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Entry  Tue Jan 17 21:59:47 2012, tara, DailyProgress, optic, 14.75MHz EOM 
    Reply  Thu Jan 19 01:19:31 2012, tara, DailyProgress, optic, 14.75MHz EOM 
       Reply  Thu Jan 19 23:43:43 2012, tara, DailyProgress, optic, RCAV is locked 2012_01_19.jpg2012_01_19b.jpg
          Reply  Fri Jan 20 15:31:08 2012, Frank, DailyProgress, optic, RCAV is locked 
Message ID: 785     Entry time: Tue Jan 17 21:59:47 2012     Reply to this: 787
Author: tara 
Type: DailyProgress 
Category: optic 
Subject: 14.75MHz EOM 

As we decided to use lower sideband frequency (14.75MHz, instead of 35.5MHz), I replaced the Broadband EOM with 14.75MHz EOM.

==Motivation==

   The current broadband EOM give only small modulation depth (~0.06 rad with maximum power from the LO, seepsl:745) With a resonant EOM, we can get higher modulation depth with the same amount of power.

   Plus, in general, the RFPD's Q will be also higher at lower frequency, so we should get higher gain to suppress more frequency noise (the exact number of Q has not been measured yet).

==To Do/ Problems==

  We no longer use LIGO's old LO cards. All of the spares in the lab are also broken. We will use a function generator and adjust the cable length to change phase between LO and PD. 

 After I added the resonant EOM to the setup the beam path changed quite a lot, I need to re-aligned the beam before I can see the error signal and lock the cavity.

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