Return a list of blocks that makes the DBR

build_dbr.scm

(define* (add-DBR n1 n2 n-pairs wl y-pos #:optional (growth-dir +) (dbr-width infinity))
  (let
    ((layer1-t (* 0.25 (/ wl n1)))
     (layer2-t (* 0.25 (/ wl n2)))
     (make-layer (lambda (layer-t index pos) (make block
                                                  (center 0 (growth-dir pos (/ layer-t 2)) 0)
                                                  (material (make dielectric (epsilon (* index index))))
                                                  (size dbr-width layer-t dbr-width)))))
    (let
      ((make-pair (lambda (pos) (list
              (make-layer layer1-t n1 pos)
              (make-layer layer2-t n2 (growth-dir pos layer1-t))))))
      (do
        ((ii 0 (+ ii 1))
         (pos y-pos (growth-dir pos layer1-t layer2-t))
         (layer-list  '() (append layer-list (make-pair pos))))
        ((= ii n-pairs) layer-list)))))