[Yuhang, Eleonora]

We have continued the investigating about the cause of the missing PDH signal for the OPO.

1) We tested the OPO photodiode on the SHG and we were able to see a clear PDH error signal (with a IR beam with a power of about 80 uW). See  pic 1. 

2) We checked again (with a large bandwidth oscilloscope) the amplitude of the RF signal sent to the EOM. It seems to be about 18 dBm (5V pp)  which corresponds to a modualtion depth of 0.5 rad, that, for sure, is not too small.

3) FInally we removed the EOM from the bench and we ispected it. Indeed the crystal looks damaged. see pic 2. We sent the picture to Qubig and  they also confirmed that the crystal is not healty and need to be changed. They suggest us to ship the EOM back to proceed with the reparation. We are now organizing the shipping.