I am trying to obtain Px and Py for back-scattered light from a gold
nanorectangle (under mp.Ex source illumination) by defining some dft monitors
as follows
1. set reference simulation dft monitor
## Reflexion DFT monitor
box_DFT_re_ref = sim.add_dft_fields([mp.Ex,mp.Ey,mp.Hx,mp.Hy],
frq_cen,dfrq,nfrq,
center=mp.Vector3(z=-s/2+dpml+0.05),
size=mp.Vector3(s-2*dpml,s-2*dpml),
yee_grid=False)
1. run simulation
sim.run(…)
1. obtain reference flux
# DFT reflected fields ref
flux_ref=[]
flux_x_ref=[]
flux_y_ref=[]
for n in np.arange(0,nfrq,1):
nfrq_in=int(n)
(Ex,Ey,Hx,Hy) = [sim.get_dft_array(box_DFT_re_ref,nfrq,nfrq_in) for nfrq
in [mp.Ex, mp.Ey, mp.Hx, mp.Hy]]
(x,y,z,w) = sim.get_array_metadata(dft_cell=box_DFT_re_ref)
dxy = 1/resolution**2
flux_density = np.real( Ex*np.conj(Hy) -Ey*np.conj(Hx) ) # array
flux_ref=0.5*np.append(flux_ref, np.sum(flux_density*dxy)) # Total
flux_density = np.real( Ex*np.conj(Hy) ) # array
flux_x_ref=0.5*np.append(flux_x_ref, np.sum(flux_density*dxy)) # Px
flux_density = np.real( Ey*np.conj(Hx) ) # array
flux_y_ref=0.5*np.append(flux_y_ref, np.sum(flux_density*dxy)) # Py
1. reset simulation, include geometry, set DFT monitor
# DFT field reflection monitor
box_DFT_re= sim.add_dft_fields([mp.Ex,mp.Ey,mp.Hx,mp.Hy],
frq_cen,dfrq,nfrq,
center=mp.Vector3(z=-s/2+dpml+0.05),
size=mp.Vector3(s-2*dpml,s-2*dpml),
yee_grid=False)
1. run simulation
2. obtain flux
## Px and Py calculation
flux=[]
flux_x=[]
flux_y=[]
for n in np.arange(0,nfrq,1):
nfrq_in=int(n)
(Ex,Ey,Hx,Hy) = [sim.get_dft_array(box_DFT_re,nfrq,nfrq_in) for nfrq in
[mp.Ex, mp.Ey, mp.Hx, mp.Hy]]
(x,y,z,w) = sim.get_array_metadata(dft_cell=box_DFT_re)
dxy = 1/resolution**2
flux_density = np.real( Ex*np.conj(Hy) -Ey*np.conj(Hx) )
flux=0.5*np.append(flux,np.sum(flux_density*dxy)) # Total
flux_density = np.real( Ex*np.conj(Hy) )
flux_x=0.5*np.append(flux_x,np.sum(flux_density*dxy)) # Px
flux_density = np.real( Ey*np.conj(Hx) )
flux_y=0.5*np.append(flux_y,np.sum(flux_density*dxy)) # Py
1. plot results removing source flux and normalize to source
## Plot Px and Py
if mp.am_master():
plt.figure(dpi=150)
plt.plot(1/np.asarray(freqs),-(flux-flux_ref)/flux_ref
,'r-',label='P_total')
plt.plot(1/np.asarray(freqs),-(flux_x-flux_x_ref)/flux_ref ,'go',label='Px')
plt.plot(1/np.asarray(freqs),(flux_y-flux_y_ref)/flux_ref ,'c*',label='Py')
plt.plot(wl,Rs,'bo-',label='Back-scatter') #results obtained from get_flux
monitor of identical dimensions
plt.grid(True,which="both",ls="-")
plt.xlabel('wavelength, um')
plt.ylabel(Scattering')
plt.legend(loc='upper left')
plt.title('Px and Py')
plt.tight_layout()
plt.savefig("media/PxPy.png")
Yet my results are not identical to when I use get_flux (also having removed
the source flux) as seen in this link. What could be the origin of this
difference?
Image link:
https://cdn.discordapp.com/attachments/765260434419875931/776558260483391528/PxPy.png
Thank you
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