First I checked IR injection alignment. There was yaw misalignment and the mode matching was 89%.
After the alignment of yaw, the mode matching became 92% as follows. The injected BAB was 447uW. The misalignment is more or less fine, but LG is a bit larger than before.
| Mode | IR transmission |
| TEM00 | 480 |
| yaw | 102 |
| pitch | 104 |
| LG | 111 |
| offset | 95 |
By the way, during the alignment work, I noticed that the injection BAB power drifted a lot between 435uW and 465uW within a few minutes.
Then I locked CCFC and measured FDS (attached figure). CCFC calibration amplitude was 124mVpp, which is somehow lower than before. CCFC gain was 1000 and CC2 mass feedback gain was 3. The CCFC was stable and it kept locking during FDS measurement other than the squeezing quadrature. The 50, 100Hz bumps and detuning drift still exist.
Finally, I checked the nonlinear gain as follows. The nonlinear gain was 4.5 which corresponds to the generated squeezing of 10.2dB.
| green power (mW) | 0 | 20 |
| p pol PLL (MHz) | 245 | 185 |
| OPO temperature (kOhm) | 7.163 | 7.163 |
| BAB maximum (mV) | 57.2 | 256 |
| nonlinear gain | 1 | 4.5 |
I will replace the electronics for CCFC to investigate the 50 and 100 Hz bumps.
