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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: 1017     Entry time: Wed Jul 11 11:13:38 2012     In reply to: 1014
Author: Sarah 
Type: DailyProgress 
Category: Laser 
Subject: Transfer Functions 

Tara and I measured the correlation between Voltage and Power behind ACAV, and applied the found calibration to get the TF magnitude in the units of Hz/Watt.

Intro:

We wanted to convert the previously measured TF magnitude (elog 1005) into units of Hz/Watt, as opposed to the previously used Hz/RIN. See attached elog (1014) for an explanation of why these units have a more applicable meaning and application.

Setup/Data Obtained:

We measured the power immediately behind ACAV, the power immediately before the pd (there is a beam splitter between the first and second power measurements), and the corresponding voltage after the pd. The pd gain was set to 20dB. I plotted the results and fit each data set:

Voltage_Power_Calibration.png

The fit equations are:

pd fit: y = 5680.4x + 0.036843

cavity fit: y = 2923.3x + 0.027703

Where y is the voltage (Volts) after the pd and x is the power (Watts) in front of the pd for the pd fit, and right behind the cavity for the cavity fit. 

TF Magnitude in Hz/Watt:

Using the slope of the line relating the power behind the cavity to the voltage as the calibration, I was able to convert the previously measured TF magnitude into the units of Hz/Watt, and plot it against the calculated TF (elog 1014) magnitude in units of Hz/Watt (calculated using Cerdonio et al's results):

TF_calc_meas.png

Application to Noise Budget:

I also plotted the RIN induced noise using the TF in units of Hz/Watt using :

Frequency Noise = TF[Hz/Watt] * RIN * Power_in 

I used an input power of 2mW, and the RIN from 6/13 behind ACAV.

nb_TF_unit.png

The frequency noise generated is a factor of 1.4 larger than that generated using the TF in units of Hz/RIN. Since the TF in Hz/RIN was measured, it is more reliable. This discrepancy indicates that the TF magnitude is also probably too high, and there is a possible error in the calibration constant used to convert voltage to power, or possibly an error in the power readings. 

Attachment 2: TF_calc_meas.fig  31 kB  Uploaded Wed Jul 11 14:28:07 2012
Attachment 4: Voltage_Power_Calibration.fig  11 kB  Uploaded Wed Jul 11 17:47:16 2012
Attachment 5: plot_tf_unit.m.zip  2 kB  Uploaded Wed Jul 11 17:47:28 2012
Attachment 7: nb_TF_unit.fig  308 kB  Uploaded Wed Jul 11 17:50:05 2012
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