The bowtie VOPO was completely assembled. It looks quite nice, and not so difficult to work with. The crystal and mirror positions are well defined in the assembly. I haven't seen the green alignment in action, but it seems much more convenient to be able to actually see the beam path inside the OPO. Considering also the advantages in controllability, the lack of need for a GRMC ($) and ppol laser ($$$), and our regular collaboration with NTHU, I aim to use this type of OPO in all future quantum optics experiments at NAOJ or elsewhere. I asked Chien Ming and Hsun Chung to give me lots of documentation. I also gave Chien Ming the new elog link to give more details, since I couldn't be there the entire time.

I briefly came back to reality with the TAMA linear OPO. The PZT retaining ring is completely stuck. Even using gorilla force with Thorlabs SPW801 wrench I cannot move it at all. It seems more likely that I would just rip out the metal (fig 1). I tried to check the OPO but it's a bit hard to focus (fig 2). I suppose I will have to give up and use the spare front plate (in a box in my office) and spare retaining ring (somewhere...). I will need to clean them with the ultrasonic bath in the ATC.

With permission of Aso-san I took the small First Contact bottle from the speedmeter experiment, though he mentioned that he didn't know where Nishino-kun got it from originally. I spent a lot of time looking for the tabs used to peel it. Eventually I found a pack of them hiding at the back of the ATC cleanroom. I somewhat skilllessly applied a layer to the TAMA OPO incoupler convex face (fig 3). From experience last time, this won't remove the O-ring residue, but I just want to get the dust off the centre. Next time I will do the concave face.