EME: Sweep
In practice, a taper length needs to be optimized to ensure proper modal transmission and low loss. This example shows how the sweep function can be used to visualize the transmission of an EME taper simulation.
This code example is licensed under the BSD 3-Clause License.
import emodeconnection as emc
import numpy as np
## Set simulation parameters
wavelength = 1550 # [nm] wavelength
dx, dy = 20, 20 # [nm] resolution
h_core = 220 # [nm] waveguide core height
h_clad = 1000 # [nm] waveguide top and bottom clad
window_width = 3200
window_height = h_core + h_clad*2
num_modes = 4 # [-] number of modes
BC = 'TE-v'
## Connect and initialize EMode
em = emc.EMode(simulation_name = 'taper', verbose = True)
## Settings
em.settings(wavelength = wavelength,
x_resolution = dx, y_resolution = dy,
window_width = window_width,
window_height = window_height,
num_modes = num_modes, boundary_condition = BC,
background_refractive_index = 'SiO2')
## Draw shapes
em.shape(name = 'BOX', refractive_index = 'SiO2',
height = h_clad)
em.shape(name = 'core', refractive_index = 'Si',
height = h_core, etch_depth = h_core)
## Launch FDM solver and label profiles
em.shape(name = 'core', mask = 600)
em.label(label = 'a') # skips solving the modes here
em.shape(name = 'core', mask = 1200)
em.label(label = 'b') # skips solving the modes here
## Draw EME sections
em.section(profile = 'a', section_type = 'straight',
length = 2e3, num_modes = num_modes)
em.section(name = 'taper', section_type = 'taper',
profile = 'a', profile_end = 'b',
length = 6000, num_modes = num_modes,
minimum_z_step = 10, overlap_variation = 0.01)
em.section(profile = 'b', section_type = 'straight',
length = 2e3, num_modes = num_modes)
## Run EME sweep
data = em.sweep(key='section, taper, length',
values=np.arange(0, 6001, 100),
result = ['S_matrix'])
## Close EMode
em.close()
%% Set simulation parameters
wavelength = 1550; % [nm] wavelength
dx = 20; dy = 20; % [nm] resolution
h_core = 220; % [nm] waveguide core height
h_clad = 1000; % [nm] waveguide top and bottom clad
window_width = 3200;
window_height = h_core + h_clad*2;
num_modes = 4; % [-] number of modes
BC = 'TE-v';
%% Connect and initialize EMode
em = emodeconnection('simulation_name', 'taper', 'verbose', true);
%% Settings
em.settings('wavelength', wavelength, ...
'x_resolution', dx, 'y_resolution', dy, ...
'window_width', window_width, ...
'window_height', window_height, ...
'num_modes', num_modes, 'boundary_condition', BC, ...
'background_refractive_index', 'SiO2');
%% Draw shapes
em.shape('name', 'BOX', 'refractive_index', 'SiO2', ...
'height', h_clad);
em.shape('name', 'core', 'refractive_index', 'Si', ...
'height', h_core, 'etch_depth', h_core);
%% Launch FDM solver and label profiles
em.shape('name', 'core', 'mask', 600);
em.label('label', 'a'); % skips solving the modes here
em.shape('name', 'core', 'mask', 1200);
em.label('label', 'b'); % skips solving the modes here
%% Draw EME sections
em.section('profile', 'a', 'section_type', 'straight', ...
'length', 2e3, 'num_modes', num_modes);
em.section('name', 'taper', 'section_type', 'taper', ...
'profile', 'a', 'profile_end', 'b', ...
'length', 6000, 'num_modes', num_modes, ...
'minimum_z_step', 10, 'overlap_variation', 0.01);
em.section('profile', 'b', 'section_type', 'straight', ...
'length', 2e3, 'num_modes', num_modes);
%% Run EME sweep
data = em.sweep('key', 'section, taper, length', ...
'values', 0:100:6000, ...
result = ['S_matrix']);
%% Close EMode
em.close();
Console output:
EMode 0.1.1 - email
Connected on port 58718 to LM-2.
Session type: 3d
Successfully logged in to the license manager.
Sweeping section parameter 'length'...
Solving EME: length = 6000... completed in 1 min 41.2 sec
Solving EME: length = 5900... completed in 0.3 sec
Solving EME: length = 5800... completed in 0.3 sec
Solving EME: length = 5700... completed in 0.3 sec
Solving EME: length = 5600... completed in 0.3 sec
Solving EME: length = 5500... completed in 0.3 sec
Solving EME: length = 5400... completed in 0.3 sec
Solving EME: length = 5300... completed in 0.3 sec
Solving EME: length = 5200... completed in 0.3 sec
Solving EME: length = 5100... completed in 0.3 sec
Solving EME: length = 5000... completed in 0.3 sec
Solving EME: length = 4900... completed in 0.3 sec
Solving EME: length = 4800... completed in 0.3 sec
Solving EME: length = 4700... completed in 0.3 sec
Solving EME: length = 4600... completed in 0.3 sec
Solving EME: length = 4500... completed in 0.3 sec
Solving EME: length = 4400... completed in 0.3 sec
Solving EME: length = 4300... completed in 0.3 sec
Solving EME: length = 4200... completed in 0.3 sec
Solving EME: length = 4100... completed in 0.3 sec
Solving EME: length = 4000... completed in 0.3 sec
Solving EME: length = 3900... completed in 0.3 sec
Solving EME: length = 3800... completed in 0.3 sec
Solving EME: length = 3700... completed in 0.3 sec
Solving EME: length = 3600... completed in 0.3 sec
Solving EME: length = 3500... completed in 0.3 sec
Solving EME: length = 3400... completed in 0.3 sec
Solving EME: length = 3300... completed in 0.3 sec
Solving EME: length = 3200... completed in 0.3 sec
Solving EME: length = 3100... completed in 0.3 sec
Solving EME: length = 3000... completed in 0.3 sec
Solving EME: length = 2900... completed in 0.3 sec
Solving EME: length = 2800... completed in 0.3 sec
Solving EME: length = 2700... completed in 0.3 sec
Solving EME: length = 2600... completed in 0.3 sec
Solving EME: length = 2500... completed in 0.3 sec
Solving EME: length = 2400... completed in 0.3 sec
Solving EME: length = 2300... completed in 0.3 sec
Solving EME: length = 2200... completed in 0.3 sec
Solving EME: length = 2100... completed in 0.3 sec
Solving EME: length = 2000... completed in 0.3 sec
Solving EME: length = 1900... completed in 0.3 sec
Solving EME: length = 1800... completed in 0.3 sec
Solving EME: length = 1700... completed in 0.3 sec
Solving EME: length = 1600... completed in 0.3 sec
Solving EME: length = 1500... completed in 0.3 sec
Solving EME: length = 1400... completed in 0.3 sec
Solving EME: length = 1300... completed in 0.3 sec
Solving EME: length = 1200... completed in 0.3 sec
Solving EME: length = 1100... completed in 0.3 sec
Solving EME: length = 1000... completed in 0.3 sec
Solving EME: length = 900... completed in 0.3 sec
Solving EME: length = 800... completed in 0.3 sec
Solving EME: length = 700... completed in 0.3 sec
Solving EME: length = 600... completed in 0.3 sec
Solving EME: length = 500... completed in 0.3 sec
Solving EME: length = 400... completed in 0.3 sec
Solving EME: length = 300... completed in 0.3 sec
Solving EME: length = 200... completed in 0.3 sec
Solving EME: length = 100... completed in 0.3 sec
Solving EME: length = 0... completed in 0.3 sec
completed in 1 min 59.6 sec
Exited EMode
While no figures are generated in the EMode script, a separate script can be used to plot the results.
import emodeconnection as emc
import numpy as np
## Extract sweep results without an EMode license
data = emc.get(variable = 'sweep_data',
simulation_name = 'taper')
## Plot
import matplotlib.pyplot as plt
from matplotlib import rc as mplrc
fw, LW = 8/2.54, 0.5
mplrc('font',**{'family':'sans-serif','sans-serif':['Arial'],'size':7})
mplrc('axes', linewidth=LW, axisbelow=True)
mplrc('xtick', bottom=True, top=True, direction='in')
mplrc('ytick', left=True, right=True, direction='in')
mplrc('xtick.major', size=3, width=LW)
mplrc('ytick.major', size=3, width=LW)
mplrc('figure',figsize=[fw, fw/2**0.5])
fig, ax = plt.subplots(1, 1)
ax.set_xlabel('Taper length (nm)')
ax.set_ylabel('Tranmission (%)')
ax.grid(visible=True, which='major', axis='both', linewidth=LW/2, color='grey', alpha=0.25)
S = np.array(data['S_matrix'])
lines = []
for kk in range(S.shape[-1]):
line, = ax.plot(data['values'],
100*np.abs(S[:,1,0,kk,0])**2,
marker = '', linestyle = '-', lw = LW*1.5,
label = r'Mode 0$\rightarrow$%d' % kk)
lines.append(line)
ax.set_xlim([
np.min(data['values']),
np.max(data['values'])])
lg = ax.legend(handles = lines[0:1], loc = 'center right')
lg.get_frame().set_linewidth(LW/2)
lg.get_frame().set_edgecolor('k')
ax.set_ylim([80, 100])
fig.savefig('taper_1.png', dpi=600, bbox_inches='tight')
lg = ax.legend(handles = lines[1:], loc = 'upper right')
lg.get_frame().set_linewidth(LW/2)
lg.get_frame().set_edgecolor('k')
ax.set_ylim([-1, 16])
fig.savefig('taper_2.png', dpi=600, bbox_inches='tight')
Figures:
