How to find resonance frequency and boundary condition using FDTD method?

[fatemeh bagheri nasab]

Hello
i have a fiber ring resonator in my problem. i must solve it with FDTD method.How to find resonance frequency and BOUNDARY CONDITION?


thanks

 

[rrumpf]

It doesn't make sense to use FDTD to find a "boundary condition." The boundary condition is what you need to do at the edge of your grid to prevent reflections. It is part how you implement FDTD, not what FDTD is calculating.

In general, to find a resonant frequency in FDTD, you excite the problem with a pulse sourse (short Gaussian) and let it run. After it runs for a while, record the field at a point where the field is strong. Fourier transform that to convert the time domain response to frequency domain. Spikes in the frequency responce indicate a resonance. The position of the spikes in frequency indicate the resonant frequency. There may be several or many resonant frequencies.

 

[ksugahar]

If you have a look at the transfer matrix like S12, you will see a peak at a certain frequency.
That is the resonant frequency. The boundary condition depends on what you are solving.
You have three options, 1) perfect electric wall,2) perfect magnetic wall, 3) absorbing boundary condition.
Which of these is a good model for your application?

 

[fatemeh bagheri nasab]

hi
ihave a ring resonator with double coupler.two of my boundary condition is in coupler. i launch a gussian pulse in r-r and i want to caculate output power.
with this b-conditions i can not get true output power.
do you know any information about this?
MEEP: A flexible free-software package
for electromagnetic simulations by the FDTD method