SubCarrier and BAB mode-matching (MM)
In order to improve the MM of the SubCarrier beam, we slightly changed the telescope for the injection into the Faraday Isolator.
The new telescope is composed by two lenses with a focal lenght of 60 mm. The first one is placed at 302 mm from the collimator inside the SC box and the distance between the two lenses is of 123 mm.
In order to increase the BAB power reflected by the output polarizer and take it as a reference to overlap the SC beam, we rotate the HWP mounted on a motorized rotational stage (Newport model AG-PR100V6), that is located in the mechanical mount of the Faraday isolator, by using the AG-UC2 Agilis motor controller, provided by EGO optics lab.
The two beams are well overlapped but the mode matching needs to be further improved. We repeated the characterization of the BAB.
A check, consisting into the coupling of the reflected BAB into the fiber used for the SC, is ongoing.
Due to parallel activities in DET lab, we did not have time to complete this task. In the available time slot, we continued the work on the overlap of BAB and SC beams.
We coupled the BAB reflected by the Faraday Isolator into the fiber used for the SC; in figure "BABcoupling.png" we can see the spot of the BAB we observed at the input collimator of the PLL box.
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