Michael and Yuhang

As discussed in elog2784, we need to inject laser from OPO in-coupling mirror side to distinguish different OPO internal losses values. This is the reason of work reported in this elog. To achieve the measurement, we have done the followings:

1. Remove periscope and rotation stage for OPO

2. Prepare a 50:50 BS placing in front of OPO to extract OPO reflection signal information

3. Lower the height of OPO transmission BS, PD and camera

(these works are shown in Fig.1)

4. Confirm and adjust the flatness of laser beam after removing periscope

(this work is shown in Fig.2,3,4)

5. Put OPO in place and optimize its position by hand. Try to get a reasonable OPO transmission mode. We have found a TEM01 mode now.

Next step: Find OPO transmission signal on PD. Optimize OPO injection beam alignment.