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(set-param! resolution 15)
(define-param w 1) ; width of waveguide
(define-param L 10) ; length of waveguide
(define-param dair 3.0)
(define-param dpml 3.0)
;; mode frequency
(define-param fcen 0.20) ; > 0.5/sqrt(11) to have at least 2 modes
(define (run-test mode-num kpoint-func)
(reset-meep)
(let* ((sx (+ dpml L dpml))
(sy (+ dpml dair w dair dpml))
(prism_x (+ sx 1))
(prism_y (/ w 2))
(verts
(list
(vector3 prism_x prism_y)
(vector3 (* prism_x -1) prism_y)
(vector3 (* prism_x -1) (* prism_y -1))
(vector3 prism_x (* prism_y -1))))
(modes-to-check '(1 2)) ; indices of modes for which to compute expansion coefficients
(xm (- (* 0.5 sx) dpml))) ; x-coordinate of monitor
(set! geometry-lattice (make lattice (size sx sy no-size)))
(set! geometry
(list
(make prism
(center (vector3 0 0))
(vertices verts)
(height infinity)
(material (make medium (epsilon 12.0))))))
(set! pml-layers (list (make pml (thickness dpml))))
(set! sources (list
(make eigenmode-source
(src (make gaussian-src (frequency fcen) (fwidth (* 0.5 fcen))))
(center (vector3 (+ (* -0.5 sx) dpml) 0))
(component ALL-COMPONENTS)
(size (vector3 0 (- sy (* 2 dpml))))
(eig-match-freq? true)
(eig-band mode-num)
(eig-resolution 32))))
(set! symmetries
(list
(make mirror-sym (direction Y) (phase (if (odd? mode-num) 1 -1)))))
(let ((mflux (add-mode-monitor fcen 0 1
(make mode-region (center (vector3 xm 0)) (size (vector3 0 (- sy (* 2 dpml)))))))
(mode-flux (add-flux fcen 0 1
(make flux-region (center (vector3 xm 0)) (size (vector3 0 (- sy (* 2 dpml))))))))
(run-sources+ 100)
(let* ((result (get-eigenmode-coefficients mflux modes-to-check #:kpoint-func kpoint-func))
(alpha (first result))
(vgrp (second result))
(kpoints (third result))
(kdom (fourth result))
(mode-power (car (get-fluxes mode-flux)))
(test-passed #t)
(tolerance 5.0e-3)
(c0 (array-ref alpha (- mode-num 1) 0 0))) ; coefficient of forward-traveling wave for mode # mode_num
(if (or (not (vector3-close? (first kpoints) (vector3 0.604301 0 0) 1e-7))
(not (vector3-close? (second kpoints) (vector3 0.494353 0 0) 1e-2))
(not (vector3-close? (first kdom) (vector3 0.604301 0 0) 1e-7))
(not (vector3-close? (second kdom) (vector3 0.494353 0 0) 1e-2)))
(begin
(print "Test failed")(newline)
(exit 1)))
(map (lambda (nm)
(if (not (= mode-num nm))
(let ((cfrel (/ (magnitude (array-ref alpha (- nm 1) 0 0)) (magnitude c0)))
(cbrel (/ (magnitude (array-ref alpha (- nm 1) 0 1)) (magnitude c0))))
(if (or (> cfrel tolerance) (> cbrel tolerance))
(set! test-passed #f)))))
modes-to-check)
;; test 1: coefficient of excited mode >> coeffs of all other modes
(if (not test-passed)
(begin
(print "Test failed")(newline)
(exit 1)))
;; test 2: |mode coeff|^2 = power
(if (> (abs (- 1 (/ mode-power (* (magnitude c0) (magnitude c0))))) 0.1)
(begin
(print "Test failed")(newline)
(exit 1)))))))
(run-test 1 '())
(run-test 2 '())
(run-test 1 (lambda (freq mode) (vector3 0 0)))
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