Hi meep users,
I am trying to obtain transmission spectrum in order to see band gap
like in the Meep Tutorial/Band diagram, resonant modes, and
transmission in a holey waveguide example.
I look at the waveguide output flux with and without periodic
structures at same flux point and size. After than I take ratio of the
periodic structures output flux to only waveguide output flux.
But I do not understand some points on the graphics. At some points
and flux size, output flux of periodic structures is bigger than only
waveguide output flux. Especially at low frequencies nearly zero and
bigger frequencies of 1.2.
Bigger frequencies at 1.2, periodic structures flux value bigger than
only waveguide flux value at the level of 10^-3. its very small
difference but ratio is very high as a result.
I increase resolution but nothing is changed.
What is the reason? Should I ignore about zero freq. and bigger freq.
than 1.2.
Thanks for your advice.
Onder
-------output flux of waveguide without periodic structure------
;; only waveguide
(set! geometry-lattice (make lattice (size 45 12 no-size)))
(define-param eps 1) ; air
(set! default-material (make dielectric (epsilon eps)))
;;Geometry
(set! pml-layers (list (make pml (thickness 2.0))))
(set! resolution 20)
(set! geometry
(list
(make block (center 0 0) (size 20 12 infinity)
(material (make dielectric (epsilon eps)
)
)
)
)
)
;;Source
(define-param fcen 0.32) ; source freq
(define-param fmin (/ fcen 10)) ; freq 0.032 --> 1.6
(define-param fmax (* fcen 5))
(define-param df (- fmax fmin))
(define-param samp 100)
(define-param nfreq 500) ; number of frequencies at which to compute flux
(define-param srcsize 8) ; source size (- width of waveguide (* 2
pml))
(define-param flxsize 8) ; flux region size
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen)(fwidth df)))
(component Ez)(center -19 0) (size 0 srcsize) (amplitude
samp)
)
))
;;Flux
(define-param flxdout 15) ; output flux region location
(define-param flxdin -18) ; input flux region location
(define transout
(add-flux (* 0.5 (+ fmin fmax)) (- fmax fmin) nfreq
(make flux-region
(center flxdout 0) (size 0 flxsize)
)
)
)
(define transin
(add-flux (* 0.5 (+ fmin fmax)) (- fmax fmin) nfreq
(make flux-region
(center flxdin 0) (size 0 flxsize)
)
)
)
;Stop sources
(run-sources+
(stop-when-fields-decayed 50 Ez
(vector3 -19 0 ) 1e-3)
)
(display-fluxes transin transout)
-------------------------------------------
-------------------------------------------
-------------------output flux of waveguide with periodic
structure-------------------------------
;; waveguide with periodic structure
(set! geometry-lattice (make lattice (size 45 12 no-size)))
(define-param eps 1) ; air
(set! default-material (make dielectric (epsilon eps)))
;; Epsilon function
(define I
(lambda (p) (+ 3 (* 2 (cos (* 8 (vector3-x p)))))
)
)
(set! pml-layers (list (make pml (thickness 2.0))))
(set! resolution 20)
(set! geometry
(list
(make block (center 0 0) (size 20 12 infinity)
(material (make material-function
(epsilon-func I)
)
)
)
)
)
;;Source
(define-param fcen 0.32)
;; freq 0.032 --> 1.6
(define-param fmin (/ fcen 10))
(define-param fmax (* fcen 5))
(define-param df (- fmax fmin))
(define-param samp 100)
(define-param nfreq 500) ; number of frequencies at which to compute flux
(define-param srcsize 8) ; source size (- width of waveguide (* 2 pml))
(define-param flxsize 8) ; flux region size
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen)(fwidth df)))
(component Ez)(center -19 0) (size 0 srcsize) (amplitude
samp)
)
))
;; Flux
(define-param flxdout 15) ; output flux region location
(define transout
(add-flux (* 0.5 (+ fmin fmax)) (- fmax fmin) nfreq
(make flux-region
(center flxdout 0) (size 0 flxsize)
)
)
)
;Stop sources
(run-sources+
(stop-when-fields-decayed 50 Ez
(vector3 -19 0 ) 1e-3)
)
(display-fluxes transout)
------------------------------------------------------------
Pamukkale University
Electrical-Electronics Eng.Dept.
20070 Kinikli-Denizli TURKEY
Tel: (+90 258) 296 3213
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