I realigned the beam into the cavity using the last two steering mirrors. I was able to get the signal on the transmission PD to come back to the level it was at before the pumpdown. Having said that I think it is close to (or actually) saturating the PD, so we don't have a good measure of the change in transmitted power. I measure 48mW transmitted with 108mW incident on the input mirror.
EDIT: I turned the beamsplitter at the output a bit to reduce the power incident on the PD, and added a beamdump for the reflected beam. It's not saturating now (it has 20mW on it, whereas before it had 25mW) but it only a bit below this level. I wasn't able to improve the alignment any further. I wanted to try maximizing the transmission moving the lenses in our modematching, but one is at the max of the range on the translation stage, and the other isn't on a movable stage. We should replace that and move the other one to the middle of the range so that we can optimize. |