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; Calculating 2d ring-resonator modes using cylindrical coordinates,
; from the Meep tutorial.
(define-param n 3.4) ; index of waveguide
(define-param w 1) ; width of waveguide
(define-param r 1) ; inner radius of ring
(define-param pad 4) ; padding between waveguide and edge of PML
(define-param dpml 2) ; thickness of PML
(define sr (+ r w pad dpml)) ; radial size (cell is from 0 to sr)
(set! dimensions CYLINDRICAL)
(set! geometry-lattice (make lattice (size sr no-size no-size)))
; in cylindrical coordinates, the phi (angular) dependence of the fields
; is given by exp(i m phi), where m is given by:
(set-param! m 3)
(set! geometry (list
(make block (center (+ r (/ w 2))) (size w infinity infinity)
(material (make dielectric (index n))))))
(set! pml-layers (list (make pml (thickness dpml))))
(set-param! resolution 10)
; If we don't want to excite a specific mode symmetry, we can just
; put a single point source at some arbitrary place, pointing in some
; arbitrary direction. We will only look for Ez-polarized modes.
(define-param fcen 0.15) ; pulse center frequency
(define-param df 0.1) ; pulse width (in frequency)
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen) (fwidth df)))
(component Ez) (center (+ r 0.1) 0))))
; note that the r -> -r mirror symmetry is exploited automatically
(run-sources+ 200 (after-sources (harminv Ez (vector3 (+ r 0.1)) fcen df)))
; Output fields for one period at the end. (If we output
; at a single time, we might accidentally catch the Ez field when it is
; almost zero and get a distorted view.) We'll append the fields
; to a file to get an r-by-t picture. We'll also output from -sr to -sr
; instead of from 0 to sr.
(run-until (/ 1 fcen)
(in-volume (volume (center 0) (size (* 2 sr)))
(at-beginning output-epsilon)
(to-appended "ez"
(at-every (/ 1 fcen 20) output-efield-z))))
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