[Yuhang, Eleonora]

We have locked the infrared mode cleaner. 

Some details:

1) P_in = 10mW  P_tra = 7.5mW  => Transmissvity: 75%   less then expected (90%) but enough for the homodine detection.

2) we locked it in reflection using a TAMA PD. See attached pic 1 and 2.

3) Since we use 15 MHz sidebands (same EOM as SHG) we could use TAMA demodulation board

4) We use a SR560 as temporary servo (1st order low pass, cut of frequency at 3 Hz, gain 10 after lock is engaged and 1 to acquire it) 

5) An attenuation of 40 dB had to be put on the demodulated signal before the SR560,  in order to avoid overload and be able to acquire the lock.

6) We measured the optical-mechanical TF (cavity + piezo). See attached plot (Fig 3). It Note that the high pass filter to compensate the low pass of the piezo driver has not be used. 

We have uploaded the data and the plot on the TFs wiki section.