Marc, Michael

GRMC/MZ lock had problems but was somehow recovered by adjusting the gain and threshold of the control servo (I don't know how that worked).

We looked at squeezing in an attempt to see and check the glitch noise. Indeed, it was present again in the CC2 error signal, as usual. We recovered squeezing but could only measure about 1 dB squeezing and 3 dB antisqueezing, which is very low for 25 mW green injection (should be ~ 5 dB squeezing).

We looked at the spectrum of CC2 error signal. It has quite a broad bump that rolls off about 10-15 kHz, which is about the width of the FC control loop, among other things.

Homodyne shot noise spectrum seems ok but it was found that there is some bright spot leaking from the OPO to the homodyne. The homodyne was rebalanced to the local oscillator and the erroneous homodyne signal remained. The homodyne should just be noise around 0 with a rough amplitude of about 1 mV, but instead there is a strong oscillation with an amplitude of about 50 mV that goes away when I block CC to OPO. Measuring this bright spot gives only 5-10 uW (really sensitive sensor card it seems). Still it seems there is some error with homodyne. Perhaps we should double check and optimize CC and BAB to OPO, as well as green alignment (ppol seems fine).