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ID Date Authorup Type Category Subject
  17200   Wed Oct 19 11:09:20 2022 RadhikaUpdateBHDBH55 RF output amplified

[Anchal, Radhika]

We selected a 102K (1 nF) ceramic capacitor and a 100 uF electrolytic capacitor for the RF amplifier power pins. I soldered the connections and reinstalled the amplifier [Attachments 1, 2].

Quote:

1) please remember to follow the loading and power up instructions to avoid destroying our low noise RF amplifiers. Its not as easy as powering up any usual device.

2) also, please use the correct decoupling capacitors at the RF amp power pins. Its going to have problems if its powered from a distant supply over a long cable.

 

Attachment 1: IMG_3840.jpeg
IMG_3840.jpeg
Attachment 2: IMG_3847.jpeg
IMG_3847.jpeg
  17243   Tue Nov 8 11:18:39 2022 RadhikaUpdateAUXAUX PZT transfer function fitting + filtering

Here I describe efforts to cancel the AUX laser PZT mechanical resonances from ~200 kHz-400kHz. While these may not be the resonances we end up wanting to suppress, I chose this region as an exercise because it contains the most significant peaks.

The PZT transfer measurement was taken on 09/06 by myself and Anchal. The Moku:Go outputted a swept-sine (1kHz - 1MHz) I sent to the AUX laser PZT. The beat note between the AUX and frequency-doubled PSL was sent to the DFD, and the I and Q channels were routed back as input to the Moku:Go. We also took a calibration transfer function of the Moku:Go, sending output 1 to inputs 1 and 2. 

Almost all of the signal was present in the I channel, so I proceeded to use the I data for fitting/next steps. After normalizing the measured frequency response by the calibration measurement (and adjusting for the calculated time delays in the loop - see [17131]), I fit the resulting data using vectfit [Attachment 1]. I supplied the function with n_poles=16, which in reality fit for 16 complex pairs of poles. This complexity of fit was not necessary to capture the 3 prominent peaks, but would likely be needed to fit any of the more heavily-damped resonances. 

I chose to invert all fitted poles between 200 kHz and 367 kHz and the corresponding fitted zeros. The result of this filter applied to the original frequency response data can be seen in Attachment 2, where the blue-shaded region contains the inverted poles/zeros. In total, 9 pairs of poles and 9 pairs of zeros were inverted. 

Next steps:

- Determine which resonances we want to suppress
- Send filter coefficients to Moku:Go (write scripts to streamline)
- Set up Moku:Go in series in loop; take TF measurement
Attachment 1: AUX_PZT_TF_vectfit.pdf
AUX_PZT_TF_vectfit.pdf
Attachment 2: AUX_PZT_TF_filtered.pdf
AUX_PZT_TF_filtered.pdf
  17271   Wed Nov 16 11:56:21 2022 RadhikaUpdatePSLPMC input beam aligned again, IMC

[Yuta, JC, Radhika]

PMC input beam was aligned again, bringing transmission from 0.70 to ~0.75. To avoid blocking the PMC refl beam, I found success handling the yaw knob of the first steering mirror from below.

Attachment 1: Screen_Shot_2022-11-16_at_12.04.18_PM.png
Screen_Shot_2022-11-16_at_12.04.18_PM.png
  17291   Mon Nov 21 11:52:50 2022 RadhikaSummaryCalibrationSingle arm cal with 5 lines

[Paco, Radhika]

We set out to realign the YARM AUX laser input into the arm cavity.

- We noticed that the GTRY beam was way off the center of the screen, so we went to the vertex table to align the camera.

- The beam spot at GTRY PD was large/divergent, so we shifted the PD closer to the penultimate mirror. We also doubled the PD gain. Transmission went from ~0.3 to ~0.7 (with gain doubled).

- We returned to the YARM end table to finalize alignment with the green PZT steering mirrors. GTRY was maximized to ~0.77.

  17300   Tue Nov 22 20:46:11 2022 RadhikaUpdateALSXARM green laser lock debugging

[Paco, Anchal, Radhika]

We tried to debug why the XARM green laser isn't catching lock with the arm cavity. First I tried to improve alignment:

- Aligned the arm cavity axes by maximizing IR transmission.

- Adjusted M1 and M2 steering mirrors to align the X green beam into the arm. GTRX reached ~0.3.

     - At the vertex table, I adjusted the lens in the GTRX path to focus the beam onto the DCPD. This increased GTRX to ~0.7.

- Visually I confirmed that TEM00 of the green laser was flashing in the arm cavity, fairly centered. But it was not catching lock.

We suspected the XARM AUX PZT might be damaged/unresponsive. Paco, Anchal, and I fed several frequency signals to the PZT and looked for a peak in the AUX-PSL beatnote spectra at the expected frequency. We confirmed that the X-arm AUX PZT is responsive up to 12 kHz (limited by ADC samping rate). We have no reason to suspect the PZT wouldn't be responsive at the PDH modulation frequency of 231 kHz.

Next steps:

- Investigate PDH servo box / error signal.

  17306   Wed Nov 23 17:12:34 2022 RadhikaUpdateALSXARM green laser lock debugging

I tested the mixer by feeding it a 300 kHz signal sourced from a Moku:Go. I kept the LO input the same - 231.25 kHz from the signal generator. The mixer output was a ~70 kHz waveform as expected, so demodulation is not the issue in green locking.

Next I'll align the arm cavities with IR and check to see if the green REFL signal looks as expected. If not, we'll have to invesitage the REFL PD. If the signal looks fine, and we now know it's being properly demodulated, the issue must lie further downstream.

  17330   Fri Dec 2 15:59:55 2022 RadhikaUpdateALSXARM green laser lock debugging

I took a transfer function measurement of the XEND PDH servo box, from servo input to piezo output [Attachment 1]. The servo gain knob was set to 10. The swept sine input was 50 mVpp, as to not saturate the servo components. I toggled the local boost on/off for these measurements. With the boost on, coherence was lost from ~100Hz-10kHz, and the saturation light indicators were flashing. I will retake this measurement shortly.

Atachment 2 is from a previous measurement of this PDH servo TF, found here. For this measurement, boost was off and the gain knob was set to 2.0. (If there is a more recent measurement than 2010, please point me to it.)

Attachment 1: XEND_green_pdhservo_TF.pdf
XEND_green_pdhservo_TF.pdf
Attachment 2: G1_PDHbox_TF.png
G1_PDHbox_TF.png
  17340   Tue Dec 6 15:29:35 2022 RadhikaUpdateALSXARM green laser lock debugging

[Radhika, JC]

We retook transfer function measurements of the XEND PDH servo box, this time setting the gain knob to 3.5 to avoid saturation. Once again I toggled the boost on/off. Attachment 1 shows the resulting bode plots, which now resemble the previous measurements circa 2010. This measurement along with the previous one suggest that setting the gain knob too high might affect the loop shape in an unpredictable way. With this accounted for, it seems the PDH servo box is functioning as expected.

Attachment 1: XEND_PDH_servo_TF_boost_on_off.pdf
XEND_PDH_servo_TF_boost_on_off.pdf
  17341   Tue Dec 6 15:59:46 2022 RadhikaUpdateALSXARM green laser lock debugging

[Radhika, Paco]

Paco suggested that alignment could still be the primary reason why the XEND green laser is not catching lock. With the xarm cavity aligned with IR, I adjusted the M1 and M2 steering mirrors for the green laser, looking at the REFL PD output in an oscilloscope. Paco joined and was able to achieve better mode matching by adjusting mirrors and rotating the half-wave plate. At this point, we could see TEM00 consistently flashing. Green transmission also reached a value of 3, from around 0.5 that I was able to achieve previously (this channel is not normalized).

We broke the loop to make sure the demodulated signal looked as expected, and indeed it resembled a PDH error signal. After reconnecting the loop (with the gain knob set to 3.5), Paco lowered the REFL PD gain by 3 stages and I was able to raise the gain knob to 8 without the servo saturating. I turned boost on and toggled the servo inversion until the laser started to hold lock for a few seconds. The piezo output signal looked reasonable at this point, without clipping on either end. 

After some final adjustments to the steering mirrors and the half-wave plate, the green laser can hold lock for around 5 seconds. However it's unclear why the loop isn't more stable, and more updates are to come. 

  17350   Fri Dec 9 10:08:54 2022 RadhikaUpdateASCYEND green alignment chronicles

Today I set out to align and lock the YEND green laser, and observe the expected PDH error signal and PZT control signal. 

- I took note of PDH servo knobs:

    - gain knob: 10.0
    - LO phase knob: 2.86
    - boost: on
    - inversion: -

- Disconnected PDH servo PZT output to break loop

- Scanned pitch and yaw of steering mirrors 1 and 2 [Attachment 1] and achieved transmission ~1.2.

- Re-engaged the loop and with TEM00 locked, and did fine adjustment of steering mirrors to maximize transmission to 1.4.

- At this point I broke the loop again to look at the PDH error signal and piezo control signal in an oscilloscope. The error signal had high frequency noise, so the SR560 was used to low pass it before sending it to the scope.

- Once I reconnected the loop and locked to TEM00, I noticed lots of noise in green transmission. Paco took spectra of GTRY and found it was line noise at multiples of 60 Hz. I checked if any BNC shields at the servo box were touching. I shifted the LO frequency from 213.12 kHz to 213.15 kHz, so that the modulation/demodulation was not an integer multiple of 60 Hz. However, these steps didn't get rid of the line noise. To be further investigated.

Next I plan to revisit the XEND AUX loop and try to reach higher lock stability. 

Attachment 1: IMG_3982.jpg
IMG_3982.jpg
  17355   Fri Dec 9 21:54:40 2022 RadhikaUpdateASCMoku digital filter for low-frequency resonances (ALS/calibration)

[Radhika, Paco]

I modeled a digital filter for adding a resonance at a desired frequency (Q~100), with a complex-conjugate pole pair and 2 real zeros (2nd order system). Paco suggested I start with a 575 Hz resonance. I loaded the digital filter onto the Moku using the Moku python API (script at labutils/moku/mokuGoPro/mokuDigitalFilter.py). I tested the filter by feeding the Moku a 2 Vpp signal around 575 Hz and looking for some noticeable gain - however the signal passed though unchanged. There might be an additional Moku command for enabling the filter - I'll look into this.

TODO:

- Debug deployment of digital filter to Moku:Go
- Test on preset low-pass filter, before custom filter
- Once successful, add multiple resonances helpful for calibration
- Deploy filters in xarm AUX-PDH loop
  17358   Wed Dec 14 12:37:20 2022 RadhikaUpdateALSXARM green laser lock debugging

On Monday I aimed to measure the transfer function of the x-arm AUX PDH loop while momentarily locked, with a Moku:Go. I re-aligned the XEND green beam input to the arm cavity with M1 and M2 steering mirrors. I got GTRX to ~1.4 and the TEM00 mode nominally locked (back to ~5 seconds of lock, like last time). Previously Paco and I had achieved transmission of 3, so there was still a good way to go in mode matching. 

However I noticed the backwards-propagating beam started to drift relative to the opening of the Faraday isolator (located after the shutter). During manual alignment the backwards beam cleared through the aperture of the FI, but around 5 minutes later it had drifted too high and the beam spot was visible against the FI body, missing the aperture. At this point transmission had dropped to 0, and I realigned the beam to clear through the opening. I tried to further increase transmission but the drift continued to occur within a few minutes of re-alignment. I double checked that there was no dithering of ITMX or ETMX. It seemed there was high residual motion of the ETM, but I was not sure how to decrease this (damping filters were on). I moved on to setting up the TF measurement and decided to return to alignment once the loop excitation was configured.

I chose to inject an excitation from the Moku at the error point of the PDH servo box. I set up the measurement from 100 kHz to 100 Hz, zoomed in around the loop UGF. I passed the mixer output / error signal (alpha) to a T-splitter and sent one copy to input A of an SR560, and routed the Moku excitation to input B. The summed output of the SR560 was sent to the PDH servo input (beta). I passed the second copy of the error signal (alpha) to the Moku, along with the servo input monitor signal (beta) from the PDH box. The Moku measured the transfer function alpha/beta to obtain G_OLG. 

I returned to align the green beam and recovered flashing of the TEM00 mode. However when I closed the loop (with excitation), it didn't catch lock. I quickly reverted the loop back to its original state and confirmed that TEM00 locked for ~5 seconds. This made me think the excitation signal was too large relative to the error signal, so I reduced its amplitude to 500 mVpp. This still didn't recover the lock, and at this point the alignment had drifted again so I decided to wrap up. 

TODO:

- Investigate alignment drift; confirm ITM/ETM motion within expected range
- Recover GTRX of ~3
- Calculate optimal excitation amplitude relative to error signal
- Inject excitation at control point if the previous step doesn't recover lock.

I am working remotely for the next week, so I can carry out these steps in January.

 

  17396   Thu Jan 12 15:31:27 2023 RadhikaUpdateALSXARM green laser lock debugging

[Radhika, Anchal, Paco]

AUX PDH Loop Stability

Today I tried aligning the XEND green beam into the arm cavity. Using M1 and M2 steering mirrors, I reached a max transmission ~1.2 of TEM00. In this configuration there was a "donut" mode also flashing, with transmission exceeding that of TEM00. Scanning all 4 degrees of freedom, I couldn't get TEM00 transmission to exceed 1.2, or significantly suppress the other modes. Not great mode matching. (PD gain: 20 dB; servo gain: 10.0.) 

In an earlier conversation Paco had recommended I preamplify the green REFL signal with an SR560 before feeding it to the RF mixer. (For yarm this is done with an SR560 gain of 1000.) I did so and raised the gain on the SR560 until it overloaded (PD: 0 dB; SR560: 100). This didn't immediately improve the lock quality, but because alignment still needed work I wasn't surprised. 

Anchal suggested the laser mode might be distorted by some lenses further upstream. We noticed some vertical spreading/distortion of the green beam by the first lens after SHG. I adjusted the pitch of an IR steering mirror until it disappeared. We then used the irises by the entrance to the arm cavity to coarsely align the input beam with M1 and M2. This time, fine alignment brought green transmission to just under 4. After slightly adjusting the half-wave plate, green transmission peaked at 4. (This is the highest I've seen it - previous max was 3.) The final combination of PD gain, SR560 gain, and servo gain that maximized transmission and duration of lock was (PD: 10 dB; SR560: 20; servo: 4.0). At its longest, lock on TEM00 was maintained for ~10 seconds.

AUX PDH Loop OLTF

In parallel with above, I was trying to take an OLTF of the loop whenever it was temporarily locked. I set up the measurement configuration like in the previous ELOG (injection at error point). Like last time, the loop would not lock when summing the PDH error signal with the excitation. I confirmed this was true even when I turned off the Moku excitation output. Checking the summed signal output, the Moku was adding an offset to the error signal. Buffering the excitation with an SR560 solved this issue.

The locked mode was switching pretty rapidly during the time I tried to measure the OLTF, and I ended up moving onto trying to improve lock. I might return today to try to take a measurement - I'll post it here.

Attachment 1: IMG_4166.jpg
IMG_4166.jpg
  17420   Wed Jan 25 12:49:14 2023 RadhikaUpdateALSXARM green laser lock debugging

I returned the half-wave plates on the XEND table back to their original angles, and restored the loop configuration with the PDH servo box. I returned the PD gain to 40 dB (original setting), and set the servo gain knob to 6. This was the region of highest loop stability, with the lock holding for a few seconds (as before). The control signal on the scope did not look intuitive - the peaks of the control signal corresponded with zero crossings of the error signal. 

Paco encouraged me to retake transfer function measurements of the PDH servo box. The main takeaway is the PDH servo (boost on) has the expected frequency response at a gain setting of 3 or under, up to 100 mVpp of input. Attachment 1 shows the frequency response at a servo gain of 2, for varying input amplitudes. 

The rest of the bode plots correspond to servo gain of 4, 6, 8, and 10 (boost on). The saturation LED would turn on above a gain value of ~3.25, so these results can't be analyzed or interpreted. But it does seem like a steep, low-frequency jump is a signature of the saturated servo. This jump doesn't appear with 10 mVpp input, at least at or above 1 Hz. 

Attachment 1: XEND_PDHservo_boost_on_gain2.pdf
XEND_PDHservo_boost_on_gain2.pdf
Attachment 2: XEND_PDHservo_boost_on_gain4.pdf
XEND_PDHservo_boost_on_gain4.pdf
Attachment 3: XEND_PDHservo_boost_on_gain6.pdf
XEND_PDHservo_boost_on_gain6.pdf
Attachment 4: XEND_PDHservo_boost_on_gain8.pdf
XEND_PDHservo_boost_on_gain8.pdf
Attachment 5: XEND_PDHservo_boost_on_gain10.pdf
XEND_PDHservo_boost_on_gain10.pdf
  7624   Thu Oct 25 15:38:06 2012 RajiUpdateAlignmentTransmitance Measurements on LaserOptik mirror

I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6

Here is the data

Polarization Input Angle Input Power(mW) Output Power(mW) Transmittance (%)
p 0 6.2 2.67 48
p 0 100 52 52
p 45 6.2 0.76 12
p 45 100 1,5 1
s 0 8.2 3.15 38
s 0 100 40 0.4
s 45 8.2 0.5 6
s 45 100 0.66 0.006

The mirror is not a good reflector at 0 deg.

  7644   Wed Oct 31 12:58:17 2012 RajiUpdateAlignmentTransmitance Measurements on LaserOptik mirror

Quote:

I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6

Here is the data

Polarization Input Angle Input Power(mW) Output Power(mW) Transmittance (%)
p 0 6.2 2.67 48
p 0 100 52 52
p 45 6.2 0.76 12
p 45 100 1,5 1
s 0 8.2 3.15 38
s 0 100 40 0.4
s 45 8.2 0.5 6
s 45 100 0.66 0.006

The mirror is not a good reflector at 0 deg.

 More data on the transmission. Measured the tranmission as a funtion of incidence angle at 1064nm

Attachment 1: Transmission-plot@1064nm.pdf
Transmission-plot@1064nm.pdf
Attachment 2: Transmission-data@1064nm.pdf
Transmission-data@1064nm.pdf
  3241   Fri Jul 16 23:53:27 2010 RanaUpdatePSLReference Cavity Insulation

From the trend, it seems that the Reference Cavity's temperature servo is working fine with the new copper foil. I was unable to find the insulating foam anywhere, but that's OK. We'll just get Frank to make us a new insulation with his special yellow stuff.

The copper foil that Steve got is just the right thickness for making it easy to form around the vacuum can, but we just have to have the patience to wrap ~5-10 more layers on there. We also have to get a new heater jacket; this one barely fits around the outside of the copper wrap. The one we have now seems to have a good heating wire pattern, but I don't know where we can buy these.

I also turned the HEPA's Variac back down to the nominal value of 20. Please remember to turn it back up to 100 before working on the PSL.

  3280   Fri Jul 23 16:02:16 2010 RanaUpdatePSLReference Cavity Insulation

This is the trend so far with the copper foil wrapping. According to Megan's calculation, we need ~1 mm of foil and the thickness of each layer is 0.002" (1/20th of a mm), so we need ~20 layers. We have ~5 layers so far.

As you can see the out-of-loop temperature sensor (RCTEMP) is much better than before. We need another week to tell how well the frequency is doing -

the recent spate of power cycles / reboots of the PSL have interrupted the trend smoothness so far.

Attachment 1: Untitled.png
Untitled.png
  3282   Fri Jul 23 21:14:29 2010 RanaUpdatePSLReference Cavity Insulation

I wrapped another ~3 layers onto there. It occurs to me now that we could just get some 2mm thick copper plates made to fit over the stainless steel can.

They don't have to completely cover it, just mostly. I also took the copper circles that Steve had made and marked them with the correct beam height

and put them on Steve's desk. We need a 1" dia. hole cut into these on Monday.

To compensate for the cooling during my work, I've set the heater for max heating for 1 hour and then to engage the temperature servo.

I also noticed the HEPA VARIAC on the PSL was set to 100. Please set it back to 20 after completing your PSL work so that it doesn't disturb the RC temperature..

  7869   Fri Dec 21 16:50:30 2012 RanaUpdateSUSTT in vac DB25 pin swapping

[Koji, Rana, Nic, Steve]

We went to the 25-pin D cable which connects to the TT1 quadropus and succeeded eventually in swapping pins 12/24 into the 13/25 positions.

  1. The D-sub connector is a custom made LIGO part and so it doesn't at all work to use the standard pin extractor tools to move the pins out; we should have investigated this before spending all this time poking at and possibly damaging the existing connector.
  2. To move the pins, we have to partially dis-assemble the connector and fish the pins/wires through the appropriate holes. Unfortunately, the design is such that we nearly lose all of the pins when trying to do this. Pictures describe the story better than words.
  3. After the swap we tried to test the TT, but again wasted some time because the vac feedthrough was incorrectly labeled. The 25-pin feedthrough labeled as "PZT1" does not, in fact, connect to the TT. Instead, its the one slightly above it that is labeled "Pico". I have moved the PZT1 sticker up to match the actual connector. In order to discover this, we beeped through several stages of the coil driver, cable system. WE need to order some in-line D-sub breakouts for 25pin, 37pin, and 9pin which are similar to the ones we have now for 15pin. These are better than the green terminal block breakouts.
  4. After this, we were able to see the TT move, but elected to leave the final piece of the work (determining which microD goes with which coil) to when Jamie gets back.
  5. The TT screen is not good: it needs to be just like the usual sus screen so that we can put in offsets, excitations, etc. Perhaps also the ASC-TT screen can link to the TT:SUS screens. We can just copy the eLIGO TT screens to get going.
  8395   Tue Apr 2 21:11:42 2013 RanaUpdateoptical tablesOptical Table Toolboxes Update

Quote:

A heavy duty plastic box is the likeliest candidate for the optical table toolbox. It measures 5 9/16 in. x 11 5/8 in. x 4 5/8 in. and fits all the tools comfortably. ( http://www.mcmaster.com/#plastic-bin-boxes/=m4yh4m  ,  under Heavy Duty Plastic Bin Boxes)

The list of tools has been updated to include a pen and a wire cutter as well as everything previously stated.

In addition, Steve has recommended that boxes should be secured to the walls or surfaces near the optical tables as opposed to the optical tables themselves, as to keep the tables from wobbling when tools are being exchanged.

A diagram of tentative box placements will go out soon.

 No, the small boxes must be attached to the optical tables. They won't be heavy enough to change the table tilt.

Also, all tools must be color coded according to the optical table using the 3M Vinyl table color code:

http://www.3m.com/product/images/Vinyl-Electrical-Color-Tape-300.jpg

  9316   Wed Oct 30 03:33:17 2013 RanaUpdateLSCLSC demod boards need some thought

 

 0309.png

I worked on the script SPAG4395A.py tonight with Masayuki's help. This sets up the parameters on the Agilent 4395A and then acquires the spectrum data. It had a couple of bugs before: no matter what channel you requested, you always got channel R. It also would disobey any requests to reduce the attenuation and left the Auto Atten ON. The version now in the SVN allows you to choose the channel and the attenuation.

It then makes this plot using matplotlib. The attached image is from the REFL165 pickoff at a time tonight when the arm powers were ~5-10. I have converted the spectrum from RF electrical Watts into Volts (V = 50*sqrt(W)). To go from the analyzer input to the demod board input we should scale this spectrum by a factor of ~15 (to account for the 20 dB from the coupler and the 3 dB of the splitter and a little more for losses). On the oscilloscope we see Vpp ~5 mV, so that's ~75 mVpp at the output of the BBPD which we're using for REFL165. Perhaps we can handle another factor of ~2-3 ? I'm not sure what we have in terms of linearity measurements on this thing.

EDIT: Evan is right, its V = sqrt(50*W), not V = 50*sqrt(W). ignore y-axis above

  16061   Wed Apr 21 11:01:37 2021 RanaUpdateCDS40m LSC simPlant model

The controller would be in the c1sus model, and connects to the c1sup plant model. So the controller doesn't go in the plant model.

Both the controller and the plant can be modeled using a single filter module in each separate model as you've drawn, but they go in separate models.

 

  1954   Wed Aug 26 19:58:14 2009 Rana, AlbertoUpdatePSLReference Cavity Temperature Control: MINCO PID removed

Summary: This afternoon we managed to get the temperature control of the reference cavity working again.

We bypassed the MINCO PID by connecting the temperature box error signal directly into EPICS.

We couldn't configure the PID so that it worked with the modified temperature box so we decided to just avoid using it.

Now the temperature control is done by a software servo by using the channel C1:PSL-FSS_MINCOMEAS as error signal and driving C1:PSL-FSS_TIDALSET (which we have clip-doodle wired directly to the heater input).

 

We 'successfully' used ezcaservo to stabilize the temperature:

ezcaservo -r C1:PSL-FSS_MINCOMEAS -s 26.6 -g -0.00003 C1:PSL-FSS_TIDALSET

 

We also recalibrated the channels:

C1:PSL-FSS_RMTEMP

C1:PSL-FSS_RCTEMP

C1:PSL-FSS_MINCOMEAS

with Peter King on the phone by using ezcawrite (EGUF and EGUL) but we didn't change the database yet. So please do not reboot the PSL computer until we update the database.

 

More details will follow.

Attachment 1: rc.png
rc.png
  8776   Thu Jun 27 22:52:38 2013 Rana, Gabriele, FrancescoSummaryComputer Scripts / ProgramsLIGO-DV installed

I installed ligoDV in the /ligo/apps/ligoDV/

Now, by pointing the tool at the local NDS2 server (megatron:31200) you can access the recent local data (raw, trends, etc.)

by running /ligo/apps/ligoDV/ligodv from the command line.

Attachment 1: ldv.png
ldv.png
  8387   Tue Apr 2 10:22:37 2013 Rana, Gabriele, JenneUpdateLSCPRMI lock

We locked the PRMI, this time really on the sidebands, using the two REFL55 signals.

Here are the parameters: triggering on POP22_I in at 140, out at 20. No normalization. MICH gain -0.15, PRCL gain 0.1

It seems that the lock is not very stable. It seems likely to come from some large angular motion of one of the mirrors. We'll need to calibrate the optical lever signals to understand which one is moving too much.

 

Attachment 1: lock_prmi_sb.pdf
lock_prmi_sb.pdf
  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.

  3102   Wed Jun 23 12:28:34 2010 RazibSummaryPhase CameraWeeekly Summary

This past week I have completed the following tasks:

 

1. Built a trigger and power box for the camera GC 750M (06058) and took some test images to see whether the trigger box really works. Result: It is doing fine!

2. Went over the setup that is already sitting on the table. Ref: Aidan's elog entry

3. Attended seminars and talks given by Alan, Jahms, Koji and Rana.

4. Attended the mandatory laser safety training by Peter.

 

Expected task for this week (could be more):

1. Work out analytical expressions of the power of the carrier and sidebands going to the camera in the setup. (As suggested by Rana and Joe)

2. Work on producing beat signal to the camera using the He-Ne laser setup.

3. Move,if possible, to the Nd:YAG setup.

4. Go over the codes and paper by the past SURFers on the phase camera experiment.

 

trigger-box_circuit.png

 


 

Attachment 2: test1.png
test1.png
  3146   Wed Jun 30 12:20:49 2010 RazibUpdatePhase CameraWeekly update

This week I have completed following tasks:

1. Worked out the analytical expressions for the amount of power of the DC and oscillatory part going into the camera.

2. Realigned the He-Ne PhaseCam setup as we had to replace the first steering mirror after the laser with a silvered mirror ( one without a dielectric coating for 1064 nm).

3. Gone through the code written by a previous surfer (Zach Cummings).

4. Read the paper 'Real-time phase-front detector for heterodyne interferometers'- F. Cervantes et. el. where they talk about constructing a phase detector for LISA pathfinder mission. One interesting fact I found was that, they used InGaAs chip for their CCD Cam which has a amazing QE of 80% @ 1064 nm. Unfortunately, the one we are using (Micro MT9V022 CMOS) has only ~5% QE for 1064 nm and 50% for 633 nm. One top of it MT9V022 has a built-in infra-red filter infront of it to make it more insenstive to 1064. In such limitations, we may have to find a work-around for this issue. Any idea?

5. Read about the EOM and AOM and their vibrating (!) way to add on and alter the incident light on them. (Source: Intro to Optical Electronics-Yariv)

 

One task that we couldn't accomplish even though I planned on doing is:

1. Move,if possible, to the Nd:YAG setup.

 

Task for this week:

1. Produce breathtaking calibration of the camera at He-Ne setup.

2. Read 'Fringe Analysis'-Y.Surrel and 'Phase Lock Technique'-Gardner.

3. Modify the phasecam code.

4. Produce an alternate triggerbox using diodes instead of Op-Amp as op-amp is suspected to fail at some point driving the camera due to impedance mismatch.

5. Answer Koji's question at Aidan's ELOG .

  3167   Wed Jul 7 12:17:36 2010 RazibUpdatePhase CameraWeekly update

I have completed the following tasks:

1. Find a simplified calibration of the exposure time for the current He-Ne setup. Basically, I triggered the camera to take 20 snapshots with a 20 Hz driving signal at different exposure time beginning from 100 us (microsecond) upto 4000 us with an increment of 200 us.

    Result: The current power allows the camera to have an exposure time of ~500 us before the DC level begans to saturate.

2. Aidan and I did some alignment and connected the AOM and corrected the driving frequency of its PZT to 40 Mhz(which apparently was disconnected which in turn gets the credit of NO beat signal for me until Tuesday 07/06/2010 5:30 PST) .

    Result: I got the beat signal of 1 Hz and 5 Hz. Image follows (the colormap shows the power in arbitrary units).

3. Finished writing my Progress Report 1 .

DC_1Hz_beat_sig.jpgDC_5Hz_beat_sig.jpg

Attachment 1: DC_1Hz_beat_sig.jpg
DC_1Hz_beat_sig.jpg
  3187   Fri Jul 9 12:07:26 2010 RazibUpdatePhase CameraWeekly update

Here are some more details about the current phasecam setup. We are using a He-Ne laser setup

phase_cam_setup_09_08_10.jpg

A crude snap shot of the setup....

mod_setup_(copy)_annotated.jpg

 

We sent light through SM2 (Steering Mirror 2)  to BS1(Beam-Splitter 1) where the laser light is split into two parts, one going to the AOM and the other to the EOM. The EOM adds 40 MHz sidebands to the incoming carrier light after SM3, and the AOM shifts the frequency of the incident light on it to 40.000 005 MHz. The purpose for doing this juggling is to intentionally create a beat signal off the reference beam from the AOM with the sidebands added at the EOM. Note that, we are driving the AOM at 7dBm and the EOM at 13 dBm with 0 (nil) modulation. The two lights are combined at the BS2 and sent off through SM5 to the camera. The CMOS of the camera contains silicon based Micro MT9V022 chip which has a quantum efficiency of 50% at 633 nm. Thus we expected a fairly good response to this He-Ne setup from the camera. 

Using a trigger circuit, we triggered the camera at 20 Hz by sending a 20Hz sinusoidal signal to it. The trigger circuit converts this to a positive square waves. Then I roughly figured out the optimum exposure time for the camera before the DC levels saturates it by writing a code for taking a series of 25 images at different exposure time. I found that 500µs seems to be a reasonable exposure time. So, using this data, I took 20 consecutive images and sent them through a short Fourier Transform segment using Matlab to see the beat signal. Note that the DC component from these processing of the images have some fringe pattern which is due to the ND 2.5 filter that we were using to reduce the light power incident on the camera. The FT method also gave us the presence of the beat signal at the corresponding bin of the FT (for example: for 5Hz beat signal, I got the DC at bin 1 of the FT and 5Hz component at bin 6 as expected). Then I changed the AOM driving frequency to 40.000 001 MHz in order to see a 1 Hz beat signal. The results for both is in my previous post. 

Quote:

I have completed the following tasks:

1. Find a simplified calibration of the exposure time for the current He-Ne setup. Basically, I triggered the camera to take 20 snapshots with a 20 Hz driving signal at different exposure time beginning from 100 us (microsecond) upto 4000 us with an increment of 200 us.

    Result: The current power allows the camera to have an exposure time of ~500 us before the DC level begans to saturate.

2. Aidan and I did some alignment and connected the AOM and corrected the driving frequency of its PZT to 40 Mhz(which apparently was disconnected which in turn gets the credit of NO beat signal for me until Tuesday 07/06/2010 5:30 PST) .

    Result: I got the beat signal of 1 Hz and 5 Hz. Image follows (the colormap shows the power in arbitrary units).

3. Finished writing my Progress Report 1 .

DC_1Hz_beat_sig.jpgDC_5Hz_beat_sig.jpg

 

  3215   Wed Jul 14 11:51:48 2010 RazibUpdatePhase CameraWork near 1Y2 yesterday

Quote:

Razib and I were attempting to get the output of a photodiode (PD55A in this case) recorded, so that we could independently measure the slow (~1-10 Hz) fluctuations of the light incident on the camera.  This would then allow us to subtract those fluctuations out, letting us get at the camera noise in the case with signal present (as opposed to just a dark noise measurement when we look at the noise with no signal present).

Originally I was thinking of using one empty patch panel BNCs used for PEM channels down by the 1Y7 rack and go through a 110B, although Alberto pointed out he had recently removed some monitoring equipment, which watched the amplitude modulation at various frequencies of the RF distribution (i.e. 33 MHz, etc).  This equipment output a DC voltage proportional to the amplitude of the RF signals.  The associated channel names were C1:IOO-RFAMPD_33MHZ, C1:IOO-RFAMPD_33MHZ_CAL, C1:IOO-RFAMPD_133MHZ, etc.  These are slow channels, so I presume they enter in via the slow computers, probably via pentek (I didn't check that, although in hindsight I probably should have taken the time to find exactly where they enter the system).  The connections them selves were a set of BNCs on the south side, half way up the 1Y2 rack.

We simply chose one, the 33 MHz channel in this case, and connected.  At around this time, the MC did become unlocked, although it looked like it was due to the MC2 watchdog tripping.  The initial theory was we had bumped the Mode Cleaner while looking around for some BNC cables, although from what Rana had to do last night, it probably was the connection.  We were able to restore the watchdog and confirm that the optic started to settle down again.  Unfortunately, I had to leave about 5 minutes later, and didn't do as thorough an investigation as was warranted.

 Before I left, I disconnected the PD55, so the 33 MHz channel wasn't physically connected to anything!!! Only one end of the wire was connected to the rack while the other was free...

So it wasn't the PD connection that is responsible for MC tripping at the later time...

  3217   Wed Jul 14 12:12:03 2010 RazibSummaryPhase CameraWeekly update

This week I was mainly interested in investigating the noise source at the phase camera. So having this issue in mind, my activities are the following:

1. I worked on producing multiple beat signal (1Hz and 5Hz). Elog entry.

2. I altered the setup so that instead of triggering the camera from the signal generator, we are now triggering it from the beat signal from the reference beam and sideband.

3. I made the nice little aluminium table for all the amplifiers, mixer and splitters to sit at one place instead of floating around.

4. I talked with Aidan and Joe and verified my calculation and extended it to further investigation of the noise source in the setup.

 

Plan for the upcoming week:

1. Measure and calibrate the camera w.r.t the power incident on it.

2. Investigate the noise source.

  3258   Wed Jul 21 12:20:58 2010 RazibUpdatePhase CameraWeekly update

This past week I have worked on the following:

1. Setting up the infrastructure to do noise analysis: We added a temporary channel on the DAQ to connect to the PD 55 which we are using to take the power measurement. Before that, I connected the PD55 to an oscilloscope and recorded the power.

    phase_cam_setup_21_07_2010.jpg

The power at PD55 as measured using the oscilloscope = 600 µV.

Then I tried to calibrate the channel by sending up a signal from the function generator and measuring up the offset.. However, the channels seems noisy enough, especially due to electronics noise as suggested by the measurements and FFT calculation.

2. I worked on trying to sync the data acquisition of the PD and the CAM. After sometime spent on fiddling with the software method such as taking images at stamped time and then lining them up with the daq timestamps, I found a hardware method as suggested by Aidan. It was putting up a shutter (Uniblitz shutter and driver VMMD1) in the setup. I synced the shutter with the camera for which I had to tear apart the previously made trigger box and add a sync output from the camera (took a while as I also had to make a new cable).

3. I worked (still working) on making a differential amplifier to blow up the signal from the PD.

 

 

 

  3309   Wed Jul 28 13:06:47 2010 RazibUpdatePhase Camera 

Attached are some calculation that I did previously for the phasecamera setup. This shows the nature of the beat signal that we are measuring.

I am also trying to characterize the noise source of the camera also. Following images shows the mean dark noise (with no light on the camera) and the standard deviation for 100 snaps at an exposure time of 500 µs.

mean_100_snaps.pngstd_100_snaps.png

My target now is to measure the response gain of each pixel and how they vary over intensity. I already have a simplified setup on the table and will work on it today. Details will follow at the end of the day.

Attachment 3: phase_cam_calc.pdf
phase_cam_calc.pdf phase_cam_calc.pdf phase_cam_calc.pdf
  3411   Thu Aug 12 16:52:02 2010 RazibUpdatePhase CameraSideband power measurement (updated)

I made some measurement of the SCR (signal to contrast ratio) from the signal from the EOM and the AOM.

The recipe for that was:

1. Trigger the camera at 20 Hz (from function generator).

2. Take a series of 20 images.

3. Do FFT to take out the DC component.

4. Extract the beat signal out of the FFT'd data.

5. Block the EOM.

6. Take another set of images of the AOM beam.

7. Take more(!) images, but this time of the background (blocking both EOM and AOM).

 

So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry.

The plot for that is:

SCR.jpg

 After measuring the SCR, I also measured the amplitude of the sideband and made an amplitude profile of the 40 MHz sideband.

The amplitude measurement is done as follows:

We know that the our 5 Hz signal consists of,

Sig = A_r * A_sb    where A_r = amplitude of the reference beam, A_sb= amplitude of the sideband

So, A_sb = Sig / A_r .

But,  A_r = sqrt ( P_AOM - Background),

Thus  A_sb = Sig / sqrt( P_AOM - Background) .

So the amplitude profile is done by taking the 5 Hz beat signal and dividing by the square root of the AOM beam minus the background light.

The plots looks like this:

DC_sig_sideband_profile.jpg

The solo sideband profile looks like this:

sideband_profile.jpg

Next we plan to trigger the camera with a 1 KHz signal and take snaps at n* T/4 (where n=0,1,2,3) of the period of the beat signal. So the plan is to trigger the camera at the point where the red dots appear in following cartoon.

sine_trig.jpg

Some more details of this setup will be posted later.

  

Quote:
 

 

Attachment 4: sine_trig.jpg
sine_trig.jpg
  3413   Thu Aug 12 17:28:28 2010 RazibUpdatePhase CameraSideband power measurement (updated)

Quote:

This sounds very relieving although this could be a lower bound of the number.
Why didn't you use the output on the PD which just give us the direct observation of your so-called SCR.

Quote:

So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry. 

 

 The SCR was at first measured using the output of the PD. That was exactly from where we got our 0.09 (previous elog entry). The second measurement was from the CCD.

  3360   Wed Aug 4 16:52:59 2010 Razib, AidanUpdatePhase CameraSideband power measurement (updated)

Aidan and I made some attempt to measure the power of the sidebands so that we can calculate our expected signal strength.

Our setup looks like the following:

Setup_08_04_2010.jpg

 

As light from the laser is split into two at BS1, the transmitted beam has higher power as our BS1 is only coated for 1064nm. We get two reflected beams from BS1, one reflected of the front surface and the other from the back surface. We took the stronger back reflected beam to the EOM driven at 40 MHz (also at 25 MHz at  a later time). The AOM produced a reference beam with 40 .000 005 MHz offset which we recombined with the sidebands obtained from the EOM. The beat produced is sent off to PDA 10CF connected to 4395A spectrum analyzer.

The plots for 40MHz sidebands and 25 MHz sidebands looks like this:

power_40MHz.png

From the above spectra, at 40 MHz sideband regime:

Power of the carrier @ 40 MHz = -39.72 dBm

Power of the sideband @ 80 MHz = -60.39 dBm

 

 

power_25MHz.png

At 25 MHz sideband regime,

Power of the carrier @ 40 MHz = -40.22 dBm

Power of the upper sideband @ 65 MHz = -61.72 dBm

Power of the lower sideband @ 15 MHz = -60.99 dBm

 

Power Measurement:

We made some necessary power measurement using a PD connected to a voltmeter after the EOM and the AOM when the EOM is driven at 40 MHz:

___________________________________________________________

Dark :  0.025 V

AOM on: 4.10 V    (EOM blocked)

EOM : 2.425 V      (AOM blocked)

___________________________________________________________

 From the earlier calculation (ref: Elog entry July 28) the power that we expect to see at the PD is,

P= A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 +2* A_r* A_sb * cos ( w_(r,sb) t ) ,                         where A_c= carrier;   A_r= reference beam;     A_sb=Upper sideband;    A_(-sb)= Lower sideband,     w_(r,sb) = w_r - w_sb

P = A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 +2* A_r* A_sb  , letting cos (w_(r,sb) go to 1) is order to approximate the maximum signal

So the signal that we expect to see relative to the DC ( i.e    A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2,    the first four terms of the power equation) is,

Sig = 2* A_r* A_sb    / { A_c ^2 + A_r^2 + A_(-sb)^2+ A_sb ^2 },

Since the modulation index is small, the power in the sideband is very small compared to carrier and the reference beam. So we can ignore the sideband power for the signal expression.

So,

Sig = 2* A_r* A_sb  /  ( A_c ^2 + A_r^2 )

So if we want to maximize this signal w.r.t the reference then,

d (sig)/ d(A_r) = 2 { ( A_c ^2  - A_r^2) *A_sb } / {( A_c^2 + A_r^2)} ^2

Thus, the signal is maximized when,

A_r^2 = A_c^2

 

We adjusted the AOM to be driven at + 7.7 dBM so that the new power at the AOM matched the EOM power, which is 2.397 in the voltmeter.

So the power at both the AOM and the EOM are:

P_AOM = ( V_AOM - V_dark) / (PD responsitivity * Transimpedance gain)

               = ( 2.397 - 0.025 ) / ( 0.45  * 1.5 x 10 ^5 )

               = 3.51 x 10 ^ - 5  W

P_EOM = (V_EOM - V _dark) / (PD responsitivity * Transimpedance gain)

               = ( 2. 425 - .0.025) / ( 0.45 * 1.5 x 10 ^5 )

               = 3.55 x 10^ - 5  W

 

From the spectra of the 40 MHz sideband above, the ratio of the carrier and the sideband amplitude is:  A_c / A_sb = 10.8 .

P_EOM = A_c ^2 + 2 A_sb ^2

Therefore, A_sb = sqrt ( P_EOM / 118.64) = 5.47 x 10^ - 4   V/m

Thus,     A_c = 5.908 x 10^ -3   V/m

and    A_r = sqrt ( P_AOM) = 5.92 x 10 -3    V/m.

 

This measurement can be used to calculate the signal to contrast ratio (SCR) that we expect to see:

SCR = 2 A_r * A_sb  / ( A_c^2  + A_r^2 )  = 0.09

 

Our next step is to measure the actual signal to constrast ratio as seen by the camera. Details of that will be posted soon.

  10221   Wed Jul 16 21:24:41 2014 ReetikaUpdateElectronicsVCO Driver inside 40m

  

I found the VCO driver, that Rana asked me to locate, inside the 40m. I already have one VCO from PSL lab. Now, I have kept both of them inside the 40m lab(one on the cart in the side of the Y-arm and the other near the X-arm electronics table).

  7747   Mon Nov 26 19:27:59 2012 RijuHowTo Testing AG4395A+GPIB

Riju, Jenne

We have checked the transfer function of a bandpass filter using AG4395A network analyzer and retrieved the data through GPIB. The RF out signal of AG4395A had been divided by splitter with two outputs of the splitter going to through R and the filter which was connected to the A channel of the network analyzer. The GPIB data came in complex data format, from which the absolute value and phase had to be retrieved. 

 

The plot for the TF is as following

Attachment 1: tfmag.jpg
tfmag.jpg
Attachment 2: tfphase.jpg
tfphase.jpg
  7756   Tue Nov 27 19:06:16 2012 RijuUpdate Testing AG4395A+GPIB

 I ve tested another bandpass filter today with similar set-up. This time I took the data with corrected reference level. To set this reference-level the filter was disconnected and the cable was connected "thru" according to the instructions provided in the manual of AG4395A at http://cp.literature.agilent.com/litweb/pdf/04395-90040.pdf, page 3-10. The transfer functions are as follows 

Attachment 1: tfmag1.jpg
tfmag1.jpg
Attachment 2: tfphase1.jpg
tfphase1.jpg
  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.

  7817   Wed Dec 12 17:26:47 2012 RijuUpdate Testing AG4395A+GPIB

I repeated my experiment to get noise level. To get that I disconnected the bandpass filter SBP-10.7  from channel A of network analyzer AG4395A and terminated both the open ends (open end of filter and open end of channel A) with 50ohm terminator.

Reference level had been corrected, signal and noise data had been collected separately w.r.t that level.

Command for GPIB:   ./netgpibdata.py -i 192.168.113.105 -d AG4395A -a 10 -f filename

The result is as follows

 

Attachment 1: TFbandpassfilter.pdf
TFbandpassfilter.pdf
  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:

Attachment 1: PDA10CF.pdf
PDA10CF.pdf
  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.

Attachment 1: PDA10CFrepeat.pdf
PDA10CFrepeat.pdf
Attachment 2: darknoiseVpda10cf.pdf
darknoiseVpda10cf.pdf
Attachment 3: darknoiseApda10cf.pdf
darknoiseApda10cf.pdf
Attachment 4: PDA10CF_z.pdf
PDA10CF_z.pdf
  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.

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

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

 

Attachment 1: TFreflpd.pdf
TFreflpd.pdf
Attachment 2: REFL_z.pdf
REFL_z.pdf
Attachment 3: darknoiseVreflpd.pdf
darknoiseVreflpd.pdf
Attachment 4: darknoiseAreflpd.pdf
darknoiseAreflpd.pdf
  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).

Attachment 1: analyzernoiseV.pdf
analyzernoiseV.pdf
  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.)

Attachment 1: PDA255.pdf
PDA255.pdf
Attachment 2: PDA255_z.pdf
PDA255_z.pdf
Attachment 3: darknoiseVpda255.pdf
darknoiseVpda255.pdf
Attachment 4: darknoiseApda255.pdf
darknoiseApda255.pdf
Attachment 5: darknoise_comparison.pdf
darknoise_comparison.pdf
ELOG V3.1.3-