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import unittest
import meep as mp
class TestModeDecomposition(unittest.TestCase):
def test_mode_decomposition(self):
resolution = 10
w1 = 1
w2 = 2
Lw = 2
dair = 3.0
dpml = 5.0
sy = dpml + dair + w2 + dair + dpml
half_w1 = 0.5 * w1
half_w2 = 0.5 * w2
Si = mp.Medium(epsilon=12.0)
boundary_layers = [mp.PML(dpml)]
lcen = 6.67
fcen = 1 / lcen
symmetries = [mp.Mirror(mp.Y)]
Lt = 2
sx = dpml + Lw + Lt + Lw + dpml
cell_size = mp.Vector3(sx, sy, 0)
prism_x = sx + 1
half_Lt = 0.5 * Lt
src_pt = mp.Vector3(-0.5 * sx + dpml + 0.2 * Lw, 0, 0)
sources = [mp.EigenModeSource(src=mp.GaussianSource(fcen, fwidth=0.2 * fcen),
component=mp.Ez,
center=src_pt,
size=mp.Vector3(0, sy - 2 * dpml, 0),
eig_match_freq=True,
eig_parity=mp.ODD_Z + mp.EVEN_Y)]
vertices = [mp.Vector3(-prism_x, half_w1),
mp.Vector3(prism_x, half_w1),
mp.Vector3(prism_x, -half_w1),
mp.Vector3(-prism_x, -half_w1)]
sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=boundary_layers,
geometry=[mp.Prism(vertices, height=mp.inf, material=Si)],
sources=sources,
symmetries=symmetries)
mon_pt = mp.Vector3(-0.5 * sx + dpml + 0.5 * Lw, 0, 0)
flux = sim.add_flux(fcen, 0, 1, mp.FluxRegion(center=mon_pt, size=mp.Vector3(0, sy - 2 * dpml, 0)))
sim.run(until_after_sources=mp.stop_when_fields_decayed(50, mp.Ez, src_pt, 1e-9))
res = sim.get_eigenmode_coefficients(flux, [1], eig_parity=mp.ODD_Z + mp.EVEN_Y)
incident_coeffs = res.alpha
incident_flux = mp.get_fluxes(flux)
incident_flux_data = sim.get_flux_data(flux)
sim.reset_meep()
vertices = [mp.Vector3(-prism_x, half_w1),
mp.Vector3(-half_Lt, half_w1),
mp.Vector3(half_Lt, half_w2),
mp.Vector3(prism_x, half_w2),
mp.Vector3(prism_x, -half_w2),
mp.Vector3(half_Lt, -half_w2),
mp.Vector3(-half_Lt, -half_w1),
mp.Vector3(-prism_x, -half_w1)]
sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=boundary_layers,
geometry=[mp.Prism(vertices, height=mp.inf, material=Si)],
sources=sources,
symmetries=symmetries)
refl_flux = sim.add_flux(fcen, 0, 1, mp.FluxRegion(center=mon_pt, size=mp.Vector3(0, sy - 2 * dpml, 0)))
sim.load_minus_flux_data(refl_flux, incident_flux_data)
sim.run(until_after_sources=mp.stop_when_fields_decayed(50, mp.Ez, src_pt, 1e-9))
res = sim.get_eigenmode_coefficients(refl_flux, [1], eig_parity=mp.ODD_Z + mp.EVEN_Y)
coeffs = res.alpha
taper_flux = mp.get_fluxes(refl_flux)
self.assertAlmostEqual(abs(coeffs[0, 0, 1])**2 / abs(incident_coeffs[0, 0, 0])**2,
-taper_flux[0] / incident_flux[0], places=4)
if __name__ == '__main__':
unittest.main()
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