[Sheila, Haocun, Nutinsee, Terry]
We managed to take a cavity scan of OMC with beams from squeezer.
We first used a full power SEED beam going in, but an OPO temperature not at exact dual resonance (because of the homodyne readouts fluctuations due to NLG).
- Input power: ~0.37mW (from homodyne)
- OMC 00 mode power: 0.29mW
This gave us an output even higher than the input..
Then we used CLF beam going in, which has a lower power, and at the peak of dual resonance.
This gave us stabler readouts on the homodyne, but the alignment were not as good as compared with using SEED.
We were also able to lock the OMC with CLF.
- Input power: 0.13mW
- OMC locking power: 0.06mW (should be 0.06mA, ~0.07mW *)
- SRM transmission: 32.34%
--> 18.7% loss (too much less than expected..?)
I am doing more calculations with the cavity scan data, and will add more follow-up details.
Next Tuesday we can work on centering loops using seed, from ZM1, ZM2 to AS_A/B.
How do you get 19% with those numbers?
0.06/(0.13*(1-0.325)) = 0.68
This is more like 30% loss.
Do I misunderstand what you mean?
Lisa, the OMC locking power should be 0.06mA on the DCPD, which means 0.07mW after calibration, but the 19% is probably under-estimated.
More numerical results (including corrections) from the cavity scan:
Using CLF:
From the plot:
| Mode | 00 | 01/10 | 20 | higher |
| mA | 0.0562 | 0.011 | 0.005 | 0.0021 |
Total: 0.0743mA --> 0.0885mW
Power input from Homodyne power is 0.123*1.13*(1-0.3234)=0.094mW (factor 1.13: calibration factor of Homondynes which was forgot) --> Loss from propagation: 5.8%
00 mode: 75.6% --> Loss due to alignment and mode matching = 24.4%
10/01 mode: 14.8%
20 mode: 6.7%
Using SEED:
| Mode | 00 | 01/10 | 20 | higher |
| mA | 0.245 | 0.01 | 0.023 | 0.003 |
Total: 0.281mA --> 0.335mW (This is higher than the power input from Homodyne power, which is 0.37*1.13*(1-0.3234)=0.284mW)
00 mode: 87.2% --> Loss due to alignment and mode matching = 12.8%
10/01 mode: 3.5% (Alignment better than CLF)
20 mode: 8.2%
Conclusion:
Loss from Faraday and propagation: 6%;
Cavity loss due to alignment and mode matching is around 24.4%, in which mode matching accounts for ~7-8%.
We will try to take another measurement with higher stable power.