from __future__ import division

import meep as mp


# Example file illustrating an eigenmode source, generating a waveguide mode
# (requires recent MPB version to be installed before Meep is compiled)

cell = mp.Vector3(16, 8)

# an asymmetrical dielectric waveguide:
geometry = [
    mp.Block(center=mp.Vector3(), size=mp.Vector3(mp.inf, 1, mp.inf),
             material=mp.Medium(epsilon=12)),
    mp.Block(center=mp.Vector3(y=0.3), size=mp.Vector3(mp.inf, 0.1, mp.inf),
             material=mp.Medium())
]

# create a transparent source that excites a right-going waveguide mode
sources = [
    mp.EigenModeSource(src=mp.ContinuousSource(0.15), size=mp.Vector3(y=6),
                       center=mp.Vector3(x=-5), component=mp.Dielectric,
                       eig_parity=mp.ODD_Z)
]

pml_layers = [mp.PML(1.0)]

force_complex_fields = True  # so we can get time-average flux

resolution = 10

sim = mp.Simulation(
    cell_size=cell,
    geometry=geometry,
    sources=sources,
    boundary_layers=pml_layers,
    force_complex_fields=force_complex_fields,
    resolution=resolution
)

sim.run(
    mp.at_beginning(mp.output_epsilon),
    mp.at_end(mp.output_png(mp.Ez, "-a yarg -A $EPS -S3 -Zc dkbluered", rm_h5=False)),
    until=200
)

flux1 = sim.flux_in_box(mp.X, mp.Volume(center=mp.Vector3(-6.0), size=mp.Vector3(1.8, 6)))
flux2 = sim.flux_in_box(mp.X, mp.Volume(center=mp.Vector3(6.0), size=mp.Vector3(1.8, 6)))

# averaged over y region of width 1.8
print("left-going flux = {}".format(flux1 / -1.8))

# averaged over y region of width 1.8
print("right-going flux = {}".format(flux2 / 1.8))