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unit test for reciprocity of mode coefficients (#1802)
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* unit test for reciprocity of mode coefficients

* second test for changing DFT monitors and fixed k-point
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@oskooi
oskooi authored Oct 27, 2021
1 parent 577109d commit dd4662f
Showing 1 changed file with 150 additions and 7 deletions.
157 changes: 150 additions & 7 deletions python/tests/test_mode_coeffs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,19 +34,19 @@ def run_mode_coeffs(self, mode_num, kpoint_func, nf=1, resolution=15):
fcen = 0.20 # > 0.5/sqrt(11) to have at least 2 modes
df = 0.5*fcen

source=mp.EigenModeSource(src=mp.GaussianSource(fcen, fwidth=df),
eig_band=mode_num,
size=mp.Vector3(0,sy-2*dpml,0),
center=mp.Vector3(-0.5*sx+dpml,0,0),
eig_match_freq=True,
eig_resolution=2*resolution)
source = mp.EigenModeSource(src=mp.GaussianSource(fcen, fwidth=df),
eig_band=mode_num,
size=mp.Vector3(0,sy-2*dpml,0),
center=mp.Vector3(-0.5*sx+dpml,0,0))

symmetries = [mp.Mirror(mp.Y, phase=1 if mode_num % 2 == 1 else -1)]

sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=boundary_layers,
geometry=geometry,
sources=[source],
symmetries=[mp.Mirror(mp.Y, phase=1 if mode_num % 2 == 1 else -1)])
symmetries=symmetries)

xm = 0.5*sx - dpml # x-coordinate of monitor
mflux = sim.add_mode_monitor(fcen, df, nf, mp.ModeRegion(center=mp.Vector3(xm,0), size=mp.Vector3(0,sy-2*dpml)))
Expand Down Expand Up @@ -133,6 +133,149 @@ def test_eigensource_normalization(self):
max_exp, max_obs=max(p_exp), max(p_obs)
self.assertLess(abs(max_exp-max_obs), 0.5*max(abs(max_exp),abs(max_obs)))

def test_reciprocity_kpoint(self):
resolution = 40

sx = 7.0
sy = 5.0
cell_size = mp.Vector3(sx,sy)

dpml = 1.0
pml_layers = [mp.PML(thickness=dpml)]

w = 1.0
geometry = [mp.Block(center=mp.Vector3(),
size=mp.Vector3(mp.inf,w,mp.inf),
material=mp.Medium(epsilon=12))]

fsrc = 0.15
sources = [mp.EigenModeSource(src=mp.GaussianSource(fsrc,fwidth=0.2*fsrc),
center=mp.Vector3(x=-0.5*sx+dpml),
size=mp.Vector3(y=sy),
eig_parity=mp.EVEN_Y+mp.ODD_Z)]

symmetries = [mp.Mirror(mp.Y)]

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

tran = sim.add_mode_monitor(fsrc, 0, 1,
mp.ModeRegion(center=mp.Vector3(x=0.5*sx-dpml),
size=mp.Vector3(y=sy)),
yee_grid=False)

sim.run(until_after_sources=50)

res_fwd = sim.get_eigenmode_coefficients(tran,
[1],
eig_parity=mp.EVEN_Y+mp.ODD_Z,
direction=mp.NO_DIRECTION,
kpoint_func=lambda f,n: mp.Vector3(+1,0,0))

res_bwd = sim.get_eigenmode_coefficients(tran,
[1],
eig_parity=mp.EVEN_Y+mp.ODD_Z,
direction=mp.NO_DIRECTION,
kpoint_func=lambda f,n: mp.Vector3(-1,0,0))

print("S11:, {}, {}".format(res_fwd.alpha[0,0,1],res_bwd.alpha[0,0,0]))
print("S21:, {}, {}".format(res_fwd.alpha[0,0,0],res_bwd.alpha[0,0,1]))

# |S11|^2
self.assertAlmostEqual(abs(res_fwd.alpha[0,0,1])**2, abs(res_bwd.alpha[0,0,0])**2, places=4)

# |S21|^2
self.assertAlmostEqual(abs(res_fwd.alpha[0,0,0])**2 / abs(res_bwd.alpha[0,0,1])**2, 1.00, places=2)

def test_reciprocity_monitor(self):
resolution = 25

sx = 7.0
sy = 5.0
cell_size = mp.Vector3(sx,sy)

dpml = 1.0
pml_layers = [mp.PML(thickness=dpml)]

w = 1.0
geometry = [mp.Block(center=mp.Vector3(),
size=mp.Vector3(mp.inf,w,mp.inf),
material=mp.Medium(epsilon=12))]

fsrc = 0.15

# source is at the left edge of the waveguide
sources = [mp.EigenModeSource(src=mp.GaussianSource(fsrc,fwidth=0.2*fsrc),
center=mp.Vector3(x=-0.5*sx+dpml),
size=mp.Vector3(y=sy),
eig_parity=mp.EVEN_Y+mp.ODD_Z)]

symmetries = [mp.Mirror(mp.Y)]

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

# monitor is at the right edge of the waveguide
tran = sim.add_mode_monitor(fsrc, 0, 1,
mp.ModeRegion(center=mp.Vector3(x=0.5*sx-dpml),
size=mp.Vector3(y=sy)),
yee_grid=False)

sim.run(until_after_sources=50)

res_fwd = sim.get_eigenmode_coefficients(tran,
[1],
eig_parity=mp.EVEN_Y+mp.ODD_Z)

print("S11:, {}".format(res_fwd.alpha[0,0,1]))
print("S21:, {}".format(res_fwd.alpha[0,0,0]))

sim.reset_meep()

# source is at the right edge of the waveguide
sources = [mp.EigenModeSource(src=mp.GaussianSource(fsrc,fwidth=0.2*fsrc),
center=mp.Vector3(x=0.5*sx-dpml),
size=mp.Vector3(y=sy),
direction=mp.NO_DIRECTION,
eig_kpoint=mp.Vector3(-1,0,0),
eig_parity=mp.EVEN_Y+mp.ODD_Z)]

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

# monitor is at the left edge of the waveguide
tran = sim.add_mode_monitor(fsrc, 0, 1,
mp.ModeRegion(center=mp.Vector3(x=-0.5*sx+dpml),
size=mp.Vector3(y=sy)),
yee_grid=False)

sim.run(until_after_sources=50)

res_bwd = sim.get_eigenmode_coefficients(tran,
[1],
eig_parity=mp.EVEN_Y+mp.ODD_Z)

print("S12:, {}".format(res_bwd.alpha[0,0,1]))
print("S22:, {}".format(res_bwd.alpha[0,0,0]))

# |S21|^2 = |S12|^2
self.assertAlmostEqual(abs(res_fwd.alpha[0,0,0])**2 / abs(res_bwd.alpha[0,0,1])**2, 1.00, places=2)

# |S11|^2 = |S22|^2
self.assertAlmostEqual(abs(res_fwd.alpha[0,0,1])**2, abs(res_bwd.alpha[0,0,0])**2, places=2)


if __name__ == '__main__':
unittest.main()

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