- I removed the flip-mount that was installed on the EY in-air table for the mode-spectroscopy project (see Attachment #1). The Transmon QPD at EY sees IR light again.
- Dark noise checkout - see Attachment #2.
- Light-level expectations:
- For the current config, let's say 0.8 W reaches the PRM, and we will have a PRG of 50.
- This implies ~5.5 kW circulating power in the arms.
- This implies ~70mW will get transmitted through the ETM, of which at most half makes it to the QPD.
- In the nominal operating condition, we expect more like 6 W circulating in the arm cavity. So something like 30uW is expected to make it out onto the Trans QPDs.
- But in this condition, we expect to run with the high-gain Thorlabs PD.
- In reality the number is likely to be somewhat smaller. But we should set the transimpedance gain of this photodiode accordingly. Currently, there are a bunch of ND filters installed on this photodiode, which probably should be removed.
- Angular control
- The other purpose these QPDs are expected to serve is to stabilize the angular motion of the cavities when locked with high circulating power.
- Need to calculate what the sensing noise requirement is.
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