Test code for cylindrical wg modesolver

examples/tcyl.py

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+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()