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
|
import importlib
import gdspy
import numpy as np
from matplotlib import pyplot as plt
import meep as mp
# core and cladding materials
Si = mp.Medium(index=3.4)
SiO2 = mp.Medium(index=1.4)
# layer numbers for GDS file
RING_LAYER = 0
SOURCE0_LAYER = 1
SOURCE1_LAYER = 2
MONITOR_LAYER = 3
SIMULATION_LAYER = 4
resolution = 50 # pixels/μm
dpml = 1 # thickness of PML
zmin = 0 # minimum z value of simulation domain (0 for 2D)
zmax = 0 # maximum z value of simulation domain (0 for 2D)
def create_ring_gds(radius, width):
# Reload the library each time to prevent gds library name clashes
importlib.reload(gdspy)
ringCell = gdspy.Cell(f"ring_resonator_r{radius}_w{width}")
# Draw the ring
ringCell.add(
gdspy.Round(
(0, 0),
inner_radius=radius - width / 2,
radius=radius + width / 2,
layer=RING_LAYER,
)
)
# Draw the first source
ringCell.add(
gdspy.Rectangle((radius - width, 0), (radius + width, 0), SOURCE0_LAYER)
)
# Draw the second source
ringCell.add(
gdspy.Rectangle((-radius - width, 0), (-radius + width, 0), SOURCE1_LAYER)
)
# Draw the monitor location
ringCell.add(
gdspy.Rectangle((radius - width / 2, 0), (radius + width / 2, 0), MONITOR_LAYER)
)
# Draw the simulation domain
pad = 2 # padding between waveguide and edge of PML
ringCell.add(
gdspy.Rectangle(
(-radius - width / 2 - pad, -radius - width / 2 - pad),
(radius + width / 2 + pad, radius + width / 2 + pad),
SIMULATION_LAYER,
)
)
filename = f"ring_r{radius}_w{width}.gds"
gdspy.write_gds(filename, unit=1.0e-6, precision=1.0e-9)
return filename
def find_modes(filename, wvl=1.55, bw=0.05):
# Read in the ring structure
geometry = mp.get_GDSII_prisms(Si, filename, RING_LAYER, -100, 100)
cell = mp.GDSII_vol(filename, SIMULATION_LAYER, zmin, zmax)
src_vol0 = mp.GDSII_vol(filename, SOURCE0_LAYER, zmin, zmax)
src_vol1 = mp.GDSII_vol(filename, SOURCE1_LAYER, zmin, zmax)
mon_vol = mp.GDSII_vol(filename, MONITOR_LAYER, zmin, zmax)
fcen = 1 / wvl
df = bw * fcen
src = [
mp.Source(mp.GaussianSource(fcen, fwidth=df), component=mp.Hz, volume=src_vol0),
mp.Source(
mp.GaussianSource(fcen, fwidth=df),
component=mp.Hz,
volume=src_vol1,
amplitude=-1,
),
]
sim = mp.Simulation(
cell_size=cell.size,
geometry=geometry,
sources=src,
resolution=resolution,
boundary_layers=[mp.PML(dpml)],
default_material=SiO2,
)
h = mp.Harminv(mp.Hz, mon_vol.center, fcen, df)
sim.run(mp.after_sources(h), until_after_sources=100)
plt.figure()
sim.plot2D(fields=mp.Hz, eps_parameters={"contour": True})
plt.savefig("ring_fields.png", bbox_inches="tight", dpi=150)
wvl = np.array([1 / m.freq for m in h.modes])
Q = np.array([m.Q for m in h.modes])
sim.reset_meep()
return wvl, Q
if __name__ == "__main__":
filename = create_ring_gds(2.0, 0.5)
wvls, Qs = find_modes(filename, 1.55, 0.05)
for w, Q in zip(wvls, Qs):
print(f"mode: {w}, {Q}")
|
