[Aritomi, Yuhang, Yuefan (remotely)]

Yesterday we found IR reflection from filter cavity was only 33% of injection and IR on PR reference was 15% of injection. The reason was that polarization after faraday on the bench we recently installed was not s-polarization due to faraday rotator and some of BAB were lost in PBS before and after faraday in PR chamber. So we put HWP just after faraday on the bench and optimized the polarization. As a result, reflection from filter cavity becomes 85%.