Hi Gerardo, the output seems to be truncated, is it that what you are also seeing when > you refer as "funny effect"? > Maybe, I am not sure what you mean by truncated. What I see wrong in the output is that transmission seems to have a decaying exponential factor, and also goes greater than 1 at some points. I expect to see just a sinusoidal shape with the consistent peak/trough magnitudes.
(define-param kdir (vector3 (cos theta_rad) (sin theta_rad))) > (define k (vector3-scale (* 2 pi fcen) kdir)) > > (define ((pw-amp k) y) (exp (* 0+1i (vector3-dot k y))) ) > > Why do you define k using (* 2 pi fcen) and do not use kdir directly? As > far as I understand in meep one uses the vector directly, without scales. > And, what about the vector3-dot with the imaginary part. What literature are > you using? > > I'll try to explain these lines: kdir is the direction of the wavevector. k is the wavevector itself, which is the direction scaled by the wavenumber. In this case, I don't think we can use kdir directly. pw-amp is function to be multiplied with the source. It only modulates the phase of the source to produce the desired angle, which is why is has the vector3-dot 0+1i. Hm, I think I am beginning to see the, or at least a problem. This code was originally written for single frequency sources; with a gaussian source, I don't think the pw-amp function will work as desired. Is there a way to make oblique incidence gaussian sources? One idea that comes to mind is to make the pw-amp function vary in time as the source is produced, but I don't know if that is even possible. Also, as for the source, I got this code from a post I found on the meep-discuss archives by searching "oblique". Thanks for the reply, I think you got me on the right track, Matt On Fri, Jun 18, 2010 at 2:22 PM, G S <[email protected]> wrote: > Hello Matt, > > the output seems to be truncated, is it that what you are also seeing when > you refer as "funny effect"? > > I want to help, but I don't understand very clearly the following lines of > your program: > > (define-param kdir (vector3 (cos theta_rad) (sin theta_rad))) > (define k (vector3-scale (* 2 pi fcen) kdir)) > > (define ((pw-amp k) y) (exp (* 0+1i (vector3-dot k y))) ) > > Why do you define k using (* 2 pi fcen) and do not use kdir directly? As > far as I understand in meep one uses the vector directly, without scales. > And, what about the vector3-dot with the imaginary part. What literature are > you using? > > Hope it helps, > Gerardo. > > > > 2010/6/18 <[email protected]> > >> Send meep-discuss mailing list submissions to >> [email protected] >> >> To subscribe or unsubscribe via the World Wide Web, visit >> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss >> or, via email, send a message with subject or body 'help' to >> [email protected] >> >> You can reach the person managing the list at >> [email protected] >> >> When replying, please edit your Subject line so it is more specific >> than "Re: Contents of meep-discuss digest..." >> >> >> Today's Topics: >> >> 1. Oblique Incience (Matthew Miskiewicz) >> >> >> ---------------------------------------------------------------------- >> >> Message: 1 >> Date: Thu, 17 Jun 2010 12:57:26 -0400 >> From: Matthew Miskiewicz <[email protected]> >> Subject: [Meep-discuss] Oblique Incience >> To: [email protected] >> Message-ID: >> <[email protected]> >> Content-Type: text/plain; charset="iso-8859-1" >> >> Hi, >> >> I'm learning to use meep and am attempting some simple simulations. I'm >> getting a weird result when calculating the wideband transmission of a >> plane >> wave at oblique incidence on a thin dielectric slab. When I use normal >> incidence, I get a perfect result. For oblique incidence, the >> oscillations >> in the transmission look correct, but something else funny is happening. >> Any ideas on how to fix this? Is something set up wrong in the ctl file? >> >> Picture of transmission: >> >> http://picasaweb.google.com/lh/photo/wxSYCr_M9_PsHYS_Klllzr00Wanc329Uua6LuGynryc?feat=directlink >> >> Thanks! >> Matt Miskiewicz >> >> Research Assistant, Optoelectronics and Lightwave Engineering Group >> North Carolina State University >> >> >> >> Here is the ctl file: >> >> (define-param pmlthick 2) >> (define-param sy .5) >> (define-param sx 10) >> (define-param ref true) >> >> >> (set! geometry-lattice (make lattice (size (+ sx (* pmlthick 2)) sy >> no-size))) >> (set! geometry (list >> (make block (center 0 0) (size (- sx 5) sy) >> (material (make dielectric (index (if ref 1 1.5))))))) >> >> >> (set! resolution 30) >> >> (set! pml-layers (list (make pml (thickness pmlthick) (direction X)))) >> >> (define-param theta_deg 0) ; angle in degrees. >> (define theta_rad (/ (* pi theta_deg) 180)) >> (define-param fcen 0.75) ; pulse center frequency >> (define-param df 0.5) ; pulse bandwidth >> (define-param dfe 0.5) ; data extraction bandwidth >> (define wlength (/ 1 fcen)) ; pulse wavelength >> (define-param kdir (vector3 (cos theta_rad) (sin theta_rad))) >> (define k (vector3-scale (* 2 pi fcen) kdir)) >> >> (define ((pw-amp k) y) >> (exp (* 0+1i (vector3-dot k y)))) >> >> (set-param! k-point (vector3 0 (* fcen (sin theta_rad)) 0)) >> >> (set! sources (list >> (make source >> (src (make gaussian-src (frequency fcen) (fwidth df))) >> (component Ez) >> (center (+(/ sx -2) 1) 0) >> (size 0 sy 0) >> (amp-func (pw-amp k))))) >> >> (define-param nfreq 200) ; number of frequencies at which to compute flux >> (define trans ; transmitted flux >> (add-flux fcen dfe nfreq >> (make flux-region >> (center (- (/ sx 2) 1) 0) (size 0 sy)))) >> >> (run-until 10000) >> >> (display-fluxes trans) >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: < >> http://ab-initio.mit.edu/pipermail/meep-discuss/attachments/20100617/bc919741/attachment.html >> > >> >> ------------------------------ >> >> _______________________________________________ >> meep-discuss mailing list >> [email protected] >> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss >> >> End of meep-discuss Digest, Vol 52, Issue 15 >> ******************************************** >> > > > _______________________________________________ > meep-discuss mailing list > [email protected] > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss >
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