Dear Steven and list, I'm simulating with Meep resonant cavities like add-drop ring and disk resonators and obtain the resonant spectrum with the flux function or harminv. Everything seems fine except that I noticed how the spectrum is always red or blue shifted relative to the source spectrum (i.e., using a Gaussian input pulse, the Gaussian profile of the output resonant spectrum is clearly shifted). It looks like that the the bandwidth of the source determines the output resonant peak positions (while, except for fwidth df, all the code remains unchanged): larger source bandwidth returns the same (or negligibly altered) FSR but with the spectrum profile largely red-shift, even of dozens of nm on a 1500 nm center source wavelength. The dimension of the cell seems to have a similar effect: in order to accomodate two cavities, doubling the cell size, leads to a double redshift. Moreover, I noticed that at some point when the refractive index is set beyond a threshold (say between 3.2 and 3.3 in my case) suddenly the spectrum is split, i.e. one sees two Gaussian spectra, one blue- the other red-shifted abruptly in an even more unpredictable manner. Working with higher resolution or simulation times won't change much the situation.
I'm confused. I'm certainly missing something important here, but I can't give myself an explanation of this. Is it a numerical effect or is there some obvious physical explanation? Can anybody help? Andreas. __________________________________________________ Do You Yahoo!? Poco spazio e tanto spam? Yahoo! Mail ti protegge dallo spam e ti da tanto spazio gratuito per i tuoi file e i messaggi http://mail.yahoo.it
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