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Message ID: 17076     Entry time: Thu Aug 11 17:15:33 2022
Author: Cici 
Type: Update 
Category: General 
Subject: Measuring AUX Laser UGF with Red Pitaya 

TL;DR: Have successfully measured the UGF of the AUX laser on my Red Pitaya! Attached is one of my data runs (pdf + txt file). 


  • Figured out how to get a rudimentary coherence (use scipy.signal.coherence to get Cxy = abs(Pxy)**2/(Pxx*Pyy), then find what point is the closest to the frequency I'm inserting on that iteration of the swept sine and get the coherence closest to that). Not precisely the coherence at the frequency I'm inserting though, so not perfect... more of a lower bound of coherence.
  • Figured out how to get the UGF from the data automatically (no error propagation yet... necessary next step)
  • Put my red pitaya in the X-arm AUX laser control electronics (thank you to Anchal for help figuring out where to put it and locking the x-arm.) Counts dropped from 4500 to 1900 with the x-arm locked, so 58% mode matching. I lose lock at an amplitude >0.05 or so.
  • Wrote a little script to take data and return a time-stamped text file with all the parameters saved and a time-stamped pdf of the TF magnitude, UGF, phase, and coherence, so should be easy to take more data next time!


  • need to take more accurate coherence data
  • need to propagate uncertainty on UGF (probably high...)
  • take more data with higher coherence (the file attached doesn't have great coherence and even that was one of my better runs, will probably increase averaging since increasing amplitude was a problem)
Attachment 1: rpi_OLG_2022_08_11_16_51_53.pdf  28 kB  Uploaded Thu Aug 11 18:17:02 2022  | Hide | Hide all | Show all
Attachment 2: rpi_OLG_2022_08_11_16_51_53.txt  5 kB  Uploaded Thu Aug 11 18:27:17 2022  | Show | Hide all | Show all
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