Yuhang and Yuefan

As we discussed in the last filter cavity meeting, we may have a beam cut issue in AOM/EOM/iris. We checked again these optics by putting a steering mirror/lens after it and look at beam shape far.

For the cut issue of the iris, we found a better point where the higher-order diffraction beams are more separated. Attached pictures 1 and 2 show the position where we were putting the iris and we are putting it now. This more separated point is located just after the first lens after AOM. The new set-up is shown in the attached picture 3.

We also checked the beam cut issue of Faraday isolator and AOM. The checking point is just before the injection to PR chamber. We found out the main cut comes from AOM. We could see from the attached picture 4 that the most powerful center part could go through AOM/FI but not centered. After twinking a bit the position of AOM, we made the beam go through AOM from the center part(as shown in the attached picture 5). 

So although the aperature of AOM and FI are not ideal, we confirmed that the most powerful center part is not cut.