[Aritomi, Yuhang]

The procedure we did for aligning homodyne is:

1. Lock IMC and driving IMC end mirror with a ramp signal(1kHz 50mV). This will drive the output of IMC moving around the locking point. If we lock well on the peak value of IMC transmission. We will see the double frequency of the end mirror driving frequency. In this case we can use the modulated IMC transmission signal.

2. Connect homo-dyne and put it roughly in a good height and good horizental position. Here look at modulated IMC tra signal and make it maximum. Then fix homodyne.

3. Put lens in roughly the corresponding focal length of lens away from homodyne. Then roughly make the signal maximum again. Then fix lens.

4. Adjust lens so that we can further maximize.

After that we take the modulated signal both on oscilloscope and spetrum analyzer. Also take the signal when one of PD blocked or neither of them blocked.

The first three attached figure is for oscilloscope. The first one is when the second PD is blocked. The second figure is when the first PD is blocked. The third figure is when neither if them is blocked. (first PD is the nearest PD to IMC) (note here IMC is not locked on peak)

The next three figure is for block second PD, block first PD and no block. (here IMC is locked on peak)

Optimization is still needed.