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> > To: Eoin Murray <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> >> Subject: flux spectrum of continuous source >> Date: 1 May 2015 15:14:20 BST >> To: 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>>
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