[Tanaka,Saito]

Based on the optical layout plan in klog:36739, we installed a newly purchased FI, a beam sampler, and mirrors. The transmission of the FI reached approximately 85%.

• We replaced the contaminated FI reported in klog:36739 with a newly purchased one (Photo 1). This FI has an aperture of 3 mm. Since the laser beam radius at the planned position in the optical layout is about 1.2 mm, we placed the HWP, PBS, and mirrors upstream of the FI as close together as possible, reducing the beam radius at the FI position to approximately 0.8 mm. After alignment, the input power was about 154 mW and the output power was about 131 mW, corresponding to a transmission of approximately 85%. A beam sampler with a reflection-to-transmission ratio of 9:1 was installed after the FI. Six mirrors were placed on the reflection side of the beam sampler.

Unfortunately, since the right-side wall shown in Photo 1 cannot be removed, it is difficult to install an additional mirror and perform alignment.