[Jeff, Torrey]

The background for this is we have noticed 10's of kHz ringing up in the timeseries of the error signal when the gain on the fast controller gets too high. On the computer app where we can control multiple instruments at once we have increased the gain and taken spectrums while the cavity is locked. The plan is to do this for the thorlabs laser and the teraxion laser and compare the two. We are waiting on an optical isolator to conduct the teraxion half of this experiment, in the mean time here is the thorlabs laser data.

The following data is for locking OFC1, with the thorlabs laser, while controlling from the computer app. thorlabslaservaryingcontrollergain.png are the results. We can see a clear increase in the noise around 20 kHz as the controller gain is increased. It will be interesting to see if a similar feature is there when using the teraxion laser. Note the controler UGFs are listed between 2-18 hz, but there are several gain increases between the controller and the laser, so they should not be taken as the UGF of the whole loop.

We still plan on taking TF's instead of this analysis. For now, the smallest excitation strength on the moku (1mV) is too large. We are working on this.