On Thu, 18 Oct 2007, Gao Jie wrote: > 1. What do you mean by time-harmonic point dipole source? The Gaussian point > source defined in MEEP is fine?
No, I meant a CW source (a continuous source, in Meep). If you put in a CW source, and wait for the initial transients to die away, the result is the Green's function (for that source position and frequency), by definition. However, as I said, it is more efficient to use a pulse source and Fourier-transform the output. > 2. Which output file I should use, sfield or efield? If you are using an electric current source, you should use the E field. > Then need to normalize with no photonic crystal slab and take imaginary > part to get LDOS? No, you still need to normalize to the current source's spectrum (at least, if you are using a Gaussian pulse like I suggested) and take the imaginary part. Really, the LDOS corresponds to the real part of J* E for unit J, i.e. the rate of work done by the current source; the prescription to take the imaginary part has to do with the phase choice in the usual way the Green's function is defined. > 3. LDOS is a function of position and frequency. Actually I want to see the > change of LDOS at different frequencies (not information integrated over a > wide bandwidth of frequencies). In this case, I need to define df in my > source extreamly small? If you Fourier transform the response to a short pulse like I suggested, you can separate out information over many frequencies at once using a short pulse, which is much more efficient than making df small and looking at one frequency at a time, and gives the same informatoin. Anyway, the point is that Meep will solve Maxwell's equation for any source that you want. You just need to review the definition of LDOS and figure out what question you want to ask. Regards, Steven G. Johnson _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
