NAOJ GW Elog Logbook 3.2
Marc, Michael, Yuhang
Recently, homodyne alignment was optimized. Frequency independent squeezing was remeasured. From this measurement, 6.5dB squeezing was measured. Compared with the measurement in elog1837, 1dB more squeezing has been achieved. The main difference between these two measurements is the homodyne alignment.
In this measurement, 37mW pump power was used. Therefore, there should be 15dB original squeezing.
If we assume 20mrad of phase noise, 6.5dB squeezing corresponds to 19% optical losses.
If we assume 30mrad of phase noise, 6.5dB squeezing corresponds to 17% optical losses.
The old measurement was indicating 26% optical losses. Therefore, at least 7% optical losses has been reduced.
The known losses are 1-(1-7e-2)*(1-1e-2)*(1-3e-2)*(1-2e-2)*(1-3e-2)*(1-1e-2) = 16%. 7% OPO intra-cavity losses, 1% dichroic mirror, 3% Faraday isolator, 2% mirror and lens losses, 3% homodyne efficiency/quantum efficiency, 1% classicial noise. Therefore, about 1% to 3% optical losses are not figured out. We will make more characterization tomorrow.
We made further anti-squeezing and squeezing measurement. This measurement indicates optical losses to be 19.1%, phase noise to be 20.5mrad.
Therefore, we still have 3% optical losses which are not known.
The ideal sqz-asqz for current set-up and improved set-up are shown as well.