Marc, Michael and Yuhang

We tried to tilt the lenses of homodyne to reduce back scattered noise at low frequency. However, it seems it didn't work.

After the improvement of IRPS, we confirmed that there is not amplitude noise or beam jittering noise from the LO. So the input mirror feedback loop really reduced the back scattered noise.

Note: to close input mirror feedback loop, we had to improve the gain of the old loop.

We made a few more comparison yesterday. The noise and reduction is shown in the attached figures. From this measurement, the reduction of back scattered noise is not the same at all frequencies.