R&D (FilterCavity)
EleonoraCapocasa - 08:04, Monday 14 May 2018 (773)
Comment to Comparison of old and new servo (Click here to view original report: 760)

The error signals for green and infrared account for the closed loop laser frequency noise filtered by the pole of the cavity  (which is different for green and IR).

In the fist attached plot, the error spectra has been divided for the corrispondig pole in order to go back to the close loop laser frequency noise.

freq nois =  err sig * ( sqrt( 1+(f/f0)^2)     with f0 = 55 Hz for IR and 1.45 kHz for green

The two curves obtained shoud be coincindents. The discrepancy (about a factor 2.5) suggests that there is maybe an issue with the calibration.

Images attached to this comment
773_20180514005813_irvsgreefn.png