Hello Stephan, Here is an answer of Steven Johnson for a similar question: ==================================================================
Hi Stephane, I've attached a couple of files I used to compute gap maps for holey fibers. See in particular the use of the "poly-grid" routine that I wrote as a quick hack for this purpose. As it turns out, however, the extrema of all the gaps that I've ever found in PC fibers occur around the boundaries of the Brillouin zone, so I usually don't bother to look in the interior. If you find any exceptions, please let me know! Cordially, Steven G. Johnson ============================================================================ As far as I understand, if you try to iterate for all the k-points (kx,ky and kz), mpb will try to find a valid band gap for all the kx,ky,kz. That will work only if your requested kz range is within a band gap. What you want to do is to ask mpb to find the band range for each kz. You have to setup an iteration where you will perform a call to (run) for each kz (instead of once for all the kz). If you want to setup an out of plane band gap diagram, you will have to output the minimum and maximum values of each band (calculated by mapping your Brillouin zone in the kx-ky direction) at each kz. Then, for each kz, you find the band gaps, determine the minimum and maximum value of the gaps, and discard all maximum and minimum band values that do not correspond to a band gap. Hope it will help, Stef -----Message d'origine----- De : [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] De la part de Stephan Smolka Envoyé : 26 avril 2006 12:07 À : mpb-discuss@ab-initio.mit.edu Objet : [MPB-discuss] How to calculate bandgaps in photonic crystal fibers? Dear Steven, MPB users, I'm a student and I write my final exam in potonic crystal fibers. It is a rather new topic for me and that is why I a a simple question. You can often see in papers or in presentations (e.g. L5-fiber by Steven G. Johnson) that there are areas where you have bandgaps. I took the mpb and simulate a simple photonic crystal in 2d (silica with air holes) with the proagation k-vector in z-direction. If you take the k-vector in x and y direction I understand the bandgaps but what's about a bandgap in z-direction? In the following picture I like to know how to calculate the blue and red areas! http://nano.physik.hu-berlin.de/images/Stephan_bandgap.gif This is the modeplot of my program http://nano.physik.hu-berlin.de/images/Stephan_freqs.png Thank you very much in advanced! Best regards Stephan PS: And here is my program (set! geometry-lattice (make lattice (size 1 1 no-size) (basis1 (sqrt 0.75) 0.5) (basis2 (sqrt 0.75) -0.5))) (define-param kx 0) (define-param ky 0) (set! k-points (list (vector3 kx ky 0) (vector3 kx ky 3))) (set! k-points (interpolate 16 k-points)) (define-param eps 2.1316) ;refraction index silica (define-param r 0.45) (set! default-material (make dielectric (epsilon eps))) (set! geometry (list (make cylinder (center 0) (material air) (radius r) (height infinity)))) (set-param! resolution 32) (set-param! num-bands 8) (run) ;grep by freqs and plot _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
tri-holes.ctl
Description: tri-holes.ctl
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