; Photonic crystal slab consisting of a triangular lattice of air; holes in a finite-thickness dielectric slab, optionally with a; substrate on one side of the slab.  See the paper: S. G. Johnson,; S. Fan, P. R. Villeneuve, J. D. Joannopoulos, L. A. Kolodziejski,; "Guided modes in photonic crystal slabs," PRB 60, 5751 (August; 1999).; Note that this structure has mirror symmetry throught the z=0 plane,; and we are looking at k-vectors in the xy plane only.  Thus, we can; break up the modes into even and odd (analogous to TE and TM), using; the run-zeven and run-zodd functions.(define-param h 0.5) ; the thickness of the slab(define-param eps 12.0) ; the dielectric constant of the slab(define-param loweps 1.0) ; the dielectric constant of the substrate(define-param r 0.3) ; the radius of the holes(define-param supercell-h 4) ; 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 cylinder (material air)		  (center 0) (radius r) (height supercell-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 4)   ; 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:(run-zeven (output-at-kpoint K output-hfield-z))(run-zodd (output-at-kpoint K output-dfield-z))(display-eigensolver-stats)