Dear MEEP users!
As i mentioned before that i am trying to calculate the Near
field enhancement and scattering cross section of a nano sphere. Some of you
had made a few comments, thanks to them (especially to Stephan). But that
comments was not enough for me to solve the problem.
In the code below i have tried to calculate the scattering cross section. At
1st i run the simulation without a sphere, which was the total field, then in
the 2nd run i included the sphere and collect the field at each side as given
in the code. So the Scattered field would be: E-scattered = E_total -
E_incident, But i am not sure that this is correct or not. Please make a few
comments on this.
I have also seen on the MEEP GROUP that Mr. Alexander S. McLeod has suggested
someone how to calculate the near field enhancement and the scattering cross
section. Sir, i have some questions from you.
- You have mentioned that to compute near field enhancement, just output field
values Ex, Ey, and Ez in the region of interest of your simulation using a 2-
or 3-D volume. Enhancement is given by |E|^2=|Ex|^2+|Ey|^2+|Ez|^2. My
question is that to find Ex, Ey and Ez, should i choose three plans i.e. xy, yz
and zx ? but in all these plans i have to change the position and size of the
source as well. For example in the code given below, the postion of the source
is (0 0 -0.6) and its size is (1 1 0) and this is zx-plane, so to find Ey i
will choose this plane. For the xy-plane the position of the source would be
(-0.6 0 0) and its size would be (0 1 1), so here i will find Ez and so on. Am
i correct. Please clarify me here.
- You have also mentioned that to calculate the scattering cross section you
have to define 2-D volume surfaces that surround your structure in a cubic
fashion, and output the in-plane E and B-field components for each of these
volumes. Do the same with a "normalization" run. Obtain "scattered field"
values as E_scat=E_total-E_norm for each field component. My question here is
that from 2D volume surfaces you mean the same three planes as i mentioned
above i.e. xy, yz and zx ? And also tell me how to calculate E_norm. Please
clarify me here. I will be very thankful to you.
Best regards,
Jack
(set! eps-averaging? false)
(set! geometry-lattice (make lattice (size 1 1 2)))
(set! geometry
(list
(make sphere (center 0 0 0) (radius 0.125)
(material (make dielectric (epsilon 1)
(polarizations
(make polarizability
(omega 1e-20)
(gamma 0.052)
(sigma 2.45e44))
))))
))
(set! pml-layers (list (make pml (thickness 0.2))))
(set! resolution 50)
(define fcen 1.29) ; Pulse center frequency
(define-param df 2) ; Pulse width (in frequency)
(set! sources (list
(make source
(src(make gaussian-src (frequency fcen) (fwidth df)))
(component Ey)
(center 0 0 -0.6)
(size 1 1 0)
)
)
)
(define-param nfreq 300)
(define incident1
(add-flux fcen df nfreq
(make flux-region
(center 0 0 0.7) (size 1 1 0) (direction Z)
)
))
(define incident2
(add-flux fcen df nfreq
(make flux-region
(center 0 0 -0.7) (size 1 1 0) (direction Z)
)
))
(define incident3
(add-flux fcen df nfreq
(make flux-region
(center 0 0.7 0) (size 1 0 1) (direction Y)
)
))
(define incident4
(add-flux fcen df nfreq
(make flux-region
(center 0 -0.7 0) (size 1 0 1) (direction Y)
)
))
(define incident5
(add-flux fcen df nfreq
(make flux-region
(center 0.7 0 0) (size 0 1 1) (direction X)
)
))
(define incident6
(add-flux fcen df nfreq
(make flux-region
(center -0.7 0 0) (size 0 1 1) (direction X)
)
))
(run-sources+ (stop-when-fields-decayed 30 Ey (vector3 -0.65 0 0) 1e-3)
(to-appended "y-efield" output-efield-y)
)
(display-fluxes incident1 incident2 incident3 incident4 incident5 incident6)
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