Group index

import numpy as np
import matplotlib.pyplot as plt
import modes
import opticalmaterialspy as mat

ms = modes.group_index?

wavelength = np.arange(1500, 1600, 10)*1e-3
widths = np.arange(400, 601, 50)*1e-3

for width in widths:
    ng = [modes.group_index(w, width=width) for w in wavelength]
    plt.plot(wavelength, ng, label=f'{width*1e3}')
plt.legend()
plt.xlabel('Wavelength (um)')
plt.xlabel('ng')

Text(0.5, 0, 'ng')

w = wavelength[0]
modes.group_index(w, width=width)

[4.003720129511326]

widths = np.array([490, 500, 510])*1e-3
ng = [modes.group_index(w, width=width)[0] for width in widths]

np.diff(ng)/np.diff(widths) # dng/dw [/um]

array([-2.96626677, -2.78207519])

thicknesss = np.array([200, 220, 240])*1e-3
ng = [modes.group_index(w, thickness=thickness)[0] for thickness in thicknesss]

np.diff(ng)/np.diff(thicknesss) # dng/dh [/um]

array([0.10379131, 0.58652733])

plt.plot(thicknesss*1e3, ng, '-o')
plt.ylabel('ng')
plt.xlabel('thickness (nm)')

Text(0.5, 0, 'thickness (nm)')