Louis, Vicky

In 72525, on SQZT7 Sheila and I adjusted the beamsplitter angle between the OPO_IR_TRANS PD & camera, which changed the beam-splitter ratio between refl / trans slightly. Today Louis and I re-measured and updated the OPO_IR_PD calibration. If we want to try a SQZ single-bounce measurement through the AS port, it'll be important to have an accurate calibration of the squeezer's injected power at the beam diverter. I think this calibration update is likely good to within ~2% (and very likely good to within ~3.5%)**.

With ~10mW into the seed fiber, using the Ophir PD (calibrated 10/18, at least the filter is part of S/N 889882), at 11:05AM PT we measured 52.7uW on the OPO_IR_TRANS PD, and then at 11:08am PT, we measured like OPO_IR_TRANS = 99-100uW going into the beam-splitter. While the epics calibration was fine, the slowcontrols calibration was off, so we accordingly updated the PD responsivity (0.23 to 0.235) and the PD splitter ratio (59% to 53.5%); SDF screenshot attached.

** This is assuming we trust the Ophir PD calibration into watts, but this PD was last calibrated 2018, and it wanted to be re-calibrated in 2020, but was not. We first measured with a Thorlabs PD, but that PD was inaccurate and reported the uW high by >10%. We are assuming the Thorlabs PD is inaccurate b/c the Ophir reading was closer to the former PD calibrations in slowcontrols/epics, so we are deciding to trust that one.