[Aritomi, Eleonora, Yuhang]

Since we found the problem of unbalance of homodyne, we replaced the wrong coating lens. 

After that we measured the noise spectrum. We can see from this spectrum that

1. The shot noise is limiting above 900Hz. However, there are several peaks still existing in the shot noise region.

2. There is a noise with slope of 1/sqrt(f) below 300Hz. Noise source could be scattering, beam jittering, vibration.

3. We recognize there is 600Hz which comes from molecular pump for vacuum.