On Fri, 28 Dec 2007, Huazhong Wang wrote: > I have a question about the magnitude of source. A gaussian TM (Ez) > point source is used in my simulation. the amplitude of source is 1.0 > (default). I found that the maximum of Ez at source center is 0.887. I > also did the same simulation under the cw source TM(Ez). I also found > that the maximum of Ez at source center is 0.887. I thought that the > maximum value of Ez should be 1. I don't know why the maximum value is > 0.887 in simulation.
The magnitude of the Ez field and the current source have no fixed relationship; it depends upon the local density of states. It also depends upon the resolution, for a point source---when you do a point source, Meep treats it as if it were a delta function with that magnitude, and thus scales the current to have that integral. So, as you increase the resolution, the peak magnitude of the current will get larger and larger. Also, if you have a point source that doesn't fall exactly onto a grid point, Meep will interpolate it onto the grid. That means instead of having one "pixel" with that magnitude current, you will have several pixels with a slightly smaller magnitude (but the same integral). In any case, the most important point is to realize that the current amplitude is pretty meaningless since the resulting field depends on the surrounding medium and geometry. (And the absolute magnitude of the field is meaningless anyway unless you are doing a nonlinear simulation; if you are doing a nonlinear simulation you must normalize the power, not the current, as described in the manual.) Regards, Steven G. Johnson _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
