Turns out the 35MHz sidebands are way too weak to resolve from the resonance when doing a PZT scan.
I connect the IFR2023B function generator on the PSL table to the EOM instead of the FSS box and set it to generate 150MHz at 13dbm.
To observe the resulting weak sideband I place a PDA55 at the peak-off path from the transmission of the PMC where there is much more light than the transmission of the PMC head mirror. Whoever is using this path there is a PD blocking it right now.
I do a PZT scan by connecting a triangular signal to the EXT DC on the PMC servo with and without the EOM (Attachment 1). A weak sideband can clearly be spotted now.
Using the above 150MHz sideband calibration I can find the roundtrip time to be 1.55ns.
I take a high-resolution scan of a resonance peak and fit it to a Lorentzian (Attachment 2) and find a roundtrip loss of 1.3%.
Using the above results the cavity decay time is 119ns.
We should investigate what's going on with the ringdown measurements. |