hi shiv, Here is my best guess - someone correct me if I'm wrong. Try one or both of the following:
1. increase the width of the gaussian source. It seems to be a very tight spike: check if it is comparable to resolutions. The grid will propagate a pulse better if is spread out across more delta-t's. Of course, you are trying to simulate a pulse, I understand but this approach would be good for debugging. Discretization methods work best when the resolution is at least 1/20th the smallest feature size in your problem. 2. A point source radiates spherically about it, in your case, circularly. So the energy is dissipated along the circumference. The larger this is, the less you are going to see of the wave. So the wave might have dissipated esp. if it is a very tight spike. Aside, you have many constants in your .ctl file that you are not using. If you are sending such a file to the group, please make sure to remove extraneous information and keep only what is strictly relevant to the problem. Makes it easier for others to read the problem and get to the point :-) cheers! Manoj shiv chawla wrote: > Hello Everyone > > I am trying to simulate the propagation of very short time pulse in a > waveguide. However, In my case I donot observe any significant field at > any point other than source. Please help me as I need this for Project. > Thank You. > > (reset-meep) > (define-param a 1e-6) ; base unit in meters (1e-6 = > 1 um) > (define-param fequency-center 2e15) ; central frequency in hertz > (define-param fequency-width 2e12) ; consider picosecond pulse > (define-param eps-hi 2.25) ; the slab dielectric constant > (define-param eps-lo 1) ; the surrounding low-dielectric material > (define-param w 2) ; the thickness of the slab (arbitrary units) > (define-param l 50) ;the length of the slab > > (define-param X 10) ; the size of the computational cell in the x direction > (define-param Z 20) ; the size of the computational cell in the z direction > > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > ; Define the structure and the computational cell > > ; Here we define the size of the computational cell. Since it is 2d, > ; it has no-size in the z direction. > > (set! geometry-lattice (make lattice (size 200 10 no-size))) > > ; the default-material is what fills space where we haven't placed objects > (set! default-material (make dielectric (epsilon eps-lo))) > > ; a list of geometric objects to create structures in our computational > cell: > ; (in this case, we only have one object, a block to make the waveguide) > (set! geometry > (list (make block ; a dielectric block (a rectangle) > (center 0 0 0) ; centered at origin > (size infinity w infinity) ; block is finite only y direction > (material (make dielectric (epsilon eps-hi)))))) > > > (set-param! resolution 10) > > > (set! pml-layers (list (make pml (thickness 1) (direction X) (side High)) > (make pml (thickness 1) (direction X) (side Low)) > (make pml (thickness 0.1) (direction Y) (side Low)) > (make pml (thickness 0.1) (direction Y) (side > High)))) > > > (set! sources (list (make source > (src (make gaussian-src (frequency 1) (fwidth 0.001))) > (component Ez) (center -99 0)))) > (use-output-directory "/home/shiv/Desktop/examples/FDTD/Output") > (define (Field) > (print "Field:, " (meep-time) ", " > (get-field-point Ez (vector3 -98 0 0)) ", " (get-field-point Ez > (vector3 0 0 0)) "\n")) > (run-until 2000 Field) > > Regards > Shiv > IIT-Delhi > > ------------------------------------------------------------------------ > 5, 50, 500, 5000 - Store N number of mails in your inbox. Click here. > <http://in.rd.yahoo.com/tagline_mail_4/*http://help.yahoo.com/l/in/yahoo/mail/yahoomail/tools/tools-08.html/> > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > meep-discuss mailing list > [email protected] > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
