Vicky, Naoki, Daniel, Dhruva
Today we tried to investigate seeding. In the morning, we noticed that turning up the AOM drive and turning down the optical power seemed to be the best configuration for seeing maximum squeezing. We tried to find carrier leakage on the electronic path to the AOMs and found that we saw some crosstalk on the input to the 200 MHz AOM. We managed to get rid of that crosstalk and improve things a tiny bit by attaching alligator clips to the AOM cable shields and grounding them. The plot shows the HD spectrum with the SQZ laser offset by 1kHz. We still see a lot of seeding though.
We managed to get up to around 4.9 to 5 dB of squeezing on the homodyne by turning down the CLF optical power to as low as we can and keeping the AOM drive at around 30 dBm.
9dB of attentuation was also added to the RLF. FC locks well with this RLF-CLF level.
We see ~5dB HD SQZ with CLF AOM1's RF @ 31dBm, launching CLF~100uW into the SQZT0 fiber, for ~12uW at the CLF_RF6 RFPD. This means maxing out the AOM1 drive (200MHz w/ISS), then dumping ~98% of the light after both AOM's. The CLF RF6 PD's mini-circuits about +20dB amp was not re-installed, so CLF servo gains are all cranked up to lock (common +31, fast +25). LO_HD_RF3 gains are at (comm +10, fast 0).
Screenshot comparing to recent 3.5dB FDS quiet times from 66784, where ~3dB DARM-SQZ was consistent with ~3dB HD SQZ-- we are driving CLF AOM1 harder, rejecting most of it, but still getting ~2x more CLF optical power:
* CLF launch power 3x higher
* AOM1_ISS driving at +31dBm vs 14.5dBm (maxed now). Most optical power is getting dumped at the SQZT0 PBS.
* ~2x optical power at CLF RF6 PD
* CLF RF6 level down by -20 (from mini-circuit amp removal)
* FC_WFS Q-dip is about 2x lower
