Logan, Michael

Logan learned about how to adjust the transmission and blocking polarizer setup of the Faraday isolator. It seems everything was mostly in place regarding polarization - the required input is p-pol for IO-5-1064-HP. With current QWP/HWP setup about 300 to 1 p-pol vs s-pol could be reached, checked via PBS and power meter.

We thought there were some issues with the FI not transmitting close to 100% but this turned out to be putting the power meter too far upstream, and then also small alignment tweaks. I could get about 95%+ transmission just aligning by hand. I tried to tweak with the micro adjusters but it turns out the platform is stuck and adjusting yaw makes it bump upwards (hard to describe without a picture). We should buy a better mount.

The initial point of this exercise was to check the contribution of the FI to some weird possible HOM seen on the beam profiler, hence why I put the micro-adjuster underneath to adjust pitch and yaw of the FI. I think at this stage we should just get on with it - check the output of the FI with the beam profiler and see if we can get rid of the weird mode. Super optimal transmission is not so important.