M. Todd, S. Dwyer
We moved the OPO crystal around again, following the work we did last week. We had much better luck this time with the translation stage controller (until the end, where we seemed to lose where we were).
After we took the measurement at -1100, we decided that given the historesis in the controller the better way to go back to a "position" was to set our OPO temperature to the value that corresponded to that position and move the controller until we re-found the green/ir coresonance.
We tried this, and then got veeery lost. But eventually found our way closer to our high NLG and ~31.4 OPO crystal temp, but it was not at the position we expected it to be at. This method may be refined in the future, where instead of doing finite steps with the controller to map out the NLG parameter space, we could sweep the OPO temp and follow it with the controller position via the co-resonance.
Regardless, we are at a much higher NLG than when we started!
| Position | Max | Thermistor | Green Launch | Unamplified | Dark | NLG | Pthres | P | Notes |
| 0 | 6.70E-02 | 30.28 | 29.4 | 7.11E-03 | -2.70E-05 | 9.39 | 117.51 | 105 | 9:22:03 AM |
| 100 | 4.52E-02 | 30.14 | 22.5 | 7.11E-03 | -2.70E-05 | 6.34 | 124.67 | 105 | 9:45:12 AM |
| -100 | 5.98E-02 | 30.214 | 27.7 | 7.11E-03 | -2.70E-05 | 8.38 | 119.22 | 105 | 9:59:40 AM |
| -300 | 7.83E-02 | 30.42 | 30.7 | 7.11E-03 | -2.70E-05 | 10.97 | 115.53 | 105 | 10:07:48 AM |
| -500 | 1.08E-01 | 30.719 | 30 | 7.11E-03 | -2.70E-05 | 15.14 | 112.43 | 105 | 10:16:46 AM |
| -700 | 1.20E-01 | 31.164 | 27 | 7.11E-03 | -2.70E-05 | 16.82 | 111.64 | 105 | 10:26:05 AM |
| -900 | 2.11E-01 | 31.397 | 31 | 7.11E-03 | -2.70E-05 | 29.57 | 108.68 | 105 | 10:33:52 AM |
| -1100 | 1.62E-01 | 31.348 | 27 | 7.11E-03 | -2.70E-05 | 22.70 | 109.84 | 105 | 10:48:45 AM |
| -2880 | 1.70E-01 | 31.364 | 27 | 7.11E-03 | -2.70E-05 | 23.82 | 109.60 | 105 |
I think that what has been happening is that we have slowly drifted away from our phase matching temperature in the OPO as we have moved spots. Conceptualy, we'd like to adjust the translation stage for co-resonance with the temperature servo set to keep the crystal at the phase matching temperature. In reality, the actual temperature temperature that we get for a particular temperature servo set point is not the same for different crystal positions because of local heating from green absorption. This last week's expirience leaves me more conviced that we can't rely on the translation stage counts for information about where we are in the crytsal.
In the end, we did improve the nonlinear gain today, but our squeezing angle servo was not doing well in the previous lock and seemed to be causing large range fluctuations. We dropped out of observing for a few moments to turn off the servo and scan the squeezing angle, but this didn't restore us to a good range. Now we have lost lock for some other reason, and I've set the OPO trans power set point down to 80 uW (it was 105), which according to RF6 gives us a similar NLG to what we had before the crystal move. I've adjsuted the OPO temperature for this green power.
For operators: When we relock, we will want to run scan sqz ang again before going to observing, and we might need to run it again later once the IFO has thermalized.