Aritomi and Yuhang

The AA loop helps to stabilize both GR and IR beam alignment (elog 2226), but is currently introducing length fluctuation which results in a worse locking accuracy (elog 2227).

With AA loop closed, FDS is measured with detuning of ~550Hz to check if detuning is also stable for FDS measurement. (the whole set-up is the same with the one we used in this Feb)

All the measurement was done in a time scale of 20 minutes. The result is shown in the attached figure.

1. The fit result of detuning is changing within 12Hz.

2. The maximum measured squeezing is about 2.5dB.

3. FC could change anti-squeezing(~7dB) into squeezing(~1dB).