There was some discussion about the prospects for pushing up the CARM bandwidth to better suppress frequency noise above several kilohertz. Since we currently run with a 20 kHz UGF or so, adding more gain would require a UGF that approaches (or exceeds) the FSR.

The attachment shows the CARM OLTF taken in the viscinity of the FSR, showing the expected dip and (overcoupled) phase feature in the optical plant. The feature does not have infinite Q, so in principle any secondary UGFs could be eliminated, though it would be tricky. The HWHM is 0.6 Hz, consistent with CARM intensity TFs taken previously.