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import math
import meep as mp
def refl_planar(theta, kz_2d):
resolution = 100
dpml = 1.0
sx = 10
sx = 10 + 2 * dpml
cell_size = mp.Vector3(sx)
pml_layers = [mp.PML(dpml)]
fcen = 1.0
# plane of incidence is XZ
k = mp.Vector3(z=math.sin(theta)).scale(fcen)
sources = [
mp.Source(
mp.GaussianSource(fcen, fwidth=0.2 * fcen),
component=mp.Ey,
center=mp.Vector3(-0.5 * sx + dpml),
)
]
sim = mp.Simulation(
cell_size=cell_size,
boundary_layers=pml_layers,
sources=sources,
k_point=k,
kz_2d=kz_2d,
resolution=resolution,
)
refl_fr = mp.FluxRegion(center=mp.Vector3(-0.25 * sx))
refl = sim.add_flux(fcen, 0, 1, refl_fr)
sim.run(
until_after_sources=mp.stop_when_fields_decayed(
50, mp.Ey, mp.Vector3(-0.5 * sx + dpml), 1e-9
)
)
input_flux = mp.get_fluxes(refl)
input_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(0.5 * sx, mp.inf, mp.inf),
center=mp.Vector3(0.25 * sx),
material=mp.Medium(index=3.5),
)
]
sim = mp.Simulation(
cell_size=cell_size,
geometry=geometry,
boundary_layers=pml_layers,
sources=sources,
k_point=k,
kz_2d=kz_2d,
resolution=resolution,
)
refl = sim.add_flux(fcen, 0, 1, refl_fr)
sim.load_minus_flux_data(refl, input_data)
sim.run(
until_after_sources=mp.stop_when_fields_decayed(
50, mp.Ey, mp.Vector3(-0.5 * sx + dpml), 1e-9
)
)
refl_flux = mp.get_fluxes(refl)
freqs = mp.get_flux_freqs(refl)
return -refl_flux[0] / input_flux[0]
# rotation angle of source: CCW around Y axis, 0 degrees along +X axis
theta_r = math.radians(19.4)
Rmeep_real_imag = refl_planar(theta_r, "real/imag")
Rmeep_complex = refl_planar(theta_r, "complex")
Rmeep_3d = refl_planar(theta_r, "3d")
n1 = 1
n2 = 3.5
# compute angle of refracted planewave in medium n2
# for incident planewave in medium n1 at angle theta_in
theta_out = lambda theta_in: math.asin(n1 * math.sin(theta_in) / n2)
# compute Fresnel reflectance for S-polarization in medium n2
# for incident planewave in medium n1 at angle theta_in
Rfresnel = (
lambda theta_in: math.fabs(
(n2 * math.cos(theta_out(theta_in)) - n1 * math.cos(theta_in))
/ (n2 * math.cos(theta_out(theta_in)) + n1 * math.cos(theta_in))
)
** 2
)
print(
f"refl:, {Rmeep_real_imag} (real/imag), {Rmeep_complex} (complex), {Rmeep_3d} (3d), {Rfresnel(theta_r)} (analytic)"
)
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