Dear Meep community,
I am using Meep to simulate the propagation on a singlemode waveguide in a
2D space.
As I found on the Meep tutorial, I compute the transverse eigenmode of my
waveguide
to define my eigen-source.
Then I look at the the evolution of my field (which is TE by the way) the
shape of the
singlemode is preserved along the waveguide (as expected).
Nevertheless, I observe that there is a damping of the mode intensity along
the waveguide.
Since the mode is supposed to be supported by total internal reflection
there should be no damping.
Hence, I believe that I made a mistake.
Does someone have any idea what I made wrong?
I join the code below.
Best regards
(define-param eps 2.280100) ; dielectric constant of waveguide
(define-param n_out 1.400000) ; dielectric constant of outside
(define-param w 0.900000) ; width of waveguide
(define-param sy 15.000000) ; size of cell in y direction (perpendicular to
wvg.)
(define-param pad 1.000000) ; padding between last hole and PML edge
(define-param dpml 1.000000) ; PML thickness
(define-param sx 100.000000) ; size of cell in x direction
; geometry
(set! default-material (make dielectric (index n_out)))
(set! geometry-lattice (make lattice (size sx sy no-size)))
(set! geometry
(append ; combine lists of objects:
(list (make block (center 0 0) (size infinity w infinity)
(material (make dielectric (epsilon eps))))
)))
; PML
(set! pml-layers (list (make pml (thickness dpml))))
(set-param! resolution 10.000000)
; Source TE
(define-param fcen 1.060000) ; pulse center frequency
(define-param df 0.500000) ; pulse width (in frequency)
(set! k-point (vector3 6.660176 0 0)); Direction of eigen-source
(set! sources (list
(make eigenmode-source
(src (make gaussian-src (frequency fcen) (fwidth 0.001000)))
(component Ey)
(size 0 (- sy (* 0 dpml)))
(center (+ dpml (* -0.5 sx) pad) 0)
(eig-kpoint k-point)
(eig-match-freq? true)
(eig-parity EVEN-Z)
)
))
; RUN
(run-until 600.000000
(at-beginning output-epsilon)
(to-appended "ey" (at-every 600.000000 output-efield-y))
)
--
----------------------------------------------------------
Nicolas Bachelard, PhD
NSF Nanoscale Science and Engineering Center (NSEC),
University of California, Berkeley 3112 Etcheverry Hall,
UC Berkeley, California 94720, USA
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