Vicky, Dhruva

Yesterday and today, we spent some time taking transfer functions of the LO, CLF and OPO loops at different levels of green pump power. The transfer functions for the LO loops were mesaured at both squeezing and anti-squeezing. I've plotted the transfer functions for the various loops at various pump powers/NLGs, along with plotting the UGFs and phase margins of all the loops as they vary with green power. 

OPO Loop 

Of all the loops, the OPO loop is most senstive to green power. The UGF goes from around 1kHz to about 2.2 kHz as the green OPO launch power increases from 4mW to 13.5mW. The phase margin reduces from 80 degrees to 60 degrees

CLF Loop 

As the non-linear gain increases, the CLF loop UGF increases from 1.3 to 1.7kHz where it levels off. The phase margin is around 24 degrees and doesn't vary too much with NLG. 

LO Loop 

For squeezing, the LO loop has a much higher UGF than for antisqueezing. This is expected as the LO error signal on squeezing has a much higher optical gain (this is because the error signal forms an ellipse in demod space where squeezing is close to the minor axis of the ellipse). The UGF is around 3.2kHz for SQZ and 1.2-1.5kHz for anti-squeezing. This doesn't vary much with NLG. The phase margin is around 50 deg for SQZ and 40 deg for antiSQZ 

I'm also attaching the raw data in zip files to the log along with screenshots of the CMB settings and a few .txt files that contain information about the green power, various RF levels and and non-linear gain.