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(set-param! resolution 25) ;; pixels/um
(define-param dpml 1.0) ;; PML thickness
(define-param dsub 2.0) ;; substrate thickness
(define-param dpad 2.0) ;; padding between zone plate and PML
(define-param zh 0.5) ;; zone-plate height
(define-param zN 25) ;; number of zones (odd zones: pi phase shift, even zones: none)
(define-param focal-length 200) ;; focal length of zone plate
(define-param spot-length 100) ;; far-field line length
(define-param ff-res 10) ;; far-field resolution (points/um)
(set! pml-layers (list (make pml (thickness dpml))))
(define-param wvl-cen 0.5)
(define frq-cen (/ wvl-cen))
(define dfrq (* 0.2 frq-cen))
(define r (map (lambda (n)
(sqrt (* n wvl-cen (+ focal-length (/ (* n wvl-cen) 4)))))
(arith-sequence 1 1 zN)))
(define sr (+ (list-ref r (- zN 1)) dpad dpml))
(define sz (+ dpml dsub zh dpad dpml))
(define cell (make lattice (size sr 0 sz)))
(set! geometry-lattice cell)
(set! dimensions CYLINDRICAL)
(set-param! m -1)
(set! sources (list (make source
(src (make gaussian-src (frequency frq-cen) (fwidth dfrq) (is-integrated? true)))
(center (* 0.5 sr) 0 (+ (* -0.5 sz) dpml))
(size sr 0 0)
(component Er))
(make source
(src (make gaussian-src (frequency frq-cen) (fwidth dfrq) (is-integrated? true)))
(center (* 0.5 sr) 0 (+ (* -0.5 sz) dpml))
(size sr 0 0)
(component Ep)
(amplitude 0-1i))))
(define glass (make medium (index 1.5)))
(set! geometry (list (make block
(material glass)
(size sr 0 (+ dpml dsub))
(center (* 0.5 sr) 0 (+ (* -0.5 sz) (* 0.5 (+ dpml dsub)))))))
(set! geometry (append geometry
(map (lambda (n)
(make block
(material (if (= (modulo n 2) 0) glass vacuum))
(size (list-ref r n) 0 zh)
(center (* 0.5 (list-ref r n)) 0 (+ (* -0.5 sz) dpml dsub (* 0.5 zh)))))
(reverse (arith-sequence 0 1 zN)))))
(define n2f-obj (add-near2far frq-cen 0 1
(make near2far-region (center (* 0.5 (- sr dpml)) 0 (- (* 0.5 sz) dpml)) (size (- sr dpml) 0 0))
(make near2far-region (center (- sr dpml) 0 (- (* 0.5 sz) (* 0.5 (+ dsub zh dpad)))) (size 0 0 (+ dsub zh dpad)))))
(run-sources+ 100)
(output-farfields n2f-obj "r" (volume (center (* 0.5 (- sr dpml)) 0 (+ (* -0.5 sz) dpml dsub zh focal-length)) (size (- sr dpml) 0 0)) ff-res)
(output-farfields n2f-obj "z" (volume (center 0 0 (+ (* -0.5 sz) dpml dsub zh focal-length)) (size 0 0 spot-length)) ff-res)
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