I have a simple gaussian line source between 60 and 300 THz launched
into vacuum. I save the field data in an X slice at each time step,
then import the data for a point of the slice into matlab.
I then plot the FFT of the data, and find that the center frequency is
not 180 THz, but something a bit higher (188 THz).
I'm pretty certain that the matlab script is correct. Is there
something in meep which could be causing the frequency shift?
Kind Regards,
Matt
complete meep script: http://pastebin.com/f40f6a200
matlab fft script:
file = hdf5info('pulsetest2-refl-slice.noscat.h5');
refl_noscat = hdf5read(file.GroupHierarchy.Datasets);
file = hdf5info('pulsetest2-trans-slice.noscat.h5');
trans_noscat = hdf5read(file.GroupHierarchy.Datasets);
a = refl_noscat(:,2);
L = length(a);
c = 299792458;
dt = (1/80)*1e-6/c;
NFFT = 2^nextpow2(L); % Next power of 2 from length of data
A = fft(a,NFFT)/L;
f = (1/dt)/2*linspace(0,1,NFFT/2);
y=plot(f,2*abs(A(1:NFFT/2)));
grid on;
line([180e12 180e12],[0 0.05]); % line representing center freq
axis([0 400e12 0 0.05]);
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