I took from general TAMA storage a couple of polarizer mounts (one Thorlabs an done Newport), as well as rail mounts and ND filters from the squeezing clean room. 

Last Friday I checked a bit the beam size based roughly on a recalculated version of the OPO MMT from Logan. While in principle we could design the beam to be a little bit too small (~20um) and then fine tune it upwards in size, in reality I was having trouble approaching the required 25 um radius. Somehow I seem to be having more trouble with this than I expected. Last time it "just worked" straight out of JamMT. Sometimes I see a very small beam on the sensor card but the detector tells me it is 0.5mm diameter as well.

I suspected a bit that we might be saturating the detector but according to the specs that doesn't seem to be the case (approximate intensity = 0.002 W /(pi*(0.020 mm)^2 = 1.6 W/mm^2 - max dynamic range 10W/mm^2, damage threshold 200 W/mm^2). Still, I brought stronger ND filtering to check anyway.

I disassembled the OPO input optics assembly and took out the input mirror. The PZT retaining rings seems slightly dusty. I tried to check with my weak phone light if the input mirror was dirty but I couldn't see anything. Like last time, there seems to be some residue from the O-ring where it is pressing against the input coupler clamp. I left the input mirror on top of some Alpha wipes with Akutsu-san's stuff but then saw that they were a bit dirty, there is even a mosquito on the cloth. Also I have some soldering gear (iron, heater) sitting outside the ATC cleanroom but I won't be available to finish the soldering job until Thursday unfortunately.