Hsun Chung, Te Hui, Chien Ming, Logan, Michael

A rough account of various activities, I do not have all of the details.

Te-Hui and Hsun-Chung brought two of their homemade homodyne detectors and tested the dark noise. One of them is better than the other. The old spectrum analyser formerly of TAMA seems to have some issue with the window covering the screen - the bottom left corner of the screen cover has become somewhat opaque (cause unknown) and that part of the display cannot be seen.

The VOPO picomotor stage requires a Windows 10 PC to use the software. Hsun-Chung bought a secondhand W10 laptop from HardOff.

I took an oscilloscope from TAMA storage, as well as about 10 M6 x 15 screws and some 25 mm posts and 30 mm post holder. I also took two beam dumps and the +/- 25V power supply from the filter cavity cleanroom. Marc apparently found 6 Glan Taylor polarizers (100,000 extinction ratio, versus 300 for a typical PBS) that didn't have any designated use.

The green mode matching telescope (to go to the VOPO) was set up. We used some Thorlabs lenses which were quite dirty so we cleaned them with acetone.

Chien-Ming informed me of some minor issues regarding the setup. For one, there is some elliptical polarization reaching the PBS. I set up the input Faraday to optimize for p-polarization at the input, as per the Thorlabs manual. It then outputs 45 degrees. However, Chien-Ming told me that there is some elliptical polarization at the PBS, since the Fresnel effect causes differing phase delay for s and p polarization at nonzero angle of incidence. But it's not a huge problem. To mitigate, we could either send 45 degrees in, s or p out (cheap), or use HWP after the FI (more $). Also my beam profile was precise (correct beam waist) but inaccurate (maybe 10cm offset from the actual position).

We put First Contact on both faces of the PPKTP crystal. The layer that I left on the linear OPO input mirror didn't peel easily so I put some more on as per the LIGO instructions. I also put in a spare PZT inner retaining ring in the linear OPO holder. The correct position is reached when it is screwed in to the limit of easy motion (see figure 1 of 2690)