Sheila, Daniel, Terry, Nutsinee, Craig, Jenne, and others who were cheering in the control room
Today H1 saw (pre-O3) squeeze/anti-squeeze for the first time.
0.9 dB SQZ and 3.3 dB ASQZ at a non linear gain of 2.28.
We used the lowest amount of CLF we could reasonably operate at, 0.05mW into the coupler. 20.5 mW of pump was sent into the coupler on the ISCT6 (this corresponds to ~2.6-2.7 mW hitting the OPO, the nlg wasn't optimized before we injected the squeezing but that's about the best we've seen). We read -15dB of 3MHz demod signal from the Homodyne. The common gain at the LO common mode board was 7dB which gave us a UGF of 10kHz with plenty of gain margin. Boost 1 and 2 on the common path was turned on.
Sheila has the sqz/asqz plot and the OMC DCPC traces. I have LO phase noise measurement. We will be posting these plot later.
Things we could optimize still is the alignment (which wasn't done at the beginning of the lock acquisition, we did try our best to optimize it while the LO was locked). A single bounce measurement with tonight's alignment should give us a loss estimate.
We locked the interferometer in a state that had a lot of DHARD noise, so that we would have a chance to make some measurements with the squeezer. The DHARD noise is dominating the spectrum below about 300 Hz.
Some times:
First set of measurements, before Nutsinee pushed the LO loop ugf to about 10 kHz and added the boosts:
After the LO loop was set and we made some small alignment tweaks:
The second attachment shows what these squeezing and anti-squeezing levels roughly mean for a nonlinear gain of 2.3 which is what Nutsinee measured. This indicates that our total efficency is something around 50%, since we have 19.5% known losses this means that we have almost an additional 40% losses somewhere. We tried to walk the beam a littel using ZM1+2, but we would like to take some time with the squeezer beam reflected off the SRM and the interferometer unlocked to make sure that we are not close to clipping on anything. The first measurement taken before Nutsinee adjusted the LO loop implies something between 350-375 mrad of phase noise, after tuning the loop we saw a bit more squeezing but this still implies a large phase noise, something between 300 and 350 mrad.
NICE!!!!!
Fantastic!
Nicely done LHO Team!
Here's a quick look at the sqz angle phase noise from that night. I haven't had time to add them all up but this plot should give you all the information you need. Right now we believe that LO is mostly seeing CLF noise and its own sensing noise. So the low limit sqz angle phase noise is sqrt(CLF rms^2 + CLF sensing rms^2 + LO sensing rms^2). Look at ~100Hz for example, the low limit of sqz angle phase noise would be sqrt(11.4^2+0.69^2+0.88^2) = 11.5 mrad.
Also attached a very crude plot of an in-loop TTFSS spectrum up to 5 MHz for those who might be interested. Overall noise projection is coming.
*update* The previous TTFSS plot wasn't calibrated properly. I've replaced the plot with a new one that's actually in Hz/sqrt(Hz).
Awesome!