/
special_kz.py
155 lines (117 loc) · 5.55 KB
/
special_kz.py
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from __future__ import division
import unittest
import meep as mp
import cmath
import math
from time import time
class TestSpecialKz(unittest.TestCase):
def refl_planar(self, theta, kz_2d):
resolution = 100 # pixels/um
dpml = 1.0
sx = 3+2*dpml
sy = 1/resolution
cell_size = mp.Vector3(sx,sy)
pml_layers = [mp.PML(dpml,direction=mp.X)]
fcen = 1.0 # source wavelength = 1 um
k_point = mp.Vector3(z=math.sin(theta)).scale(fcen)
sources = [mp.Source(mp.GaussianSource(fcen,fwidth=0.2*fcen),
component=mp.Ez,
center=mp.Vector3(-0.5*sx+dpml),
size=mp.Vector3(y=sy))]
sim = mp.Simulation(cell_size=cell_size,
boundary_layers=pml_layers,
sources=sources,
k_point=k_point,
kz_2d=kz_2d,
resolution=resolution)
refl_fr = mp.FluxRegion(center=mp.Vector3(-0.25*sx),
size=mp.Vector3(y=sy))
refl = sim.add_flux(fcen,0,1,refl_fr)
sim.run(until_after_sources=mp.stop_when_fields_decayed(50,mp.Ez,mp.Vector3(),1e-9))
empty_flux = mp.get_fluxes(refl)
empty_data = sim.get_flux_data(refl)
sim.reset_meep()
geometry = [mp.Block(material=mp.Medium(index=3.5),
size=mp.Vector3(0.5*sx,mp.inf,mp.inf),
center=mp.Vector3(0.25*sx))]
sim = mp.Simulation(cell_size=cell_size,
boundary_layers=pml_layers,
geometry=geometry,
sources=sources,
k_point=k_point,
kz_2d=kz_2d,
resolution=resolution)
refl = sim.add_flux(fcen,0,1,refl_fr)
sim.load_minus_flux_data(refl,empty_data)
sim.run(until_after_sources=mp.stop_when_fields_decayed(50,mp.Ez,mp.Vector3(),1e-9))
refl_flux = mp.get_fluxes(refl)
Rmeep = -refl_flux[0]/empty_flux[0]
return Rmeep
def test_special_kz(self):
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 P-polarization in medium n2
# for incident planewave in medium n1 at angle theta_in
Rfresnel = lambda theta_in: math.fabs((n1*math.cos(theta_out(theta_in))-n2*math.cos(theta_in))/(n1*math.cos(theta_out(theta_in))+n2*math.cos(theta_in)))**2
theta = math.radians(23)
start = time()
Rmeep_complex = self.refl_planar(theta, 'complex')
t_complex = time() - start
start = time()
Rmeep_real_imag = self.refl_planar(theta, 'real/imag')
t_real_imag = time() - start
Rfres = Rfresnel(theta)
self.assertAlmostEqual(Rmeep_complex,Rfres,places=2)
self.assertAlmostEqual(Rmeep_real_imag,Rfres,places=2)
self.assertLess(t_real_imag,t_complex)
def eigsrc_kz(self, kz_2d):
print(kz_2d)
resolution = 30 # pixels/um
cell_size = mp.Vector3(14,14)
pml_layers = [mp.PML(thickness=2)]
geometry = [mp.Block(center=mp.Vector3(),
size=mp.Vector3(mp.inf,1,mp.inf),
material=mp.Medium(epsilon=12))]
fsrc = 0.3 # frequency of eigenmode or constant-amplitude source
bnum = 1 # band number of eigenmode
kz = 0.2 # fixed out-of-plane wavevector component
sources = [mp.EigenModeSource(src=mp.GaussianSource(fsrc,fwidth=0.2*fsrc),
center=mp.Vector3(),
size=mp.Vector3(y=14),
eig_band=bnum,
eig_parity=mp.EVEN_Y,
eig_match_freq=True)]
sim = mp.Simulation(cell_size=cell_size,
resolution=resolution,
boundary_layers=pml_layers,
sources=sources,
geometry=geometry,
symmetries=[mp.Mirror(mp.Y)],
k_point=mp.Vector3(z=kz),
kz_2d=kz_2d)
tran = sim.add_flux(fsrc, 0, 1, mp.FluxRegion(center=mp.Vector3(x=5), size=mp.Vector3(y=14)))
sim.run(until_after_sources=50)
res = sim.get_eigenmode_coefficients(tran,
[1,2],
eig_parity=mp.EVEN_Y)
total_flux = mp.get_fluxes(tran)[0]
mode1_flux = abs(res.alpha[0,0,0])**2
mode2_flux = abs(res.alpha[1,0,0])**2
mode1_frac = 0.99
self.assertGreater(mode1_flux/total_flux, mode1_frac)
self.assertLess(mode2_flux/total_flux, 1-mode1_frac)
d = 3.5
ez1 = sim.get_field_point(mp.Ez, mp.Vector3(2.3,-5.7,4.8))
ez2 = sim.get_field_point(mp.Ez, mp.Vector3(2.3,-5.7,4.8+d))
ratio_ez = ez2/ez1
phase_diff = cmath.exp(1j*2*cmath.pi*kz*d)
self.assertAlmostEqual(ratio_ez.real,phase_diff.real,places=10)
self.assertAlmostEqual(ratio_ez.imag,phase_diff.imag,places=10)
def test_eigsrc_kz(self):
self.eigsrc_kz("complex")
self.eigsrc_kz("real/imag")
if __name__ == '__main__':
unittest.main()