Photodiode Angular Weights

This example demonstrates how to build a custom angular mask on top of the single-detector Fibonacci mesh using angular_weights.

import numpy as np
import matplotlib.pyplot as plt

from PyMieSim.units import ureg
from PyMieSim.polarization import PolarizationState
from PyMieSim.single.source import Gaussian
from PyMieSim.single.scatterer import Sphere
from PyMieSim.single.detector import Photodiode
from PyMieSim.single.setup import Setup


source = Gaussian(
    wavelength=1064 * ureg.nanometer,
    polarization=PolarizationState(angle=0 * ureg.degree),
    optical_power=1 * ureg.watt,
    numerical_aperture=0.25,
)

scatterer = Sphere(
    diameter=1200 * ureg.nanometer,
    material=1.46,
    medium=1.0,
)

detector = Photodiode(
    numerical_aperture=0.18,
    phi_offset=30 * ureg.degree,
    gamma_offset=10 * ureg.degree,
    sampling=500,
)

setup = Setup(
    scatterer=scatterer,
    source=source,
    detector=detector,
)

baseline_coupling = setup.get("coupling")

# Rebuild the current mesh explicitly so the example can derive weights from it.
detector.initialize_mesh(scatterer)

x_coordinates = np.asarray(detector.mesh.cartesian.x.magnitude)
y_coordinates = np.asarray(detector.mesh.cartesian.y.magnitude)
z_coordinates = np.asarray(detector.mesh.cartesian.z.magnitude)

# Keep only one side of the collectio n cone to form a simple half-aperture mask.
active_points = x_coordinates >= 0.50
angular_weights = np.zeros(detector.sampling, dtype=np.complex128)
angular_weights[active_points] = 1.0

detector.angular_weights = angular_weights

weighted_active_points = np.abs(detector.angular_weights) > 0.0

masked_coupling = setup.get("coupling")

figure = plt.figure(figsize=(15, 5))

full_mesh_axis = figure.add_subplot(1, 3, 1, projection="3d")
full_mesh_axis.scatter(
    x_coordinates,
    y_coordinates,
    z_coordinates,
    s=18,
    c="#1f77b4",
    label="full detector",
)
full_mesh_axis.set(
    title="Full detector mesh",
    xlabel="x",
    ylabel="y",
    zlabel="z",
)
full_mesh_axis.legend(loc="upper left")

masked_mesh_axis = figure.add_subplot(1, 3, 2, projection="3d")
masked_mesh_axis.scatter(
    x_coordinates[weighted_active_points],
    y_coordinates[weighted_active_points],
    z_coordinates[weighted_active_points],
    s=18,
    c="#1f77b4",
    label="active",
)
masked_mesh_axis.scatter(
    x_coordinates[~weighted_active_points],
    y_coordinates[~weighted_active_points],
    z_coordinates[~weighted_active_points],
    s=18,
    c="#d9d9d9",
    label="masked",
)
masked_mesh_axis.set(
    title="Masked detector mesh",
    xlabel="x",
    ylabel="y",
    zlabel="z",
)
masked_mesh_axis.legend(loc="upper left")

for axis in (full_mesh_axis, masked_mesh_axis):
    axis.set_xlim(-1.0, 1.0)
    axis.set_ylim(-1.0, 1.0)
    axis.set_zlim(-1.0, 1.0)
    axis.view_init(elev=22, azim=38)

coupling_axis = figure.add_subplot(1, 3, 3)
coupling_values = [
    baseline_coupling.to("microwatt").magnitude,
    masked_coupling.to("microwatt").magnitude,
]
coupling_axis.bar(
    ["full detector", "masked detector"],
    coupling_values,
    color=["#4c72b0", "#dd8452"],
)
coupling_axis.set(
    ylabel="Coupling [$\\mu$W]",
    title="Effect of the angular mask",
)

figure.suptitle("Single photodiode with custom angular weights")
figure.tight_layout()

if plt.get_backend().lower() != "agg":
    plt.show()