Naoki, Vicky

Today we tested higher generated SQZ level and FC detuning, summary screenshot here. We turned up non-linear gain from NLG 11 to 17, so gen sqz level from 14.7dB to 17dB, and very barely got more sqz (< 0.2dB?). We set it back to the "normal" 80uW operating point, leaving the injected sqz level unchanged. We ended up changing FC detuning from -25 Hz to -28 Hz. Notes:

• no sqz 1376852952 - 1376853678.  (OPO taken down at 1376853301)
• Re-injected FDS with OPO_TRANS = 95uW (NLG=17, Gen Sqz = 16.95 dB). Adjusted OPO temp to maximize CLF_RF6_ABS and watching SQZ level in DARM.
• 19:37 - 19:41 High NLG at 95uW, fc detuning -28
  • Barely more sqz, probably not more than 0.2 dB sqz at high freq (including trying different angles, after adjusting OPO temp). I was a little surprised, I thought we would have seen more squeezing with the NLG increase..
• At FC detuning = -28 Hz (was -25 Hz), set OPO TRANS back to 80 uW.
• Ran a slow-ish sqz angle sweep from about 1376855983-1376856425. Will try using this slower sweep to improve calibration fits of the clf_demod_phase to the true sqz angle.
  • Reminder: clf_demod_phase is what we use to change the sqz angle (e.g. 71902), but they are not the same thing. See 49026 for equation relating sqz angle and clf demod phase.
• Leaving FC detuning at -28 Hz (was -25 Hz). Naoki accepted this in SDF. Not sure if this is really better, but it's possible, so we will try this for now.
   
• Briefly tried to see whether there is excess noise with the beam diverter open, opo unlocked, and pump flipper blocked (clf shutter open). In principle, if there's scatter from the squeezer that's above DARM, maybe we would see it in this configuration? From the blue trace in this screenshot of no-sqz traces, I don't see a noticeable amount of excess noise when comparing this state with the regular "no squeezing" reference taken ~1 hour ago, but I didn't take a back-to-back proper no-sqz reference, so the traces are not as comparable as I'd like.