camilla.compton@LIGO.ORG - posted 12:19, Wednesday 25 June 2025 - last comment - 14:27, Wednesday 25 June 2025(85329)
SQZ HD Dataset
Yesterday 85295 we took HD data just at the nominal 95uW OPO trans setpoint, today we changed the NLG and retook data, saved at /camilla.compton/Documents/sqz/templates/dtt/20250625_HD.xml
Strangely, when I started checking the NLG with 95uW, once the seed was injected, this dropped to 65uW, I then increased injected seed power form 0.5mW to 0.6mW, I also increased the pump power as we were close to the edge of the AOM range.
Used SQZ_MANAGER SQZ_READY_HD (needed to change LO gain, see sdf).
| Type | NLG | Angle | SQZ (@500Hz) | DTT Ref |
| LO shot noise | N/A | N/A | Used as 0dB | ref 1 |
| ASQZ | 10 | (+) 206 | 14.3dB | ref 2 |
| SQZ | 10 | (-) 112 | 6.9dB | ref 3 |
| Mean SQZ | 10 | N/A | 11.3dB | ref 4 |
| ASQZ | 18 | (+) 210 | 17.2dB | ref 5 |
| SQZ | 18 | (-) 112 | 7.3dB | ref 6 |
| Mean SQZ | 18 | N/A | 14.1dB | ref 7 |
| ASQZ | 21 | (+) 210 | 17.5dB | ref 8 |
| SQZ | 21 | (-) 110 | 7.4dB | ref 9 |
| Mean SQZ | 21 | N/A | 14.7dB | ref 10 |
| ASQZ | 14 | (+) 206 | 15.6dB | ref 11 |
| SQZ | 14 | (-) 113 | 7.4dB | ref 12 |
| Mean SQZ | 14 | N/A | 12.7dB | ref 13 |
| OPO Setpoint | Amplified Max | Amplified Min | UnAmp | Dark | NLG | OPO Gain |
| 95uW | 0.0730506 | 0.002413 | 0.006841 | 8.4e-5 | 10.81 | -8 |
| 115uW | 0.122166 | 0.002215 | 18.08 | -8 | ||
| 120uW | 0.141799 | 0.0021763 | 20.99 | -8 | ||
| 105uW | 0.0942627 | 0.0023351 | 13.95 | -8 |
Plot attached, we think that the SQZ is worse at NLG 10 that the other NLGs and we are considering running with NLG = 14.
Here's a fit of Camilla's data, it shows that our OPO threshold has increased compared to 83070, and we still have the same efficiency for squeezing, which implies 6% unexplained loss, which hasn't been fixed by moving the crystal.
This plot was made using this script
We decided that an OPO TRANS setpoint of 105uW for an NLG of 14 gave us slightly better squeezing, see attached BLRMS. Leaving this in.
If the Operators have any issues keeping the OPO locked at this higher output power, they could lower it slightly following the instructions in 70050 to drop it down to 100uW or 95uW.