Hi Steven and Meep users,I am trying to define a structure with a defect and eventually look at the Q. However, I already obtain inconsistent results in the defined perfect crystal depending on whether I set the symmetry or not (please see attachments). One would expect half a hole at all sides of the cell, not just two of them (in the case without defined symmetry). Hence we should have 8 periods in the (1 0) direction. I assume setting the symmetry takes the mirror symmetry of the two sides without the additional half-hole, hence we end-up with 6 periods instead of the expected 8.
Thanks for any advice or solution to this problem.
Fred ; square lattice ; define cell size(define-param sx 8) (define-param sy 6) (define-param sz 3) (define-param res 20) ; resolution
(define-param h 0.75) ; thickness of waveguide
(define-param r 0.2) ; radius of holes
(define-param n 3.46) ; index of waveguide
(set! eps-averaging? true)
(set! geometry-lattice (make lattice (size sx sy sz)))
; define periodic array
(set! geometry
(append
(list (make block (center 0) (size sx sy h)
(material (make dielectric (index n)))))
(geometric-objects-lattice-duplicates
(list
(make cylinder (center 0) (radius r) (height h)
(material air))))))
(set-param! resolution 20)
; set-up symmetry or assume none
;(set! symmetries (list (make mirror-sym (direction Y) (phase -1))
; (make mirror-sym (direction X) (phase
;-1))))
(run-until 200 (at-beginning output-epsilon))
--
Frederic Brossard
Hitachi Cambridge Laboratory
Cavendish Laboratory
J J Thomson Avenue
Cambridge CB3 0HE
<<attachment: nosym.jpg>>
<<attachment: withsym.jpg>>
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