Phase spectrum of a transmitted wave



I have a quick question. I am trying to take a look at the phase spectrum from the ring resonator, which is the example from the Lumerical website.

I am not sure just seeing the angle spectrum from the ‘through’ mornitor in the simulation shows the phase spectrum of the transmitted wave.

Otherwise, how to calculate the phase spectrum correctly ?

The phase spectrum I want to demonstrate should look like this (phase versus wavelength).

ring_resonator_angle_question_example.lms (586.9 KB)

Thank you in advance,.
Hwaseob Lee


Hi @hwaseob

I am not sure how you obtained the phase results. You can use a time monitor to record the complex field data at the output and then calculate the phase spectrum by calculating the Fourier transform of time domain field results. Please visit the link below for more details in this regard:

Hope this solves the problem.


Hi @bkhanaliloo

Thank you for replying to me, I see, I thought there might be another way, This is because when I get the data from the ‘through’ monitor in the previously attached simulation. I could choose to see the angle spectrum versus wavelength. What does the angle of it describing then?

Thank you in advance

Hwaseob Lee

what does the angle of it imply


Hi @hwaseob

You can use through monitor (varFDTDFrequencyMonitor) or time monitor spectrum to obtain the phase spectrum. If you want the results of time monitor to match the frequency monitor, you need to do a proper normalization as is shown the ring_group_delay_mode.lsf.

Angle shows the phase of electric field, and its unit is discussed here:
What is the unit of angle in FDTD visualizer

Hope I could answer your inquiry.