Hi, I am trying to obtain the band diagram of a photonic crystal slab with triangular hole lattice on insulator.When I simulated it , The corners of the every band graph enters to inside of light cone and this situation causes all gaps disappear.When I simulated same design as airbridged without insulator,this situation has gone and I could determine the gaps. I am attaching the graph I obtained and the code I am using below.Especially Professor Johnson, if you can help me I will be grateful. Thank you The graph's link is :http://imageshack.com/a/img661/9831/sQB1jl.jpg

(define-param h 0.5755) ; the thickness of the slab (define-param h_sub 2.4) ; the thickness of the oxide (define-param eps 12.0) ; the dielectric constant of the slab (define-param eps_sub 2.25) ; the dielectric constant of the slab (define-param loweps 1.0) ; the dielectric constant of the substrate (define-param r 0.419) ; the radius of the holes (define-param supercell-h 6) ; height of the supercell ; triangular lattice with vertical supercell: (set! geometry-lattice (make lattice (size 1 1 supercell-h) (basis1 (/ (sqrt 3) 2) 0.5) (basis2 (/ (sqrt 3) 2) -0.5))) (set! geometry (list (make block (material (make dielectric (epsilon loweps))) (center 0 0 (* 0.25 supercell-h)) (size infinity infinity (* 0.5 supercell-h))) (make block (material (make dielectric (epsilon eps))) (center 0) (size infinity infinity h)) (make block (material (make dielectric (epsilon eps_sub))) (center 0 0 (- 0 (/ (+ h h_sub) 2))) (size infinity infinity h_sub)) (make cylinder (material air) (center 0) (radius r) (height h)))) ; 1st Brillouin zone of a triangular lattice: (define Gamma (vector3 0 0 0)) (define M (vector3 0 0.5 0)) (define K (vector3 (/ -3) (/ 3) 0)) (define-param only-K false) ; run with only-K=true to only do this k-point (define-param k-interp 32) ; the number of k points to interpolate (if only-K (set! k-points (list K)) (set! k-points (interpolate k-interp (list Gamma M K Gamma)))) (set-param! resolution (vector3 32 32 16)) (set-param! num-bands 9) ; Run even and odd bands, outputting fields only at the K point: (if (= loweps 1.0) (begin ; we only have even/odd classification for symmetric structure (run-zeven (output-at-kpoint K output-hfield-z)) (run-zodd (output-at-kpoint K output-dfield-z))) (run (output-at-kpoint K output-hfield-z) display-zparities)) (display-eigensolver-stats) -- Murat Can Sarıhan Electrical - Electronics Engineering Junior Student Middle East Technical University / Ankara, Turkey Phone: +90 545 454 38 38 Mail : mcansari...@gmail.com _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss