P-polarization Maps of OSTM (SK)

[Simon, Pengbo]

We have started to analyze the coated OSTM.

First, we took out the OSTM and inspected the mirror visually. We found pencil marks on the barrel and among them an arrow that indicates the thicker side of the wedged substrate and shows toward the HR side of the mirror.

The orientation which we choose for the measurement is to put the thicker side upside first and then rotate it by 90 degrees(with the thinner side facing the PC). Thus we only need to consider the horizontal deflection of the beam. After the adjustment of the sample, we found no output beam from the other side of the sample which mainly due to the coating absorption. So we removed one of the two ND filters to increase the laser power.

Second, we started the adjustment of the IU.

Due to the deflection effect, we first changed the lens position to make sure the beam goes through its center. Secondly, we rotated the second PBS slightly to have a perpendicular incident of the beam. Then, we adjusted the position of the two photodiodes so that the s-polarized beam and the p-polarized beam can hit the center area, respectively. Because we were doing the P-polarization measurement, the s polarized beam is nearly invisible, so we used the oscilloscope to finish the adjustment.

Then we ran the polarization map scan in the center with a 15mm radius. Attached to this report is the P-polarization map.