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Entry  Thu Sep 16 15:21:21 2021, Paco, DailyProgress, 1418 nm AUX ECDL, Free space AOM 
    Reply  Wed Sep 22 16:44:34 2021, Radhika, DailyProgress, 1418 nm AUX ECDL, Free space AOM 
       Reply  Mon Oct 4 17:44:34 2021, Radhika, DailyProgress, 1418 nm AUX ECDL, Free space AOM 
          Reply  Tue Oct 19 13:52:03 2021, Radhika, DailyProgress, 1418 nm AUX ECDL, 1418nm ECDL Frequency noise ECDL_diagram.pdfECDL_FNM_13-10-2021_151524.pdf
             Reply  Tue Mar 8 09:32:56 2022, Paco, DailyProgress, 1418 nm AUX ECDL, 1418nm ECDL Frequency noise schematic.pngraw_bn_spectrum.pngphase_timeseries.pngecdl_freqnoise.png
Message ID: 1924     Entry time: Thu Sep 16 15:21:21 2021     Reply to this: 1925
Author: Paco 
Type: DailyProgress 
Category: 1418 nm AUX ECDL 
Subject: Free space AOM 

[Paco,  Radhika]

Uninstalled the fiber AOM and temporarily removed the third fiber 2x2 port beamsplitter. We are now using this free-space AOM. Then, I managed to launch one of the outputs of the second fiber beamsplitter into free space using a F220APC-1550 fixed collimator. The beam clears the  AOM aperture nicely and lands on the other side.

This AOM operates at a RF frequency of 35 MHz, so we set up a sweep on the Marconi to cover a window of 35 MHz +- 15 MHz. Using an IR detector card, we looked for evidence of 1st-order diffraction (from the setup geometry, the 1st order beam should have been visibly discernable). We first scanned the AOM across yaw but did not notice diffraction. Then, Paco lowered the height of the fixed collimator and we repeated scanning across yaw. We eventually saw the beam "jump" - diffraction! We adjusted yaw until we recovered both 0th and 1st order beams, at 50/50 intensity.

In summary, the free-space AOM works and we have managed to see 1st order diffraction. Next steps will be to quantitatively measure this diffraction while sweeping across RF frequency and power.

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