def test():
# Create structure
st = LifetimeTmm()
st.set_vacuum_wavelength(lam0)
# st.add_layer(1e3, si)
st.add_layer(1900, sio2)
st.add_layer(100, si)
st.add_layer(20, sio2)
st.add_layer(100, si)
# st.add_layer(1900, sio2)
st.add_layer(1e3, air)
st.info()
st.set_polarization('TM')
st.set_field('H')
st.set_leaky_or_guiding('guiding')
alpha = st.calc_guided_modes(normalised=True)
st.set_guided_mode(alpha[0])
result = st.calc_field_structure()
z = result['z']
z = st.calc_z_to_lambda(z)
E = result['field']
# Normalise fields
# E /= max(E)
plt.figure()
plt.plot(z, abs(E) ** 2)
for z in st.get_layer_boundaries()[:-1]:
z = st.calc_z_to_lambda(z)
plt.axvline(x=z, color='k', lw=1, ls='--')
plt.show()
def guiding_plot():
""" Find the guiding modes (TE and TM) for a given structure.
First plot s_11 as a function of beta. When s_11=0 this corresponds
to a wave guiding mode. We then solve the roots (with scipy's brentq
algorithm) and plot these as vertical red lines. Check that visually there
is a red line at each pole so that none are missed.
"""
# Create structure
st = LifetimeTmm()
st.set_vacuum_wavelength(lam0)
st.set_field('E')
st.set_leaky_or_guiding('guiding')
# st.add_layer(0 * lam0, air)
# st.add_layer(1 * lam0, si)
# st.add_layer(0 * lam0, air)
st.add_layer(300, sio2)
st.add_layer(100, si)
st.add_layer(20, sio2)
st.add_layer(100, si)
st.add_layer(300, air)
st.info()
# Prepare the figure
fig, (ax1, ax2) = plt.subplots(2, 1, sharex='col', sharey='none')
# TE modes
st.set_polarization('TE')
[beta, s_11] = st.s11_guided()
ax1.plot(beta, s_11, label='TE')
roots = st.calc_guided_modes(normalised=True)
for root in roots:
ax1.axvline(root, color='r')
# TM modes
st.set_polarization('TM')
[beta, s_11] = st.s11_guided()
ax2.plot(beta, s_11, label='TM')
roots = st.calc_guided_modes(normalised=True)
for root in roots:
ax2.axvline(root, color='r')
# Format plot
# fig.tight_layout()
ax1.set_ylabel('$S_{11}$')
ax1.axhline(color='k')
ax2.set_ylabel('$S_{11}$')
ax2.set_xlabel('Normalised parallel wave vector (k_11/k)')
ax2.axhline(color='k')
ax1.legend()
ax2.legend()
if SAVE:
plt.savefig('../Images/guided modes.png', dpi=300)
plt.show()