Learning Forum

[omnia]

Hello,

I am working in the field of cavities, rings, disks, and Phcs.

My question is what is the highest Q factor that can be detected by the simulation? for example, if some kind of cavity has 10^8 Q factor, can it be detected in the simulation (even with very long simulation time). In the example from lumerical website, it uses high Q analysis group for 10^3 Q value (which is much far away from what I want).

Or it cannot be done in the simulation

[Guilin Sun]

I believe it can be that high. Early in 2009 Harvard first published result with Q higher than 1million. However, as you said it may need a little longer simulation time, depending on the method you used. For the
findresonances
it is a decomposition method, you may not need very long simulation.
For the FFT method, in order to capture the low decay, a longer simulation time may be needed.
For both methods, you will need to test. or estimate the simulation time to resolve the extremely high Q, by dt*df.

[omnia]

Thank you for your reply.
Q factor For SiN more than 10^8 has been reported.
can you elaborate on how to estimate the simulation time for such high Q factor

[Guilin Sun]

Thank you for letting me know this.
Estimation of the simulation time is a more theoretical question and there is no direct guideline in Lumerical website. Using different methods may need different simulation time. I would suggest to use both methods, and verify each other with different simulation time. You can compare the results with different simulation time and see if there is any improvement or change, and the time scale can be 10 times fro one to another to get meaningful comparison.