Hi Prof. Steven and Meep users,
I am totally confused about the harminv function in Meep. I am trying to
figure out the modes supported in a normal waveguide by using harminv. When
I change the location of the point where the harminv is run, output of
harminv changes, which I can not understand. why would this be different
for different locations in the waveguide? Also the other problem is, say if
harminv outputs 3 frequencies, and I select the first for fcen of the
gaussian, it again outputs more than one, shouldn't this be then one,
corresponding to the fundamental mode then? There is something wrong
somewhere, I assume it is the way I interpret this and use it, so if someone
could tell me what I am doing wrong here, that would be a great help and
help me alot o advance in my work. Currently I am stuck here and have been
stuck for two or three weeks now. My code attached below
thanks alot
geeth
; material chosen is silicon
; simulate a straight waveguide, with a thickness so that it is multimoded
; want to extract how many modes are supported by the waveguide using
; harminv
; a=1 um, so lambda=1.55
(reset-meep)
; source parameter setting
;--------------------------------------------------------------------
(define-param fcen 0.645)
(define df 0.01)
(define freq 0.15)
(define-param w 0.2 ) ; width of waveguide
;computational window setting
;---------------------------------------------------------------------
(set! geometry-lattice (make lattice (size 16 16 no-size)))
; Simulation object parameters
;----------------------------------------------------------------------------
(set! geometry (list
(make block (center 0 0) (size infinity w infinity)
(material (make dielectric (epsilon 12))))))
;Light source for field excitation setting & boundary condition
;--------------------------------------------------------------------------
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen) (fwidth df)))
(component Hz) (center -7 0) (size 0 w))))
(set! pml-layers (list (make pml (thickness 1.0))))
; output resolution
;-------------------------------------------------------------
(set! resolution 10)
(use-output-directory)
;%% setting the field extracting point, collects field at a set point
;------------------------------------------------------------
(define (my-field-point)
(print (meep-time) "\t"
(get-field-point Hz (vector3 7 0)) "\n"))
(run-sources+ 200
(at-beginning output-epsilon)
(at-every 1 my-field-point)
(at-end output-hfield-z)
(at-end output-efield-y)
(after-sources (harminv Ey (vector3 7 0) fcen (/ 100 df))))
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