Dear MEEP users,****
Recently, I am doing the simulation of DBR structure on a substrate(LiNbO3)*
***
My purpose is to reflect the wavelength at 1550nm.****
According to the phase matching condition 2*2*pi*n/lambda=m*2*pi/period.****
After simplifying, the equation turns to period =lambda/2n.****
According to the sellmeier equation of LiNbO3 ,refractive index of
wavelength at 1550nm at room temperature is 2.1476.
Therefore, we can calculate the period equals to 1550/(2*2.1476)=360nm.****
In meep wavelength unit = a/lambda.****
If a =1, So theoretically, the spectrum will have a dip at 1/1.55=0.6451.***
*
I use Meep to simulate the structure showing at below.****
But I can't get the result that I expect. Did I do anything wrong?
___ ___ ___ ___ ****
* **│** **│*__*│** **│*__*│** **│*__*│ **│*
* **│** * * **│*****
*│** * * **│ ......*****
_______________________****
Codes with structures****
(reset-meep)
(define-param eps 4.61218576) ; dielectric constant of waveguide****
****
(define-param w 6) ; width of waveguide ****
(define-param fcen 0.645) ****
(define-param df 0.6)
(set! geometry-lattice (make lattice (size 100 50 no-size)))
(set! geometry****
(append ; combine lists of
objects: ****
(list (make block (center 0 0) (size infinity w infinity)****
(material (make dielectric (epsilon eps) ))))****
(geometric-object-duplicates (vector3 0.36 0) 0 50****
(make block (center 0 3) ( size 0.18 1 infinity)****
(material (make dielectric (epsilon 1)))))****
(geometric-object-duplicates (vector3 -0.36 0) 0 50****
(make block (center 0 3) (size 0.18 1 infinity)****
(material (make dielectric (epsilon 1))) )) ))
(set! resolution 20)
(set! pml-layers (list (make pml (thickness 1.0))))****
(set! sources (list****
(make source****
(src (make gaussian-src (frequency fcen) (fwidth df)))****
(component Ey)****
(center -20 0)****
(size 0 w))))****
(define trans ; transmitted flux ***
*
(add-flux fcen df 500****
(make flux-region****
(center 20 0) (size 0 w))))****
(run-sources+ (stop-when-fields-decayed 50 Ey (vector3 20 0) 1e-3))****
(display-fluxes trans) ; print out the flux spectrum****
Codes without structure****
(reset-meep)
(define-param eps 4.61218576) ; dielectric constant of waveguide
(define-param w 6) ; width of waveguide ****
(define-param fcen 0.645) ****
(define-param df 0.6)
(set! geometry-lattice (make lattice (size 100 50 no-size)))
(set! geometry****
(append ; combine lists of objects:
****
(list (make block (center 0 0) (size infinity w infinity)****
(material (make dielectric (epsilon eps) )))) ))
(set! resolution 20)
(set! pml-layers (list (make pml (thickness 1.0))))****
(set! sources (list****
(make source****
(src (make gaussian-src (frequency fcen) (fwidth df)))****
(component Ey)****
(center -20 0)****
(size 0 w))))****
(define trans ; transmitted flux **
**
(add-flux fcen df 500****
(make flux-region****
(center 20 0) (size 0 w))))****
(run-sources+ (stop-when-fields-decayed 50 Ey (vector3 20 0) 1e-3))****
(display-fluxes trans) ; print out the flux spectrum****
****
I use the flux with structure divided by flux without structure .then I get
the transmittance as attachment.****
Can anyone tells me why I can't get the results that I expect.****
Thanks for everyone. attached the transmittance spectrum
https://docs.google.com/file/d/0B08gvJEcxym7b2psS3VyV2FoNzg/edit?usp=sharing
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