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# -*- coding: utf-8 -*-
# From the Meep tutorial: transmission around a 90-degree waveguide bend in 2d.
from __future__ import division
import meep as mp
resolution = 10 # pixels/um
sx = 16 # size of cell in X direction
sy = 32 # size of cell in Y direction
cell = mp.Vector3(sx,sy,0)
dpml = 1.0
pml_layers = [mp.PML(dpml)]
pad = 4 # padding distance between waveguide and cell edge
w = 1 # width of waveguide
wvg_xcen = 0.5*(sx-w-2*pad) # x center of vert. wvg
wvg_ycen = -0.5*(sy-w-2*pad) # y center of horiz. wvg
geometry = [mp.Block(size=mp.Vector3(mp.inf,w,mp.inf),
center=mp.Vector3(0,wvg_ycen,0),
material=mp.Medium(epsilon=12))]
fcen = 0.15 # pulse center frequency
df = 0.1 # pulse width (in frequency)
sources = [mp.Source(mp.GaussianSource(fcen,fwidth=df), component=mp.Ez,
center=mp.Vector3(-0.5*sx+dpml,wvg_ycen,0),size=mp.Vector3(0,w,0))]
sim = mp.Simulation(cell_size=cell,
boundary_layers=pml_layers,
geometry=geometry,
sources=sources,
resolution=resolution)
nfreq = 100 # number of frequencies at which to compute flux
# reflected flux
refl_fr = mp.FluxRegion(center=mp.Vector3(-0.5*sx+dpml+0.5,wvg_ycen,0),size=mp.Vector3(0,2*w,0))
refl = sim.add_flux(fcen,df,nfreq,refl_fr)
# transmitted flux
tran_fr = mp.FluxRegion(center=mp.Vector3(0.5*sx-dpml,wvg_ycen,0),size=mp.Vector3(0,2*w,0))
tran = sim.add_flux(fcen,df,nfreq,tran_fr)
pt = mp.Vector3(0.5*sx-dpml-0.5,wvg_ycen)
sim.run(until_after_sources=mp.stop_when_fields_decayed(50,mp.Ez,pt,1e-3))
# for normalization run, save flux fields data for reflection plane
straight_refl_data = sim.get_flux_data(refl)
# save incident power for transmission plane
straight_tran_flux = mp.get_fluxes(tran)
sim.reset_meep()
geometry = [mp.Block(mp.Vector3(sx-pad,w,mp.inf),center=mp.Vector3(-0.5*pad,wvg_ycen),material=mp.Medium(epsilon=12)),
mp.Block(mp.Vector3(w,sy-pad,mp.inf),center=mp.Vector3(wvg_xcen,0.5*pad),material=mp.Medium(epsilon=12))]
sim = mp.Simulation(cell_size=cell,
boundary_layers=pml_layers,
geometry=geometry,
sources=sources,
resolution=resolution)
# reflected flux
refl = sim.add_flux(fcen, df, nfreq, refl_fr)
tran_fr = mp.FluxRegion(center=mp.Vector3(wvg_xcen,0.5*sy-dpml-0.5,0),size=mp.Vector3(2*w,0,0))
tran = sim.add_flux(fcen,df,nfreq,tran_fr)
# for normal run, load negated fields to subtract incident from refl. fields
sim.load_minus_flux_data(refl,straight_refl_data)
pt = mp.Vector3(wvg_xcen,0.5*sy-dpml-0.5)
sim.run(until_after_sources=mp.stop_when_fields_decayed(50, mp.Ez, pt, 1e-3))
bend_refl_flux = mp.get_fluxes(refl)
bend_tran_flux = mp.get_fluxes(tran)
flux_freqs = mp.get_flux_freqs(refl)
import numpy as np
import matplotlib.pyplot as plt
wl = []
Rs = []
Ts = []
for i in range(0,nfreq):
wl = np.append(wl, 1/flux_freqs[i])
Rs = np.append(Rs,-bend_refl_flux[i]/straight_tran_flux[i])
Ts = np.append(Ts,bend_tran_flux[i]/straight_tran_flux[i])
plt.plot(wl,Rs,'bo-',label='reflectance')
plt.plot(wl,Ts,'ro-',label='transmittance')
plt.plot(wl,1-Rs-Ts,'go-',label='loss')
plt.axis([5.0, 10.0, 0, 1])
plt.xlabel("wavelength (μm)")
plt.legend(loc="upper right")
plt.show()
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