Sheila, Gabriele
Last week, Camilla started to get the squeezer working again in 89453, today I'm continuing that.
On Jan 29th, when we injected 74mW of seed into the CLF fiber, the rejected polarization PD in HAM7 for the IR fiber was saturated, and the CLF reflection trigger PD saw 21mW of seed, and when locked on the dither we get 0.8mW onto the OPO IR PD. Now, we inject 74 mW, the rejected PD is still saturated, we have 22mW on the CLF reflected PD (trigger diode), so the fiber coupling efficiency and transmission seems similar to January. However, we only have 0.1mW on the OPO IR PD diode (transmitted) as Camilla reported. Looking at the OPO scan, the higher order mode is 13% of the 00 mode, so the alingment from the fiber into the OPO seems OK.
The problem was the alignment of ZM2+ZM3. According to their osems, they moved during pump down as is expected. Restoring them to the osem values didn't bring us fully back to the 0.79mW OPO IR PD transmission, but I was able to walk them from there to get 0.74mW.
The OPO green transmission is much lower than with the old OPO, this is expected because we are using the transmission through a M2 which is a high reflector for 532nm and the transmission can ve very different for different mirrors. We during O4 we used 80uW as our setpoint for OPO trans, I set it to 23uW to get the pump ISS working. I also edited line 232 of the OPO guardian , to set the trigger level for channel 1 (green trans) to 0.1 rather than 0.5.
Without adjusting the translation stage, I checked the NLG at a few power levels for a threshold measurement:
| OPO green transmission | max OPO IR PD (unamplified seed = 1.49e-3) | green launch power | NLG |
| 24uW | 0.435 | 21mW | 297 |
| 12uW | 0.0114 | 10mW | 7.8 |
| 18uW | 0.0423 | 15.2mW | 28.97 |
We got rid of the global ir_locked_refl_min in the OPO guardian and replaced it with a self.ir_locked_refl_min in only the LOCKED_SEED_DITHER state.
We moved FC1 and FC2 back to where they were in O4 according to the osems, and walked ZM3 to keep the OPO IR seed dither lock on SZT7. Gabriele and I went to SQZT7 and tried to re-align the FCGS refl diode, I think I put the wrong beam on the diode.
We opened the beam diverter and we can see the seed beam on AS A, B, and C. We tried engaging the centering servos as in 88767, but this saturated ZM4. We would like to run an interferometer alignment to check the alignment of SRM, OM1, and OM2 before we walk the ZMs.
