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import numpy as np
import gdspy
from matplotlib import pyplot as plt
import importlib
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("ring_resonator_r{}_w{}".format(radius,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 = "ring_r{}_w{}.gds".format(radius,width)
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("mode: {}, {}".format(w,Q))
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