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import math
import unittest
import meep as mp
class TestEigenmodeSource(unittest.TestCase):
def test_waveguide_flux(self):
cell_size = mp.Vector3(10, 10)
pml_layers = [mp.PML(thickness=2.0)]
rot_angles = range(0, 60, 20) # rotation angle of waveguide, CCW around z-axis
fluxes = []
coeff_fluxes = []
for t in rot_angles:
rot_angle = math.radians(t)
kpoint = mp.Vector3(math.cos(rot_angle), math.sin(rot_angle), 0)
sources = [
mp.EigenModeSource(
src=mp.GaussianSource(1.0, fwidth=0.1),
size=mp.Vector3(y=10),
center=mp.Vector3(x=-3),
direction=mp.NO_DIRECTION,
eig_kpoint=kpoint,
eig_band=1,
eig_parity=mp.ODD_Z,
eig_match_freq=True,
)
]
geometry = [
mp.Block(
center=mp.Vector3(),
size=mp.Vector3(mp.inf, 1, mp.inf),
e1=mp.Vector3(1).rotate(mp.Vector3(z=1), rot_angle),
e2=mp.Vector3(y=1).rotate(mp.Vector3(z=1), rot_angle),
material=mp.Medium(index=1.5),
)
]
sim = mp.Simulation(
cell_size=cell_size,
resolution=50,
boundary_layers=pml_layers,
sources=sources,
geometry=geometry,
)
tran = sim.add_flux(
1.0, 0, 1, mp.FluxRegion(center=mp.Vector3(x=3), size=mp.Vector3(y=10))
)
sim.run(until_after_sources=100)
res = sim.get_eigenmode_coefficients(
tran,
[1],
eig_parity=mp.EVEN_Y + mp.ODD_Z if t == 0 else mp.ODD_Z,
direction=mp.NO_DIRECTION,
kpoint_func=lambda f, n: kpoint,
)
fluxes.append(mp.get_fluxes(tran)[0])
coeff_fluxes.append(abs(res.alpha[0, 0, 0]) ** 2)
print(f"flux:, {t:.2f}, {fluxes[-1]:.6f}")
print(f"coef_flux:, {t:.2f}, {coeff_fluxes[-1]:.6f}")
self.assertAlmostEqual(fluxes[0], fluxes[1], places=0)
self.assertAlmostEqual(fluxes[1], fluxes[2], places=0)
for i in range(3):
self.assertAlmostEqual(fluxes[i], coeff_fluxes[i], places=0)
# self.assertAlmostEqual(fluxes[0], fluxes[2], places=0)
# sadly the above line requires a workaround due to the
# following annoying numerical accident:
# AssertionError: 100.33815231783535 != 99.81145343586365 within 0 places
f0, f2 = fluxes[0], fluxes[2]
self.assertLess(abs(f0 - f2), 0.5 * max(abs(f0), abs(f2)))
if __name__ == "__main__":
unittest.main()
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