Participants: Yuhang, Eleonora

After achieving the OPO internal alignement (entry #963) we removed the set up we used for this activity (periscope etc..) and we placed the OPO in the final configuration on the bench. (See optical scheme on the wiki  updated by Yuhang ) 

The first rough aligment was done with low power p-pole beam, placing the OPO in order to have its reflection superposed to the incoming beam and then using the last two steering mirrors for the fine alignment.

At the begining we had some trouble with the piezo:  since we were only able to get some slowly drifting mode of the camera in trasmission, we suspected that the piezo was not working.

First we check the piezo driver (which was fine), then we check the small box containing electrical connection between BNC from piezo driver and the piezo wires. As soon as we opened the box the piezo start working again. We observed that it was very sensitive to touch. To be checked further.

In the end we could achieve a good aligment, using CC beam (s-pol). See Pic.1. Anyway the trasmission seems much lower than what we expect.

We had only 0.5 mW trasmitted power over 218 mW of the input beam. That is less than 0.25%.

Assuming R1 = 92% and R2 = 99.75%, we should find T =  T1*T2 / (1-r1*r2)^2 = 10%

Are the values of R1 and R2 correct? Is the computation of T correct? 

This measurement has been done with no temperature control, anyway once we set it on the maximum of the TEM00, transmission seems to be resonably stable to perform the measurement.