Nutsinee, Daniel, Naoki
As reported in 75902, the SHG IR injection power was 180mW and the SHG GR power was only ~40mW after PMC install. To increase the SHG IR injection power, we replaced the 50:50 BS to split the SHG path and CLF/seed path with 70:30 BS. After the replacement, the IR power is 400mW before BS, 270mW for SHG path, and 130mW for CLF/seed path. After we optimized SHG alignment with pico and optimized the SHG temperature, the SHG GR power reached 60mW with 230mW SHG IR injection. This is consistent with what we had before in 67172.
The OPO can be locked with LOCKED_CLF_DUAL. The pump ISS control mon is a bit low ~3.8 so we need to align the pump AOM and fiber. We also need to align the seed fiber.
Attached an updated power budget and a SHG scan. After setting the SHG crystal temperature to 34C this morning, the SHG mode mismatch became worse (70% mode matched instead of 80%) on the floor so I reverted to crystal temperature back to ~36C. The normalized current on the SHG BBPD was increase from 0.288mA to ~0.4 mA. SHG common mode board gain is reduced by 3dB to compensate for the factor of 1.4 higher SHG trans. In addition to the BS2 that was replaced with a 30/70 we also replaced BS11 with a 10/90 (R=10%). PMC trans diode sits at the 10% pick off. The diode hasn't been recalibrated.
CLF path has been aligned. AOM1 has about 30% 1st order throughput and AOM2 has about 50% 1st order throughput. At the nominal AOM1 ISS drive point we are capable of sending about 1.5mW to the fiber coupler (we dump most of that power at the moment. Old 1/2 waveplate setting.). We are sending ~10mW into AOM1. Haven't tried to lock the CLF yet.
We also optimized the pump alignment into the fiber. Although that probably wasn't necessary. As Naoki mentioned we were able to lock the OPO with no issues but some optimization required.
Seed has a very small fiber throughput but at least there's something to look at. Optimizing that one tomorrow.
To do list tomorrow:
- Optimize seed and pump fiber throughput. Maybe optimize LO as well if we have the time although we probably won't need this any time soon.
- Lock CLF
- Calibrate PMC trans PD
Ps. I stole the BNC to HV adapter from the OPO PZT driver and forgot to return it...