Sorry for late report.

First attached figure is the result of the measurement of old Y Prometheus PZT efficiency conduct in the same procedure as 8378 (This measurement was conducted without PLL lock).

The injection wave voltage is 1 Vp-p.

The vertical axis is normalized by the nominal value of the PZT efficiency (1.4MHz/V).

We plan to insert a notch filter in line with resonance.

We also achieved PLL locking of the old Prometheus laser to the PSL main laser.

Second figure is the OLTF of the measured PLL loop.

UGF is about 20 kHz, the phase margin is about 40 degrees.

When OLG is sufficiently larger than 1, the free-run noise of Prometheus can be estimated by multiplying the control signal from the servo filter by the PZT efficiency.

The third figure is the free-run noise of old Y Prometheus obtained from the measured control signal.