[Nutsinee, Sheila, Terry, Haocun]

We have some issues on locking the OPO with high green power, which can also effect the NLG measurements, etc.

A back-up issue is that we have this asymmetry and "cut-off" of green resonant peak when scanning the cavity. The reason was unclear and one of the postulate is that the crystal temperature increase when closing to the resonance which lengthen the cavity and the pzt is trying to compensate this effect.

At the same time, we found that when the green power is high (REFL>5mW), the control loop doesn't lock at the peak resonance, but having an "offset" which seems can be adjusted by moving pzt manually. I remember this also happened at LLO before..

We suspect these two issues can be related in some way.. Yesterday we took the cavity scan again by using different green power input with error signals. The plot showing is using 3mW, 10mW and 20mW with OPO temp = 23C. Phase matching temp gives similar results. We also moved the crystal position, trying to find some part of crystal giving less absorption, but failed.

The "cut-off" becomes serious with increasing power, and the error signals are totally abnormal when the power is higher than 3mW.

I noted that when increasing the power, (2nd attachment), some higher order modes (or carrier?) gets closer to the 00 mode, but not sure whether this can cause any problem on the error signal.