Aritomi, Yaochin, and Yuhang

Since we found there may be an issue of scattering from OPO(entry 1842), we did this check.

From the thesis of Emil,  they had 8% of power loss due to the higher-order modes from the damaged OPO. If we have the same situation with GEO600, we should have the problem reported in entry 1842. At a farther distance, the measurement of power will go down since the higher-order modes are much larger than TEM00. An easy check to tell if we have the same problem is to check OPO transmission by the camera.

We checked two positions, one is just after the dichroic mirror. Another is at some distance after the new Faraday isolator. They give almost the same result. However, as shown in the attached figures(the first is a picture taken by the camera by using the OD5 filter, the second is a picture taken by the camera by using the OD3 filter). OPO transmission doesn't have a special problem. (There are some points in the photo, the reason to have this is still unknown)