Does anyone have a solution to this, to make a fully monochromatic light source, it seems like a fairly typical use case for an electromagnetic FDTD library.
I have found that a mono-source can be made if you run the simulation for a long time, like 1500 periods, but there must be a more efficient way to do this. I will post my solution as soon as I find one. > On 2 May 2015, at 14:30, Eoin Murray <em...@cam.ac.uk> wrote: > > Hi Filip, > > Thanks for the swift reply and for recommending the solution. I have tried > what was suggested in Gib’s post - where a smooth turn on function of around > two periods should narrow down the linewidth of the source spectrum (or power > spectrum) - however this does not seem to work for me, > > I have made a sample repo on github to show the issue, I am using a frequency > of 1.1 and a continuous-src with a 2 period turn on time (I have tried unto > 20 periods turn on and little changes), I would expect the linewidth of this > source to be approaching zero. I understand that there would be some > numerical broadening, but still the source is far to broad for me at the > moment with a width of 0.05, this should be much smaller to simulate a > close-to-monochromatic light source like an atomic dipole (which a continuous > wave src should do). > > The field does become more spectrally narrow if I run for a long time (like > 1500 periods), but I expect I should be able to achieve same after 20 periods > or something, why do the transients take so long to die out.? > > The attached repo contains a _test.ctl file with my code and graphs in the > _test-out/ folder. > > https://github.com/eoinmurray/meep-test.git > <https://github.com/eoinmurray/meep-test.git> > > Thanks again for the help. > Eoin > >> Begin forwarded message: >> >> Date: 1 May 2015 20:59:41 BST >> Subject: Re: [Meep-discuss] flux spectrum of continuous source >> From: Filip Dominec <filip.domi...@gmail.com >> <mailto:filip.domi...@gmail.com>> >> To: Eoin Murray <em...@cam.ac.uk <mailto:em...@cam.ac.uk>> >> >> Hi, Eoin, >> everything suggests you have the same problem (which is actually not a >> problem per se) as Gib: >> https://www.mail-archive.com/meep-discuss@ab-initio.mit.edu/msg05374.html >> <https://www.mail-archive.com/meep-discuss@ab-initio.mit.edu/msg05374.html> >> >> Regards, >> Filip >> >> 2015-05-01 14:17 GMT, Eoin Murray <em...@cam.ac.uk <mailto:em...@cam.ac.uk>>: >>> >>> >>> Begin forwarded message: >>> >>> From: Eoin Murray <em...@cam.ac.uk <mailto:em...@cam.ac.uk>> >>> Subject: flux spectrum of continuous source >>> Date: 1 May 2015 15:14:20 BST >>> To: meep-discuss@ab-initio.mit.edu <mailto:meep-discuss@ab-initio.mit.edu> >>> >>> I want to create a monochromatic continuous source, in air, and measure the >>> flux through some plane, so I use the following code: >>> >>>> (set! sources (list >>>> (make source >>>> (src (make continuous-src (wavelength wv) (width 0))) >>>> (component Ez) >>>> (center 0 0) (size 0 0)))) >>> >>> I thought that the flux spectrum would look like a dirac delta function, >>> instead it is quite broad, why is this? >>> How can I create a continuous wave monochromatic source in meep? >>> Attached are links to the flux spectrum I measured through a plane north of >>> the source, and also an image of the field. >>> >>> http://i.imgur.com/xeAZCte.png <http://i.imgur.com/xeAZCte.png> >>> <http://i.imgur.com/xeAZCte.png <http://i.imgur.com/xeAZCte.png>> >>> >>> http://i.imgur.com/Dza8deC.png <http://i.imgur.com/Dza8deC.png> >>> <http://i.imgur.com/Dza8deC.png <http://i.imgur.com/Dza8deC.png>> > > _______________________________________________ > 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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