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# 1d simulation of a plane wave propagating through a Kerr medium
# and generating the third-harmonic frequency component.
import argparse
import meep as mp
def main(args):
sz = 100 # size of cell in z direction
fcen = 1 / 3.0 # center frequency of source
df = fcen / 20.0 # frequency width of source
amp = args.amp # amplitude of source
k = 10**args.logk # Kerr susceptibility
dpml = 1.0 # PML thickness
# We'll use an explicitly 1d simulation. Setting dimensions=1 will actually
# result in faster execution than just using two no-size dimensions. However,
# in this case Meep requires us to use E in the x direction (and H in y),
# and our one no-size dimension must be z.
dimensions = 1
cell = mp.Vector3(0, 0, sz)
pml_layers = mp.PML(dpml)
resolution = 20
# to put the same material in all space, we can just set the default material
# and pass it to the Simulation constructor
default_material = mp.Medium(index=1, chi3=k)
sources = mp.Source(
mp.GaussianSource(fcen, fwidth=df),
component=mp.Ex,
center=mp.Vector3(0, 0, -0.5 * sz + dpml),
amplitude=amp,
)
# frequency range for flux calculation
nfreq = 400
fmin = fcen / 2.0
fmax = fcen * 4
sim = mp.Simulation(
cell_size=cell,
geometry=[],
sources=[sources],
boundary_layers=[pml_layers],
default_material=default_material,
resolution=resolution,
dimensions=dimensions,
)
# trans = sim.add_flux(0.5 * (fmin + fmax), fmax - fmin, nfreq,
# mp.FluxRegion(mp.Vector3(0, 0, 0.5*sz - dpml - 0.5)))
trans1 = sim.add_flux(
fcen, 0, 1, mp.FluxRegion(mp.Vector3(0, 0, 0.5 * sz - dpml - 0.5))
)
trans3 = sim.add_flux(
3 * fcen, 0, 1, mp.FluxRegion(mp.Vector3(0, 0, 0.5 * sz - dpml - 0.5))
)
sim.run(
until_after_sources=mp.stop_when_fields_decayed(
50, mp.Ex, mp.Vector3(0, 0, 0.5 * sz - dpml - 0.5), 1e-6
)
)
# sim.display_fluxes(trans)
print(
f"harmonics:, {k}, {amp}, {mp.get_fluxes(trans1)[0]}, {mp.get_fluxes(trans3)[0]}"
)
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.add_argument("-amp", type=float, default=1.0, help="amplitude of source")
parser.add_argument(
"-logk", type=float, default=0, help="logarithm of Kerr susceptibility"
)
args = parser.parse_args()
main(args)
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