Hello, your simulation is not exceedingly long, while divergence otfen appears if holes are in the PML region. It is quite a mysterious problem, but is well-known to those who use FDTD for PhC structures.
Bye 2011/3/26 A Noaina <[email protected]> > Dear Steven and meep users, > > Hello, > > I'm simulating a 2D-PhC based Channel Drop Filter by meep. I have > reasonable result for short time simulation, but in long time runs, I get a > divergence. I want to know what is the physical reason and how I can solve > it. The problem even exists in propagation in a triangular lattice straight > waveguide. > Another strange event is that there is no problem in long time simulation > for square lattice PhCs. My ctl file for a straight waveguide is as follow > and the simulation is done in 30 seconds. Devergence happens for times mor > that 300. > > Could somebody help me? > > > > > > (define-param A 1); lattice constant > (define-param sy (* A (* 21 (/ (sqrt 3) 2)))) ; size of cell in X direction > (define-param sx (* A 11)) ; size of cell in Y direction > (set! geometry-lattice (make lattice (size sx sy no-size))) > > (define-param res 10) ; resolution > > > (define-param trun 500) ; time of simulation > > (set! geometry-lattice (make lattice (size sx sy no-size))) > > (define-param px A) > (define-param py (* (/ (sqrt 3) 2) A)) > > > (define-param r (* A 0.35)) > (define-param nair 1.0) > (define-param nb 3.4) > (define airrod (make dielectric (index nair))) > (set! default-material (make dielectric (index nb))) > > (set! geometry (list .....)) > > > > > (define-param fcen (/ 0.25 A)) ; pulse center frequency > (define-param df (/ 0.05 A)) ; pulse width (in frequency) > (define-param dft (/ 0.003 A)) ; trans width (in frequency) > > > (set! sources (list > (make source > (src (make gaussian-src (frequency fcen) (fwidth df))) > (component Hz) > (center (* -4 px) 0) > (size 0 py)))) > > > (set! pml-layers (list (make pml (thickness (* 1 A))))) > (set-param! resolution res) > > (define-param nfreq 1000) ; number of frequencies at which to compute flux > (define trans ; transmitted flux > (add-flux fcen dft nfreq (make flux-region (center (* 4 px) 0) (size 0 > py)))) > > (run-sources+ trun (at-beginning output-epsilon)) > > (display-fluxes trans) > > > a. noaina > > > _______________________________________________ > meep-discuss mailing list > [email protected] > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss >
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