[Tahara, Sakakibara, Nakano]

We measured the FSR of the PMC by using the sideband as the frequency ruler.
We swept the modulation frequency with seeing the carrier and the sideband peaks by the cavity scan. And find the frequency where the carrier and the sideband peaks coincide.

The results are as follows (we did the same independent measurement by three and estimated the error.)

FSR: 147.35(8)

This FSR corresponds to the cavity length of 2.0208(9) m. The designed value is 2.02m, so it is consistent.

From the measurement reported on klog5555, the cavity pole was estimated as 695 (50) kHz. From those numbers, we can calculate the finesse of the PMC as follows

Finesse: 105(10)

The designed value of the finesse is 125, so it is estimated smaller than the designed value. However the cavity pole measurement has a large error, and I think we can do more accurate measurement by using the AOM. We will measure it again.