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import meep as mp
import numpy as np
import matplotlib.pyplot as plt
resolution = 40 # pixels/μm
Si = mp.Medium(index=3.45)
dpml = 1.0
pml_layers = [mp.PML(dpml)]
sx = 5
sy = 3
cell = mp.Vector3(sx+2*dpml,sy+2*dpml,0)
a = 1.0 # waveguide width/height
k_point = mp.Vector3(z=0.5)
def parallel_waveguide(s,xodd):
geometry = [mp.Block(center=mp.Vector3(-0.5*(s+a)),
size=mp.Vector3(a,a,mp.inf),
material=Si),
mp.Block(center=mp.Vector3(0.5*(s+a)),
size=mp.Vector3(a,a,mp.inf),
material=Si)]
symmetries = [mp.Mirror(mp.X, phase=-1 if xodd else 1),
mp.Mirror(mp.Y, phase=-1)]
sim = mp.Simulation(resolution=resolution,
cell_size=cell,
geometry=geometry,
boundary_layers=pml_layers,
symmetries=symmetries,
k_point=k_point)
sim.init_sim()
EigenmodeData = sim.get_eigenmode(0.22,
mp.Z,
mp.Volume(center=mp.Vector3(), size=mp.Vector3(sx,sy)),
2 if xodd else 1,
k_point,
match_frequency=False,
parity=mp.ODD_Y)
fcen = EigenmodeData.freq
print("freq:, {}, {}, {}".format("xodd" if xodd else "xeven", s, fcen))
sim.reset_meep()
eig_sources = [mp.EigenModeSource(src=mp.GaussianSource(fcen, fwidth=0.1*fcen),
size=mp.Vector3(sx,sy),
center=mp.Vector3(),
eig_band=2 if xodd else 1,
eig_kpoint=k_point,
eig_match_freq=False,
eig_parity=mp.ODD_Y)]
sim.change_sources(eig_sources)
flux_reg = mp.FluxRegion(direction=mp.Z, center=mp.Vector3(), size=mp.Vector3(sx,sy))
wvg_flux = sim.add_flux(fcen, 0, 1, flux_reg)
force_reg1 = mp.ForceRegion(mp.Vector3(0.49*s), direction=mp.X, weight=1, size=mp.Vector3(y=sy))
force_reg2 = mp.ForceRegion(mp.Vector3(0.5*s+1.01*a), direction=mp.X, weight=-1, size=mp.Vector3(y=sy))
wvg_force = sim.add_force(fcen, 0, 1, force_reg1, force_reg2)
sim.run(until_after_sources=1500)
flux = mp.get_fluxes(wvg_flux)[0]
force = mp.get_forces(wvg_force)[0]
print("data:, {}, {}, {}, {}, {}".format("xodd" if xodd else "xeven", s, flux, force, -force/flux))
sim.reset_meep()
return flux, force
s = np.arange(0.05,1.05,0.05)
fluxes_odd = np.zeros(s.size)
forces_odd = np.zeros(s.size)
fluxes_even = np.zeros(s.size)
forces_even = np.zeros(s.size)
for k in range(len(s)):
fluxes_odd[k], forces_odd[k] = parallel_waveguide(s[k],True)
fluxes_even[k], forces_even[k] = parallel_waveguide(s[k],False)
plt.figure(dpi=150)
plt.plot(s,-forces_odd/fluxes_odd,'rs',label='anti-symmetric')
plt.plot(s,-forces_even/fluxes_even,'bo',label='symmetric')
plt.grid(True)
plt.xlabel('waveguide separation s/a')
plt.ylabel('optical force (F/L)(ac/P)')
plt.legend(loc='upper right')
plt.show()
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