Dear all,
I am trying to use MEEP to simulation TFSF in mid-infrared region for 2-D
cylindrical structure. As I am new to MEEP, I need some help to proceed:
1. If the wavelength is long (maximum is around 10um), do I need very thick
PML layer?
2. If the simulation box needs to be big comparing to the structure that I
am working on, is there a way I can make the grids finer regionally at the
structure that I was simulating?
The absorption cross-section that I obtained using following code centered
around the peak of gaussian source, which is obviously artificial. Is it due
to thickness problem?
;Unit: um
(define-param sx 4) ; ' Size
of cell in X-direction
(define-param sy 4) ; ' Size of cell in
Y-direction
(define-param pad 2) ; ' padding distance between
waveguide and cell edge
(define-param dpml 1) ; ' thickness of PML Layers
3.0
(define-param w 1) ; ' width of block along
y-direction
(define-param l 0.1) ; ' lengh of block along
x-direction
(define-param underlayer 0.03) ; SiO2
passivation layer thickness
(define-param w1 0.03) ; ' width of flux-region
(define-param slen 0.2) ;source
length
(define-param offy 0) ; Offset value in
y-direction
(define-param res 200) ; resolution of simulation
box
(define-param standard? false) ;
condition for choosing sample run or reference run
(define-param d_e (/(* w_p w_p) (* w_n w_n))) ;
(define-param fmax 1) ; ' Maximum
Frequency
(define-param fmin 0.1) ; ' Minimum Frequency
(define-param fcen (* 0.5 (+ fmax fmin))) ; ' Frequency
Centered at 0.7 or wavelength = 1.428 micrometer
(define-param df (* 2 (- fmax fcen))) ; ' Frequency Width
Gives range from 0.4 to 1.0
(define-param nfreq 100) ; ' Number of Frequencies to
calculate flux
(set! geometry-lattice (make lattice (size sx sy no-size)))
(define gold (make dielectric (epsilon 5.339)
(polarizations
(make polarizability
(omega 1e-20) (gamma 0.0486) (sigma 6.2634e41))
(make polarizability
(omega 2.1201) (gamma 0.1772)(sigma 0.1906))
(make polarizability
(omega 4.4214) (gamma 1.9662)(sigma 0.9835))
(make polarizability
(omega 3.353) (gamma 1.1844)(sigma 1.5974))
(make polarizability
(omega 2.7116) (gamma 0.578)(sigma 0.6653))
(make polarizability
(omega 2.3525) (gamma 0.3012)(sigma 0.4508)))))
;=================defining simulation cell======================
(set! geometry
(append; combine all objects
;==================set standard and experiment runs=============
(if standard?
(list (make block
(center 0 (+ 0 offy))
(size w (- l underlayer))
(e1 (cos theta_rad) (* (sin theta_rad) -1) 0)
(e2 (sin theta_rad) (cos theta_rad) 0)
(e3 0 0 1)
(material air)))
(list (make cylinder
(center 0 (+ 0 offy))
(radius l)
(height infinity)
(material gold)))
))) ; end of if and append and set-geo
;================running procedure=====================
(set! pml-layers (list (make pml (thickness dpml))))
(set! resolution (* fmax res))
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen) (fwidth df)))
(component Hz)
(center -0.4 0)
(size 0 slen))))
;================total field region calc================
(define left ;left side of the region
(add-flux fcen df nfreq
(make flux-region
(center -0.15 0) (size 0 0.3)(direction X))))
(define right ;right side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0.15 0) (size 0 0.3)(direction X))))
(define top ; left side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0 0.15) (size 0.3 0)(direction Y))))
(define btm ; left side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0 -0.15) (size 0.3 0)(direction Y))))
;===============scattered field region calc==============
(define sleft ;left side of the region
(add-flux fcen df nfreq
(make flux-region
(center -0.25 0) (size 0 0.5)(direction X))))
(define sright ;right side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0.25 0) (size 0 0.5)(direction X))))
(define stop ; left side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0 0.25) (size 0.5 0)(direction Y))))
(define sbtm ; left side of the region
(add-flux fcen df nfreq
(make flux-region
(center 0 -0.25) (size 0.5 0)(direction Y))))
(run-sources+
(stop-when-fields-decayed 0.5 Hz (vector3 (- -0.01 l) 0) 1e-3)
(at-beginning output-epsilon)
(to-appended "pwr" (at-every (/ 1 fcen 20) output-dpwr)))
(display-fluxes left right top btm sleft sright stop sbtm)
--
Mike
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