hello,
Could it be due to the source in z direction but you meant to excite waveguide mode in y direction?
I believe you need to change source component to E_y and plot E_y component of electric field. I know this is inprincipal same for a rectangular geometry but your simulation is in 2d , it has no knowledge in z direction. And the other 2 things I may think of; one is normalization curve you plot has little meaning since that is the part you subtract from the second run and the second is you need to calculate the number of pixel per wavelength for your system, should be around 8 at the least, since you are using long waveguide made up of silicon the pixel number per wavelength may not be enough for that resolution you use.
I hope this
helps .
cheers!
gursoy akguc
From: prem prakash singh <[email protected]>
To: [email protected]
Sent: Wednesday, December 5, 2012 7:18 PM
Subject: [Meep-discuss] Normalized transmission across rectangular waveguide.
To: [email protected]
Sent: Wednesday, December 5, 2012 7:18 PM
Subject: [Meep-discuss] Normalized transmission across rectangular waveguide.
Dear Meep users,
I am trying to get transmission across grated waveguide ( grating inscribed in waveguide). I used MEEP tutorial for holey waveguide as a reference. Problem is, I am not getting expected transmission spectrum. So I went to check transmission spectrum across rectangular waveguide. The result is more shocking. I think may be normalization process is wrong. for normalization, I used (set! geometry (if norm? (list)
I would like to request , could any one comment on my code.
Transmission spectrum and field pattern is appended below.
Regards
Prem Prakash
***********************************************************************************
(reset-meep)
(define-param eps 12) ; dielectric constant of waveguide
(define-param w 0.23) ; thickness of waveguide
(define-param sx 34) ; size of cell in x direction
(define-param sy 4.23) ; size of cell in y direction
(define-param dpml 2) ; PML thickness
(define-param norm? false)
(set! geometry-lattice (make lattice (size sx sy no-size)))
(set! geometry (if norm?
(list)
(list
(make block (center 0 0)(size infinity w infinity)(material (make dielectric (epsilon eps)))))));device layer Si
(set! pml-layers (list (make pml (thickness dpml)))); PMl layer
(set-param! resolution 40)
(define-param fcen 0.645) ; pulse center frequency
(define-param df .2) ; pulse width (in frequency)
(define-param nfreq 500) ; number of frequencies at which to compute flux
(set! sources (list (make source (src (make gaussian-src (frequency fcen) (fwidth df)))(component Ez)(center -15 0)(size 0 w)))); Source placed just after PML
(define trans (add-flux fcen df nfreq
(make flux-region (center 14.5 0) (size 0 (* w 2))))); collect flux before PML
(use-output-directory)
(run-sources+ (stop-when-fields-decayed 50 Ez (vector3 14.5 0) 1e-3)
(at-beginning output-epsilon)
(at-end output-efield-z))
(display-fluxes trans)
*****************************************************************************************
for normalisation - norm?= true
Transmission spectrum:
Ez pattern:
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