f1/optics/gratings/materials/_materials_test.py
index b0a7db8..f888eb6 100644
--- a/esis/flights/f1/optics/gratings/materials/_materials_test.py
+++ b/esis/flights/f1/optics/gratings/materials/_materials_test.py
@@ -15,3 +15,8 @@ def test_multilayer_witness_measured():
 def test_multilayer_witness_fit():
     r = esis.flights.f1.optics.gratings.materials.multilayer_witness_fit()
     assert isinstance(r, optika.materials.MultilayerMirror)
+
+
+def test_multilayer_fit():
+    r = esis.flights.f1.optics.gratings.materials.multilayer_fit()
+    assert isinstance(r, optika.materials.MultilayerMirror)