1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
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()
|
