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Entry  Tue Feb 20 13:59:30 2018, Koji, Update, General, Modulation depth measurement for an aLIGO EOM 
    Reply  Thu Feb 22 16:11:14 2018, Koji, Update, General, aLIGO EOM crystal replacement IMG_3421.JPGIMG_3426.JPGIMG_3427.JPG
       Reply  Thu Feb 22 17:19:47 2018, Koji, Update, General, Modulation depth measurement for an aLIGO EOM IMG_3436.JPGmodulation_depth.pdfmodulation_linearity.pdfmodulation_24MHz.pdf
          Reply  Mon Apr 2 15:14:21 2018, Koji, Update, General, Modulation depth measurement for an aLIGO EOM modulation_depth.pdfimpedance_eom.pdf
Message ID: 13725     Entry time: Mon Apr 2 15:14:21 2018     In reply to: 13652
Author: Koji 
Type: Update 
Category: General 
Subject: Modulation depth measurement for an aLIGO EOM 

The new matching circuit was tested.

Results:

f_nominal  f_actual  response    required mod.  drivng power
 [MHz]      [MHz]    [mrad/V]     [rad]         needed [dBm]
  9.1       9.1        55         0.22      =>   22
118.3     118.2        16         0.01      =>    6

 45.5      45.4        45         0.28      =>   25
 24.1       N/A         2.1       0.014     =>   27

Comments:

- 9.1MHz and 118.3MHz: They are just fine.

- 24.1MHz: Definitely better (>x3) than the previous trial to combine 118MHz & 24MHz.
  We got about the same modulation with the 50Ohm terminated bare crystal (for the port1).
  So, this is sort of the best we can do for the 24.1MHz with the current approach.
  The driving power of 27dBm is required at 24.1MHz

- About the 45MHz
  - The driving power of 27dBm is required at 24.1MHz
  - The maximum driving power with the AM stabilized driver is 23dBm, nominally to say.
  - I wonder how we can reduce resistance (and capacitance) of the 45MHz further...?
  - I also wonder if the IFO can be locked with reduced modulation (0.28 rad->0.2 rad)
  - Can the driver max power be boosted a bit? (i.e. adding an attenuator in the RF power detection path)

 

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