Reply To: high Q ring resonator ring-bus sweep

[Kyle]

Q factor calculations can be very difficult, especially for high Q structures. It looks like you need to increase the simulation time even more to get reliable results.
Instead of using FDTD for this simulation, it is generally better to use INTERCONNECT for large ring resonator simulations as described on this page: /forum/discussion/27337/how-to-include-propagation-loss-and-coupling-coefficient-in-ring-resonator/p1

This is the approach used in our ring modulator and CROW filter examples:
If you don't have a license for INTERCONNECT, another more efficienct approach might be to use FDTD to get the coupling coefficients as a function of gap distance and the mode properties with the FDE solver in MODE, and put this into an analytical ring resonator model to get the Q factor. An analytical formula for the Q factor of a single bus ring resonator is given in: Bogaerts, Wim, et al. "Silicon microring resonators." Laser & Photonics Reviews 6.1 (2012): 47-73.