Hi Paolo, The error is most likely due to the absence of boundary conditions of your computation cell.
Suggestion i) set k-point (default is FALSE) to (vector3 0 0 0) ii) place air padding between source and crystal iii) place PMLs at endplanes of -x and +x axis. Try and let us know. Ma Ree On Fri, May 15, 2009 at 3:58 AM, Paolo Bardella <[email protected]> wrote: > Dear Meep users, dear Steven, > In order to gain some experience on Meep, I tried to simulate a simple > 1D Bragg reflector and to calculated its band diagram. > The .ctl file I used is reported below. > With this structure, according also to http://ab-initio.mit.edu/book/ > pag 51, the mid-gap frequency should be at 0.16146, but in my simulations > it is always below 0.16 (the corresponding wavelength is around 1600nm > and not 1550nm). > > Following the suggestions given in other posts, I tried to increase the > resolution and the final simulation time, but I still found this > difference, so I think there is a problem in the short code I prepared. > > Could you please give me some indications in order to get the correct > results? > Thank you in advance, > Best regards, > Paolo Bardella > > > (define-param Lambda0 1.55) > (define-param n1 3.0) > (define-param n2 3.2) > (define-param d1 (/ Lambda0 n1 4)) > (define-param d2 (/ Lambda0 n2 4)) > (define-param a (+ d1 d2)) > > (define-param Mat1 (make dielectric (index (* n1 n1)))) > (define-param Mat2 (make dielectric (index (* n2 n2)))) > > (set! geometry-lattice (make lattice (size 1 no-size no-size))) ; the > size is 1 > (set! default-material Mat1) > > (set! geometry (list(make block (center 0 0 0) > (size (/ d2 a) infinity infinity) (material Mat2)))) ; if the lattice > size is 1, the width of the region with n2 is d2/a > > (set-param! resolution 32 ); I also tried other values, up to 512 > > (define-param fcen 0.1615) > (define-param df .3) > > (set! sources (list (make source > (src (make gaussian-src (frequency fcen) (fwidth df))) > (component Hz) (center (* a -.45) 0)))) ; I also tried other > positions > > (define-param k-interp 9) > (run-k-points 300 (interpolate k-interp (list (vector3 0) (vector3 > 0.5)))) ;I also tried, e.g, 3000 > > > > _______________________________________________ > meep-discuss mailing list > [email protected] > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss > _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
