Yuhang and Michael
After the OPO alignment optimization, it was found that PDH signal was lost. Today, we found what is causing this problem: the OPO transmission PD is misaligned (drop from more than 5V to ~50mV). After aligning OPO transmission PD back, the PDH signal is recovered. (It was checked that the signal sent to EOM is 2Vrms, according to logbook2469, the modulation strength is 0.1-0.3rad/V, so we should have a modulation of 0.2-0.6rad. If we have 0.6rad, we should see about 10% power drop from carrier. If we have 0.2rad, the power goes to sidebands should be negligible. the modulation should be almost negligible since we didn't observe a power decrease after sending modulation)
Then we measured OPO generated green power as a function of OPO temperature. The measurement offset power on power meter is 3.3uW. We take measurement from temperature controller reading 7.7kOhm to 6.5kOhm with a step of 0.02kOhm.
These are the measurements results
| 7.700 | 7.680 | 7.659 | 7.640 | 7.620 | 7.601 | 7.579 | 7.560 | 7.540 | 7.519 | 7.500 | 7.480 | 7.459 | 7.440 | 7.420 | 7.400 | 7.380 | 7.361 | 7.339 | 7.320 | 7.299 | 7.280 | 7.260 | 7.240 | 7.220 | 7.200 | 7.179 | 7.160 | 7.140 | 7.119 | 7.099 | 7.080 | 7.059 | 7.040 | ||||||||||||||||||||||||||
| 93.0 | 93.4 | 94.0 | 94.3 | 94.5 | 94.6 | 94.6 | 93.8 | 94.2 | 93.7 | 94.6 | 96.0 | 97.7 | 99.8 | 102.2 | 105.3 | 109.0 | 112.5 | 116.8 | 120.5 | 122.8 | 123.0 | 120.0 | 114.5 | 106.9 | 99.0 | 92.5 | 87.0 | 81.7 | 77.6 | 73.0 | 68.7 | 65.0 | 62.6 |
However, during this measurement, we found that the OPO lock was having some issues due to the disturbance from temperature change while OPO kept locked.
Thus we performed again the measurements with a OPO unlock/lock between each measurement. This new measurement didn't have locking issue and will be reported later as a comment to this logbook.