Dear Steven and meep users,
I write a ctl according to some codes that Steven have given on this list, but
I can't change the position of the waist of a gaussian beam.
****************************************************************************************************************
(define-param sy 52) ; size of cell in y direction
(define-param sx 52) ; padding between last hole and PML edge
(define-param dpml 1) ; PML thickness
(set! geometry-lattice (make lattice (size sx sy no-size)))
(set! pml-layers (list (make pml (thickness dpml))))
(set-param! resolution 10)
(use-output-directory)
(define ( (my-amp sigma k x0) x)
(exp (- (* 0+2i pi (vector3-dot k (vector3+ x x0) ))
(/ (vector3-dot (vector3+ x x0) (vector3+ x x0)) (* 2 sigma sigma)))))
(define-param fcen 0.58) ; pulse center frequency
(define-param df 0.02) ; turn-on bandwidth
(define-param kdir (vector3 1 0)) ; direction of k (length is irrelevant)
(define k (vector3-scale fcen (unit-vector3 kdir))) ; k with correct length
(set! sources (list
(make source
(src (make continuous-src (frequency fcen) (fwidth df)))
(component Hz)
(center 0 0) ;
(size 0 10)
(amp-func (my-amp 1 k (vector3 -15 0 0))))))
(run-until 100
(at-beginning output-epsilon)
(at-every 0.6 (output-png Hz "-Zc gray")))
**************************************************************************************************************
I expect that I can get a gaussian beam with its waist at x=15, but this is not
true. Could you lend me a hand? Thank you very much.
yours,
Mario
PS: The width of waist seems larger than what I have specified, i.e. 1 unit.
What's wrong?
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