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Entry  Tue Mar 8 06:29:06 2011, kiwamu, Update, Green Locking, Intensity noise setup 
    Reply  Wed Mar 9 04:46:13 2011, kiwamu, Update, Green Locking, more intensity noise measurement intensity_setup.pngIntensityNoise.png
       Reply  Wed Mar 9 18:17:11 2011, kiwamu, Update, Green Locking, Intensity noise coupling diff_noise.pngIN_TF.png
          Reply  Thu Mar 10 14:06:54 2011, kiwamu, Update, Green Locking, Intensity noise limits the beatnote sensitivity diff_noise_Mar8.pngIN_TF_complete.png
             Reply  Thu Mar 10 14:22:58 2011, kiwamu, Update, Green Locking, Intensity noise limits the beatnote sensitivity 
                Reply  Thu Mar 10 14:29:05 2011, Koji, Update, Green Locking, Intensity noise limits the beatnote sensitivity 
                Reply  Thu Mar 10 14:30:53 2011, rana, Update, Green Locking, Intensity noise limits the beatnote sensitivity 
                   Reply  Thu Mar 10 16:00:53 2011, Aidan, Joe, Update, Green Locking, Intensity stabilization loop using beatnote DC. P1000313.jpgP1000314.jpgP1000315.jpgGREEN_ISS_LOOP.pdfScreenshot-C1ALS_OVERVIEW.adl.png
                      Reply  Thu Mar 10 21:45:34 2011, rana, Update, Green Locking, Intensity stabilization loop using beatnote DC. 
Message ID: 4392     Entry time: Wed Mar 9 18:17:11 2011     In reply to: 4389     Reply to this: 4397
Author: kiwamu 
Type: Update 
Category: Green Locking 
Subject: Intensity noise coupling 

Here is a new plot for the differential noise measurement. I plot a noise contribution from the intensity noise (brown curve).

If we believe this data, the differential noise is NOT dominated by the intensity noise of the PSL.

diff_noise.png

 


(intensity noise coupling measurement)

 Here is a plot for the transfer functions (TFs) from the intensity noise DCPD to the beat signal.

IN_TF.png

   In principle these TFs tell us how much intensity noise are contributed into the differential noise.

When I measured the spectra shown above, the frequency offset of the beatnote was at about 8 MHz from the zero cross point.

Keeping the same lock, I measured the transfer function (red curve) by using the swept sine technique on DTT. The setup for this measurement is depicted on the last entry (#4389).

Then I made the spectra above by multiplying the intensity spectrum by this TF.

  Later I measured another transfer function when the beatnote was at about 2 MHz from the zero cross point.

According to this measurement, our MFD gets insensitive to the intensity noise as the beat offset goes close to the zero cross point. This is consistent with what we expected.

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