Hi,
On http://ab-initio.mit.edu/wiki/index.php/Meep_C-plus-plus_Tutorial
the method for calculating the quality factor is given:
int maxbands = 5;
int ttot = int(400/f.dt)+1;
complex<double> *p = new complex<double>[ttot];
complex<double> *amps = new complex<double>[maxbands];
double *freq_re = new double[maxbands];
double *freq_im = new double[maxbands];
int i=0;
while (f.time() < f.last_source_time() + 400) {
f.step();
p[i++] = f.get_field(Ex,vol.center());
}
int num = do_harminv(p, ttot, f.dt, 0.8*w_midgap, 1.2*w_midgap,
maxbands, amps, freq_re, freq_im);
master_printf("frequency,amplitude,quality factor\n");
for (int i=0; i<num; ++i)
master_printf("%0.6g%+0.6gi,%0.5g%+0.5gi,%g\n",freq_re[i],freq_im[i],real(amps[i]),imag(amps[i]),-0.5*freq_re[i]/freq_im[i]);
But the example uses complex fields. In my simulation I have to use
fields::use_real_fields() which causes the
method above generate wrong results (like negative q-factor from the
formula -0.5*freq_re[i]/freq_im[i] ).
What should I change to use this method for real fields ?
Thank you for any help,
Thomas Jefferson
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