In two dimensions, the fields (by symmetry since the xy plane is a
> mirror plane) can be divided into two polarizations, TE (Hz, Ex, Ey)
> and TM (Ez, Hx, Hy). When you use an Ey source, it only produces TE-
> polarized fields. You get a magnetic field (and a nonzero stress
> tensor), but it is in the z direction only. Conversely, an Hx source
> produces only TM fields, by symmetry.
>
> (See also chapter 3 of our new textbook, available online at
> http://ab-initio.mit.edu/book)
>
> Obviously, the optical forces (the stress tensor) will depend on what
> source you use (and consequently what field patterns you excite). I
> have no idea what physical situation you are interested in. However,
> there is nothing physically wrong with using just a TE source,
> computing the stress tensor from the resulting (Ex,Ey,Hz) fields, and
> hence obtaining the radiation pressure on some object.
1. A quick question: how to implement (dielectric constant = -24.9 + 1.57i)
2.Back to the previous topic
I consider a model based on nearly touching gold spheres illuminated with a
plane wave incident
perpendicular to an axis through the particles' centers and with the
electrical field parallel to
the axis.
In my case, wavelengh of source is 550nm, the radius of gold sphere is 25nm
and the gap between two
spheres is 1nm. The electrical field is implemented as Ey and the
propagation is along X+.
As I am running my simulation on the Sun Grid with parallel meep, the
resolution is
set high (400) in order to get good visualization result.
My target is to calculate the stress tensor in the X-Y plane.
======
;define the simulation cell
;basic unit is 100nm
;planewave source
;frequency 1/(550nm), fwidth 0.2 (346nm~1127nm)
; Drude model of Au
(set! eps-averaging? false)
(define-param wp_au 0.67) ; resonant plasma frequency
(define-param gama_au 6.85e-3) ; gamma of Gold
(define-param e_au 9.84) ; epsilon of Gold 9.84
(define-param r 0.25)
(define-param d 0.01)
(define-param th 0.5)
(define Au
(make dielectric (epsilon e_au)
(polarizations
(make polarizability
(omega 1e-20) (gamma gama_au) (delta-epsilon (* wp_au wp_au
1e+20 1e+20))))))
(set! geometry-lattice (make lattice (size (+ th 15) (+ th 15) no-size)))
(set! geometry (list
(make block (center 0 0) (size 3 3 infinity) (material (make
dielectric (epsilon 1.77))))
(make sphere (center 0 0) (radius r) (material Au))
(make sphere (center 0 (+ (* 2 r) d)) (radius r) (material
Au))
))
(set! sources (list
(make source
(src (make continuous-src (wavelength 5.5)))
(component Ey)
(center -7 0)
(size 0 14 ))))
(set! pml-layers (list (make pml (thickness th))))
(set! resolution 400)
(use-output-directory)
(run-until 200
(at-beginning
(in-volume( volume (center 0 0) (size 1 1)) output-epsilon))
(to-appended "ey"
(at-every 1
(in-volume (volume (center 0 0) (size 1 1))
output-efield-y)))
(to-appended "ex"
(at-every 1
(in-volume (volume (center 0 0) (size 1 1))
output-efield-x)))
(to-appended "hy"
(at-every 1
(in-volume (volume (center 0 0) (size 1 1))
output-hfield-y)))
(to-appended "hx"
(at-every 1
(in-volume (volume (center 0 0) (size 1 1))
output-hfield-x)))
)
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