On Tue, 18 Jan 2011 17:27:44 +0100, Stefan Kapser <[email protected]> wrote: > Hi, > I'm trying to simulate a laser pulse falling on a dielectric structure > and don't really know where to find the necessary information. > What I am especially looking for is how to define the spectral > properties of the laser pulse. How can I for example simulate a few > cycle pulse? > And how I can define the frequency dependence of the dielectric, on > which the pulse will fall. I only found information on defining a > spatial variation of the dielectric constant.
Hi, for what regards the definition of the spectral pulse properties, the idea in a FDTD code is to define the pulse in the time domain so that the spectrum has the required properties. As far as I understand, for a few cycle pulse there is a need to pay close attention to certain details ... which I am not able to evaluate properly, but there has been a brief exchange of messages on the subject in the mailing list in December, so you may want to have a look at http://www.mail-archive.com/[email protected]/msg03839.html For what regards the dispersive properties of dielectrics, they are supported in Meep by modelling them with a sum of a constant plus Lorentzians. You can have a look here: http://ab-initio.mit.edu/wiki/index.php/Dielectric_materials_in_Meep http://ab-initio.mit.edu/wiki/index.php/Meep_Tutorial/Material_dispersion The tutorial is written for the libctl interface, I do not know if there is an equivalent tutorial for the C++ interface but it is quite helpful anyway. As a small note, as stated in the Meep documentation the terms "omega" and "gamma" in the libctl Meep interface correspond to a frequency, not an angular frequency (and in the tutorial http://ab-initio.mit.edu/wiki/index.php/Meep_Tutorial/Material_dispersion both forms of the dielectric function that appear at the beginning, after the words "corresponding to the dielectric function: " do not correspond to the material medium definition that is stated just before, the first (epsilon as a function of omega) has both resonance frequency and damping incorrect (it uses the ones that are defined in frequencies units in a an expression with the angular frequencies), the second (epsilon as a function of f) has the correct resonance frequencies but the dampings are wrong by a factor of 1/(2*pi). G. -- ================================================ Giovanni Piredda Postdoc - AK Hartschuh Phone: ++49 - (0) 89/2180-77601 Fax.: ++49 – (0) 89/2180-77188 Room: E2.062 ---------------------------------------- Message sent by Cup Webmail (Roundcube) _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
