Devika
Ansys Employee

Hello Muhammad, 

If you are using an academic license, through this forum you can ask questions and reach out to Ansys. Our support team replies most of the questions. 

You can find equation and more details here. Quality factor calculations for a resonant cavity – Ansys Optics.

If you are new to using FDTD siftware, 

You can refer this manual to learn more about the software: FDTD product reference manual – Ansys Optics

I recomend to take free course on FDTD: Ansys Lumerical FDTD – Learning Track | Ansys Courses

Thanks and reagrds

Devika

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