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Entry  Fri Apr 30 12:07:25 2021, aaron, DailyProgress, Laser, marconi locking 252D9563-0122-418B-9B97-29D44FEF83E9.jpeg
    Reply  Fri Apr 30 15:15:33 2021, rana, DailyProgress, Laser, marconi locking 
       Reply  Mon May 3 23:28:56 2021, rana, DailyProgress, Laser, delay line frequency discriminator DFD.jpg
          Reply  Wed May 5 11:54:19 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 9x
             Reply  Wed May 5 22:21:17 2021, rana, DailyProgress, General, delay line frequency discriminator 
             Reply  Thu May 6 10:48:40 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 3EFFFA27-AAF6-434F-A1AB-FE7C657A464C.jpegDL_3CH.pdf
                Reply  Tue May 11 14:37:48 2021, aaron, DailyProgress, Laser, delay line frequency discriminator, current noise measurement 
                   Reply  Wed May 12 15:35:09 2021, aaron, DailyProgress, Laser, delay line in a box 69A8E6A2-7F85-464E-BDAA-8C6BBD2910B5.jpeg1D05A31E-7DBC-448B-A2F4-A8805EFAC393.jpeg25C2DD1E-7776-491E-BBCE-5F2D1EA935E3.jpeg
                   Reply  Wed May 12 16:52:08 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 3878D102-C5BB-46AE-B90B-540CFDE3100B.jpegSPSR785_NX_12-05-2021_173959.pdfSPSR785_SX_12-05-2021_183434.pdfSPSR785_NS_12-05-2021_191513.pdf
                      Reply  Thu May 13 16:31:40 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 6x
                         Reply  Thu May 13 19:09:16 2021, rana, DailyProgress, Laser, delay line frequency discriminator 
                         Reply  Fri May 14 18:43:25 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 994ECC7F-C5FE-4E7B-8F19-B1C118DCE6CE.png
                            Reply  Thu May 20 12:50:56 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 
                               Reply  Fri May 21 14:15:21 2021, aaron, DailyProgress, Laser, current noise of custom current drivers 5012D147-8B13-478C-BB83-57A71A2B304A.jpeg467DEC59-01B1-40CD-9F4E-4D9D87183A78.jpegABC2A51B-6726-4F9C-AD88-551ED7C90EEF.jpeg
                               Reply  Tue Aug 17 14:04:27 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 3A1E242C-F4F6-4A87-B2E8-E74839BE542C.jpeg
                                  Reply  Wed Aug 18 09:55:13 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 0A96102F-5465-456B-93BF-E2B9D4A7E96C.jpegtrim.2553D656-98A0-442D-9185-4C5252B2B727.MOVtrim.787F04FC-8DED-4501-B67D-FF98EC5D5D56.MOV
                                     Reply  Thu Aug 19 14:21:35 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 007FC2D7-F29B-4636-9CE7-04CBC3B789F7.jpeg1F1E68F0-199F-4E1C-B909-883A521E06CF.jpegScreenshot_from_2021-08-19_17-53-58.png
                                        Reply  Fri Aug 20 11:03:44 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 30A43669-5DFF-400A-BEB4-7EF71BBAE1A6.jpegA3BF5DA5-32E5-42A5-A1D8-9270C3D88518.pngScreenshot_from_2021-08-20_16-11-26.pngScreenshot_from_2021-08-20_16-20-48.png
                                           Reply  Mon Aug 23 13:38:57 2021, aaron, DailyProgress, Laser, delay line frequency discriminator Screenshot_from_2021-08-23_16-42-48.png
                                              Reply  Tue Aug 24 16:44:39 2021, aaron, DailyProgress, Laser, delay line frequency discriminator beats_regions.pdfTeraxion_noise.pdfEW_timeseries.pdf
                                                 Reply  Thu Aug 26 11:58:50 2021, aaron, DailyProgress, Laser, delay line frequency discriminator 9x
                                                    Reply  Fri Aug 27 15:27:38 2021, rana, DailyProgress, Laser, delay line frequency discriminator 
                                                    Reply  Tue Aug 31 15:14:28 2021, aaron, DailyProgress, Laser, quieting the Rio W and Teraxion beat notes, but not much help beats_regions_base2.pdfbeats_regions_base2.pdfTeraxion_noise_base2.jpgDLFD_foam.pdf
                                                       Reply  Wed Sep 1 12:20:18 2021, rana, DailyProgress, Laser, quieting the Rio W and Teraxion beat notes, but not much help 
                                     Reply  Thu Aug 19 16:32:47 2021, rana, DailyProgress, Laser, delay line frequency discriminator 
       Reply  Tue May 4 10:50:22 2021, aaron, DailyProgress, Laser, marconi locking 6DC5CB12-BCDF-4550-AFB8-42D3DC354AED.jpegSPSR785_04-05-2021_152326.pdf
          Reply  Wed May 5 00:27:10 2021, rana, DailyProgress, Laser, marconi locking 
Message ID: 2807     Entry time: Tue Aug 31 15:14:28 2021     In reply to: 2802     Reply to this: 2808
Author: aaron 
Type: DailyProgress 
Category: Laser 
Subject: quieting the Rio W and Teraxion beat notes, but not much help 

Between 0.5 and 50 Hz, there are a couple of regions where the Rio W laser noise dominates the three corner hat measurement. And, below 0.3 Hz, the Teraxion laser noise dominates the measurement. Today I'm going to try to quiet these two lasers a bit to make a slightly improved three corner hat estimate.

I'll be looking at the output of the delay line frequency discriminator (DFD) on the moku spectrum analyzer, so I've swapped in the 1.9 MHz lowpass filter for the one Rana was using to check the noise out at MHz.

I saved the following traces on an SR785, but with a nonfunctioning GPIB so ended up storing them on a floppy drive.

  • Baseline Rio W x Teraxion beat note spectrum, as measured by phasemeter to Moku / SR785
  • Beat note spectrum after securing the fibers and Faraday isolators to the table, and moving the Rio W laser to a different operating point. 
  • "" after adding a layer of foam atop the fibers
  • "" after turning off the HEPA blowers. Noticed several noise lines around 100-300 Hz substantially reduced after turning off the HEPA.

I saw minor improvements to the Rio W x Teraxion beat note spectrum, and took 20 minutes of data for each beat note. Dropbox upload failed several times, so I sent it to my laptop via ipad file storage and airdrop. After swapping fiber connectors and covering with foam, the system took ~15-30 minutes to equilibrate each time (though perhaps longer would have been prudent, since I still saw low frequency drift up to 4 MHz during the 20 min measurement time). No improvement to the estimate on Teraxion laser, and if anything the West laser was even more noisy relative to Rio E and Teraxion, across a wider frequency band (almost the entire band from 30 mHz - 90 Hz). The foam and turning off the HEPA FFU did reduce the noise below 1 Hz, especially for the Rio E x Teraxion beat note. Figure 1 uses maximal averaging for every 2-fold frequency increase, on 20 minutes of data taken today (attachment 2 reproduces the relevant figure from last week's data, without the Marconi reference for better viewing). 

Attachment 3 is the updated Teraxion noise estimate. 

Update: attachment 4 is a comparison of the frequency noise (uncalibrated) for three different configurations: after taping down the fibers, after adding foam, and after turning off the HEPA blowers. I'm not sure why turning off the HEPA blowers increased the noise, maybe should have let the system settle longer? Despite the overall higher noise floor with HEPA blowers off, several peaks between 10 and 100 Hz were reduced. 

Attachment 1: beats_regions_base2.pdf  23 kB  Uploaded Wed Sep 1 00:35:35 2021  | Hide | Hide all
beats_regions_base2.pdf
Attachment 2: beats_regions_base2.pdf  23 kB  Uploaded Wed Sep 1 00:42:42 2021  | Hide | Hide all
beats_regions_base2.pdf
Attachment 3: Teraxion_noise_base2.jpg  526 kB  Uploaded Wed Sep 1 00:43:14 2021  | Hide | Hide all
Teraxion_noise_base2.jpg
Attachment 4: DLFD_foam.pdf  36 kB  Uploaded Fri Sep 10 16:24:07 2021  | Hide | Hide all
DLFD_foam.pdf
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