Hello,
I'm interested in investigating a certain 2d-periodic structure and calculating
its band diagram using Meep/harminv.
These are often referred to in literature as "Sievenpiper" structures, or
"mushrooms". They are metallo-dielectric.
The attached cartoon depicts the geometry I tried to run. The structure is in
a waveguide. It wasn't clear to me from the documentation whether boundaries
default
to PEC, so to be certain I explicitly define metal blocks at the waveguide
boundaries.
When I try running the simulation, harminv gives me no output:
Meep progress: 181.1/210.0 = 86.2% done in 16.0s, 2.6s to go
on time step 5435 (time=181.167), 0.00294547 s/step
harminv0:, frequency, imag. freq., Q, |amp|, amplitude, error
run 0 finished at t = 210.0 (6300 timesteps)
freqs:, 1, 0, 0, 0
freqs-im:, 1, 0, 0, 0
That is, the freqs: lines are always blank. I tried simplifying the
geometry quite a bit, but the behavior is always the same. I believe I
calculated the frequency correctly for this geometry, though tweaking the
source didn't show
any signs of hope.
Any hints on what I might be doing wrong?
Kind Regards,
Matt
(define-param eps 3) ; dielectric constant of
substrate
(define-param w 10) ; width of patch
(define-param r 1) ; radius of post
(define-param g 2) ; gap size
(define-param subthickness 5) ; substrate thickness
(define-param metalthickness 0.1) ; patch thickness
(define-param airgap 2) ; airgap thickness
(define-param boundmetalthick 2) ; thickness of the metal
layers at top and bottom boundaries
(define-param a (+ w g)) ; lattice constant
(set! geometry-lattice (make lattice (size a a no-size))) ; 2d periodic
;; geometry objects are in order: substrate, post, airgap, patch, upper PEC,
lower PEC
(set! geometry
(list (make block (center 0 0 0) (size infinity infinity subthickness)
(material (make dielectric (epsilon
eps))))
(make cylinder (center 0 0 0) (radius r) (height
subthickness) (material metal))
(make block (center 0 0 (/ (+ subthickness airgap) 2)) (size
infinity infinity airgap) (material air))
(make block (center 0 0 (/ (+ subthickness metalthickness)
2)) (size w w metalthickness) (material metal))
(make block (center 0 0 (+ (/ (+ subthickness
boundmetalthick) 2) airgap)) (size infinity infinity boundmetalthick) (material
metal))
(make block (center 0 0 (/ (+ subthickness boundmetalthick)
2)) (size infinity infinity boundmetalthick) (material metal))))
(set-param! resolution 15)
(define-param fcen 0.008333) ; pulse center frequency (define-param df 1)
; pulse freq. width: large df = short impulse
(set! sources (list
(make source
(src (make gaussian-src (frequency fcen) (fwidth df)))
(component Ez) (center 0.3 0 0))))
;; square lattice brillouin zone
(define k-points (list (vector3 0 0 0) ; Gamma
(vector3 (/ a 2) 0 0) ; X
(vector3 (/ a 2) (/ a 2) 0) ; M
(vector3 0 0 0))) ; Gamma
(set! k-points (interpolate 3 k-points))
(run-k-points 200 k-points)
cartoon.png
Description: cross-section cartoon
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