[Aritomi, Yuhang]

We replaced a TAMA mixer with a new mixer (ZX05-1L-S+) and a low pass filter (SLP-1.9+) for CC1. CC1 error signal with the new mixer and TAMA mixer are shown in Pic. 1,2. SNR with the new mixer seems much better and there is no offset in the new mixer. Note that CC1 servo offset should be 5.

Then we locked CC1. CC1 gain is 2 for 25mW green. Pic. 3 shows CC1 OLTF. UGF is 3.7 kHz and phase margin is 50 deg. Pic. 4 shows CC1 phase noise. CC1 rms phase noise is 84.2 mrad and squeezing phase noise from CC1 is 84.2/2 = 42.1 mrad.