After the beam size issue is solved, we proceeded to recover the alignment of SHG. Since we touched several mirrors for the path from new EOM to SHG, we had to make sure several mirrors and lens are in relatively good position.

We made several mistakes since the reflected beam from the 2-inch BS is not going along the holes on the bench. To make sure this reflected beam is roughly going along the good path, we used two lens just after the BAB pick-off BS as reference. But we found that these two lens are roughly in the imaginary plane with each other. So we need to find other reference for the rough alignment of the 2-inch BS. These references were selected to be the two lenses in front of OPO. After that we fixed 2-inch BS and the following lens.

Since the alignment was completely messed up, we also set up a camera after for SHG transmission. For monitoring higher order modes, a power meter was set up in the reflection of SHG. Now we started to align back SHG.