Aritomi and Yuhang
As reported in entry2156, different HWP has different optical losses. Especially the dirty ones have more optical losses.
So we decide to clean these HWP and measure again the optical losses of them.
The experiment set-up is the same with entry2156, but the measurement is different this time. This time, the HWP was moved slightly by hand around center or tilt a bit to find the maximum/minimum transmission. Let's remind that HWP was placed randomly last time.
The result of optical losses max/min value is summarized as following:
| maximum losses | minimum losses | |
| before cleaning | 0.97% | 0.24% |
| after cleaning | 1.4% | 0.24% |
One important point is that the minimum losses is the same before and after cleaning, which indicates that there is always a good point on the HWP to minimize optical losses.
But it was a bit strange that the maximum losses became larger after cleaning.