If you are interested in studying the types of PT structures which possess patterned no-loss --- loss regions, which are typically what is studied experimentally, using a conductivity to introduce your (spatially inhomogeneous) loss is a good way to go. However, if you really do want to use gain in your system, the only way to do this is using saturable gain, https://meep.readthedocs.io/en/latest/Materials/#saturable-gain-and-absorption, which corresponds to a slightly more complicated model for the gain than what is typically considered in the PT literature, as it includes non-linear saturation of the gain medium. You might be wondering why you can't just add "eps - 1i*gain" type of linear dielectric to your system in Meep, but the reason is that such a term will always lead to diverging fields in a time-domain simulation, the non-linear saturation present in the saturable gain model prohibits this, and also corresponds to what happens in physical systems. If you use saturable gain, you can alternate with regions of saturable loss to maintain PT of your passive structure.
On Mon, Oct 19, 2020 at 8:48 AM Cícero Julião <juliaojun...@gmail.com> wrote: > Thank you very much for your reply. However, perhaps I should explain my > question better. > > I was working on using a Gaussian pulse as a source. > I used a Gaussian font with a very short df, but there were still a lot of > resonances. > Then I thought of a continuous wave, so there would be only one frequency > for analysis. > But then the unwanted frequencies produced by the nature of the continuous > wave appear. > I didn't know what to do. > > If someone has already simulated material with PT symmetry and can provide > some help, it would be wonderful. > > > > ---------- Forwarded message --------- > De: Patrick Flanigan <flani...@etaphase.com> > Date: seg., 19 de out. de 2020 às 01:54 > Subject: Re: [Meep-discuss] pt symmetry > To: Cícero Julião <juliaojun...@gmail.com> > Cc: <meep-discuss@ab-initio.mit.edu> > > > This might help: > https://meep.readthedocs.io/en/latest/Materials/#conductivity-and-complex > > On Sun, Oct 18, 2020 at 12:23 PM Cícero Julião <juliaojun...@gmail.com> > wrote: > >> Dear friends, >> >> I'm trying to write a code to simulate material with PT symmetry. But I'm >> not sure how to include gain and loss in the dielectric constant. >> >> For example, can we use the material library to modulate material gain >> and loss? Or is it necessary to write the epsilon function by hand? >> >> Thank you very much to all. >> >> >> >> -- >> >> Cícero Julião da Silva Junior >> ____________________________________ >> Instituto Federal de Alagoas - IFAL >> Campus Murici >> http://www.ifal.edu.br/ >> _______________________________________________ >> meep-discuss mailing list >> meep-discuss@ab-initio.mit.edu >> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss > > > > -- > Patrick Flanigan > Etaphase, Inc. > 8201 NE 164th Avenue, Suite 200 > Redmond, WA 98052 > http://etaphase.com/ > > > -- > > Cícero Julião da Silva Junior > ____________________________________ > Instituto Federal de Alagoas - IFAL > Campus Murici > http://www.ifal.edu.br/ > _______________________________________________ > meep-discuss mailing list > meep-discuss@ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
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