[Sheila, Haocun, Nutinsee, Terry]
Yesterday we also did a better OMC cavity scan with beams from squeezer.
Compared with last time, we used:
- SEED power input on ISCT6: 54.2mW <--- high seed power for good alignment
- Green power input on ISCT6 : 8.8mW <--- lower green power to get rid of green depletion
- Temp: 51.63C <--- higher dual resonance crystal temperature to get rid of NLG
The results are shown in the attachment.
- Input power from IR PD: 1.24mW
- Power in the cavity: 0.78mW
---> This tells us the propagation and loss from Faraday is ~7.34%. (SRM transmission = 32.34%)
In the Cavity:
- 00 mode: 90.4%
- 10/01 mode: 0.38% --> The alignment is very good
- 20/02 mode: 8.2% This is the loss from mode matching. (Keep consistent with the former measurements.)
Nice! A couple of quick questions about:
- Input power from IR PD: 1.24mW
- Power in the cavity: 0.78mW
Where are these values measured? I imagine the input power was measured on SQZT6 (after the SQZ Faraday) and "Power in the cavity" actually means power incident on the OMC (like on AS_C). Is that correct? Is the alignment to the OMC that good because you engaged OMs alignment?
Yes,
input power was measured on SQZT6 (after the SQZ Faraday).
"Power in the cavity" means power incident on the OMC calculating from the scan, including 00 mode and higher modes.
OMC has good alignment because:
1. We are using ASC SERVO DC centering loops to align
2. We have seed power high enough
And there are some more info if you are interested in:
https://git.ligo.org/haocun.yu/lho_squeezing/wikis/Squeezing-Alignment