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Entry  Thu Sep 5 10:52:27 2013, Evan, DailyProgress, ISS, Simple ISS with SR560 ctn_rin_clopen.pdfdata.zip
    Reply  Sat Sep 7 12:38:49 2013, Evan, DailyProgress, ISS, Simple ISS with SR560 - frequency noise coupling tf_fit.pdfrin_freq_est.pdf
Message ID: 1328     Entry time: Sat Sep 7 12:38:49 2013     In reply to: 1326
Author: Evan 
Type: DailyProgress 
Category: ISS 
Subject: Simple ISS with SR560 - frequency noise coupling 

I've taken the above RIN data and combined it with the intensity-to-frequency TF in PSL:1316 to arrive at an estimate of the RIN-induced frequency noise.

By eye, I fitted the magnitude of the transfer function from Tara's farsi.m code to the following model:
 H(f) = \frac{1.6\times 10^8}{\left[1+i(f / 0.1\text{ Hz})^{0.25}\right]\left[1+i(f / 10\text{ Hz})^{0.45}\right]\left[1+i(f / 40\text{ kHz})^{0.6}\right]}
The first attachment shows this fit compared to the original TF.

I used this TF (along with the dc power 0.74 mW incident on the cavity) to convert the measured RIN (suppressed and unsuppressed) into frequency noise. I multiplied the result by a fudge factor of 3 to account for the fact that the TF we measured was a factor of 3 higher than the expectation.

The result is shown in the second attachment. Since this only with G = 500, Chas's high-gain ISS board should crush the RIN well below the expected Brownian noise.

Attachment 1: tf_fit.pdf  78 kB  | Hide | Hide all
tf_fit.pdf
Attachment 2: rin_freq_est.pdf  146 kB  | Hide | Hide all
rin_freq_est.pdf
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