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ID Date Author Type Category Subjectup
  7616   Thu Oct 25 02:01:15 2012 KojiUpdateComputer Scripts / ProgramsPhase map summary of LaserOptik mirrors

Previous phasemap data and analysis for the new 40m COC are summarized on the following page

https://nodus.ligo.caltech.edu:30889/40m_phasemap/

(Use traditional LVC authentication (not albert.einstein))

The actual instance of the files can also be found on nodus below the following directory:

/cvs/cds/caltech/users/public_html/40m_phasemap

The programs for the analysis are found in

/cvs/cds/caltech/users/public_html/40m_phasemap/40m_PRM/mat

The main program is RunThis.m

Basically this program takes ascii files converted from opd by Vision32.
(i.e. You need to go to Downs)
Then the matlab program takes care of the plots and curvature analyses.

  11761   Fri Nov 13 15:48:16 2015 gautamUpdateLSCPhase tracker calibration using Rubidium standard

[yutaro, gautam]

Quote:

Summary:

I performed a preliminary calibration of the X and Y phase trackers, and found that the slopes of a linear fit of phase tracker output as a function of driven frequency (as measured with digital frequency counter) are 0.7886 +/- 0.0016 and 0.9630 +/- 0.0012 respectively (see Attachments #1 and #2). Based on this, the EPICS calibration constants have been updated. The data used for calibration has also been uploaded (Attachment #4).

Summary:

Having obtained a working FS725 Rubidium standard and syncing it to out GPS timing unit, I wanted to have one more pass at calibrating the phase tracker output, with the RF signal generator calibrated relative to an 'absolute' source. I also extended the range of frequencies swept over to 15MHz to 110MHz. We found that the phase tracker output appears linear over the entire range scanned, but taking a closer look at the residuals suggested some quadratic structure. Restricting the fitted range to [31MHz 89MHz] yields the following calibration constants for the X and Y arm respectively: 0.9904 +/- 0.0008 and 0.9984 +/- 0.0005. This suggests that out previous calibration was pretty accurate, and that it is valid over a wider range of frequencies, so we could plausibly fit in more FSRs in future scans if necessary. I have not updated these values on the EPICS screens (though judging by how close they are to 1, I wonder if this is even necessary)...

Details:

The principle change in the setup compared to that used to collect the data presented in elog 11738 was the addition of the FS725 rubidium standard. As detailed here, I synced the Rubidium standard to our GPS timing unit (this took a while - the manual suggests it should only take minutes, but it took about 10 hours - the two photos in Attachment #1 show the status of the front panel before and after it synced to the external 1PPS input). I then took 10 MHz outputs from the FS725, and ran one to the Fluke 6061A, and the other to the AG4395A. The Fluke 6061 A has a small switch at the back which has to be set to "EXT" in order for it to use the external reference (it has now been returned to the "INT" state). We then connected the output of the signal generator via a 3-way minicircuits splitter to the AG4395A, and the two beat channels. 

I cleared the phase history on the MEDM screen, and set the phase tracker UGF. We then swept through frequencies from 15MHz to 110MHz (using the AG4395 to verify the frequency at each step). I used the following command to record the average value (over 10 seconds) and the standard deviation: z avg 10 -s C1:ALS-BEATX_FINE_PHASE_OUT_HZ >> 20151113_PT_X.dat and so on.. The amplitude of the signal generated (i.e. before the splitter) was -18dBm (chosen such that the Q outputs of either phase tracker was between 1000 and 3000), while the gains were ~100 (X) and 50 (Y). I then downloaded the data and fitted it.

Fitting details:

The output of the phase tracker looks roughly linear over the entire range of frequencies scanned - but looking at the residuals, one could say there was some quadratic structure to it (see residual plots in Attachment #2). By looking at the shapes of the residuals, I judged that if we fit in the range [31MHz   89MHz] (for both X and Y), we should see negligible structure in the residuals. Attachment #3 contains the fits and residuals for these fits. One could argue that there is still some structure in the residuals, but is markedly less than over the entire range, and, I think, small enough to be neglected. The calibration constants quoted at the beginning of the elog are from the fits over this range. In principle, we could always break this down into smaller pieces and do a linear fit over that range. But this should allow us to scan through >5 FSRs.

Other remarks:

Since the beat signal also goes to the frequency counter via the couplers, I was also collecting the readouts of the frequency counter. Attachment #5 contains the data collected. It is interesting to note that the FCs fail at ~101 MHz (corresponding to ~6146 Hz after the dividers).

Also, we had taken another dataset last night, but found that there was an anomalous kink in the X phase tracker output at (coincidentally?) 89 MHz (I've attached the data in Attachment #6). I'm not sure why this happened, but this is what led me to take another dataset earlier today (Attachment #4).

Summary of Attachments:

  1. Attachment #1: Photos showing the front panel of the FS725 before and after syncing to the external 1PPS input.
  2. Attachment #2: Fits and residuals over the entire range scanned.
  3. Attachment #3: Fits and residuals over restricted range [31 89] MHz
  4. Attachment #4: Data used for phase tracker calibration.
  5. Attachment #5: Frequency counter data.
  8795   Wed Jul 3 11:07:17 2013 AlexSummary Photodetector Characterization

 [Alex, Koji]

We characterized Koji's BBPD MOD for REFL165 (see attachment).

First, we calibrated the Agilent 4395 Network Analyzer (NA) to account for differences in cable features between the Ref PD and Test PD connections. This was done using the 'Cal' softkey on the NA. 

Then we performed transimpedance measurements for the test PD and reference PD relative to the RF output of the NA and relative to each other (see 2nd attachment. Note that the NA's RF output is split and sent to both the IR Laser and the NA's Ref input).

Next, we made DC measurements of the outputs of the photodetectors to estimate the photocurrent distribution of the transimpedance setup (like the 2nd attachment, but with the outputs of the PDs going to a multimeter). By photocurrent distribution, we mean how the beamsplitter and respective quantum efficiencies/generalized impedance/etc. of the PDs influence how much current flows through each PD at with a DC input.

Finally, we measured the output noise as a function of photocurrent (like the 2nd attachment, but with a lightbulb instead of the IR Laser). Input voltages for the lightbulb ranged from 0mV to 6V. Data was downloaded from the NA using netgpibdata from the scripts directory. Analysis is currently in progress; graphs to come soon.

 

  8940   Tue Jul 30 16:21:46 2013 Alex ColeUpdateElectronicsPhotodetector Input Modulation

 [Eric, Alex]

We successfully used our system to modulate the input to a single photodetector. The RF Out of the network analyzer went to the Mod In of our laser, which was operating at 98 mA. The laser's output was sent to our 1x16 optical splitter. This provided input signals for both our reference detector and AS55. Our reference detector's output was sent to the network analyzer's R input, while the AS55's output was sent to the network analyzer's A input. 

We still need to work out the specifics of how the modulation works. Specifically, we want to look at the amplitude of the network analyzer's output. Additionally, we may have been saturating our reference detector, causing noise problems.

  1797   Mon Jul 27 14:43:34 2009 ChrisUpdate Photodetectors

I found two ThorLabs PDA55 Si photodetectors that says detect visible light from DC to 10MHz that I'm going to use from now on.  I don't know how low of a frequency they will actually be good to.

  1252   Sat Jan 24 11:50:24 2009 AlbertoConfigurationElectronicsPhotodiode Filters' Transfer Functions
I found an elog entry by Jenne with the measurement of the transfer functions of the filters of some of our photodetectors. Since it might turn useful to us these days, while I'm thinking about posting them on the wiki sometime, I also copy the link here:
Jenne's on the PD's TF

If we still had the data for those plots, it would be great. Do we have it?
  3904   Fri Nov 12 02:51:20 2010 KevinUpdateElectronicsPhotodiode Testing

[Jenne and Kevin]

I started testing the REFL55 photodiode. With a light bulb, I saw ~270 mV of DC voltage from the photodiode but still could not see any RF signal. I connected the RF out from the spectrum analyzer to the test input and verified that the circuit was working.

I then set up the AM laser and looked at the laser light with REFL11 and an 1811 photodiode. I was able to see an RF signal and verified that the resonant frequency is 55 MHz.

The current setup is not very reliable because the laser is not mounted rigidly. Next, I will work on making this mounting more reliable and will continue to work on finding an RF signal with a flashlight.

  15516   Wed Aug 12 17:42:58 2020 gautamUpdateElectronicsPhotodiode inventory

See Attachments #1 and #2. We don't have any Q3000 QPDs in hand, at least not in the photodiode box stored in the clean optics cabinet at the south end. I also checked a cabinet along the east arm where we store some photodiodes - but didn't find any there either. The only QPDs we have in hand are the YAG-444-4AH, which I believe is what is used in the iLIGO WFS heads.

So how many do we want to get?

  15520   Wed Aug 12 20:16:52 2020 KojiUpdateElectronicsPhotodiode inventory

When I tested Q3000 for aLIGO, the failure rate was pretty high. Let's get 10pcs.

  7794   Wed Dec 5 17:38:41 2012 RijuHowTo Photodiode transimpedance

I have started making the circuit to measure the transimpedance for the photodiode PDA10CF using Jenne's laser. I will continue it tomorrow.

  7834   Fri Dec 14 14:40:31 2012 RijuUpdate Photodiode transimpedance

Photodiode PDA10CF was under test. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference and the other on PDA10CF. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection.

The result is as follows:

  7854   Tue Dec 18 16:44:00 2012 rijuUpdate Photodiode transimpedance

Today I measured the dark current of the PDA10CF. The output of the PD was connected to the A channel of the network analyzer, when there was no light falling on it. The response is collected using GPIB.

I will upload the result shortly.

  7870   Fri Dec 21 19:49:39 2012 RijuUpdate Photodiode transimpedance

I have repeated the transimpedance measurement of PDA10CF. Also made the dark current noise measurement by connecting the PDA10CF output to the A channel of network analyzer.  The results are as follows. I I started to take the reading for shot noise intercept current using a light bulb in front of the PD, changing the current through the bulb, but at higher current the bulb filament got broken, so the experiment is incomplete.

  7874   Thu Jan 3 20:34:43 2013 RijuUpdate Photodiode transimpedance

Today I have measured the transimpedance and dark-noise of the MC-REFL PD.

For transimpedance measurement I first collected the data of the reference Newfocus PD connecting it at channel B of Network-analyzer using the set-up of Jenne's laser. The data for the MC-REFL PD had been collected by connecting it to the A channel of Network Analyzer. To do that I shifted the Jenne's Laser to the table of MC-REFL PD, I moved the laser output on the table and fixed a lens and a mirror on the table. Taking the ratio of the two sets of datas I got the required trans-impedance.

Dark-noise readings were taken keeping the laser off.

I will upload the corresponding plots tomorrow.

  7875   Fri Jan 4 13:23:10 2013 ranaUpdateElectronicsPhotodiode transimpedance

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

  7880   Tue Jan 8 14:01:21 2013 RijuUpdate Photodiode transimpedance

 Here I upload the plots corresponding to my last day's measurements.

 

  7881   Tue Jan 8 14:07:04 2013 RijuUpdateElectronicsPhotodiode transimpedance

Quote:

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

 Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

  7882   Tue Jan 8 15:28:41 2013 RijuUpdateElectronicsPhotodiode transimpedance

Quote:

Quote:

You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.

For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.

 Hi,

The correction for different levels of DC photocurrent in the two devices had been taken care by one MATLAB code, the code that originally was made by Koji.

The analyzer noise I had not recorded; today I am going to record it.

Riju

 Here is the data for AG4395A network/spectrum analyzer noise data. I collected the data by putting 50ohm terminator on channel A with same input attenuation setting (0dB attenuation).

  7887   Wed Jan 9 19:32:24 2013 RijuUpdate Photodiode transimpedance

Summary:

Today I have tested the MC transmission-end RF photodiode PDA255 for transimpedance and dark noise using Jenne's Laser and AG4395A network/spectrum analyzer. The dark noise voltage distribution for the transmission and reflection PDs of MC and the analyzer has been compared.

Motivation:

I am to do the input mode cleaner cavity mode scan. The electronic and shot noise of the components used , particularly photodiode noise, will affect the peak position  of the modes, indicating the uncertainty in the measured frequencies of the modes. That will in turn give the uncertainty in the measured change of radius of curvature of the mirrors in presence of the laser beam, from which we will be able to calculate the uncertainty in the mirror-absorption  value.

Method:

For PD transimpedance measurement I used Jenne's laser along with AG4395 network analyzer. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference(Newfocus1617? PD, the DC and RF transimpedance values were taken from its datasheet ) and the other on PDA255. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection. It had been ensured that the PD under test is not going to saturation, for that the source power level was kept to -40dBm. transimpedance measurements were compensated by the ratio of DC photocurrent.

For dark noise measurement the output of the PD was connected to the A channel of the AG4395A, when there was no light falling on it. The response is collected using GPIB. The attenuation of channel A was made 0dB. ( AG4395A was kept in Spectrum analyzer mode in Noise Format).

Results:

The plots corresponding to the measurements are attached.

Discussion:

The comparison for the dark noise voltage levels of the MC transmission PD (PDA255) with MC REFL PD has been made with analyzer dark noise voltage. It is shown in the attachment (I will upload the dark noise current comparison too....since the output darknoise depends on the gain of the circuit, it is important to divide this voltage spectra by transimpedances.)

  7907   Wed Jan 16 18:58:08 2013 RijuUpdate Photodiode transimpedance

Today I have taken the reading for shot noise intercept current for the PDA255 - MC transmission RF PD. To do that I have put an incandescent bulb (JKL lamps, 222 bulbs, voltage and current rating 2.25V and 0.25A) in front of the PD and varied the current through it from 0A to 0.29A at 2.2V. I measured the corresponding DC voltage and took the noise data (4395A spectrum analyzer/ format noise, channel attenuation 0dB) through GPIB .

I will process the data and upload the result soon.

  7926   Tue Jan 22 17:29:29 2013 RijuUpdate Photodiode transimpedance

Riju

Summary:  I am stuck with the measurement of shot-noise-intercept-current of PDA255. Seeking help.

Motivation: It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector.

Method: It is as described in the elog  7907 

Result: The plot is attached here.

Discussion: The result I got is really unexpected, the noise voltage should increase with the DC current level that corresponds to the increment of light level too. But actually it is decreasing. Three times I have repeated this experiment and got the same result. I want some suggestion on this regard.

  7927   Tue Jan 22 19:51:52 2013 KojiUpdate Photodiode transimpedance

- The data should be plotted in a log-log scale.
- The data points were only taken in the high current region.

- The plot may suggest that the amplifier saturate at the RF.

PDA255 has the nomial transimpedance gain of 10^4 Ohm.
The DC current of 10^-3 gives the output of 10V.
This plot may tell that the saturation starts even at the 1/10 of the full DC range.

The plot doesn't have many points below 0.1mA.
Consult with my plots for the similar measurements.
The measured points are logarithmically spaced. Use the same technique.

- It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

  7929   Wed Jan 23 11:43:19 2013 RijuUpdate Photodiode transimpedance

Quote:

- The data should be plotted in a log-log scale.
- The data points were only taken in the high current region.

- The plot may suggest that the amplifier saturate at the RF.

PDA255 has the nomial transimpedance gain of 10^4 Ohm.
The DC current of 10^-3 gives the output of 10V.
This plot may tell that the saturation starts even at the 1/10 of the full DC range.

The plot doesn't have many points below 0.1mA.
Consult with my plots for the similar measurements.
The measured points are logarithmically spaced. Use the same technique.

- It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

 Here I am attaching the plot in loglog scale. I have taken the data-points from no light condition to the maximum light condition, the minimum variation possible in the current supply was 0.01A. The noise was visibly decreasing at higher light level.

For the noise level calculation I took the average of total noise in the range 7-60MHz. For each range the formula used was

noisevalue= sqrt(data(:,2)*100)/sqrt(2)/sqrt(channel BW);     -- this conversion is needed since the data was collected in the 2 column format: frequency, spectrum(W).

  7933   Wed Jan 23 20:27:05 2013 RijuUpdate Photodiode transimpedance

Today I have repeated the expt for shot noise intercept current. Koji found that the Spectrum analyzer is going to saturation, so we have used one DC blocker (MCL - 15542 model) in PD signal.

I will analyze the data and report.

Ed by Koji: DC BLOCK is  BLK-89-S

  7946   Mon Jan 28 17:59:02 2013 RijuUpdate Photodiode transimpedance

Summary: Measurement and plot of shot-noise-intercept-current for PDA255.

Motivation:It is to measure the shot noise intercept current for PDA255 - the MC transmission RF photodiode to get an idea for the noise current for the detector

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 3.06mA

Discussion:

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region as described in manual of PDA255 (i.e. 5e3 when it is not in High-impedance region).

On the other hand for DCcurrent calculation we must use the high-impedance value for the transimpedance i.e. 1e4 Ohm. idet is the shot noise intercept current.

For the rough calculation of the noise level we may use the following formulae:

Vnoise = gdet*sqrt[2e (iDC+idet)] = gdet*sqrt(2e in), when in=iDC+idet;

For say, in1=1mA; Vnoise1=gdet*sqrt(2e *in1)

and sqrt(2e *in1)~18pA/sqrt(Hz)

In current case dark noise is ~1.5e-7 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance = 30pA/sqrt(Hz)

i.e. sqrt(2e *in2)=30pA/sqrt(Hz)

i.e. sqrt(in2/in1)=30/18

therefore, in2~3mA (since in1=1mA)

For, iDC=0, in=idet.

Therefore the shot-noise-intercept current will be ~3mA

Then Vdc = in2*1e4 = 30V

According to the experiment  and also from the PDA255 manual the DC voltage level never goes beyond ~10V. Therefore following the photodiode characteristics(we work in reverse bias) we may infer that it can never become shot noise limited.

Also, from PDA255 manual, at 1650nm the dark noise is 30pW/sqrt(Hz) and the responsivity is 0.9A/W. Therefore the noise current level will be = noise power* responsivity ~27pA/sqrt(Hz). The value matches well with our expectation.

 

  7956   Tue Jan 29 18:40:20 2013 RijuUpdate Photodiode transimpedance

Today I have taken data for shot noise intercept current for PDA10CF. I will process the data and report.

Note: GPIB address changed, new command for AG4395A network/spectrum analyzer: ./netgpibdata.py -i 192.168.113.108 -d AG4395A -a 10 -f filename

  7972   Thu Jan 31 12:44:42 2013 RijuUpdate Photodiode transimpedance

Today I collected the data for shot noise intercept current for MC REFL PD. I didn't get many data points at higher DC voltage of the photodiode, cause the incandescent bulbs get burnt at that level; two bulbs I have burnt today. I will process the data and report.

  7974   Thu Jan 31 14:46:05 2013 JenneUpdateRF SystemPhotodiode transimpedance

Quote:

Today I collected the data for shot noise intercept current for MC REFL PD. I didn't get many data points at higher DC voltage of the photodiode, cause the incandescent bulbs get burnt at that level; two bulbs I have burnt today. I will process the data and report.

 This work was done in-situ, so no optics on the AS table were moved.  The PSL shutter was blocked since the IR beam was not necessary, and would scatter off the bulb Riju put in front of the PD. 

  7976   Thu Jan 31 15:34:22 2013 RijuUpdateRF SystemPhotodiode transimpedance

Quote:

Quote:

Today I collected the data for shot noise intercept current for MC REFL PD. I didn't get many data points at higher DC voltage of the photodiode, cause the incandescent bulbs get burnt at that level; two bulbs I have burnt today. I will process the data and report.

 This work was done in-situ, so no optics on the AS table were moved.  The PSL shutter was blocked since the IR beam was not necessary, and would scatter off the bulb Riju put in front of the PD. 

 Thanks Jenne.

  7977   Thu Jan 31 15:56:38 2013 RijuUpdate Photodiode transimpedance

Summary: Measurement and plot of shot-noise-intercept-current for PDA10CF. 

Motivation:It is to measure the shot noise intercept current for PDA10CF.

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 0.21mA

Discussion:

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region as described in manual of PDA255 (i.e. 5e3 when it is not in High-impedance region).

To get an approximate idea of the shot noise intercept current, we may follow the same procedure described in 7946 

In the present case dark-noise is 4.3e-08 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance = 8.6pA/sqrt(Hz)

 

 

Therefore the approximate shot noise intercept current ~ (8.6/18)^2=0.22mA

This value matches well with the fitted data.

From PDA10CF manual, NEP=1.2e-11W/sqrt(Hz) and responsivity~0.9A/W. Therefore the noise current level will be ~10pA.

 

 

  7984   Fri Feb 1 14:47:17 2013 RijuUpdate Photodiode transimpedance

 Summary: Measurement and plot of shot-noise-intercept-current for MC REFL PD. 

Motivation:It is to measure the shot noise intercept current for MC REFL PD.

 

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 0.041mA

Discussion:

 

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region as described in manual of PDA255 (i.e. 5e3 when it is not in High-impedance region).

To get an approximate idea of the shot noise intercept current, we may follow the same procedure described in 7946 

In the present case minimum noise value is 2.03e-08 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance = 4.06pA/sqrt(Hz)

Therefore the approximate shot noise intercept current value is (4/18)^2 ~ 0.049mA, which is close to the fitted value.

 

 ... hard to believe these numbers. Wrong DC transimpedance? (KA)

  8027   Thu Feb 7 19:24:57 2013 RijuUpdate Photodiode transimpedance

 Summary: Measurement and plot of shot-noise-intercept-current for MC REFL PD. 

Motivation:It is to measure the shot noise intercept current for MC REFL PD.

 

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 1.9mA

Discussion:

 

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region ~600

To get an approximate idea of the shot noise intercept current, we may follow the same procedure described in 7946 

In the present case minimum noise value is 1.46e-08 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance ~25pA/sqrt(Hz)

Therefore the approximate shot noise intercept current value is (25/18)^2 ~ 1.92mA, which matches well to the fitted value.

 

 

  8186   Wed Feb 27 17:43:54 2013 RijuUpdate Photodiode transimpedance

Here is the transimpedance for the other PD used for MC REFL

  8187   Wed Feb 27 18:01:46 2013 KojiUpdate Photodiode transimpedance

How much is the exact resonant frequency?

And what's the unit of the plot? The resonant "transimpedance" in the unit of Ohm can not be ~100.

  8188   Wed Feb 27 18:17:05 2013 RijuUpdate Photodiode transimpedance

Quote:

How much is the exact resonant frequency?

And what's the unit of the plot? The resonant "transimpedance" in the unit of Ohm can not be ~100.

 The exact resonant frequency is 29.38MHz. I ve uploaded the other plot. It was the output of Vectfit.

  8189   Wed Feb 27 18:38:51 2013 RijuUpdate Photodiode transimpedance

Quote:

Quote:

How much is the exact resonant frequency?

And what's the unit of the plot? The resonant "transimpedance" in the unit of Ohm can not be ~100.

 The exact resonant frequency is 29.38MHz. I ve uploaded the other plot. It was the output of Vectfit.

 Is the DC transimpedance now 10010 Ohm? I ve used 50 Ohm. Which one is correct?

  2129   Wed Oct 21 15:07:45 2009 AlbertoUpdateWIKI-40M UpdatePhotodiodes' configuration for the Upgrade

I uploaded on the Wiki (here) the results of an inventory over our current PDs, a list of the new ones that we're going to need for the new control scheme.

  41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
  819   Sun Aug 10 16:57:02 2008 ranaSummaryPhotosPhotos from Vent 8/4 - 8/8
http://www.ligo.caltech.edu/~rana/40m/VentAug08/

I've added the D40 pictures from last week to this web page. I have done some cropping and
rotating to make things look better.

On page 3, there are some over head shots of the Michelson area so that one can use screw holes
to judge what the spacing between the suspensions is and also possibly the cavity lengths. Lets
also remember to measure the ITM-BS distance accurately using a tape measure or ruler while we
have the thing open.
  2535   Thu Jan 21 10:09:27 2010 KojiSummaryIOOPhotos of the optical tables

I made a wiki page dedicated for the photos of the optical tables.
The current layouts were uploaded.

http://lhocds.ligo-wa.caltech.edu:8000/40m/Optical_Tables

  2465   Tue Dec 29 13:57:20 2009 Rana, Kiwamu, and HaixingUpdatePhotosPhotos of video switch box

Before we installed the video switch box, we also took some photos of it. We uploaded them onto the 40m Picasa.

Video Matrix

The first photo is the an entire view of the switch box. The following four photos are the details of the switch matrix.

 The slideshow below is a dump of the last several months of photos from the Olympus. The originals have been deleted.

  5056   Thu Jul 28 17:04:04 2011 NicoleUpdateSUSPhotosensor Head Calibration Curve

Here is the calibration curve (displacement versus voltage output) for the photosensor head that I made with the S5971 photodiodes and L9337 LEDs. This was made using a regular mirror. The linear region appears to be between 0.4 and 0.75cm. I will need to arrange the photosensor head so it measures displacements in the linear region of this plot. This plot was made using a 287 ohm resistor.

187K_resistor.jpg

  5188   Thu Aug 11 12:31:39 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

ps2frame.jpg

  5191   Thu Aug 11 14:22:00 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

Quote:

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

ps2frame.jpg

I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).

 

This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.

 

Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...

  5192   Thu Aug 11 14:32:12 2011 KojiSummarySUSPhotosensor Head Calibration Curve for TT Frame

The entry was quite confusing owing to many misleading wordings.

- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)

- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
  This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.

- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.

- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
  of the suspension.

Quote:

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

ps2frame.jpg

 

  4969   Thu Jul 14 20:24:32 2011 NicoleSummarySUSPhotosensor Head Lessons

Today I tested the photosensor head combination (2 Hamamatsu S5971 photodiodes and 1 Hamamatsu L9337 LED). I discovered that I had burnt out the LED and the photodiodes when I soldered them to the PCB board.

After looking up soldering information on Hamamatsu photodiodes, I learned that I need to solder at least 2 mm away from the head. I checked the pins of my burnt-out photodiodes and I had soldered 1.5 mm away from the head. To prevent this problem from happening again, Suresh suggested that I clip a lead onto photodiode/LED pin while I solder on connections to help dissipate some of the heat.

Today I was able to get a single photodiode (not attached to the PCB) to measure light emitted from an LED and I observed how voltage fluctuated as I moved the photodiode around the LED.

Suresh and Jamie also helped me to fix my photosensor head design (to make it more electrically-stable). Originally, I had planned to solder the LED and photodiodes onto a PCB and to mount that PCB to the front of a small metal Pomona Electronics box (with a whole cut out for the photodiodes and LED) using spacers, screws, and nuts.  However, the PCB I am using to solder on the LED and photodiodes has metal connections that may cause problems for the LED and photodiodes lying on the surface. Now, the plan is to have the LED and photodiodes mounted to the PCB with an insulatory PCB in between. Below is an explanatory picture.  I will determine the placement of the LED and photodiodes after making screws holes in the two PCBs to attach to the metal face of the box. I want to attach the screw holes first to make sure that the PCBs (and attached photosensor) are centered.

 

Photosensor_Head.jpg

  4970   Fri Jul 15 01:11:21 2011 KojiSummarySUSPhotosensor Head Lessons

Rotate the PDs and the LED so that you can put them as close as possible.
This is to increase the sensitivity of the sensor. Think why the closer the better.

  4971   Fri Jul 15 08:48:36 2011 JamieSummarySUSPhotosensor Head Lessons

Nicole: I thought we had decided to use teflon as the insulator between the PCB (yellow) and the LED/PDs?  I don't think you should use another circuit board with copper on it.  The copper will short the LED/PD heads to the metal box, which might be problematic.

Otherwise the design looks pretty good.  I think the PDs have three leads each, yes?

  4974   Fri Jul 15 14:23:30 2011 NicoleSummarySUSPhotosensor Head Lessons

 

 Ah! I see! Thank you!

I should put the LEDs and photodiodes closer together so that more of the reflected light falls on the photodiodes and the photodiodes have a higher response.

Also the reflectivity of the mirror will be optimized if the incident light is normal to the mirror surface. We will be setting up the photosensor and mirror so that the LEDs

emit light normal to the mirror surfaceDuring displacement, this light may be slightly off-normal but still close to normal incidence. We want the photodiodes to be close to the LED since we want

them to detect light that is close to the path of normal incidence (small angles of reflection). [Thanks to Jenne for helping me figure this one out!]

 

Thank you for the suggestion ^___^

  4975   Fri Jul 15 14:29:30 2011 NicoleSummarySUSPhotosensor Head Lessons

 

 You are right Jamie! Thank you for the correction! I will now use the Teflon sheet instead of the PCB piece.

The photodiodes do have three legs, but I imagined the third one lying on a different plane, since it is spaced apart from the two I have drawn.

I should include this third leg in my drawing?

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