-
Notifications
You must be signed in to change notification settings - Fork 0
/
mmi2x2
203 lines (142 loc) · 4.1 KB
/
mmi2x2
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
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
"""
Joaquin Matres [email protected]
May 2013
"""
from pylab import *
from camfr import *
W = 6.0
L = 46
offset = 1.03
w = 0.5
w1 = 0.5
w2 = 2.0
h = 0.220
Ltaper = 60.0
nmodes = 50
set_lambda(1.55)
set_N(nmodes)
set_polarisation(TE)
# Materials
Si = 3.43
SiO2 = 1.46
#Si = sqrt(10.6684293*wav**2/(wav**2-0.301516485**2)+0.003043475*wav**2/(wav**2-1.13475115**2)+1.54133408*wav**2/(wav**2-1104.0**2)+1)
#SiO2 = 1.4639-0.0173*wav+0.0055*wav**2-0.0016*wav**3
#Air=1.0
# Sub. spec
SOI = 0.22 # SOI thickness (um)
BOX = 3.0 # BOX thickness (um)
CLAD = 2.0
y_range = 2*W
sub = Material(Si) # substrate
box = Material(SiO2) # BOX
soi = Material(Si) # SOI
clad = Material(SiO2) # Over clad
# Effective index (y-direction)
verticalSlab = Slab(box(BOX)+soi(SOI)+clad(CLAD))
verticalSlab.calc()
n_ridge=verticalSlab.mode(0).n_eff() # Ridge index
print "verticalSlab index=", abs(n_ridge)
#Effective index of WG (xy-plane)
set_polarisation(TM) # TE in 3D is equivalent to TM in 2D
WGcore = Material(n_ridge)
WGclad = Material(SiO2)
WGin=Slab(WGclad(y_range/2-w1/2)+WGcore(w1)+WGclad(y_range/2-w1/2))
WGin.calc()
#
neff_in=WGin.mode(0).n_eff() # Effective index of WG
print "Effective index of input WG=", abs(neff_in)
# Perfectly matched layer
pml=0.4
set_lower_PML(-pml)
set_upper_PML(-pml)
g=Geometry(clad) # Background
Lin = 60.0
dx=0.005 # Step in x
dy=0.005 # Step in z
L = 41.5
P0PIratio = []
Rrange = []
Trange = []
#offsetRange=linspace(0.91,1.10,10)
offset = 1.03
g+=Rectangle(Point(0.0, y_range/2 -offset-w/2.), Point(Lin, y_range/2 -offset + w/2.), WGcore) # Input waveguide
g+=Rectangle(Point(Lin, y_range/2 - W/2), Point(Lin+L, y_range/2 + W/2), WGcore) # MMI region
g+=Rectangle(Point(L+Lin,y_range/2 -offset-w/2.), Point(L+2*Lin, y_range/2 - offset + w/2.), WGcore) # Output waveguide 1
g+=Rectangle(Point(L+Lin,y_range/2 +offset-w/2.), Point(L+2*Lin, y_range/2 + offset + w/2.), WGcore) # Output waveguide 2
## Calc.
design=g.to_expression(0.0, L+2*Lin, dx, 0, y_range, dy)
camfr_stack=Stack(design)
inc = zeros(N())
inc[0] = 1
camfr_stack.set_inc_field(inc)
camfr_stack.calc()
#camfr_stack.plot()
beta = camfr_stack.inc().mode(0).kz()
#extract the field at the input and output position
#y_positions = numpy.arange(0,10,0.01)
y_positions = arange(0, y_range, dy)
IH2= zeros(len(y_positions), dtype=complex)
OH2= zeros(len(y_positions), dtype=complex)
OH2mmi= zeros(len(y_positions), dtype=complex)
print "Now extracting the fields..."
i=0
for y_pos in y_positions:
coord_input = Coord(y_pos, 0.0 , 0.0)
coord_mmiOutput = Coord(y_pos, 0.0, L+Lin)
coord_output = Coord(y_pos, 0.0, L+2*Lin)
field_input = camfr_stack.field(coord_input)
field_output = camfr_stack.field(coord_output)
coord_mmiOutput = Coord(y_pos, 0.0, L+Lin)
field_mmiOutput = camfr_stack.field(coord_mmiOutput)
IH2[i] = field_input.H2()
OH2[i] = field_output.H2()
OH2mmi[i] = field_mmiOutput.H2()
i=i+1
#we need the absolute value, not the complex number
IH2 = abs(IH2)
OH2 = abs(OH2)
#normalize
IH2_max = max(IH2)
IH2 = IH2 / IH2_max
OH2 = OH2 / IH2_max
OH2mmi = abs(OH2mmi)/IH2_max
#plot
print"Now plotting..."
figure(5)
title('integral over $E^2$ input/output')
plot(y_positions, IH2, 'k')
plot(y_positions, OH2, 'y')
plot(y_positions, OH2mmi, 'b')
#savefig('mmiOutField.eps')
#show()
from scipy.integrate import trapz
PI = trapz(square(IH2))
PO= trapz(square(OH2))
print "Integral over H2 square at input : ", PI
print "Integral over H2 square at output : ", PO
print PO / PI * 100.0,"%"
P0PIratio.append(PO / PI )
guided=0
niguided=1.46
for t in range(0,nmodes):
if abs(WGin.mode(t).n_eff().imag)<niguided:
guided=t
niguided=abs(WGin.mode(t).n_eff().imag)
camfr_stack.plot()
# Reflection and transmission coefficients
R=abs(camfr_stack.R12(guided,guided))
T=abs(camfr_stack.T12(guided,guided))
print "Reflection coefficient=", R*R
print "Transmission coefficient=", T*T
Rrange.append(R*R)
Trange.append(T*T)
figure()
#plot(offsetRange,P0PIratio,'.')
#ylabel('P0PIratio')
#figure()
#plot(offsetRange,Trange,'.')
#ylabel('T')
#figure()
#plot(offsetRange,Rrange,'.')
#ylabel('R')
show()