Hi Steven and meep users:
I follow one past message to generate the Gaussian beam in a cylindrical
coordinate:
http://www.mail-archive.com/meep-discuss@ab-initio.mit.edu/msg02317.html
and I found out the results are different from that from Cartesian coordinate.
For example, I'd like the beam to propagate along z direction so I specify the
size of the source in r direction. But I found out whatever I change the size,
it still looks like a point source. In addition, there is a small source above
that point source. I think the distance between these two sources is the size I
specify.
However,this doesn't happen in the Cartesian coordinate. The size of source is
consistent to the input.
I wonder if anyone happens to have this experience and work it out.
The script is attached below.
Thank you very much
Adrian
%% Code begins
(define NTp 300) ; total time period
(define lam 0.98) ; unit: um
(define freq (/ 1 lam)) ; normalized frequency in meep
(define mTp lam) ; 1 time period in meep
;%%% basic structure parameter %%%
(define lr 6) ; normalized r-length in meep
(define lz 18) ; normalized z-length in meep
(define dpml 1.5) ; normalized PML thickness in meep
(define dl 50) ; resolution in meep
(define waist 1) ; gaussian beam waist
;%%% total region setting %%%
(set! dimensions CYLINDRICAL)
(set! m 1)
(set! geometry-lattice (make lattice (size lr 0 lz)))
;%%% 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 freq) (width (* 4 mTp))))
(component Er)
(center 0 0 (+ (* -0.5 lz) (* 0.9 dpml)))
(size 1.3 0 0)
(amp-func (ampgauss waist (vector3 0 0 0)))
)
)
)
;%%% PML setting %%%
(set! pml-layers (list (make pml (thickness dpml))))
;%%% RUN meep %%%
(set! output-single-precision? true)
(set! resolution dl)
(run-until (* NTp mTp)
(at-end (synchronized-magnetic output-efield-r output-efield-z
output-hfield-p))
(at-end output-png Er "-Zc dkbluered")
)
%%%%%%%%%%%
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