I am ready to start the OPO mirror swaps in the next few days.

I've removed the squeezer Faraday from the platform and stored the associated optics in the "SQZ optics" bin, and the mechanical parts in the VOPO bins.  The Faraday Rotator itself is in a wooden box in the blue bin of squeezer things in my office.  I also removed most of the balance masses from the platform because those will be in the way as we reqork the optical paths.

When we worked on the VIP in the optics lab before O3 we used a "class B" fiber, which was the same type as the 1064 fibers used in chamber in O3a for both 1064 and 532.  We don't have something like that this time, so our inital plan was to use a brand new low insertion loss thorlabs fiber in the green collimator (this collimator will be replaced later in this rebuild).  The mode matching with the different fiber is different enough that this won't work.  For now I have reconnected the 532 fiber used in O3b to the collimator, with the fiber and feedthrough in the modified storage pan covered in foil.  Reassuingly the mode matching is good, the 1st misalignment peak is 12% of the 00 peak and the next peak is about 6% of the 00 peak. 

Interestingly, I am scanning just over 9 FSRs for green by dirving the PZT from 0-75 volts using a Thorlabs MDT694 PZT driver.  While the OPO was installed in chamber, we were only able to see 2 FSRs with the full 100 V range (52289 for example), which we never understood.  I remembered seeing many FSRs while working with the OPO in the optics lab before O3, it is interesting that the different set up in the optics lab still has the same behavoir.  I have removed D1700238 and stored it.  I have the same class B dSub that we used before O3, connected directly to the connector on the OPO box itself.  Off the platform, this class B cable is connected to a breakout D sub to BNC cable that Filiberto made for this purpose, with the pin out based on D1700308, I'm currently driving pin 4/9, although Fil also added a BNC for the other PZT (pin 3/8), so I will plan to try that PZT next time I'm in the lab. 

I also spent some time fixing the mode matching from the prometheus into the green fiber.  I spent some time adjusting the fiber port with the fiber laser to get a better collimated beam out, which made matching into it easier.  I now have PLCX-25.4-206.0-UV-532 at 0.36 meters from the Prometheus, and placed the fiber port (PAF-X-5-A) at 1.13 meters from the Prometheus.  This gives us a coupling efficency of just under 50%, with 5 mW available out of the fiber. (first attempt is described in 57169).