According to the measurement yesterday, we made the new design for the telescope, this time seems we could use one telescope to get gouy phase around 90 degree difference in two axis of the beam.

Firstly, we calculated the reflection beam waist position according to the measuremnt. (colors refer to different curves in last entry)

The size of the waist in two direction seems much closer than all the measurement we did before.

Then because the space limitation, we fixed the two quadrant position as before, which is around 1.9m and 2.3m from the FI, and both the positions have some margin of 5cm.

The beam we used to first determine the lens is the orange one, because it has smaller divergence than the other one. So with the orange as the initial beam, we tried to put different focal length, and move the lens position to have the beam waist around 2.1m which is in the middle of the two quadrants. By checking the gouy phase difference, we could know that we need longer focal length or shorter.

The final results we got is to put a lens with focal length of 1m, and 0.82m from the FI. 

Then the quadrants information are as below

Then use the distance to calculate the gouy phase of the other beam axis (blue). By slightly adjusting the lens position and the quadrants position, we could get the gouy phase difference around 90 degree for both axises. In this case the lens position is 0.75m.