Aritomi and Yuhang

We checked power at several points this Monday and make IRMC transmission set at 1.7mW.

Actually, this means we increased also the error signal(or increase gain). Today we checked the error signal, and actually, it was quite close to oscillation. So we adjusted the gain while looking at the error signal and measured transfer function again. In the end, we put the gain value of the control board from 1.3 to 0.8.

The open-loop transfer function now is as the attached figure 1.

We also measured the IRMC error signal spectrum while IRMC is unlocked and locked. As shown in the attached figure 2. From this locking performance, we could see that the loop suppresses the even harmonics of a fundamental 9Hz oscillation while there are still some odd harmonics left. Also, the 50Hz and its harmonics are introduced after closing the loop. So the PD doesn't introduce any 50Hz noise.