getting started

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getting started#

demonstration of basic pymiediff functionality:

  • Extinction, scattering and absorption spectra

  • Angular scattering patterns

author: P. Wiecha, 03/2025

imports#

import matplotlib.pyplot as plt
import torch
import pymiediff as pmd

setup#

we setup the particle dimension and materials as well as the environemnt. This is then wrapped up in an instance of Particle.

# - config
wl0 = torch.linspace(500, 1000, 50)
k0 = 2 * torch.pi / wl0

r_core = 70.0
r_shell = 100.0
mat_core = pmd.materials.MatDatabase("Si")
mat_shell = pmd.materials.MatDatabase("Ge")
n_env = 1.0

# - setup the particle
p = pmd.Particle(
    r_core=r_core,
    r_shell=r_shell,
    mat_core=mat_core,
    mat_shell=mat_shell,
    mat_env=n_env,
)
print(p)

core-shell particle
 - core radius    = 70.0nm
 - shell radius   = 100.0nm
 - core material  : Si
 - shell material : Ge
 - environment    : eps=1.00

efficiency spectra#

Calculate extinction, scattering and absorption spectra

cs = p.get_cross_sections(k0)

# - plot
plt.figure()
plt.plot(cs["wavelength"], cs["q_ext"], label="$Q_{ext}$")
plt.plot(cs["wavelength"], cs["q_sca"], label="$Q_{sca}$")
plt.plot(cs["wavelength"], cs["q_abs"], label="$Q_{abs}$")
plt.xlabel("wavelength (nm)")
plt.ylabel("Efficiency")
plt.legend()
plt.tight_layout()
# plt.savefig("ex_01a.svg", dpi=300)
plt.show()
ex 01 getting started

angular scattering#

Calculate angular radiation patterns of the scattering

theta = torch.linspace(0.0, 2 * torch.pi, 100)
angular = p.get_angular_scattering(k0, theta)

# - plot every 10th wavelength
plt.figure(figsize=(7, 3))
for i, i_k0 in enumerate(range(len(k0))[::5]):
    ax = plt.subplot(2, 5, i + 1, polar=True)
    plt.title(f"{wl0[i_k0]:.1f} nm")
    ax.plot(angular["theta"], angular["i_unpol"][i_k0], label = "$i_{unpol}$")
    ax.plot(angular["theta"], angular["i_par"][i_k0], label = "$i_{par}$")
    ax.plot(angular["theta"], angular["i_per"][i_k0], label = "$i_{per}$")
    ax.set_xticklabels([])
    ax.set_yticklabels([])
ax.legend(loc='center left', bbox_to_anchor=(1.4, 0.5))
plt.tight_layout()
# plt.savefig("ex_01b.svg", dpi=300)
plt.show()
500.0 nm, 551.0 nm, 602.0 nm, 653.1 nm, 704.1 nm, 755.1 nm, 806.1 nm, 857.1 nm, 908.2 nm, 959.2 nm

Total running time of the script: (0 minutes 1.445 seconds)

Estimated memory usage: 593 MB

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