I did some analysis on the ring heater cavity scan measurements from yesterday. I've plotted the region around [0.37, 0.63] FSRs. This region encompasses the PDH TEM00 sideband resonances [0.45 FSRs and 0.55 FSRs] and also the LG10 sideband resonances. I've taken this section of data for each cavity scan and removed the constant phase offset and also the linear variation in phase with FSR. I've then plotted the scans as a movie. Despite the noise and the relatively quick speed, you can clearly see the response of a higher order mode shifting in frequency [0.53 FSRs to 0.58 FSRs] as time progresses. This is consistent with the cavity g-factor changing as the ring heater is applied.

I've yet to quantify the frequency shift.