Marc, Yuhang
First we checked the LO alignment into the AMC and found misalignment in both pitch and yaw.
We tuned the Homodyne balance and checked the visibility.
After some tweaking we measured visibility about 0.92 % which is lower than expected (99%).
We found that the BAB was heavily misaligned in the AMC and after tweaking we could reach about 95.7 % visibility.
However, because our goal is to make sure that the system is in an understood state we decided to go towards FIS measurement.
(Actually we also found out that there were large scattering noise below 100 Hz, maybe due to grass cutting.. Even if the situation improved with the better homodyne visibility, we should also try to check this measurement at lower frequency)
We measured FIS with following conditions :
| Green power [mW] | 25 | 30 | 35 | 40 |
| SQZ phase [deg] | 90 | 90 | 90 | 95 |
| ASQZ phase [deg] | 160 | 160 | 150 | 145 |
| OPO temp [kOhm] | 7.15 | 7.154 | 7.161 | 7.17 |
| p pol freq /5 [MHz] | 39 | 39 | 39 | 39 |
Results are computed in figure 1 where we could reach 5.9 dB squeezing with 40 mW of green power.
With the fit of ASQZ versus SQZ in figure 2, we have optical losses = ( 20.9+/-0.93 ) % and phase noise = (25.46 +/-3.14 ) mrad.
From our wiki, we expect 19.1% optical losses but taking into account the lower visibility, the expected losses become 23.6 %.
For the phase noise, we have quite large uncertainty because from 45 mW of green power the CC1 became really noisy. We will investigate this issue tomorrow.
During the alignment tuning, I made a mistake and moved the pitch of the steering mirror close to the mirror labelled 'FIS'. Before measuring FDS we should make sure to recover its alignment using the irises on the table.
