Daniel, Naoki, Nutsinee

A following up of LHOalog68991 we injected frequency dependent squeezing with high CLF into DARM and looked at the coherence between our sqz laser intensity noise and DARM. In the end we increased CLF power by a factor of 8 and made DARM noise around 1.3kHz worse by 10.8%. Multiplying our previous CLF intensity noise projection of 3.7e-21m/sqrt(Hz) by sqrt(8) then add to our DARM noise floor at nominal CLF power of 2.95e-20 m/sqrt(Hz) in quadrature you get

sqrt((2.95e-20)^2+(10.46e-21)^2) = 3.13e-20 m/sqrt(Hz)

that is off from what we observed, 3.27e-20 m/sqrt(Hz), by 4.5%. It's not too crazy. Daniel's theory was intensity noise tumbles in phase but the ADF peak doesn't. If we tumble the phase of the ADF peak and project our noise floor from the mean value instead we might be closer. Something we intend to do during the next lock.

A coherence measurement between DARM and SQZ intensity noise demodulated at 3.125 MHz doesn't show much coherence but it's not nothing. The coherence is small but it does go up with CLF power. We are not sure what this means but the measurement could be an indication that our high CLF power could be intensity noise related.