Sheila, Matt, Camilla
We aligned and took some SQZ HD data this morning but realized that the ZM optics were noisy with HAM7 tripped and the increased (60mph!! wind). After un-tripping HAM7, Matt and Sheila rechecked balancing and visibility, started at 98.3% but noisy, improved to 99.0%. Since then HAM7 tripped and was un-tripped again but assumed nothing would have changed.
NLG Measurements:
| opo_grTrans_ setpoint_uW | Amplified Max | Amplified Min | UnAmp | Dark | NLG (usual) |
| 120 | 0.108354 | 0.000573291 | 0.0018491 | 6.6e-5 | 60 |
| 110 | 0.0656167 | 0.000599855 | 36.8 | ||
| 100 | 0.0413918 | 0.00062871 | 23.2 | ||
| 80 | 0.0209032 | 0.000681607 | 11.7 | ||
| 60 | 0.0121804 | 0.000745147 | 0.0018428 | 6.2e-5 | 6.8 |
| 40 | 0.00710217 | 0.000852173 | 3.98 |
Data saved to camilla.compton/Documents/sqz/templates/dtt/20250225_GOOD_HD.xml
FC2 is misaligned during this dataset.
| Type | NLG | SQZ dB @ 1kHz | Angle | DTT Ref | Notes |
| Dark Noise | N/A | N/A | ref 0 | This and shot noise was noisy <300Hz at times when the OPO was locking or scanning, unsure why. | |
| Shot Noise | N/A | N/A | ref 10 |
Blocked SEED, LO only.
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| SQZ | 60 | -7.4 | 167 | ref1 | opo_grTrans_setpoint_uW = 120uW, OPO gain -14 |
| ASQZ | 60 | 22.6 | 225 | ref2 | |
| MSQZ | 60 | 19.6 | N/A | ref3 | |
| SQZ | 37 | -7.3 | 164 | ref4 | opo_grTrans_setpoint_uW = 110uW |
| ASQZ | 37 | 20.2 | 229 | ref5 | |
| MSQZ | 37 | 17.2 | N/A | ref6 | |
| SQZ | 23 | -7.4 | 161 | ref7 | opo_grTrans_setpoint_uW = 100uW |
| ASQZ | 23 | 18.0 | 233 | ref8 | |
| MSQZ | 23 | 15.0 | N/A | ref9 | |
| SQZ | 12 | -7.3 | 151 | ref11 | opo_grTrans_setpoint_uW = 80uW, OPO gain -8 |
| ASQZ | 12 | 14.5 | 246 | ref12 | |
| MSQZ | 12 | 11.7 | N/A | ref13 | |
| SQZ | 7 | -7.0 | 143 | ref14 | opo_grTrans_setpoint_uW = 60uW |
| ASQZ | 7 | 11.7 | 253 | ref15 | |
| MSQZ | 7 | 8.7 | N/A | ref16 | |
| SQZ | 4 | -5.9 | 132 | ref17 | opo_grTrans_setpoint_uW = 40uW |
| ASQZ | 4 | 8.9 | (-)85 | ref18 | |
| MSQZ | 4 | 6.0 | N/A | ref19 |
I'm also attaching pictures of SR785 measurements of various loop gains.
This data set is nicely fit by standard squeezing equations, and suggests we have 6% unexplained losses and very little phase noise.
In the attached PDF I took the median of the ASD from 500-700 Hz, subtracted dark noise in quadrature from each ASD, then calculated the dB relative to shot noise for squeezing, anti-squeezing and mean squeeze. I used the squeezing and anti-squeezing and opo transmission numbers to fit for the OPO threshold (in units of transmitted power), total efficiency of squeezing, and phase noise. The attached plot shows the resulting model plotted against the data, including mean squeezing and NLG measurements that were not used for fitting. The NLG plot does suggest that we are slightly underestimating our NLG with our measurements.
This suggests that the OPO threshold is at 156uW transmitted power, and that the totall efficiency is 83%. This can be compared to 73365 and to the expected losses from the loss tracking sheet and sqz wiki. Expected losses:
With the measured efficiency of 0.833, this means we have 6% unexplained losses in HAM7 or SQZT7.