Hi Rob,
Though I don't have a solution to your problem, I have a related
question;
I have been running similar simulations on photonic crystal slabs and
when I run the simulation without symmetry, I get a couple of modes in
the band gap, with Qs in the few-thousands. Now, when I run the _same_
simulation after specifying symmetry {since my structure has symmetry in
x,y,z} I get completely erroneous results, with the mode {which is at
the same frequency as in the previous simulation minus-symmetry} being
no longer localized, and harmiv says that the error is comparable with
the imaginary part of the frequency, suggesting the lack of confidence
in the result. The only difference in the two simulations is the
specification of symmetry.
Any clues as to what might be happening?
Warm regards,
Uday
On 27-Apr-07 12:27 PM, Rob wrote;
> I'm working on finding Q factors and resonant frequencies of point defects in
> hexagonal lattices in photonic crystal slabs. I first found the photonic band
> gap for my particular structure to be 0.25281 - 0.32389 (normalized
> frequencies)
> using MPB. With this in mind, I used a Gaussian point source placed in a
> non-symmetric location within the defect area. The center frequency of the
> source was set at the mid-gap frequency and the frequency width of the source
> set to make the highest source frequency = gap top frequency and lowest source
> frequency = gap bottom frequency.
>
> My problem is that I seem to getting resonant frequencies near the gap bottom
> frequency that (based on trying to repeat simulations from literature) I do
> not
> believe are the actual fundamental modes of the cavity. For my example, the
> modes appear at frequencies such as 0.2553, 0.2571, 0.25509, and 0.2607 and
> have
> both negative and postive Q values in the +/- 200 to 600 range. In addition
> to
> these lower frequency modes near the gap bottom, I get higher frequency modes,
> which I believe are the actual fundamental cavity modes (again based on
> literature).
>
> I am working with defects that are enlarged air holes in a hexagonal lattice
> of
> air holes - acceptor type defects - that theoretically should pull states into
> the band gap from the lower frequency dielectric band. Thus, it makes
> physical
> sense that some of these types of defects could produce defects just above the
> gap bottom frequency.
>
> My question - is there anything wrong with my approach and the use of the
> Gaussian source with frequency width = band gap frequency range. Based on
> what
> I've written, do you think these lower frequency modes near the gap bottom are
> real resonant defect modes? If not, is there any way to eliminate them and
> determine the true fundamental cavity modes?
> Thank you,
> Rob
_______________________________________________
meep-discuss mailing list
[email protected]
http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
