fdfd_tools/examples/tcyl.py

93 lines
2.5 KiB
Python

import importlib
import numpy
from numpy.linalg import norm
from fdfd_tools import vec, unvec, waveguide_mode
import fdfd_tools
import fdfd_tools.functional
import fdfd_tools.grid
from fdfd_tools.solvers import generic as generic_solver
import gridlock
from matplotlib import pyplot
__author__ = 'Jan Petykiewicz'
def test1(solver=generic_solver):
dx = 20 # discretization (nm/cell)
pml_thickness = 10 # (number of cells)
wl = 1550 # Excitation wavelength
omega = 2 * numpy.pi / wl
# Device design parameters
w = 800
th = 220
center = [0, 0, 0]
r0 = 8e3
# refractive indices
n_wg = numpy.sqrt(12.6) # ~Si
n_air = 1.0 # air
# Half-dimensions of the simulation grid
y_max = 1200
z_max = 900
xyz_max = numpy.array([800, y_max, z_max]) + (pml_thickness + 2) * dx
# Coordinates of the edges of the cells.
half_edge_coords = [numpy.arange(dx/2, m + dx/2, step=dx) for m in xyz_max]
edge_coords = [numpy.hstack((-h[::-1], h)) for h in half_edge_coords]
edge_coords[0] = numpy.array([-dx, dx])
# #### Create the grid and draw the device ####
grid = gridlock.Grid(edge_coords, initial=n_air**2, num_grids=3)
grid.draw_cuboid(center=center, dimensions=[8e3, w, th], eps=n_wg**2)
dxes = [grid.dxyz, grid.autoshifted_dxyz()]
for a in (1, 2):
for p in (-1, 1):
dxes = fdfd_tools.grid.stretch_with_scpml(dxes, omega=omega, axis=a, polarity=p,
thickness=pml_thickness)
wg_args = {
'omega': omega,
'dxes': [(d[1], d[2]) for d in dxes],
'epsilon': vec(g.transpose([1, 2, 0]) for g in grid.grids),
'r0': r0,
}
wg_results = waveguide_mode.solve_waveguide_mode_cylindrical(mode_number=0, **wg_args)
E = wg_results['E']
n_eff = wl / (2 * numpy.pi / wg_results['wavenumber'])
print('n =', n_eff)
print('alpha (um^-1) =', -4 * numpy.pi * numpy.imag(n_eff) / (wl * 1e-3))
'''
Plot results
'''
def pcolor(v):
vmax = numpy.max(numpy.abs(v))
pyplot.pcolor(v.T, cmap='seismic', vmin=-vmax, vmax=vmax)
pyplot.axis('equal')
pyplot.colorbar()
pyplot.figure()
pyplot.subplot(2, 2, 1)
pcolor(numpy.real(E[0][:, :]))
pyplot.subplot(2, 2, 2)
pcolor(numpy.real(E[1][:, :]))
pyplot.subplot(2, 2, 3)
pcolor(numpy.real(E[2][:, :]))
pyplot.subplot(2, 2, 4)
pyplot.show()
if __name__ == '__main__':
test1()