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import argparse
import math
import meep as mp
def main(args):
resolution = args.res
dpml = 1.0 # PML thickness
sz = 10 + 2 * dpml # size of computational cell (without PMLs)
cell_size = mp.Vector3(0, 0, sz)
pml_layers = [mp.PML(dpml)]
wvl_min = 0.4 # min wavelength
wvl_max = 0.8 # max wavelength
fmin = 1 / wvl_max # min frequency
fmax = 1 / wvl_min # max frequency
fcen = 0.5 * (fmin + fmax) # center frequency
df = fmax - fmin # frequency width
nfreq = 50 # number of frequency bins
# rotation angle (in degrees) of source: CCW around Y axis, 0 degrees along +Z axis
theta_r = math.radians(args.theta)
# plane of incidence is XZ
k = mp.Vector3(math.sin(theta_r), 0, math.cos(theta_r)).scale(fmin)
# if normal incidence, force number of dimensions to be 1
dimensions = 1 if theta_r == 0 else 3
sources = [
mp.Source(
mp.GaussianSource(fcen, fwidth=df),
component=mp.Ex,
center=mp.Vector3(0, 0, -0.5 * sz + dpml),
)
]
sim = mp.Simulation(
cell_size=cell_size,
boundary_layers=pml_layers,
sources=sources,
k_point=k,
dimensions=dimensions,
resolution=resolution,
)
refl_fr = mp.FluxRegion(center=mp.Vector3(0, 0, -0.25 * sz))
refl = sim.add_flux(fcen, df, nfreq, refl_fr)
sim.run(
until_after_sources=mp.stop_when_fields_decayed(
50, mp.Ex, mp.Vector3(0, 0, -0.5 * sz + dpml), 1e-9
)
)
empty_flux = mp.get_fluxes(refl)
empty_data = sim.get_flux_data(refl)
sim.reset_meep()
# add a block with n=3.5 for the air-dielectric interface
geometry = [
mp.Block(
size=mp.Vector3(mp.inf, mp.inf, 0.5 * sz),
center=mp.Vector3(0, 0, 0.25 * sz),
material=mp.Medium(index=3.5),
)
]
sim = mp.Simulation(
cell_size=cell_size,
geometry=geometry,
boundary_layers=pml_layers,
sources=sources,
k_point=k,
dimensions=dimensions,
resolution=resolution,
)
refl = sim.add_flux(fcen, df, nfreq, refl_fr)
sim.load_minus_flux_data(refl, empty_data)
sim.run(
until_after_sources=mp.stop_when_fields_decayed(
50, mp.Ex, mp.Vector3(0, 0, -0.5 * sz + dpml), 1e-9
)
)
refl_flux = mp.get_fluxes(refl)
freqs = mp.get_flux_freqs(refl)
for i in range(nfreq):
print(
f"refl:, {k.x}, {1 / freqs[i]}, {math.degrees(math.asin(k.x/freqs[i]))}, {-refl_flux[i] / empty_flux[i]}"
)
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.add_argument(
"-res", type=int, default=200, help="resolution (default: 200 pixels/um)"
)
parser.add_argument(
"-theta",
type=float,
default=0,
help="angle of incident planewave (default: 0 degrees)",
)
args = parser.parse_args()
main(args)
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