FEM: SOI
The SOI waveguide of the “Basic: SOI” example, solved with the finite-element mode solver. The mesh follows every material interface, and the solver refines it where the modes are under-resolved. The refinement history shows how the effective indices settle.
This code example is licensed under the BSD 3-Clause License.
import emodeconnection as emc
## Set simulation parameters
wavelength = 1550 # [nm] wavelength
dx, dy = 10, 10 # [nm] resolution of the grid used for plotting
w_core = 600 # [nm] waveguide core width
w_trench = 800 # [nm] waveguide side trench width
h_core = 500 # [nm] waveguide core height
h_clad = 800 # [nm] waveguide top and bottom clad
num_modes = 2 # [-] number of modes
## Connect and initialize EMode
em = emc.EMode()
## Settings: the same waveguide as the SOI example, plus the FEM mesh settings
em.settings(
wavelength = wavelength, x_resolution = dx, y_resolution = dy,
window_width = w_core + w_trench*2, window_height = h_core + h_clad*2,
num_modes = num_modes, background_material = 'Air',
fem_points_per_wavelength = 10, fem_max_refinements = 2)
## Draw shapes
em.shape(name = 'BOX', material = 'SiO2', height = h_clad)
em.shape(name = 'core', material = 'Si', width = w_core, height = h_core)
## Launch the FEM solver, which refines the mesh where the modes need it
## (em.solve(solver_method='FEM') does the same)
result = em.FEM()
## Show how the effective indices settled as the mesh was refined
refinement = result['refinement']
print('Refinement level Unknowns n_eff (per mode)', flush = True)
for level, (dofs, n_eff) in enumerate(zip(refinement['num_dofs'], refinement['n_eff_history'])):
print(f'{level:16d} {dofs:8d} ' + ' '.join(f'{n.real:.6f}' for n in n_eff), flush = True)
print(f"Stopped by: {refinement['stopped_by']}", flush = True)
## Display the effective indices, TE fractions, and core confinement
em.report()
## Plot the fields with the triangle mesh the FEM solved on
em.plot(mesh_display = True)
## Close EMode
em.close()
Console output:
EMode3D 1.0.5 - email
Meshing completed in 0.4 sec
Solving modes completed in 1.4 sec
Refinement level Unknowns n_eff (per mode)
0 11613 3.013305 2.966522
1 12481 3.013291 2.966504
2 15407 3.013285 2.966500
Stopped by: max_refinements
Wavelength: 1550.0 nm Solver: FEM
Mode # n_eff TE % Loss (dB/m)
-------- -------- ------ -------------
TE-0 3.013285 99.6 % 0.000
TM-1 2.966500 0.6 % 0.000
Exited EMode
Figures:
