Field monitors: output Fourier Transform (DFT), flux calculations?

[erikshipton]

A common use case is calculating the response of a system vs frequency (transmission vs frequency/wavelength, antenna radiation vs frequency/wavelength, scattering amplitude/angle vs frequency/wavelength...ok you get the idea). This is really the strength of using time domain solver...you can put in a short pulse in time that has a large bandwidth and get the response at all frequencies in a single simulation. Using FDTD or FITD we usually solve the fields as a function of time and then do a temporal Fourier Transform.

(I just learned latex...check this out) $E(\omega) = \frac{1}{\sqrt{2\pi}} \int e^{i\omega t} E(t) dt$

This is nice in principle but often takes a ton of memory. So instead we accumulate the FFT's during the time stepping. A better explanation is found here https://meep.readthedocs.io/en/master/Introduction/#transmittancereflectance-spectra.

Is there a function to output the fields in some region of the simulation (for example in a surface bounding a scatterer/radiator so we can get the nearfields on the surface and use those to calculate the farfield radiation pattern) as a function of frequency? Ie instead of $E(x,y,z, t)$ --> $E(x,y,z, \omega)$.

[elenafuengar]

Frequency domain field monitors are now supported thanks to @elleanor-lamb contribution in PR#18 😸

[erikshipton]

This is a great feature addition. You guys kick ass!!