Complex electric field, meaning of Re(E)


#1

Hello,

When I use a DFTMonitor, I can display either the magnitude, real part or imaginary part of the complex E field.
I understand that this complex E(r,w) field is the fourier transform of the temporal electric field E(r,t), but according to this link : https://kb.lumerical.com/en/layout_analysis_monitor_data_complex.html , the real and imaginary part of E(r,w) are still taken at a given instant t.
Does anyone know how this instant t is chosen by the software ?

Thank you for any help on this

Clément R.


#2

The E(r,w) result gives the Fourier transformed time domain fields so the result is the steady-state response for the specified phase of the source at the source position. If you wanted to see the steady-state response as you step through time then you could step the phase of the fields like discussed in the following CW movie example:
https://kb.lumerical.com/en/index.html?layout_analysis_cw_movie.html

Let me know if it is still unclear.


#3

Thanks for you reply, this is clear, but it does not answer my question. I will try to rephrase it :

Here https://kb.lumerical.com/en/layout_analysis_monitor_data_complex.html it says > If you want to see what the actual field values would be at a particular instant in time, you can plot the real (or imaginary) part of the data

So when I look at Re(E(r,w)) or Im(E(r,w)) in the monitor’s results, at which instant t are displayed the real and imaginary part of E ?

Hope it is clear

Clement R.


#4

Thanks for clarifying. It is unclear exactly what was the meaning behind that particular line of the documentation so I have made a note that it should be updated to clarify.

It could be that the comment was referring to the CW movie discussed in the prior bullet point where you could interpret the field profile returned by the monitor to be start (time = 0) of the continuous wave movie.

Otherwise if you wanted to see the fields at a certain instant of the simulation you could get this from a time-domain monitor.


#5

Thank you very much, I will keep an eye at the update.