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import math
import unittest
import numpy as np
from numpy import linalg as LA
import meep as mp
class TestNear2FarPeriodicBoundaries(unittest.TestCase):
def test_nea2far_periodic(self):
dpml = 1.0 # PML thickness
dsub = 3.0 # substrate thickness
dpad = 20.0 # padding between grating and PML
gp = 10.0 # grating period
gh = 0.5 # grating height
gdc = 0.5 # grating duty cycle
sx = dpml + dsub + gh + dpad + dpml
sy = gp
pml_layers = [mp.PML(thickness=dpml, direction=mp.X)]
wvl = 0.5 # center wavelength
fcen = 1 / wvl # center frequency
df = 0.05 * fcen # frequency width
src_pt = mp.Vector3(-0.5 * sx + dpml + 0.5 * dsub)
sources = [
mp.Source(
mp.GaussianSource(fcen, fwidth=df),
component=mp.Ez,
center=src_pt,
size=mp.Vector3(y=sy),
)
]
glass = mp.Medium(index=1.5)
geometry = [
mp.Block(
material=glass,
size=mp.Vector3(dpml + dsub, mp.inf, mp.inf),
center=mp.Vector3(-0.5 * sx + 0.5 * (dpml + dsub)),
),
mp.Block(
material=glass,
size=mp.Vector3(gh, gdc * gp, mp.inf),
center=mp.Vector3(-0.5 * sx + dpml + dsub + 0.5 * gh),
),
]
k_point = mp.Vector3(0, 0, 0)
symmetries = [mp.Mirror(mp.Y)]
n2f_pt = mp.Vector3(-0.5 * sx + dpml + dsub + gh + 1.0)
dft_pt = mp.Vector3(0.5 * sx - dpml)
res = [20, 25, 30]
norm = np.empty(3)
for j in range(3):
sim = mp.Simulation(
resolution=res[j],
cell_size=mp.Vector3(sx, sy),
boundary_layers=pml_layers,
geometry=geometry,
k_point=k_point,
sources=sources,
symmetries=symmetries,
)
n2f_obj = sim.add_near2far(
fcen,
0,
1,
mp.Near2FarRegion(center=n2f_pt, size=mp.Vector3(y=sy)),
nperiods=10,
)
dft_obj = sim.add_dft_fields(
[mp.Ez], fcen, 0, 1, center=dft_pt, size=mp.Vector3(y=sy)
)
sim.run(until_after_sources=300)
n2f_Ez = sim.get_farfields(
n2f_obj, res[j], center=dft_pt, size=mp.Vector3(y=sy)
)
dft_Ez = sim.get_dft_array(dft_obj, mp.Ez, 0)
norm[j] = LA.norm(n2f_Ez["Ez"] - dft_Ez[1:-1])
print(f"norm:, {res[j]}, {norm[j]:.5f}")
sim.reset_meep()
self.assertGreater(norm[0], norm[1])
self.assertGreater(norm[1], norm[2])
if __name__ == "__main__":
unittest.main()
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