Dear, Steven and meep users.
I tried to make Gaussian beam in a cylindrical coordinate because I want to
calculate some phi-symmetry cylinder structures.
And, their field components have to include only (Er, Hp, Ez) which are TM
polarization in a cylindrical coordinate.
Firstly, I made Gaussian amplitude function for Gaussian beam which propagates
along z-axis in a free space.
Secondly, I applied this Gaussian amplitude function to Er source.
However, it doesn't work well.
Especially, fields around (r=0) is too small.
I believe that fields around (r=0) must be larger than their surrounding
because it is Gaussian beam.
I attached my script.
Please help me...
------------------------------------------------------------------------------
;%%% length unit %%%
(define nm 1e-9) ; nano-meter unit
(define um 1e-6) ; micro-meter unit
(define lu 1e-6) ; base length unit in meep
;%%% basic wave parameter %%%
;%---------------------------------------------------------------------%
(define lam (* 532 nm)) ; wavelength
(define NTp 30) ; total time period
;%---------------------------------------------------------------------%
(define mlam (/ lam lu)) ; normalized wavelength in meep
(define mfreq (/ lu lam)) ; normalized frequency in meep
(define mTp mlam) ; 1 time period in meep
;%%% basic structure parameter %%%
;%---------------------------------------------------------------------%
(define lr (* 5 um)) ; total r-length
(define lz (* 10 um)) ; total z-length
(define tpml (* 200 nm)) ; PML thickness
(define dl (* 20 nm)) ; discretization length
;%---------------------------------------------------------------------%
(define mlr (/ lr lu)) ; normalized r-length in meep
(define mlz (/ lz lu)) ; normalized z-length in meep
(define mtpml (/ tpml lu)) ; normalized PML thickness in meep
(define mdl (/ lu dl)) ; resolution in meep
;%%% gaussian beam parameter %%%
;%---------------------------------------------------------------------%
(define waist (* 800 nm)) ; gaussian beam waist
;%---------------------------------------------------------------------%
(define mwaist (/ waist lu)) ; normalized gaussian beam waist
;%%% total region setting %%%
(set! dimensions CYLINDRICAL)
(set! m 0)
(set! geometry-lattice (make lattice (size mlr 0 mlz)))
;%%% source setting %%%
(define ((ampgauss sigma_d k) r)
(exp (- (* 0+2i pi (vector3-dot k r)) (/ (vector3-dot r r) (* 2 sigma_d
sigma_d))))
)
(set! sources
(list
(make source
(src (make continuous-src (frequency mfreq) (width (* 2 mTp))))
(component Er)
(center 0 0 (+ (* -0.5 mlz) (* 2 mtpml)))
(size mlr 0 0)
(amp-func (ampgauss mwaist (vector3 0 0 0)))
)
)
)
;%%% PML setting %%%
(set! pml-layers
(list
(make pml
(thickness mtpml))
)
)
;%%% RUN meep %%%
(set! output-single-precision? true)
(set! resolution mdl)
(run-until (* NTp mTp)
(at-end (synchronized-magnetic output-efield-r output-efield-z
output-hfield-p))
)
________________________________________________________
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