I am going to conclude measurements of the finesse of the 775 filter cavity path. Currently my measurement yields 256.9 +/- 0.21 for the finesse of this path.

Brief recap on how this is done incase you missed the last few posts.

1) Lock the cavity with the 775 light.

2) Have a fast PD (BW > 1/100ns) in reflection and/or transmission of the cavity.

3) (If using REFL ensure channel is DC coupled.) Set the trigger mode on the moku to decaying edge, triggering on either probe point A or probe point B. Zoom in on the time axis to an appropriate window or the resolution won't be high enough to see the decay. The decay time for 775 light is on the order of 100's of nanoseconds.

4) Use the other moku that is power the AOM RF drive, and turn off the drive. 

5) You should see a decaying exponential, save data and repeat if necessary.

I have done this 5 times and saved the data in "\Nextcloud\GQuEST\B102\Output Filter Cavity\multiple_775_ringdowns\*.csv". Attached is a simple script that will parse all .csv files in a directory. Note for glob to work the directory should contain nothing but the data files you want to process. You should also uncomment the plotting lines to ensure your fits are working correctly. 

Now onto the 1550 path!