The cavity pole was estimated again from the transfer function of the ISS AOM and the PD. The result is 610(10) kHz, and it is consistent with the design value.

The transfer function is shown in the attached figure. The fitting parameter is the overall gain, the time delay, and the pole around 600 kHz. Each result is as follows:
Overall gain: 0.126(1)
Time delay: 1.171(2) usec
pole: 610(10) kHz