Yuhang and Michael
We replaced the mirror mount for the beam splitter that goes into the SHG. The new mirror mount is much smaller, allowing us to more easily remove ghost beams and scattered light from the squeezer bench.
The beam splitter was replaced by roughly using an iris, SHG opening and GRMC EOM as beam position references. First, the beam splitter was moved by hand to align to the references. Fine tuning allowed us to recover the SHG mode matching to slightly better than the previous alignment condition.
Reference SHG alignment is shown in figure 1 and 2. BS model number is in figure 3. The mirror mount type is shown in figure 4.
A proper beam dump thorlabs LB2 (1um - 12um) is installed for the newly replaced BS mount (as shown in Fig.1).
Although we can see some green light, let's remind that it is because the camera sensor is more sensitive to green as our eye. There are proper Dichroic mirrors to remove them.