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Entry  Wed Jun 13 19:00:26 2012, Sarah, DailyProgress, Laser, Transfer Functions 12x
    Reply  Fri Jun 22 22:34:28 2012, tara, DailyProgress, NoiseBudget, RIN coupling to Frequency noise 
    Reply  Wed Jun 27 18:51:56 2012, Sarah, DailyProgress, Laser, Transfer Functions Slide1.pngtf_oa_calc_measured.pngTF_allfreq.pngTF_fit_allfreq.pngnb_allfreq.png
       Reply  Fri Jul 6 18:59:49 2012, tara, DailyProgress, Laser, Transfer Functions IMG_1447.jpgRIN_Fnoise.pngRIN_Fnoise.png
          Reply  Tue Jul 10 02:55:37 2012, tara, DailyProgress, Laser, Transfer Functions 
             Reply  Mon Jul 16 19:08:34 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) 
                Reply  Tue Jul 17 19:05:32 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) 7x
                   Reply  Tue Jul 24 17:02:35 2012, Sarah, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) 8x
                      Reply  Fri Aug 3 02:46:15 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) RIN_coupling_2012_08_03.pngRIN_coupling.fig
                         Reply  Tue Aug 13 21:45:51 2013, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) farsi_2013_08_13.pngfarsi_2013_08_13.figRIN_TO_algaas.pngRIN_TO_algaas.fig
                            Reply  Fri Aug 16 04:35:58 2013, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) RIN_req_algaas.pngRIN_req_algaas.fig
                            Reply  Thu Aug 22 13:36:19 2013, tara, DailyProgress, NoiseBudget, Transfer Functions (RIN to Frequency noise via photothermal) fasi_2013_08_22.pngFarsi_compare.fig
          Reply  Wed Jul 11 11:13:38 2012, Sarah, DailyProgress, Laser, Transfer Functions 7x
          Reply  Sun Jul 15 23:20:32 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (power fluctuation to Frequency noise via photothermal effect) Farsi_compare.pngFarsi_compare.fig
             Reply  Thu Jul 19 03:01:26 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (power fluctuation to Frequency noise via photothermal effect) Farsi_compare.pngFarsi_compare.fig
                Reply  Thu Jul 19 23:56:45 2012, rana, DailyProgress, NoiseBudget, Transfer Functions (power fluctuation to Frequency noise via photothermal effect) 
                   Reply  Fri Jul 20 01:32:45 2012, tara, DailyProgress, NoiseBudget, Transfer Functions (power fluctuation to Frequency noise via photothermal effect) 
Message ID: 1032     Entry time: Fri Aug 3 02:46:15 2012     In reply to: 1029     Reply to this: 1298
Author: tara 
Type: DailyProgress 
Category: NoiseBudget 
Subject: Transfer Functions (RIN to Frequency noise via photothermal) 

I fixed the calculation for photothermal noise and compare it with the measured results. This time, they agree quite well.

  I include Thermo expansion and Thermo refractive effects in coatings in to the calculation, and make sure that they are treated coherently. However I still use Farsi's calculation, not GWINC code (see below for why).  Now the calculated TF shape agrees well with the measurement. However, the magnitude is still off by a factor of ~5. This can come from the calibration from power to Volt on the PD_trans_dc (from PSL:xx), the measurement data is taken from PSL:1021.  The absorption I use for calculation is 5ppm, finesse is 7500. These numbers contribute to the magnitude of the calculated TF. I'll try to plot it with confidence interval to see if it will be close to the measured result or not.

RIN_coupling_2012_08_03.png

 

 

==why not GWINC?==

      Since GWINC code has a section(s) for thermo-optic noise (TO) calculation (following Evans 2008 paper), we should be able to modify it to produce the result for RIN induced noise in our case. However, there is one complication for this option. GWINC calculates (TO) by using the [ Power spectral of temperature fluctuation on surface] x [dphi/dT]. [dphi/dT] is derived from the coating structure and materials' properties. However, the temperature fluctuation on the surface is derived by fluctuation-dissipation theorem then averaged over a guassian beam profile(see Levin,2002).  Hence, to use GWINC code to calculate our result, we need to calculate the pwr spectral density of the surface temperature which is heated up by gaussian beam profile, and averaged over gaussian beam as well. I'll try to do this later when I have more free time.

     I reviewed Farsi calculation carefully They follow the sign for TE and TR in the coating(practically following Evans' paper),so I think it is valid as well. Even though Farsi calculates the effect from the first few layers which, as they claim, contribute most to TR, their argument agrees with the result provided by Evans' paper where they compare TR effect between ITM(8doublets), and ETM(19doublets) which are almost the same.

Plus, the effect from coating becomes comparable to that of substrate around 100 Hz and higher frequency. This means the contribution from substrate and coating must be calculated together, which is nicely done by Farsi as well. (This means you cannot just calculate the effect from a bare substrate, ie. from cerdonio, and add the effect from the coating on top of one another) Since we are going to use the calculation from substrate with coating from them, why not the coating calculation as well?

Attachment 2: RIN_coupling.fig  146 kB  Uploaded Fri Aug 3 16:36:22 2012
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