Group Index and Velocity of Fused Silica

This example demonstrates how to compute and plot the group index and group velocity of fused silica using PyOptik.

import numpy
import matplotlib.pyplot as plt
from TypedUnit import ureg

from PyOptik import MaterialCatalog


# Retrieve the material
catalog = MaterialCatalog.from_snapshot()
material = catalog.get("main/SiO2/Malitson").load()

# Compute values over a wavelength range
wavelengths = numpy.linspace(0.5, 1.6, 200) * ureg.micrometer
n_g = material.compute_group_index(wavelengths)
v_g = material.compute_group_velocity(wavelengths)

fig, ax1 = plt.subplots()

ax1.set(
    xlabel="Wavelength [µm]",
    ylabel="Group index",
    title="Fused Silica Group Properties",
)
ax1.plot(wavelengths, n_g, label="n_g")
ax1.legend(loc="upper left")

ax2 = ax1.twinx()
ax2.set(ylabel="Group velocity [m/s]")
ax2.plot(
    wavelengths,
    v_g.to("m/s"),
    color="tab:red",
    label="v_g",
)
ax2.legend(loc="upper right")

plt.show()

/opt/hostedtoolcache/Python/3.11.16/x64/lib/python3.11/site-packages/matplotlib/cbook.py:1408: UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.
  return np.asanyarray(x, float)