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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: 1019     Entry time: Sun Jul 15 23:20:32 2012     In reply to: 1014     Reply to this: 1023
Author: tara 
Type: DailyProgress 
Category: NoiseBudget 
Subject: Transfer Functions (power fluctuation to Frequency noise via photothermal effect) 

I calculated the photothermal noise following the method from Farsi etal 2012 paper. The results is plotted below. I think I did something wrong, by looking at the low frequency part, the results from Cerdonio and Farsi do not agree. I'm still checking on it.

==Cerdonio  vs Farsi==

Cerdonio calculated the displacement noise due to thermal expansion of substrate induced by shot noise. This can be modified to estimate the noise due to absorption of RIN (see PSL:). Farsi extended the calculation to take thermal expansion and thermo refractive effect from coating into account. Since our measurement does not match up with Cerdonio's calculation that well.  I check if the mismatch comes from coating expansion or not. (I did not expect much, since the spotsize is 291 um, and the coating thickness is ~4um. Heat diffusion length ( ~ sqrt(k/2piCf ) )tells us that the effect from coating will be ~ 1000 Hz and above)

==result==

Farsi_compare.png

There are a few things that make me uncertain about my calculation code:

  1. The effect from substrate is going up with wrong slope while it should match the calculation from Cerdonio at low frequency because the thermal diffusion length is much longer than the coating thickness and most of the effect comes from substrate only.
  2. With our parameters the effect from coating is not significant until ~ a few kHz while it is dominating around 100 Hz for their setup.Their spot size on the mirror is~ 100um, so I expect that for our setup, the effect from the coating should kick in before 1kHz.

I'll double check my calculation again.

 

Attachment 2: Farsi_compare.fig  57 kB  Uploaded Mon Jul 16 03:33:56 2012
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