The field is monitored within the defect region of the crystal at a position with low symmetry. This will be used by Q-Finder to compute the spectral response of the cavity. Unlike the energy decay method, which may also be used, the Fast Harmonic Analysis (FHA) method, used by Q-Finder, is able to extract accurate complex frequencies from relatively short propagation.
Several FullWAVE simulations of increasing length are performed in order to determine the resonant frequency and mode profile of the cavity mode of interest. Each simulation successively launches the mode found in the previous step in order to produce a clean mode profile. Once the simulations are completed, the final spectrum is analyzed using the FHA method to determine the Q value. This method finds a Q value of 3363 at a resonant frequency of 0.63497 μm-1, and a mode volume of 0.12.