40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Categorydown Subject
  17101   Wed Aug 24 10:49:43 2022 CiciUpdateGeneralMeasuring DFD output/X-arm laser PZT TF with Moku

We measured the TF of the X-arm laser PZT using the Moku so we can begin fitting to that data and hopefully creating a digital filter to cancel out PZT resonances. 

-------------------------------------------------------------

We calculated the DFD calibration (V/Hz) using:

Vrf = 0.158 mV (-6 dBm), Km = 1 (K_phi = Km*Vrf), cable length = 45m,  Tau = cable length/(0.67*3*10^8 m/s) ~ 220 ns. 

We've taken some preliminary data and can see the resonances around 200-300 kHz.

---------------------------------------------------------

Next steps are taking more data around the resonances specifically, calibrating the data using the DFD calibration we calculated, and adjusting parameters in our model so we can model the TF.

 

Attachment 1: AUX_PZT_Actuator_nofit.pdf
AUX_PZT_Actuator_nofit.pdf
  17103   Wed Aug 24 16:37:52 2022 CiciUpdateGeneralMore DFD/AUX PZT resonance measurements

Some more measurements of the PZT resonances (now zoomed in!) I'm adjusting parameters on our model to try and fit to it by hand a bit, definitely still needs improvements but not bad for a 2-pole 2-zero fit for now. I don't have a way to get coherence data from the moku yet but I've got a variety of measurements and will hopefully use the standard deviation to try and find a good error prediction...

 

Attachment 1: AUX_PZT_Actuator_narrow_fit.pdf
AUX_PZT_Actuator_narrow_fit.pdf
  17106   Thu Aug 25 16:39:31 2022 CiciUpdateGeneralI have learned the absolute basics of github

I have now added code/data to my github repository. (it's the little victories)

  17107   Fri Aug 26 12:46:07 2022 CiciUpdateGeneralProgress on fitting PZT resonances

Here is an update of how fitting the resonances is going - I've been modifying parameters by hand and seeing the effect on the fit. Still a work in progress. Magnitude is fitting pretty well, phase is very confusing. Attempted vectfit again but I can't constrain the number of poles and zeros with the code I have and I still get a nonsensical output with 20 poles and 20 zeros. Here is a plot with my fit so far, and a zip file with my moku data of the resonances and the code I'm using to plot.

Attachment 1: PZT_fit.zip
Attachment 2: AUX_PZT_Actuator_narrow_fit_1.pdf
AUX_PZT_Actuator_narrow_fit_1.pdf
  17110   Mon Aug 29 13:33:09 2022 JCUpdateGeneralLab Cleanup

The machine shop looked a mess this morning, so I cleaned it up. All power tools are now placed in the drawers in the machine shop. Let me know if there are any questions of where anything here is placed. 

Attachment 1: EDE63209-D556-41F1-9BF2-89CD78E3D7B7.jpeg
EDE63209-D556-41F1-9BF2-89CD78E3D7B7.jpeg
  17112   Mon Aug 29 18:25:12 2022 CiciUpdateGeneralTaking finer measurements of the actuator transfer function

Took finer measurements of the x-arm aux laser actuator tranfer function (10 kHz - 1 MHz, 1024 pts/decade) using the Moku.

--------------------------------------

I took finer measurements using the moku by splitting the measurement into 4 sections (10 - 32 (~10^4.5) kHz, 32 - 100 kHz, 100 - 320 kHz, 320 - 1000 kHz) and then grouping them together. I took 25 measurements of each ( + a bonus in case my counting was off), plotted them in the attached notebook, and calculated/plotted the standard deviation of the magnitude (normalized for DC offset). Could not upload to the ELOG as .pdf, but the pdf's are in the .zip file.

--------------------------------------

Next steps are to do the same stdev calculation for phase, which shouldn't take long, and to use the vectfit of this better data to create a PZT inversion filter.

Attachment 1: PZT_TF_fine.png
PZT_TF_fine.png
Attachment 2: PZT_TF_fine_mag_stdev.png
PZT_TF_fine_mag_stdev.png
Attachment 3: ATF_fine.zip
  17114   Wed Aug 31 00:32:00 2022 KojiUpdateGeneralSOS and other stuff in the clean room

Salvage these (and any other things). Wrap and double-pack nicely. Put the labels. Store them and record the location. Tell JC the location.

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  17115   Wed Aug 31 00:46:56 2022 KojiUpdateGeneralVertex Lab area to be cleaned

As marked up in the photos.

 

Attachment 5: The electronics units removed. Cleaning half way down. (KA)

Attachment 6: Moved most of the units to 1X3B rack ELOG 17125 (KA)

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  17116   Wed Aug 31 01:22:01 2022 KojiUpdateGeneralAlong the X arm part 1

 

Attachment 5: RF delay line was accommodated in 1X3B. (KA)

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  17117   Wed Aug 31 01:24:48 2022 KojiUpdateGeneralAlong the X arm part 2

 

 

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  17118   Wed Aug 31 01:25:37 2022 KojiUpdateGeneralAlong the X arm part 3

 

 

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  17119   Wed Aug 31 01:30:53 2022 KojiUpdateGeneralAlong the X arm part 4

Behind the X arm tube

Attachment 1: PXL_20220831_020757504.jpg
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  17120   Wed Aug 31 01:53:39 2022 KojiUpdateGeneralAlong the Y arm part 1

 

 

Attachment 1: PXL_20220831_021118213.jpg
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  17121   Wed Aug 31 01:54:45 2022 KojiUpdateGeneralAlong the Y arm part 2
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  17125   Wed Aug 31 16:11:37 2022 KojiUpdateGeneralVertex Lab area to be cleaned

The analog electronics units piled up along the wall was moved into 1X3B rack which was basically empty. (Attachments 1/2/4)

We had a couple of unused Sun Machines. I salvaged VMIC cards (RFM and Fast fiber networking? for DAQ???) and gave them to Tega.
Attachment 3 shows the eWastes collected this afternoon.

Attachment 1: PXL_20220831_224457839.jpg
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Attachment 4: PXL_20220901_021729652.jpg
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  17128   Fri Sep 2 15:26:42 2022 YehonathanUpdateGeneralSOS and other stuff in the clean room

{Paco, Yehonathan}

BHD Optics box was put into the x-arm last clean cabinet. (attachment 5)

OSEMs were double bagged in a labeled box on the x-arm wire racks. (attachment 1)

SOS Parts (wire clamps, winches, suspension blocks, etc.) were put in a box on the x-arm wire rack. (attachment 3)

2"->3" optic adapter parts were put in a box and stored on the xarm wire rack. (attachment 3)

Magnet gluing parts box was labeled and stored on the xarm rack. (attachment 2)

TT SUS with the optics were stored on the flow bench at the x end. Note: one of the TT SUS was found unsuspended. (attachment 4)

InVac parts were double bagged and stored in a labeled box on the x arm wire rack. (attachment 2)

Attachment 1: osem_sus.jpeg
osem_sus.jpeg
Attachment 2: magnet_gluing.jpeg
magnet_gluing.jpeg
Attachment 3: 2-3inch_adapter_parts.jpeg
2-3inch_adapter_parts.jpeg
Attachment 4: TTs.jpeg
TTs.jpeg
Attachment 5: BHD_optics.jpeg
BHD_optics.jpeg
  17129   Fri Sep 2 15:30:10 2022 AnchalUpdateGeneralAlong the X arm part 1

[Anchal, Radhika]

Attachment 2: The custom cables which were part of the intermediate setup between old electronics architecture and new electronics architecture were found.
These include:

  • 2 DB37 cables with custom wiring at their connectors to connect between vacuum flange and new Sat amp box, marked J4-J5 and J6-J7.
  • 2 DB15 to dual head DB9 (like a Hydra) cables used to interface between old coil drivers and new sat amp box.

A copy of these cables are in use for MC1 right now. These are spare cables. We put them in a cardboard box and marked the box appropriately.
The box is under the vacuum tube along Yarm near the center.

 

  17130   Fri Sep 2 15:35:19 2022 AnchalUpdateGeneralAlong the Y arm part 2

[Anchal, Radhika]

The cables in USPS open box were important cables that are part of the new electronics architecture. These are 3 ft D2100103 DB15F to DB9M Reducer Cable that go between coil driver output (DB15M on back) to satellite amplifier coil driver in (DB9F on the front). These have been placed in a separate plastic box, labeled, and kept with the rest of the D-sub cable plastic boxes that are part of the upgrade wiring behind the tube on YARM across 1Y2. I believe JC would eventually store these dsub cable boxes together somewhere later.

  17132   Tue Sep 6 09:57:26 2022 JCSummaryGeneralLab cleaning

DB9 Cables have been assorted and placed behind the Y-Arm. Long BNC Cables and Ethernet Cables have been stored under the Y-Arm. 

Quote:

We held the lab cleaning for the first time since the campus reopening (Attachment 1).
Now we can use some of the desks for the people to live! Thanks for the cooperation.

We relocated a lot of items into the lab.

  • The entrance area was cleaned up. We believe that there is no 40m lab stuff left.
    • BHD BS optics was moved to the south optics cabinet. (Attachment 2)
    • DSUB feedthrough flanges were moved to the vacuum area (Attachment 3)
  • Some instruments were moved into the lab.
    • The Zurich instrument box
    • KEPCO HV supplies
    • Matsusada HV supplies
  • We moved the large pile of SUPERMICROs in the lab. They are around MC2 while the PPE boxes there were moved behind the tube around MC2 area. (Attachment 4)
  • We have moved PPE boxes behind the beam tube on XARM behind the SUPERMICRO computer boxes. (Attachment 7)
  • ISC/WFS left over components were moved to the pile of the BHD electronics.
    • Front panels (Attachment 5)
    • Components in the boxes (Attachment 6)

We still want to make some more cleaning:

- Electronics workbenches
- Stray setup (cart/wagon in the lab)
- Some leftover on the desks
- Instruments scattered all over the lab
- Ewaste removal

 

Attachment 1: 982146B2-02E5-4C19-B137-E7CC598C262F.jpeg
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  17143   Mon Sep 19 17:02:57 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.


ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:

SUSSIDE_GAIN 1250->50

SUSPOS_GAIN 200->150

SUSYAW_GAIN 60->30

These action seem to make things better.

  17145   Tue Sep 20 07:03:04 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

[JC, Tega, Paco ]

I would like to mention that during the Vacuum startup, after the AUX pump was turned on, Tega and I were walking away while the pressure decreases. While we were, valves opened on their own. Nobody was near the VAC Desktop during this. I asked Koji if this may be an automatic startup, but he said the valves shouldn't open unless they are explicitely told to do so. Has anyone encountered this before?

Quote:

Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.


ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:

SUSSIDE_GAIN 1250->50

SUSPOS_GAIN 200->150

SUSYAW_GAIN 60->30

These action seem to make things better.

 

  17162   Wed Sep 28 19:15:56 2022 KojiUpdateGeneralTesting 950nm laser found in trash pile

I don't know what was wrong with the past setup but the 950nm laser (QPHOTONICS QFLD-950-3S) just worked fine up to ~300MHz with basically the same setup.

A 20dB coupler picks up a small amount of the driving signal from the source signal of the network analyzer. This was fed to CHR. The fiber-coupled NewFocus PD RF output was connected to CHA.
The calibration of the response was done with the thru response (connect the source signal to the CHA via all the long cables).

Attachment 1 shows the response CHA/CHR. The output is somewhat flat up to 20MHz and goes down towards 100MHz, but still active up to 500MHz as long as the normalization with the New Focus PD works.
The structure around 200MHz~300MHz changes with how the wires of the clips are arranged. I have twisted and coiled them as shown and the notch disappeared. For the permanent setup we should keep the lines as short as possible and take care of the stray capacitance and the inductance.

Attachment 2 shows the setup at the network analyzer side. Nothing special.

Attachment 3 shows the setup at the laser side. The DB9 connector on the Jenne's laser has the negative output of the LD driver connected to the coax core and the positive output connected to the shield of the coax. Therefore the coax core (red clip) has to be connected to Pin 9 and the coax shield (black clip) to PIn 5.

Attachment 1: PXL_20220929_013850989.MP.jpg
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  17224   Thu Nov 3 16:00:58 2022 alexSummaryGeneralSensoray updates

I am currently working on getting the driver reinstalled on Donatella for the sensoray. An issue keeps arising that will not allow me to run "make" successfully in the unzipped driver folder. Will continue to remedy this.

This is why there is no light showing up on the device while plugged in. The computer does see the device, but does not show its model due to the inability for it to communicate without the driver.

 

-Alex

  17233   Mon Nov 7 12:37:26 2022 KojiUpdateGeneralBorrowed the fiber tester for the OMC lab

I am borrowing the fiber illuminator / fiber tester / VisiFault for the OMC lab. It has been stored in the top drawer at the center work bench.

==> Returned

Attachment 1: PXL_20221107_202016688.MP.jpg
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  17239   Mon Nov 7 21:57:42 2022 alexUpdateGeneralSensoray

I have made little progress in getting the sensoray driver installed on Donatella. I have confirmed that it is indeed the reason why none of the hardware is working. I am now working through changes on a virtual machine that is running Scientific Linux to find something that may work. If no progress is made soon, I will ensure that software for a replacement video encoder is able to be installed before requesting we order one.

  17247   Tue Nov 8 21:39:12 2022 alexSummaryGeneralSensoray & SDI Video Encoder selection

I have been looking at various replacements for the sensoray, and have found that the majority of new usb video encoders don't have drivers anymore and now just work through being embedded with video-capturing software. This means that the hardware must be used with a compatible video player such as VLC or OBS. VLC can natively be run with terminal commands, and because OBS is open source, there are packages that can be downloaded to use terminal commands to control the software as well. I am not sure to what extent the usb video encoder can then be controlled with these commands, but this seems to be the easiest method so far. I will finish picking which new unit we should purchase tomorrow, and order it through JC. 

  17258   Fri Nov 11 19:11:50 2022 JCUpdateGeneralWFS Whitening and Demod Boards

WFS Whitening and Demod boards were scavenged. ' iLIGO WFS cards are in big plastic boxes placed on the north wall around Section Y5 or Y6 (not under the arm). The WFS head PCBs, empty WFS housing, WFS components, I/Q demod components are at SectionY10 under the arm tube. ' - Koji . I have taken pictures of the boards and will upload them to the DCC once I find a way to add a Serial Number . (I will upload this to the eLog as a HowTo) The next step is to search for at least 2 extender boards to troubleshoot these board and find if there are any issues. We may have replace some components and retune the boards. Attachment #1 is an example of the WFS Whitening Filter and Attachment #2 is and example of the the WFS Demod Board.

If you use the Camera DO NOT remove the strap. I have also purchased lens caps for the camera, so after usage PUT THE LENS CAP BACK ON. 

Attachment 1: IMG_6419.JPG
IMG_6419.JPG
Attachment 2: IMG_6424.JPG
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  17267   Tue Nov 15 16:34:55 2022 alexUpdateGeneralDebian with Sensoray

I have confirmed the ability to install the sensoray drivers on Debian 11 in a virtual machine environment. I will do testing with the sensoray device on this tomorrow and if all works, begin working on code for capturing images. I will then test this out on Donatella once Tega finishes installing Debian across all computers in the coming week or so. 

Attachment 1: sensoray_debian_VM_1.png
sensoray_debian_VM_1.png
  17276   Thu Nov 17 09:06:35 2022 JCSummaryGeneralLight Replace

Electrical Shop came in today to replace the lightbulbs around 40m. I supervised the entire visit, inside and outside the lab area. I was sure to use the ladders which were already inside the lab area. Although, while I was crawling under the MC beam tube, I came up too quickly and bumped it. This may have caused MC to become misaligned. Anyways, Yehonathan and I are realigning now.

 

  17292   Mon Nov 21 14:55:58 2022 JCConfigurationGeneralLED Instead of Incandescent Lights

Electrical came by today to see the lights. The issue may be the switches, but they will come by tomorrow to solve the issue. A couple light bulbs were noticed to be out, but they no longer have incandescent lights. . . only LED. I figured this would be preffered because of the reduction on noise. I would prefer to go ahead and ask to change all the incandescent bulbs to LED bulbs. Are there any objections to this?

  14518   Fri Apr 5 11:40:57 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • Attachment #1 shows the present experimental setup. The photodiode is now replaced with PDA255. The farther end of the fiber (output of the delayed arm) is coupled through a collimator and aligned such that the beam from the delayed path fall on the detector along with the undelayed path of MZI. We tried to measure the frequency noise of the laser with this setup, but we didn’t get anything sensible.
  • One of the main draw backs of the measurement was the polarisation was not aligned properly in the setup. So, then the next step was to identify the polarisation at different locations in the beam path and to maximise the polarisation to either S or P component.

  • So, we introduced HWP at the input beam path after isolator as shown in attachment #1. Also, the polarisation was tested at positions P1, P2, P3, and P4 shown in attachment #1 by placing a polarisation beam splitter at these locations and then by observing the transmitted (P component) and reflected light (S component) using power meter.

  • The observations at different locations are as the follows

Position Input power (mW) P component (mW) S component (mW)
P1 279 145 123
P2 255 113 137
P3 129 67 58
P4 124 66 53

 

  • These observations show that the P and S components are almost equal, and this is not a good polarisation arrangement. At this point, we also had to check whether the incoming beam is linearly polarised or not.

  • To test the same, the PBS was placed at position P1 and the P and S components were observed with power meter as the HWP is rotated.Attachment # 2 shows the results of the same, that is the variation in P and S component as the HWP is rotated.

  • This result clearly shows that the input beam is linearly polarised. The HWP was then adjusted such that the P component is maximum and coupled to the MZI. With this orientation of HWP, the polarisation observed at different positions P1, P2, P3, and P4 are as follows.

Position Input (mW) P component (mW) S component (mW)
P1 283 276 5
P2 248 228 7
P3 126 121 2
P4 128 117 1
  • This shows that the polarisation is linearly polarised as well as it is oriented along the P direction (parallel to the optical table).

  • We have the polarisation maintaining fiber (PM 980) as the delay fiber. The polarisation of the light as it propagates through a PM fiber depends on how well the input beam is coupled to the axis (slow or fast) of the fiber. So, the next task was to couple the light to one of the axes of the fiber.

  • The alignment key on the fiber is a good indication of the axis of the fiber. In our case, the alignment key lines up with the slow axis of the fiber. We decided to couple the light to the fast axis of the fiber. Since the incoming beam is P polarised, the output fiber coupler was  aligned such that the fast axis is parallel to optical table as possible.

  • A PBS was then introduced after the fiber output collimator . There is a HWP (marked as HWP2 in attachment 1) in front of the input coupler of the fiber as well. This HWP was then rotated and observed the P and S component from the PBS that is now placed after the output coupler with a power meter.The idea was , when the light is coupled to the fast axis of the fiber, we will see the maximum at the P componet at the output

  • Attachment # 3 shows the observation. 

  • In this way I tried to find the orientation of the HWP2 such that the P component is maximum at the output. But I was not succeeded in this method and observed that the output was fluctuating when the fiber was disturbed. One  doubt we had was whether the fiber is PM or not . Thus we checked the fiber end with fiber microscope and confirmed that it is PM fiber. 

  • Thus, we modifed the setup as shown in attachement # 4.The photodetector (PDA55) was monitoring the S component and the output of the detector was observed on an oscilloscope. We rotated the HWP2 such that the S component is almost minimum. At the same time, we were disturbing the fiber and was observing whether the output is fluctuating. The HWP2 angle was tweaked around the minimum of S component and observed the output with disturbing the fiber. This way we found the orientation of HWP2  such that the light is coupled to the fast axis of the fiber and the output was not fluctuating while we disturb the fiber. We tested it  by heating the fiber with a heat gun as well and confirmed that the output is not fluctuating and thus the light is coupled to the fast axis of the fiber.

Attachment 1: Modified_experimental_setup.JPG
Modified_experimental_setup.JPG
Attachment 2: Checking_polarisation.pdf
Checking_polarisation.pdf
Attachment 3: Checking_the_polarisation_alignment_of_the_delay_fiber.pdf
Checking_the_polarisation_alignment_of_the_delay_fiber.pdf
Attachment 4: Setup_to_test_the_polarisation_alignment_of_delay_fiber.JPG
Setup_to_test_the_polarisation_alignment_of_delay_fiber.JPG
  14520   Sat Apr 6 02:07:40 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • The alignment of the output beam from the delayed path of MZI to the photodetector was disturbed when we did the polarisation characterisation yesterday. So, today we tried to align the output beam from the delayed path of MZI to the detector .
  • We then observed the beat output from the detector on oscilloscope.We initialy observed a dc shift . We then applied a frequency modulation on the input laser and observed the output on oscilloscope. We expected to see variation in output frequency in accordance with variation of input frequency modulation. But we didnt observe this and we were not really getting the interference pattern. 
  • We tried to make the alignment better. With a better alignment, we could see the interference pattern. We also observed that the output frequency was varying in accordance with variation in the input frequency modulation. We would expect a better result with proper mode matching of the two beams on the photodetector.
  14529   Wed Apr 10 00:33:09 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source
  • Attachement #1 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 100 Hz
  • Attachement #2 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 30 Hz
  • The output frequency is varying in accordance with variation in modulation frequency. It is observed that, for a given modulation frequency also, the output frequency is fluctuating. There could be multiple reasons for this behaviour. One of the main reasons is the frequency noise of the laser itself. Also, there could be acoustic noise coupled to the system (eg, by change in length of the fiber).
  • The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier  the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55. 
  • We then applied frequency modulation on the input laser and observed the output of the two photodiodes. But we didn't get the results as we expected and observed earlier (shown in attachment #1 &2). Looks like, the problem is poor mode matching between the two beams. 
Quote:
  • The alignment of the output beam from the delayed path of MZI to the photodetector was disturbed when we did the polarisation characterisation yesterday. So, today we tried to align the output beam from the delayed path of MZI to the detector .
  • We then observed the beat output from the detector on oscilloscope.We initialy observed a dc shift . We then applied a frequency modulation on the input laser and observed the output on oscilloscope. We expected to see variation in output frequency in accordance with variation of input frequency modulation. But we didnt observe this and we were not really getting the interference pattern. 
  • We tried to make the alignment better. With a better alignment, we could see the interference pattern. We also observed that the output frequency was varying in accordance with variation in the input frequency modulation. We would expect a better result with proper mode matching of the two beams on the photodetector.
Attachment 1: Modulation_frequency_100Hz.jpg
Modulation_frequency_100Hz.jpg
Attachment 2: Modulation_frequency_30Hz.jpg
Modulation_frequency_30Hz.jpg
Attachment 3: Modified_setup.JPG
Modified_setup.JPG
  14540   Fri Apr 12 01:22:27 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

The alignement was disturbed after the replcement of the beam splitter. We tried to get the alignment back . But we are not succeeded yet in getting good interfernce pattern. This is mainly because of poor mode matching of two beams. We will also try with the spooled fiber.

Quote:

 

  • The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier  the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55. 
 
 
  14544   Mon Apr 15 22:39:10 2019 gautamUpdateFrequency noise measurementAlternate setup with PSL pickoff

[anjali, gautam]

just main points, anajli is going to fill out the details.

To rule out mode-matching as the reason for non-ideal output from the MZ, I suggested using the setup I have on the NW side of the PSL enclosure for the measurement. This uses two identical fiber collimators, and the distance between collimator and recombination BS is approximately the same, so the spatial modes should be pretty well matched. 

The spooled fiber we found was not suitable for use as it had a wide key connector and I couldn't find any wide-key FC/PC to narrow-key FC/APC adaptors. So we decided to give the fiber going to the Y end and back (~90m estimated length) a shot. We connected the two fibers at the EY table using a fiber mating sleeve (so the fiber usually bringing the IR pickoff from EY to the PSL table was disconnected from its collimator). 

In summary, we cannot explain why the contrast of the MZ is <5%. Spatial mode-overlap is definitely not to blame. Power asymmetry in the two arms of the MZ is one possible explanation, could also be unstable polarization, even though we think the entire fiber chain is PM. Anjali is investigating.

 


We saw today that the Thorlabs PM beam splitters (borrowed from Andrew until our AFW components arrive) do not treat the two special axes (fast and slow) of the fiber on equal footing. When we coupled light into the fast axis, we saw huge asymmetry between the two split arms of the beamsplitter (3:1 ratio in power instead of the expected 1:1 for a 50/50 BS). Looking at the patch cord with an IR viewer, we also saw light leaking through the core along it. Turns out this part is meant to be used with light coupled to the slow axis only.

  14547   Wed Apr 17 00:43:38 2019 gautamUpdateFrequency noise measurementMZ interferometer ---> DAQ
  1. Delay fiber was replaced with 5m (~30 nsec delay)
    • The fringing of the MZ was way too large even with the free running NPRO (~3 fringes / sec)
    • Since the V/Hz is proportional to the delay, I borrowed a 5m patch cable from Andrew/ATF lab, wrapped it around a spool, and hooked it up to the setup
    • Much more satisfactory fringing rate (~1 wrap every 20 sec) was observed with no control to the NPRO
  2. MZ readout PDs hooked up to ALS channels
    • To facilitate further quantitative study, I hooked up the two PDs monitoring the two ports of the MZ to the channels normally used for ALS X.
    • ZHL3-A amps inputs were disconnected and were turned off. Then cables to their outputs were highjacked to pipe the DC PD signals to the 1Y3 rack
    • Unfortunately there isn't a DQ-ed fast version of this data (would require a model restart of c1lsc which can be tricky), but we can already infer the low freq fringing rate from overnight EPICS data and also use short segments of 16k data downloaded "live" for the frequency noise measurement.
    • Channels are C1:ALS-BEATX_FINE_I_IN1 and C1:ALS-BEATX_FINE_Q_IN1 for 16k data, and C1:ALS-BEATX_FINE_I_INMON and C1:ALS-BEATX_FINE_I_INMON for 16 Hz.

At some point I'd like to reclaim this setup for ALS, but meantime, Anjali can work on characterization/noise budgeting. Since we have some CDS signals, we can even think of temperature control of the NPRO using pythonPID to keep the fringe in the linear regime for an extended period of time.

  14571   Thu Apr 25 03:32:25 2019 AnjaliUpdateFrequency noise measurementMZ interferometer ---> DAQ
  • Attachment #1 shows the time domain output from this measurement. The contrast between the maximum and minimum is better in this case compared to the previous trials.
  • We also tried to extract the frequency noise of the laser from this measurement. Attachment #2 shows the frequency noise spectrum. The experimental result is compared with the theoretical value of frequency noise. Above 10 Hz, the trend is comparable to the expected 1/f characteristics, but there are other peak also appearing. Similarly, below 10 Hz, the experimentally observed value is higher compared to the theory.
  • One of the uncertainties in this result is because of the length fluctuation of the fiber. The phase fluctuation in the system could be either because of the frequency noise of the laser or because of the length fluctuation of the fiber.  So,one of the reasons for the discrepancy between the experimental result and theory could be because of  fiber length fluctuation. Also, there were no locking method been applied to operate the MZI in the linear range.
  • The next step would be to do a heterodyne measurement. Attachment #3 shows the schematic for the heterodyne measurement. A free space AOM can be inserted in one of the arms to do the frequency shift. At the output of photodiode, a RF heterodyne method as shown in attachment #3 can be applied to separate the inphase and quadrature component. These components need to be saved with a deep memory system. Then the phase and thus the frequency noise can be extracted.
  • Attachment #4 shows the noise budget prepared for the heterodyne setup. The length of the fiber considered is 60 m and the photodiode is PDA255. I also have to add the frequency noise of the RF driver and the intensity noise of the laser in the noise budget.
Quote:
  1. Delay fiber was replaced with 5m (~30 nsec delay)
    • The fringing of the MZ was way too large even with the free running NPRO (~3 fringes / sec)
    • Since the V/Hz is proportional to the delay, I borrowed a 5m patch cable from Andrew/ATF lab, wrapped it around a spool, and hooked it up to the setup
    • Much more satisfactory fringing rate (~1 wrap every 20 sec) was observed with no control to the NPRO
  2. MZ readout PDs hooked up to ALS channels
    • To facilitate further quantitative study, I hooked up the two PDs monitoring the two ports of the MZ to the channels normally used for ALS X.
    • ZHL3-A amps inputs were disconnected and were turned off. Then cables to their outputs were highjacked to pipe the DC PD signals to the 1Y3 rack
    • Unfortunately there isn't a DQ-ed fast version of this data (would require a model restart of c1lsc which can be tricky), but we can already infer the low freq fringing rate from overnight EPICS data and also use short segments of 16k data downloaded "live" for the frequency noise measurement.
    • Channels are C1:ALS-BEATX_FINE_I_IN1 and C1:ALS-BEATX_FINE_Q_IN1 for 16k data, and C1:ALS-BEATX_FINE_I_INMON and C1:ALS-BEATX_FINE_I_INMON for 16 Hz.

At some point I'd like to reclaim this setup for ALS, but meantime, Anjali can work on characterization/noise budgeting. Since we have some CDS signals, we can even think of temperature control of the NPRO using pythonPID to keep the fringe in the linear regime for an extended period of time.

Attachment 1: Time_domain_output.pdf
Time_domain_output.pdf
Attachment 2: Frequency_noise.pdf
Frequency_noise.pdf
Attachment 3: schematic_heterodyne_setup.png
schematic_heterodyne_setup.png
Attachment 4: Noise_budget_1_micron_in_Hz_per_rtHz.pdf
Noise_budget_1_micron_in_Hz_per_rtHz.pdf
  14573   Thu Apr 25 10:25:19 2019 gautamUpdateFrequency noise measurementHomodyne v Heterodyne

If I understand correctly, the Mach-Zehnder readout port power is only a function of the differential phase accumulated between the two interfering light beams. In the homodyne setup, this phase difference can come about because of either fiber length change OR laser frequency change. We cannot directly separate the two effects. Can you help me understand what advantage, if any, the heterodyne setup offers in this regard? Or is the point of going to heterodyne mainly for the feedback control, as there is presumably some easy way to combine the I and Q outputs of the heterodyne measurement to always produce an error signal that is a linear function of the differential phase, as opposed to the sin^2 in the free-running homodyne setup? What is the scheme for doing this operation in a high bandwidth way (i.e. what is supposed to happen to the demodulated outputs in Attachment #3 of your elog)? What is the advantage of the heterodyne scheme over applying temperature feedback to the NPRO with 0.5 Hz tracking bandwidth so that we always stay in the linear regime of the homodyne readout?

Also, what is the functional form of the curve labelled "Theory" in Attachment #2? How did you convert from voltage units in Attachment #1 to frequency units in Attachment #2? Does it make sense that you're apparently measuring laser frequency noise above 10 Hz? i.e. where do the "Dark Current Noise" and "Shot Noise" traces for the experiment lie relative to the blue curve in Attachment #2? Can you point to where the data is stored, and also add a photo of the setup?

  14576   Thu Apr 25 15:47:54 2019 AnjaliUpdateFrequency noise measurementHomodyne v Heterodyne

My understanding is that the main advantage in going to the heterodyne scheme is that we can extract the frequecy noise information without worrying about locking to the linear region of MZI. Arctan of the ratio of the inphase and quadrature component will give us phase as a function of time, with a frequency offset. We need to to correct for this frequency offset. Then the frequency noise can be deduced. But still the frequency noise value extracted would have the contribution from both the frequency noise of the laser as well as from fiber length fluctuation. I have not understood the method of giving temperature feedback to the NPRO.I would like to discuss the same.

The functional form used for the curve labeled as theory is 5x104/f. The power spectral density (V2/Hz) of the the data in attachment #1 is found using the pwelch function in Matlab and square root of the same gives y axis in V/rtHz. From the experimental data, we get the value of Vmax and Vmin. To ride from Vmax to Vmin , the corrsponding phase change is pi. From this information, V/rad can be calculated. This value is then multiplied with 2*pi*time dealy to get the quantity in V/Hz. Dividing V/rtHz value with V/Hz value gives  y axis in Hz/rtHz. The calculated value of shot noise and dark current noise are way below (of the order of 10-4 Hz/rtHz) in this frequency range. 

I forgor to take the picture of the setup at that time. Now Andrew has taken the fiber beam splitter back for his experiment. Attachment #1 shows the current view of the setup. The data from the previous trial is saved in /users/anjali/MZ/MZdata_20190417.hdf5

 

Quote:

If I understand correctly, the Mach-Zehnder readout port power is only a function of the differential phase accumulated between the two interfering light beams. In the homodyne setup, this phase difference can come about because of either fiber length change OR laser frequency change. We cannot directly separate the two effects. Can you help me understand what advantage, if any, the heterodyne setup offers in this regard? Or is the point of going to heterodyne mainly for the feedback control, as there is presumably some easy way to combine the I and Q outputs of the heterodyne measurement to always produce an error signal that is a linear function of the differential phase, as opposed to the sin^2 in the free-running homodyne setup? What is the scheme for doing this operation in a high bandwidth way (i.e. what is supposed to happen to the demodulated outputs in Attachment #3 of your elog)? What is the advantage of the heterodyne scheme over applying temperature feedback to the NPRO with 0.5 Hz tracking bandwidth so that we always stay in the linear regime of the homodyne readout?

Also, what is the functional form of the curve labelled "Theory" in Attachment #2? How did you convert from voltage units in Attachment #1 to frequency units in Attachment #2? Does it make sense that you're apparently measuring laser frequency noise above 10 Hz? i.e. where do the "Dark Current Noise" and "Shot Noise" traces for the experiment lie relative to the blue curve in Attachment #2? Can you point to where the data is stored, and also add a photo of the setup?

 

Attachment 1: Experimental_setup.JPG
Experimental_setup.JPG
  14579   Fri Apr 26 12:10:08 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

From the earlier results with homodyne measurement,the Vmax and Vmin values observed were comparable with the expected results . So in the time interval between these two points, the MZI is assumed to be in the linear region and I tried to find the frequency noise based  on data available in this region.This results is not significantly different from that we got before when we took the complete time series to calculate the frequency noise. Attachment #1 shows the time domain data considered and attachment #2 shows the frequecy noise extracted from that. 

As discussed, we will be trying the heterodyne method next. Initialy, we will be trying to save the data with two channel ADC with 16 kHz sampling rate. With this setup, we can get the information only upto 8 kHz. 

Attachment 1: Time_domain_data.pdf
Time_domain_data.pdf
Attachment 2: Frequency_noise_from_data_in_linear_region.pdf
Frequency_noise_from_data_in_linear_region.pdf
  14586   Tue Apr 30 17:27:35 2019 AnjaliUpdateFrequency noise measurementFrequency noise measurement of 1 micron source

We repeated the homodyne measurement to check whether we are measuring the actual frequency noise of the laser. The idea was to repeat the experiment when the laser is not locked and when the laser is locked to IMC.The frequency noise of the laser is expected to be reduced at higher frequency  (the expected value is about 0.1 Hz/rtHz at 100 Hz ) when it is locked to IMC . In this measurement, the fiber beam splitter used is Non PM. Following are the observations

1. Time domain output_laser unlocked.pdf : Time domain output when the laser is not locked. The frequency noise is estimated from data corresponds to the linear regime. Following time intervals are considered to calculate the frequency noise (a) 104-116 s (b) 164-167 s (c) 285-289 s

2. Frequency_noise_laser_unlocked.pdf: Frequency noise when the laser is not locked. The model used has the functional form of 5x104/f as we did before. Compared to our previous results, the closeness of the experimental results to the model is less from this measurement. In both the cases, we have the uncertainty because of the fiber length fluctuation. Moreover, this measurement could have effect of polarisation fluctuation as well.

3.Time domain output_laser locked.pdf :Time domain output when the laser is locked. Following time intervals are considered to calculate the frequency noise (a) 70-73 s (b) 142-145 s (c) 266-269 s. 

4. Frequency_noise_laser_locked.pdf : Frequency noise when the laser is locked

5. Frequency noise_comparison.pdf : Comparison of frequency noise in two cases. The two values are not significantly different above 10 Hz. We would expect reduction in frequency noise at higher frequency once the laser is locked to IMC. But this result may indicate that we are not really measuring the actual frequency noise of the laser.

Attachment 1: Homodyne_repeated_measurement.zip
  12828   Tue Feb 14 10:43:06 2017 gautamBureaucracyEquipment loanEquipment to Cryo Lab

PZT Buzzer Box (Thorlabs HV Supply + Manual + 2*PZT Buzzers) ---> Cryo Lab (Brittany + Aaron)

  13324   Wed Sep 20 16:14:17 2017 gautamUpdateEquipment loanImpedance test kit borrowed from Downs

I borrowed the HP impedance test kit from Rich Abbott today. The purpose is to profile the impedance of the NPRO PZTs, as part of the AUX PDH servo investigations. It is presently at the X-end. I will do the test in the coming days.
 

  14170   Mon Aug 20 14:04:53 2018 johannesBureaucracyEquipment loanTwo C30642G PDs removed

EDIT: After discussing with Koji and checking the existing M2ISS PDs I put the two C30642G back and took two C30665GH (active diameter: 3mm) diodes. Only one of this type remains in storage.

I removed two C30642G photodiodes from the stash for the new M2ISS hardware and updated the wiki page accordingly.

  14174   Tue Aug 21 17:32:51 2018 awadeBureaucracyEquipment loanOne P-810.10 Piezo Actuators element removed

I've taken a PI Piezo Actuator (P-810.10) from the 40m collection. I forgot to note it on the equipment checklist by the door, will do so when I next drop by.

  14565   Wed Apr 24 11:22:59 2019 awadeBureaucracyEquipment loanBorrowed Zurich HF2LI Lock in Amplifer to QIL

Borrowed Zurich HF2LI Lock in Amplifer to QIL lab Wed Apr 24 11:25:11 2019.

  14616   Fri May 17 10:12:07 2019 AnjaliSummaryEquipment loanBorrowed component

I borrowed one Marconi (2023 B) from 40 m lab to QIL lab.

  14618   Fri May 17 16:07:25 2019 gautamSummaryEquipment loanBorrowed component

ZHL-3A (2 units) —-> QIL

Quote:

I borrowed one Marconi (2023 B) from 40 m lab to QIL lab.

  14753   Thu Jul 11 17:58:38 2019 gautamUpdateEquipment loanTT suspension --> Downs

Arnaud has taken 1 TT suspension from the 40m clean lab to Downs for modal testing. Estimated time of return is tomorrow evening.

  14822   Thu Aug 1 13:55:34 2019 DuoBureaucracyEquipment loanGpib module taken to QIL lab

vanna --> QIL.

gautam 20190804: The GPIB module + power supply were returned to me by Duo ~5pm today at the 40m.

ELOG V3.1.3-