Nutsinee Terry Daniel

We started commissioning the CLF path of the squeezer. While adjusting the CLF polarization, we noticed that there was no half-wave plate in the first rotation stage. Then, we found that the half-wave plate for adjusting the CLF power was for green.

Since we were on a roll, we started investigating why the half-wave plate in the green reflected path of the OPO that adjusts the power onto the photodetector with a polarizing cube, let us only go as low as ~6% in the rejected path. First, we removed the half-wave plate altogether and saw no difference. Then, we used a quarter-wave plate and were able to reduce the rejected light to about 3%. Finally, we used both half- and quarter-wave plates and saw a reduction down to <1%. We are concluding that about 5% of the light in the OPO path on SQZT6 is p-polarized with a 90° phase shift (meaning circular polarized). How?