Marc, Yuhang

In order to prepare for OPO measurement, we measured some preliminary FIS spectrum.

New measurements with better tuning are planned.

We checked the OPO non-linear gain after realigning the BAB and GR beam into it.

we measured without green 550 mV in transmission and with 25.6 mW of green 2540 mV which corresponds to non-linear gain of 4.47.

This is a bit lower than expected (should be about 5).

We tried to tune the OPO temperature (starting at 7.130 kOhm with 10 Ohm increment) but it seems we were already around the optimal temperature. The p pol PLL frequency in this condition was 225 MHz.

We also had to realign the GRMC and had some issue with the error signal sign before locking it.

We tuned the Homodyne balance by injecting noise into the IRMC (sine with 1.2 V Pk2Pk at 800 Hz) and trying to minimize it from the homodyne sub DC channel.

We checked the LO and BAB matching into the AMC and after some tuning could reach about 99.9 % mode-matching for each field into the AMC.

Finally we measured shot-noise and FIS.

We tried to change the phase of the FIS but could not reach more than 4 dB.

Possible reasons are that we forgot to optimize the OPO non-linear gain or the Homodyne visibility.

Furthermore, we had to tweak alignment at several places so we might have to retune it today to have a more stable alignment.