import importlib import numpy from numpy.linalg import norm from meanas.fdmath import vec, unvec from meanas.fdfd import waveguide_mode, functional, scpml from meanas.fdfd.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) epsilon = grid.allocate(n_air**2, dtype=numpy.float32) grid.draw_cuboid(epsilon, 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 = scmpl.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 epsilon), '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()