Cavity Resonance


Dear Nancy,

I want to thank you for all of your help thus far in addressing the issues I have encountered in my FDTD simulations, ma’am. I have done what you recommended: changed the material of the plates from aluminum to PEC, changed the profile to “steep angle” in the boundary conditions tab (I chose 24 layers - double the default value of 12), and enabled monitor apodization to “start” with the center time of this apodization setting to 2 ns and the time width to 1 ns. I am concerned whether or not I have correctly implemented the monitor apodization here.

I was also wondering how to utilize the Q factor analysis specific to my simulation. I have seen the scripts provided in the example .fsp files in the link you provided, but cannot get any results when I attempt to run the script within my file. Essentially, I am trying to reproduce the plots shown in Figures 2A and 2B in the attached paper below, particularly Figure 2B which shows transmitted power (in dB) as a function of frequency.

I feel that I am close to getting these exact, or very similar, results shown in the two aforementioned figures from this paper. I am seeking to make sure my settings are indeed correct for obtaining those results, but have hit a wall

I have attached my updated simulation file and reference paper whose results I am attempting to recreate below.

Simulation File:

Fig_2a_Ag_Plates_Dipole_1mm_Outside_No_Apod_PEC.fsp (269.3 KB)

Reference Paper:

Young et al. - 2013 - Enhanced resonant transmission of electromagnetic .pdf (896.8 KB)



With the monitor apodization settings, you want the apodization window to include the portion of the time signal which includes the resonant fields that remain after the source has been injected, and you also want to remove any effects of ending the simulation before the resonant fields have fully decayed since truncating the time signal at the end of the simulation can cause artifacts like described on the following page:

Since the resonant fields don’t fully decay by the end of the simulation, I think you should use “Full” apodization rather than “Start” apodization.

To exclude the initial source pulse, the center time should be set to a later time since it is currently including the source injection. You can check this by editing the source and viewing the “signal vs time” plot at the bottom right of the Frequency/Wavelength tab to see the signal of the source pulse that is injected:

To test the settings you could try a center time, eg. 12 ns, and if you also try a later time, eg. 16 ns, and the shape of the field profile looks the same between the two settings, this would indicate that the source pulse and initial transient fields has been fully excluded and only the resonant fields are included in the apodization window.

For the Q factor analysis group, I think you should be able to set it up in a similar manner to the following example which uses the time monitor inside the resonator cavity:

If you are running into some error with the analysis, please let me know what type of error you are seeing and I can look into it.

I haven’t had a chance to look into the paper in detail, but if you are still having trouble getting the results please let me know!



I have tried to implement the Q factor analysis but cannot get it to work
for my specific simulation. As a result of my progression in my research, I
have changed my simulation to operate under optical frequencies. Should I
attach my updated simulation file on the community chat for you to see what
I am currently working with, or can I simply attach it in an email?



Hi Casey,

Feel free to upload a copy of your simulation file here on the KX. If you are using a premium license you may also email us for support at