david.feldbaum@LIGO.ORG - posted 20:12, Thursday 23 August 2012 (3959)
FI alignment in the H1 PSL
After Mike R. has transitioned to high-power operation I went ahead and aligned the FI with the CWPs, TGGs and Quartz. The straps for the magnet were not yet ready. Earlier I was not going to insert the TGGs into an unsecured magnet, however I decided that there is hardly any risk involved provided the platform is well secured in place.
To get a better CWP extinction ratio I had to get a better adjustible HWP rotator for the incoming beam. I found one in the PSL team's cabinet. With that:
| power p-pol | power in s-pol | extinction |
| 3.8 W | 19 µW | 53.0 dB |
| 50 W | 0.36 mW | 51.4 dB |
| 100 W | 0.70 mW | 51.5 dB |
| 125 W | 0.85 mW | 51.7 dB |
| 20 W | 0.12 mW | 52.2 dB |
| power p-pol | power s-pol | extinction |
| 50 W | 0.41 mW | 50.9 dB |
| 126 W | 1.0 mW | 51.0 dB |
| 100 W | 0.83 mW | 50.8 dB |
| 20 W | 0.16 mW | 51. 0 dB |
Inserted Magnet with TGG+Quartz, polarization should rotate by 90 degree, p-pol should be minimized
| power in | power s-pol | power p-pol | extinction |
| 8.99 W | 8.92 W | 0.42 mW | 43.3 dB |
Inserted the 2nd TGGs
| power in | power s-pol | power p-pol | Pin*sin^2(22.5 deg) |
| 10 W | 8.3 W | 1.78 W | 1.78 W |