Hello MEEP users,
I would like to compare my results from FDTD method with transfer matrix
method (TMM). I am trying to use MEEP to simulate reflections from a DBR
(10 bragg pairs SiO2/TiO2). Result from TMM is consistent with the
measurement, but from FDTD I obtained different reflection spectrum (looks
like reflections form different DBR). Below I attached my MEEP code.
Can someone tell me what is wrong with this code?
I really appreciate any help you can provide.
Best regards,
Krzysztof Sawicki
(set! geometry-lattice (make lattice (size 16 4 4)))
(define-param SiO2 (* 1.48 1.48))
(define-param TiO2 (* 2.28 2.28))
(set! geometry (list
(make block (center 0.125 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 0.3 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 0.475 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 0.65 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 0.825 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 1 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 1.175 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 1.35 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 1.525 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 1.7 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 1.875 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 2.05 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 2.225 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 2.4 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 2.575 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 2.7 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 2.925 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 3.1 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
(make block (center 3.275 0 0) (size 0.25 infinity
infinity)
(material (make dielectric (epsilon SiO2))))
(make block (center 3.45 0 0) (size 0.1 infinity infinity)
(material (make dielectric (epsilon TiO2))))
))
(set! pml-layers (list (make pml (thickness 1.0))))
(set! sources (list
(make source
(src (make gaussian-src (frequency 0.6452) (fwidth 20.0)))
(component Ez)
(center -6 0 0)
(size 0 0 0)
)))
(set-param! resolution 10)
(define-param fcen 2)
(define-param fcen 2)
(define-param df 4)
(define-param nfreq 1000)
(define tran1 ; transmitted flux
(add-flux fcen df nfreq
(make flux-region (center 6 0 0) (size 0 4 4))))
(define refl1 ; reflected flux
(add-flux fcen df nfreq
(make flux-region (center -6 0 0) (size 0 4 4))))
(use-output-directory)
(run-sources+ 100 (at-beginning output-epsilon)
; (at-every 1 (output-png Ez "-0y 0 -Zc jet"))
(to-appended "ez" (at-every 1 output-efield-z))
)
(save-flux "refl1-flux" refl1)
(save-flux "tran1-flux" tran1)
;(save-flux "refl2-flux" refl2)
;(save-flux "tran2-flux" tran2)
(display-fluxes tran1 refl1)
;(display-fluxes tran1 refl1 tran2 refl2)
(print "transmision:, " (first (get-fluxes tran1)) "\n")
(print "reflection:, " (first (get-fluxes refl1)) "\n")
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