------
below is a 2d calculation. it's simply a metal slab, a point source
and a pml around the entire domain.
if the metal slab is 'metal', there is no problem.
if the metal slab is a dispersive material ('al_mat' below) then only
if the source is Ez is the simulation stable. otherwise the energy in
the domain grows without bounds.
if i change it so the x-direction is periodic, i have no problem.
therefore, there seems to be a possible stability problem w/
dispersive materials running into a pml.
a different *.ctl file in 3d is unstable regardless of the source as
long as the slab is dispersive.
thanks for any help/suggestions.
(both meep 0.20.3 and 0.9 tried)
------
(print "starting control file...\n")
(set-param! eps-averaging? false)
(define-param print-epsilon? false) ;print eps.h5 file?
(define-param pml_h 0.5)
(define-param res 100) ; resolution
(define-param fcen 1.82) ; center = 550nm
(define-param df 0.33) ; center = 550nm, width=100nm
(define-param nfreq 201) ;number of frequency sample
points
(define x_tot (* 0.76 2))
(define y_tot 0.76)
(set! geometry-lattice (make lattice (size (+ pml_h pml_h x_tot) (+
pml_h pml_h y_tot) no-size)))
(set! resolution res)
(print "defining materials...\n")
(define al_mat (make dielectric (epsilon 1)
(polarizations (make polarizability (omega 1.0e-5)
(gamma 0.722) (delta-epsilon 1.38E+12)))))
(print "defining geometries...\n")
(set! geometry (list
(make block (center 0 -0.12 0)
; (material al_mat) (size (+ pml_h pml_h x_tot) 0.12 infinity))))
(material metal) (size (+ pml_h pml_h x_tot) 0.12 infinity))))
(print "defining pml...\n")
(set! pml-layers (list (make pml (thickness pml_h))))
(print "defining source...\n")
(set! sources (list
(make source (src (make gaussian-src (frequency fcen) (fwidth
df))) (component Ez) (center 0 -0.02 0))
; (make source (src (make gaussian-src (frequency fcen) (fwidth df)))
(component Ey) (center 0 -0.02 0))
; (make source (src (make gaussian-src (frequency fcen) (fwidth df)))
(component Ex) (center 0 -0.02 0))
))
; do the simulation
(define tim 5) ;time to sample energy in domain
(print "time to sample energy: " tim "\n")
(define tot_energy 0)
(define max_energy -1)
(define ratio 1)
(if print-epsilon? (output-epsilon))
(run-sources+ 60
(at-every tim (lambda ()
(set! tot_energy (meep-fields-field-energy-in-box fields
(volume (center 0 0 0) (size x_tot y_tot)) ))
(set! max_energy (max max_energy tot_energy))
(set! ratio (/ tot_energy max_energy))
(print "energy decay (t=" (meep-time) "s, " (meep-fields-t-
get fields) " timestep) = " tot_energy " / " max_energy " = " ratio
"\n"))
)
)
(print "done with control file\n")
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