[Hirose, Tanaka, Takano Ushiba, Fujimoto]

Abstract

We performed the phasing of AS34-I during PRMI 3f lock.
As a result, AS34-I improved from ~0.14 to ~0.18. The value measured with SRMI (f1 resonant) was also ~0.18.
The agreement between these two values is consistent with theoretical expectation.
From these results, the AS34-I value expected for DRMI is estimated to be ~5.8.

Details

While PRMI was locked with the 3f signals, we adjusted the demodulation phase so as to minimize AS34-Q:

     K1:LSC-AS-PDA2-RF34-PHASE-R: -90 -> -126

With this adjustment, AS34-I in PRMI with 1.1 W input power improved from ~0.14 to ~0.18.

In addition, AS34-I was also measured to be ~0.18 when SRMI was locked with f1 resonant.
For PRMI and SRMI, the theoretical transmissivity of the f1 sidebands to AS34 are 3.0% and 3.1%, respectively, assuming PRM reflectivity of 90%, MI reflectivity of 14% for f1, SRM reflectivity of 85%, and ideal Schnupp asymmetry, PRCL, and SRCL.
Since the two transmittances are almost the same, the agreement of the two measurement results is consistent with the theoretical expectation.

The expected transmissivity of f1 to AS when DRMI is locked is 97%.
Therefore, AS34-I in DRMI is expected to be amplified by a factor of about 32 compared to SRMI, resulting in an expected AS34-I value of ~5.8 for DRMI.