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ID Date Author Typeup Category Subject
  257   Wed Aug 12 11:19:57 2009 AidanThings to BuyGeneralNew Focus Order pending ...

Going to order 15x 2.5" pedestals from New Focus. Will submit order this afternoon.

  258   Wed Aug 12 14:12:22 2009 AidanThings to BuyGeneralNew Focus Order pending ...


Going to order 15x 2.5" pedestals from New Focus. Will submit order this afternoon.

 never mind.

  295   Mon Aug 31 00:20:23 2009 DmassThings to BuyPurchases"Can we have a pool dad?"

75$ Spectrum Analyzer

  506   Fri Dec 18 19:11:17 2009 ranaThings to BuyGYROTest of the G&H HR mirrors from MIT

Shannon Sankar has done testing at MIT of the G&H HR mirrors. The results are good. I'm attaching a PDF of the result here.

Attachment 1: GnH.pdf
  507   Fri Dec 18 22:38:25 2009 KojiThings to BuyGYROTest of the G&H HR mirrors from MIT

Oh, very good. This is like a magic mirror such that we can use either P or S, from 0 deg to 45 deg.


Shannon Sankar has done testing at MIT of the G&H HR mirrors. The results are good. I'm attaching a PDF of the result here.


  516   Tue Dec 29 05:33:25 2009 ranaThings to BuyGYROWhat Mounts to Use for the Gyro?

In our latest design, we have flat input mirrors (2" diameter) and curved corner mirrors (1" dia). We have been thinking of using the:


              Suprema SN100-F2K                                      or the SL51BCH (also from Newport)

The SL series shown here is for 2" optics and is available today (its 10 weeks for knobs). The Suprema is only available for 1" optics and is in stock.

Since the Suprema is ~5x cheaper, I think we should get the left handed and right handed of that kind now. But its worth considering the SL since it might be more stable.

I think Koji has some actual data of the long term stability of some mounts ------


  517   Tue Dec 29 18:27:41 2009 FrankThings to BuyGYROWhat Mounts to Use for the Gyro?

we have one of the 2" SL mirror mounts in the ATF, so we can have a look if the size is not too big. it's huge compared to other 2" mirror mounts.
We also have several 2" Ultima mirror mounts in the old Miller Lab (2 knobs). Maybe they are good enough for first tests...

  518   Mon Jan 4 16:05:12 2010 AlastairThings to BuyGYROWhat Mounts to Use for the Gyro?

 I've ordered six right and six left handed Suprema 1" mounts.

**edit** I've also now ordered two of the SL51BCH mounts.  We'll just have to cope with hex actuators to save the 10week wait.

  708   Thu Mar 25 12:40:28 2010 AlastairThings to BuyGeneralShoe covers on order - should be here in about 2 days

 Also ordered some solid core wire from Jameco and a couple of solderless breadboards.

  776   Mon May 17 16:46:23 2010 AlastairThings to BuyGYROmirrors

 In true CVI fashion they don't have any of the mirrors that we want.  I'm not actually certain what they keep in their warehouse but it certainly isn't optics.

Delivery time is going to be 4weeks (make that more like 6) for both the output mirror (another 2" diameter BS1- 99%) and the beam splitter for the Mach Zehnder (2" BS1 50%).  I'm going to put through the order for them now.

Edit - That's the order through Techmart now (5/18).

  846   Tue Jul 6 21:07:42 2010 ranaThings to BuyGYROIR viewer missing: found in TCS lab

We wasted some time today looking around for the IR viewer. We found that it had been taken into the TCS lab with no notice left about it being borrowed.

This is unacceptable and the second time this has happened. The next time anyone from the TCS lab tries to borrow equipment, refuse.

Tell whomever it is to come and talk to me if they have a problem with this policy.

  982   Wed Aug 25 01:28:35 2010 ranaThings to BuyGYROPossible Vacuum system for the GYRO

One possible vacuum chamber solution for the Gyro is to use long tubes for the Gyro arms and then to have a small chamber with ports at each corner.

I looked a little at using stock MDC vacuum parts for this; its not out of the question.

For the tubes, we could use something like their NW50 Kwik-Flange nipple. It has an OD of 2" and a length of 6.5". Its $63.

For the corners, we can use one of their '5-way crosses' like the 406002. Its basically 5 flanges welded onto a shell. Depending on the size its ~$250 ea.

I would prefer to get one long tube for each arm, rather than stick a bunch of short ones together, so I'll get a quote from MDC on a custom job.

Uncoated quartz viewports are ~$250 ea. I expect that we will want AR coated and angled viewports. Maybe $400 ea then.

So the total cost, without pumps would be ~5k$.

  987   Thu Aug 26 01:10:11 2010 AlastairThings to BuyGYROPossible Vacuum system for the GYRO

We're not looking for super high-vacuum though are we?  Maybe we can get away with borrowing the small turbo pumping station from the suspensions lab to pump it down and then we can just valve it off.

Also, we have the cylinder head for a tank of helium now so we should order in a tank to try that (the tanks get delivered really fast so that shouldn't be a problem).  Of course we'll at least need windows before doing that.

I've asked Gina to check on the CVI W2 window order.  The order went in on 22nd July and CVI said that they had them in stock.

  992   Thu Aug 26 17:09:08 2010 AlastairThings to BuyGYROPossible Vacuum system for the GYRO


We're not looking for super high-vacuum though are we?  Maybe we can get away with borrowing the small turbo pumping station from the suspensions lab to pump it down and then we can just valve it off.

Also, we have the cylinder head for a tank of helium now so we should order in a tank to try that (the tanks get delivered really fast so that shouldn't be a problem).  Of course we'll at least need windows before doing that.

I've asked Gina to check on the CVI W2 window order.  The order went in on 22nd July and CVI said that they had them in stock.

 I think that's right - we won't need any better than 1 mTorr. As long as there is no huge leak, we should be fine. It would be handy to have a (EPICS trendable) gauge on the system so that we can know if its leaking.

The system's total volume will be ~20 liters. So we need the leak rate to be below ~1e-6 Torr-liters / hour. A suggestion from Mike Z is to use the usual flexi-hosing from Norcal instead of the rigid nipple type of tube

I was talking about before. flexi hose link ..... I think we can use the 2" ID, 24" long tubes and make up for the difference in the length in the corner chambers. The length of each side of the gyro should be 29.5" with a 100 MHz FSR.

  1182   Tue Nov 30 11:03:55 2010 AlastairThings to BuyGYROvacuum gauge for gyro system

 I realised that I had not bought a vacuum gauge for the gyro system.  The simplest solution seemed to be to use a wide-range gauge so we don't need to worry about damaging the gauge if the pressure creeps up too high.  I've ordered a combination gauge from Kurt Lesker that gives atmosphere down to 1e-9 Torr with an analogue output so we can hook it up to a DAQ channel.

  1434   Mon Jun 20 20:12:18 2011 ZachThings to BuyGYROAll PDH2 stuff purchased

 I finished purchasing all the components for the PDH2 today, including the RF stuff from MiniCircuits and CoilCraft, SMA/SMP adapters and miscellaneous switches/LEDs/pots/etc from DigiKey, Allied and Mouser. I also ordered 6 NIM front panels from FrontPanel Express to go with the 6 boards that were ordered (in production now) form Sunstone last week. Lead times will vary I suppose, but everything I ordered was in stock.

  1778   Sat Oct 13 00:32:27 2012 KojiThings to BuyGeneralThings to buy
  • VWR While sticky mat (Large 25"x45") / VWR 18888-216 (30 layers x 8 sheets) -> delivered
  • VWR While sticky mat (Small 24"x36") / VWR 21992-042 (60 layers x 4 sheets) -> delivered
  • Thorlabs 8-32 screw kit / Thorlabs HW-KIT1 -> ordered newport equivalent
  • Pedestal Shims - Newport -> ordered (one kit and 10 additional pieces of PS-0.25, PS0.125)
SP-0.25-S-10	0.5" dia. 1/4in thick bag of 10 ($20.99)
SP-0.125-S-10	0.5" dia. 1/8in thick bag of 10 ($20.99)
SP-0.063-S-10	0.5" dia. 1/16in thick bag of 10 ($19.99)
SP-0.031-S-10	0.5" dia. 1/32in thick bag of 10 ($19.99)

PS-0.25		1" dia. 1/4in thick 1 ea. ($6.99)
PS-0.125	1" dia. 1/8in thick 1 ea. ($6.99)
PS-0.063	1" dia. 1/16in thick 1 ea. ($5.99)
PS-0.031	1" dia. 1/32in thick 1 ea. ($5.99)

Also you have a kit:
SP-KT ($199.99)
This contains
	5x PS-0.25
	5x PS-0.125
	5x PS-0.063
	5x PS-0.031
	10x SP-0.25-S-10
	10x SP-0.125-S-10
	10x SP-0.063-S-10
	10x SP-0.031-S-10

The kit is slightly more expensive than the individual ones.
Maybe due to the plastic case???


  1871   Wed May 21 11:11:08 2014 EvanThings to BuyPMC1064 nm PMC specs

I've put together coating specs for a 1064 nm PMC. They are on the DCC at E1400240-v1 and E1400241-v1.

I'm aiming for a cavity round-trip length of 24.0 cm. The two front mirrors will be both flat and will have reflectivities of 99%. The back, PZT-mounted mirror will have 1.0-m ROC and a transmissivity of 400 ppm. This should give a finesse of 300, and hence a cavity pole of 2.0 MHz.

The cavity geometry is more or less as you'd expect:


The front mirror separation is b = 2.540 cm = 1″, and the transverse distance is = 10.655 cm = 4.195″. The AOI on the back mirror is θ = 6.8° from normal.

The non-normal AOI gives a splitting the the horizontal and vertical transverse HOMs. The following plot shows the occurrence of the first 20 transverse HOMs (both spatially even and odd) as the cavity round-trip length L is varied.


I've chosen L = 24.0 cm (pink line) so that the lowest-order HOM that resonates with the TEM00 carrier is the lower sideband of the even 18th order mode. Here I've assumed a PDH frequency of 30 MHz. The width of the bands indicates the amount of spread in the horizontal/vertical modes due to the non-normal AOI.

  1885   Sun Aug 17 15:49:22 2014 EvanThings to BuyPMC1064 nm PMC

Status of hardware:

  1. Optics: ordered. Delivery expected week 45 of 2014.
  2. Spacer, endcap, clamps: am waiting for one more quote early next week, then will put in the order. Lead time of quotes I've gotten so far is 4 weeks ARO, so the metal bits will probably arrive before the optics.
  3. PZTs: already here.

Left to do:

  1. PZT driver circuit [see D060283 for OMC HV D1300024 for OMC LV]
  2. How to glue PZT + mirror? [see omc:88, perhaps others]
  3. Heater circuit
  4. Mount
  5. Sapphire seats (may delay this until after we have a few PMCs built)
  6. O-rings
  7. Strain relief for PZT wire
  8. Design guide/manual/test procedure
  2069   Mon Oct 24 16:55:24 2016 awadeThings to BuyScatterometerSummary of InGaAs cameras

I have made a summary of some InGaAs cameras: https://nodus.ligo.caltech.edu:30889/ATFWiki/doku.php?id=main:experiments:psl:ingaas_camera

It is a work in progress. Also see rana's post CryoLab:1433.

  2084   Sat Jan 28 13:02:40 2017 ranaThings to BuyCDScheap DAQ

Some more cheap DAQ interfaces, whether for coffee or in the labs without CyMac:


  2559   Wed Apr 21 09:42:35 2021 Stephen, ranaThings to BuyCryo vacuum chamberReimagining QIL Cryo Vacuum Chamber

WIP log entry - working on getting all of our ideas down on the page, then will sort and elaborate.

We met to discuss a range of topics relating to the path ahead for the Cryo Vacuum Chamber. This reconsideration of the current state of things is necessary as the chamber needs to become the workhorse for PD characterization efforts soon, in addition to a range of other tests (large suspension tests will be conducted in a different chamber, yet to be designed)

  1. Pumping station should be moved away from table, with long roughing lines perhaps coming down from above using some ceiling-mounted cable tray or similar.
  2. Primary pumping line to chamber is large and overkill in terms of conductance. Can move to a longer, more flexible, smaller diameter connection (may need to adapt using CF zero-length flange).
  3. Pumping of the external volume may be managed by valve arrangement and direct connection of both volumes to the turbo pump. Valve out the external volume once the pressure is low, and the pressure should hold well enough for conductive losses to be minimal.
  4. Viewports seem suitable, no issues throughout. I learned about common coating behavior, namely that reflectance is generally at half the wavelength of transmission, so if I see a green reflection it suggests transmission at IR. Neat!
  5. Cabling into chamber for temp sensors is pretty scary. Noticed the kink in the cable bundle caused by the flexible part of the cable extending longer than the grip of the connector's stiffening. Needs to be reassembled with the stiff cabling under the grip (could extend the grip, shorten the flexible leads, etc.) to avoid the kink.
  6. External volume feels like a misdirected design.
    1. For general case, consider mounting the cryocooler directly to chamber. Avoid losses related to thermal linkages from cold head of cryocooler to baseplate (diagram will be supplied, Rana was especially concerned that the V clamping arrangement didn't have adequate contact area in the line contacts)
    2. For vibration-sensitive experiments, would be good to have a flexible bellows reducing vibrational energy through the vacuum skin, and flexible strap reducing vibrational energy to the baseplate.
    3.  For contamination-sensitive experiments, would be necessary to implement a feedthrough as currently, but seems overkill for current slate of experiments.
    4. The intention seems to have been to devise a scaleable solution that would work for Mariner, but we are currently very far from realizing that (cryocooler needs to be Stirling cycle for vibration, no validation yet of adequate thermal conductivity through the external volume to the baseplate, etc.)
  7. Thermal straps with Mylar shielding is not the optimal implementation. Something like a rigid copper bar provides better conductivity, and can be shielded by G10 tubing with Aluminum metallization on the OD. If a flexible connection is required (for example, vibration isolation or positional uncertainty) a thermal strap may also be shielded in this sort of conduit.
  8. Need to replace the V-groove copper connections with something with much more surface area. V-grooves are nearly 1D contact lines, so they are probably the mian cooling rate limiter at the moment. Need to get some new parts fabbed ASAP to continue working on this cryostat.
  9. Vent valve should be a leak valve with a controlled, small conductance, perhaps backed by a filter. Want to allow slow, controlled venting.
  10. Skyhook Crane should be on its cart wheels for easy relocation away from the experiments.
  11. Skyhook should be replaced by a simple hoist mounted to ceiling of enclosure. Would require stiffening of some members of the enclosure's ceiling, but would permit easier access with fewer traffic jams.
  12. Yellow solvent cabinet should be removed. Solvents should be stored under fume hood.
  13. Would be great to get a stand (ie wire shelving, but heavy duty) which could hold the compressor, hold the pumping station, and provide a single location for any other items that need to be interfaced. All connections would be routed over the walkway via a run of cable rack.
  14. Moving the chamber to the center of the table width would be helpful to opening up access to more ports. Currently located in a corner, such that only half of ports are accessible. This is an extra reason that the Sky Hook should be remounted to its wheeled base.
  15. Should put all controllers on a rack, rather than consuming optical table space. All necessary serial comm cabling could then run to this singular location. We can use the rack next to the sink which has the NIM racks. The rack is completely unused right now. Need to get some rack parts to put some shelving in there.
  16. Documentation of ongoing thoughts, design efforts, modifications, etc. can be contained at the wiki!
  17. What is currently installed? Some insights from the wiki (ie gauges, pumps, viewports) should be elevated into a comprehensive diagram with a bill of materials or similar.
  18. In the diagram need to note all instruments so that Radhika can include it in her work to interface with the DAQ. i.e. no more photos and screenshots to record data.
  19. Where am I? A floorplan for this experiment (current and planned) would be worth some time, now that we are considering specific improvements.

Will sort the above into some sort of timeline (such as short term / long term).

Ruminations about the future chamber for suspension work:

  1. Stirling cryocooler for vibration isolation
  2. Straight-sided construction (i.e. rectangular prism) for more usable footprint inside
  3. If vertical (i.e. lid) use counterbalance and hinge for easy opening without hoist or crane; might need side ports large enough for hand access, since the height will be prohibitive to reach all the way down to the baseplate.
  4. Horizontal (i.e. door) might be preferred, especially with the volume in the form of a rectangular prism. This would allow access throughout the height of the chamber.
  5. Usual vacuum vendors should be able to help bring the design from a sketch to a quote, so start those conversations.
  2597   Tue Jun 29 17:29:16 2021 StephenThings to Buy2um PhotodiodesIntegrating 2um PD measurements into Cryo Vacuum Chamber

Radhika and I started discussing in detail the items needed to transfer the 2um PD setup into the Cryo Vacuum Chamber.

1) Electrical

To interface with the PD setup, it seems that we will need want to use the feedthrough already in use on the IRLabs cryostat. This square-flanged feedthrough appears to host the in-vacuum cabling. The in-air cabling would ideally also be reused.

To implement this, we will need to modify a blank 2.75" conflat flange (in hand in QIL boxes on wire shelf) with a the following features:

  • through bore, 1.18 diameter on center.
  • a 4x #4-40 tapped hole square bolt pattern, 1.062" spacing on center.
  • preferably, a hand-polished o-ring sealing area.

I will take care of this part through the PMA shop.

2) Optical

The Cryo Vacuum Chamber windows are Thorlabs VPCHW42‐C (ref. D2000310-v1). The broadband AR coating is rated for 1050-1700 nm (here's the data sheet), with a steep climb in AR coating reflectance. There is also fused silica substrate transmission to worry about. Perhaps the easiest way to proceed would be to repeat Koji's Transmission test (ref. QIL/2458) for the windows already in use on the Cryo Vacuum Chamber, and see if we can accept ~10% loss (or more).

Else, perhaps we scavange the IRLabs cryostat and create another custom blank CF modification?

Or buy a new, suitable window with CF interface? (<---- preferred option)

  2626   Fri Jul 30 14:44:56 2021 StephenThings to BuyCryo vacuum chamberUpgrades and updates in advance of PD testing

(Aidan, Stephen, Koji)

Building off of QIL/2597 after more thorough discussion in Mariner meeting today. Aidan and I will confirm details today and make moves toward installation of PDs next week.

Necessary capabilities (note: no need to scavange anything from the IRLabs dewar):

 - Cold temperatures = ready (via conductive mounting we have seen workpiece ~ 80 K, workpiece heating and CTC100 temp control is demonstrated)

 - Optical interface = ready (existing 1700 nm AR-coated window will be used at 2 micron, input power will just be calibrated with a power meter)

 - Electrical interface = almost ready, pending cabling (the cryo vacuum chamber has RTDs instrumented, so we just need the leads for the PDs, and we can create Cu twisted pair leads with in-vac crimp/solder sockets a la Koji's OSEM cabling) (also need in-air cabling with DB9 plug - trivial)

Improvements in advance of PD testing:

 - RTD cabling and Heater cabling (in vacuum) should be split with in-vac pins and insulated with PTFE tube - Koji has the magic material recommendations

Desired improvements (not necessarily in advance of PD testing):

 - Cu solid linkage (being fabricated).

 - Inner radiation shield should be clamped well to cold plate (consistent with most recent trial, but do we want better/more clamps?).

 - RTD mounting option on shields without cryo varnish (new threaded hole, new clamps).

 - RTDs consistent with planned Mariner RTDs (ref. QIL/2590).

 - Heater mounting should be directly to the workpiece via an improved clamp on the 2" x 2" grid (rather than on unused Si cantilever workpiece holder).

  2746   Tue Apr 5 11:15:13 2022 RadhikaThings to BuyPurchasesNew optical table legs for north table

The current QIL optical tables are Thor Labs PTH503 (discontinued, replaced by PTH603 - also discontinued) which are 700mm tall and offer a closed pneumatic isolation system (passive isolation). This model is only available at the 700mm height and 600mm, which would only be ~4 inches lower than our current legs.

Newport's equivalent model (SL Series Closed Pneumatic Vibration Isolators without Re-Leveling) comes in a 13.5-inch (343mm) height, which would drop our table height by 14 inches. This would be our ideal table height. The cost for 4 legs would come out to $3,047.

  2747   Tue Apr 5 12:20:09 2022 ranaThings to BuyPurchasesNew optical table legs for north table

we don't really need Pneumatic legs. How much for rigid legs?


  2748   Tue Apr 5 16:41:17 2022 RadhikaThings to BuyPurchasesNew optical table legs for north table

The 13.5" rigid legs would cost $1,891.

  2071   Thu Nov 10 19:04:28 2016 awadeUpdateScatterometerTesting InGaAs camera

Yesterday we had a meeting with Nick Lechocinski from Axiom Optics about InGaAs cameras.  He went over various products they sell, which pretty much fall in the pixel count/noise/price range of the various other competitors.  They have lent us a logarithmic response InGaAs camera.

I have been trying to get the camera to talk to the software on a windows laptop we have in the lab.  It turns out that the interface HAS to be USB 3.0 or higher, which we don't have on any windows computers I know about (unless there is one at the 40m). I've spent a good chunk of time trying to get USB 3.0 ports on my Macbook pro to forward to an instance of Windows 7 on VirtualBox. It frustrating as USB 3 was supposed to be backward AND forward compatible but in this case the camera is not working for whatever reason.  

Having tried various things with VirtualBox (including installing all the extra windows Guest Additions), I'm not sure its worth pushing on with that option. Mike and Christian don't have any PC laptops with USB 3.0 spare.  I may repartition a spare MacMini of mine tomorrow to see if that works and maybe ask around more for a laptop. 

Pictures of camera attached.


Attachment 1: 2016-11-09_18.05.48.jpg
Attachment 2: 2016-11-09_18.05.55.jpg
  2119   Fri Jun 9 16:58:35 2017 DhruvaUpdateWOPOWOPO Experiment Stuff

Today, Eric and I unboxed and inventoried the WOPO experiment components that Andrew had ordered. 

Attached, is a pdf with pictures of the components with the packaging lists. 

Attachment 1: ATF_WOPO_inventory.pdf
ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf ATF_WOPO_inventory.pdf
  2122   Fri Jun 16 18:55:40 2017 DhruvaUpdateWOPOMode Matching the 1064nm Beam into fibre

In order to collimate the 1064nm beam from the laser into the fibre, we are using the Thorlabs F240-APC-1064 fixed focus collimation package. The required beam diameter for this is 1.76mm. I used ABCD Propagation to try and come up with an optimal 3 lens solution to obtain a collimated beam of this size. The solution is as follows - 

f1 = 30cm at z = 105cm ( z = 0 being the location of the Diabolo waist)

f2 = 20cm at z = 122.5cm

f3 =12.5cm at z = 146cm

I profiled the beam after the first and second lenses in order to correct my estimation of initial beam waist and location. 

I have positioned the third lens in such a way that the spot size 43.5cm (waist location in ABCD prop) from the lens is around 880 microns as required by the collimator 

I have also placed the collimator at the above mentioned location and have connected it to the 1064 single mode fibre. At the other end of the fibre, I have placed a photodiode and am attempting to get a signal from it in order to maximize coupling efficiency. 



Note: The 400mW beam has been attentuated to 4mW by an HWP and PBS.


Attachment 1: 3_lens_solution.pdf
Attachment 2: 1064_f1_profile.pdf
Attachment 3: 1064_f2_profile.pdf
Attachment 4: Mode_Matching_Lenses.jpg
  2124   Mon Jun 26 10:55:02 2017 DhruvaUpdateWOPOTemperature Control of the PPKTP Waveguide

For the temperature control of the non linear waveguide, we will be using the Newport 3040 Temperature Controller. The phase matching temperature of the crystal is 62.3 C. The TEC will be run with the following settings - 

Lower Lim Temp = 20 C

Upper Lim = 70 C

Max Current = 0.65A

Gain Mode = 10 Fast 

C1 = 1.0445e-3

C2 = 2.5075e-4

C3 = 0 


The waveguide has been mounted on a ThorLabs LM14S2 Universal Butterfly Pin Mount. The TEC Driver is a 9 pin input while the TEC output from the controller is a 15 pin output so I made an adapter for the two different configurations.

Upon testing the Temperature Control of the Waveguide, we found that the equilibrium temperature always falls about 1.1 C below the set temperature.




Plot phase matching curves of SHG in the crystal. 





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  2125   Tue Jun 27 11:34:00 2017 DhruvaUpdateWOPOMode Matching Woes - Fibre issues

The WOPO experiment has been quite stagnant for the last two weeks because ineffective coupling of the 1064 light into the fibre (max 10%). Beam profiling says that the ABCD simulation results were correct, and there is no problem with the fibre collimation package. Yesterday, Andrew and I found a possible culprit. On examining the fibre with a microscope we found that the core of one of the ends is fine while the other has been damaged. I am attaching pictures of both the ends. 

We will attempt to clean the fibre. If that doesn't work out, then we will order a new one. 


Attachment 1: image2.JPG
Attachment 2: image4.JPG
  2126   Wed Jun 28 13:24:35 2017 awadeUpdateWOPOPDs for homodyne detector

I asked Koji if he had any hight QE photodiodes to use in a ballenced homodyne detector.  None of the Ad LIGO ones can be used for this but Zach had a small stockpile in the ATF lab.

Pictures attached of the boxes (two in total).  I need to track down the PO or part numbers to work out what they are.  They look like they are ~1.5 mm^2 area, all with windows still on.



Attachment 1: 2017-06-28_13.21.32.jpg
Attachment 2: 2017-06-28_13.17.32.jpg
Attachment 3: 2017-06-28_13.17.00.jpg
Attachment 4: 2017-06-28_13.16.51.jpg
  2127   Wed Jun 28 20:05:02 2017 KojiUpdateWOPOPDs for homodyne detector

I beieve that they are Exelitas C30642.
FYI: There also is one on the former-gyro optical table. This one doesn't have the cap.

  2128   Thu Jun 29 22:42:28 2017 awadeUpdateWOPOMode Matching Woes - Fibre issues

I've reordered fiber that was damaged.  

Need to profile the beam actually going into the fiber after the third lens.  If the slit profiler isn't large enough for the 1760 µm beam then maybe try the WinCamD CCD profiler.  You might need to ask around to find which lab its in. 


The WOPO experiment has been quite stagnant for the last two weeks because ineffective coupling of the 1064 light into the fibre (max 10%). Beam profiling says that the ABCD simulation results were correct, and there is no problem with the fibre collimation package. Yesterday, Andrew and I found a possible culprit. On examining the fibre with a microscope we found that the core of one of the ends is fine while the other has been damaged. I am attaching pictures of both the ends. 

We will attempt to clean the fibre. If that doesn't work out, then we will order a new one. 



  2129   Fri Jun 30 12:17:07 2017 KojiUpdateWOPOMode Matching Woes - Fibre issues

Measure the profile of the back propagation beam by injecting a beam from the other side.
This gives you how the input mode should be.

  2130   Sun Jul 2 19:47:35 2017 awadeUpdateWOPOMode Matching Woes - Fibre issues

Do you recall if there are any fiber coupled 1064 nm lasers anywhere in the 40m or other bridge west labs?


Measure the profile of the back propagation beam by injecting a beam from the other side.
This gives you how the input mode should be.


  2131   Sun Jul 2 21:21:39 2017 KojiUpdateWOPOMode Matching Woes - Fibre issues

Jenne's laser at the 40m PD testing table is a fiber coupled 1064nm DL.

But you just can couple 5~10% of the beam from the other side of the fiber to know the mode at the input side.
It does not require too much effort if you have the fiber testing illuminator to align the beam.

  2132   Wed Jul 5 16:44:34 2017 KojiUpdateWOPOPDs for homodyne detector

Correction: If the diode is 3mm x 3mm, it is Excelitas C30665.

  2133   Thu Jul 6 15:03:07 2017 DhruvaUpdateWOPOHomodyne Design

I am attaching a schematic of the proposed design for the Homodyne detector. The damping capacitance in the two photodetectors has to be decided based on what we estimate the capacitance of the photodiode to be. 

Please let me know if there's anything I can do to make this better suited for homodyne detection.


Attachment 1: Homodyne.pdf
  2135   Mon Jul 10 12:12:26 2017 DhruvaUpdateWOPOEfficient Fibre Coupling and Phase Matching Plot

Using the 632nm laser provided by Gautam to back couple the 1064nm light into the fibre, I managed to finally get efficient mode matching. For 25.4mW of light going into the collimator, the fibre outputs 19.3mW (~76%).  Now that efficient mode matching has been achieved, I finally managed to plot the SHG Phase matching curve for the PPKTP Waveguide (a plot of output power (532nm) against the temperature). I fit the data obtained to the function 


Here, the normalised sinc(x) fiunction is given by 

\frac{sin(\pi x)}{\pi x}

The optimised values are 

P_0 = 65.3 \mu W Maximum SHG Power

T_0 = 60.99  Optimum Phase Matching Temperature.

a = 2.609  

That gives the FWHM as 2.32 C.

The maximum output is much lower than expected as that is because of loss at the fibre coupling at the waveguide. This loss is visible and I am attaching a couple of pictures. 

Attachment 1: Phase_Matching.pdf
Attachment 2: Green_Loss_1.jpg
Attachment 3: Green_Loss_2.jpg
  2141   Tue Jul 18 22:09:14 2017 DhruvaUpdateWOPOPhotodetector Dark Noise

These are the plots of the dark noise of the Thorlabs photodetectors lying in the ATF lab using the FFT network analyser. For higher frequency ranges, I have to configure the other network analyser. 

These are the settings that the analyser was running on - 

Measure Group: FFT
Measurement: FFT 1
Num of extracted Points: 401
FFT Lines:  400 
Window: Hanning
Averaging Mode: RMS
Averaging Type: Exp. / Cont.
Overload reject: On

Edit : I've added a stiched plot of all the collected data. The noise from 10-100KHz is around the order of 40nV. We're hoping to see if we can do better by designing our own photodetectors. We also see a lot of peaks that correspond to the harmonics of the 60Hz mains. 


Edit 2: The Photodetector is the Thorlabs PDA55 detector.  We CANNOT use this detector as it is silicon and has a terrible quantum efficiency at 1064nm. 

Attachment 1: 20170714-pda55noise.pdf
  2142   Thu Jul 20 18:16:33 2017 ranaUpdateWOPOPhotodetector Dark Noise

Ugh - I deleted those 1000 bad plots. Just give us 1 trace per PD, all on one plot. Each trace should also include the model # of the PD. Just 'stuff we have laying around' is not useful.

Also, what are the requirements on the PD? Describe how these are computed.

  2144   Sat Jul 22 14:25:55 2017 DhruvaUpdateWOPOTable Noise Issues

Yesterday, with a lot of help from Koji, we built the transimpedance circuit (Gain = 10k) for the photodetectors of the homodyne circuit.

While doing so, we encountered a most bizzare issue. The circuit shows a significantly larger amount of noise (especially in the 10-100kHz band) when it is on the table as opposed to when it is suspended in air. I'm attaching pictures if the setup as well as a comparative plot. We still cannot ascertain the reason behind this extra noise.

Attachment 1: 20170721-_table_noise.pdf
Attachment 2: 20170721_Circuit_in_Air.jpg
Attachment 3: 20170721_Circuit_on_Table.jpg
  2145   Sat Jul 22 14:41:07 2017 DhruvaUpdateWOPOPhotodetector Dark Noise



Yesterday, with a lot of help from Koji, we built the transimpedance circuit (Gain = 10k) for the photodetectors of the homodyne circuit.a

I connected the Excelitas C30665 photodiode to the above transimpedance circuit and measured the dark noise while suspended in air (please refer previous elog on table noise). 

For a mW of light and a quantum efficiency of about 87%, we expect to see about 0.68mA of current. This gives the shot noise to be 14.7pA/sqrt(Hz) which corresponfs to about 147nV/sqrt(Hz) for a 10k gain which is significantly higher than the noise floor of the circuit between 10 and 100KHz.

Attachment 1: 20170721-dark_noise.pdf
  2146   Sat Jul 22 14:43:16 2017 DhruvaUpdateWOPOSubtractor Circuit Noise

I also made a op-amp subtractor circuit for the homodyne detector and measured the noise. It is significantly lower than the shot noise.

Attachment 1: 20170721-subnoise.pdf
  2198   Sat May 5 06:08:35 2018 EricUpdate LabJack U3 New Setup

Changed the setup for LabJack testing so that we can better isolate problems with the DAC and ADC (if they exist). The previous setup consisted of passing two signals through the LabJack and comparing their outputs using the Rayleigh statistic. Since there are problems activating two DACs and two ADCs on the LabJack at once, we needed a different design that would only use one of these at a time. The new design (Figure 1) inputs a digital signal which is stored as a control signal to compare against. Next, the digital signal is passed through the DAC and comes out as an Analog signal through terminal DAC0. Since only the DAC or the ADC can run at one time, the DAC is then paused until the ADC converts the signal back to digital, at which point the ADC is paused and the DAC resumes functioning. Theoretically, this conversion should be happening at 100 Hz, and in practice, this number will be very close to 100 Hz. With this setup, problems occur after running the LabJack where either the DAC or the ADC stops passing through data. This doesn’t happen immediately but will happen seconds to minutes after the test begins. This seems to occur because the DAC and ADC are being turned on and off too quickly. However, if we run the DAC and ADC at too low of a rate then we lose resolution on the test wave and it becomes harder to run statistics on the data set. I believe I can get this setup to work by tuning the sampling frequency of the DAC and ADC so we're in a spot that allows the LabJack to both pass through data but also allows us to have a high enough resolution to run other tests on the data set.

I will attempt to get the first setup to work. However, if I can’t resolve the issues with the DAC or ADC not passing through data, we could also attempt a different setup that moves the Analog to Digital conversion out of the LabJack so that the DAC doesn’t need to be switched on and off (Figure 2). With this setup, we would need to purchase an ADC that can be soldered onto a Raspberry Pi (MCP3008).

Attachment 1: Figure1.JPG
Attachment 2: Figure2.JPG
  2258   Tue Oct 30 10:17:44 2018 RahulUpdate SHI Cryocooler

We have received the SHI cryocooler CH-104 (figure attached), which has been moved to the QIL. I have inspected all the components after unboxing it. Cold head test report supplied by SHI is attached below.

The cryocooler comes with a HC-4A Zephyr air cooled helium compressor. This compressor is a single stage, air cooled and designed to deliver high pressure helium gas to the cryocooler.

There are 2 helium supply/return (although both the hose says supply, which I am not sure why, hence will check it out) hose along with a kit to install it. This is currently charged with helium pressure of 280 psi, however, once it is installed then the helium pressure has to be adjusted (I am currently reading the manual to assemble the system).

The cryoocoler cold head will be finally placed on a bench which we have bought. I plan to use a breadboard to clamp it down. The compressor will be placed a few feet (based on hose length) away from it. Typically the compressors are noisy, hence later on we can get longer hose to keep the compressors further away.

The vacuum chamber (collar) will be moved in the lab and on the optical bench this Thursday (although this was supposed to be moved in last week, however due inadequate communication by the Caltech moving service this couldn't happen).

The top and bottom flange covers for the vacuum chamber (fabricated by Kurt Lesker) has been shipped on 24 Oct and we should be receiving it this week.

Attachment 1: cryocooler.jpg
Attachment 2: compressor.jpg
Attachment 3: supply_hose.jpg
Attachment 4: Cold_test_report_SHI.jpg
  2259   Fri Nov 2 08:59:26 2018 RahulUpdate Vacuum chamber

We have our shiny new vacuum chamber (fabricated by Nor-Cal), now sitting on the optical bench.

Attachment 1: IMG_0005.jpg
Attachment 2: IMG_0008.jpg
Attachment 3: IMG_0007.jpg
  2260   Fri Nov 9 14:57:54 2018 RahulUpdate Cryo-vacuum chamber

SHI Cryocooler – Vacuum chamber assembly

The attached picture shows a schematic of the assembly/connection of SHI cryocooler to the vacuum chamber. The cryocooler has warm flange mounting holes. Using a mating flange – hose/bellows will be connected to the cryocooler. The mating flange will have a port for roughing pump and vacuum gauge connection. The hose/bellows will be connected to the flange reducer which will be bolted to the CF (4-5/8 size) flange of the cryostat.

I will upload a CAD model of the mating hose and will also look for an appropriate size hose and flange reducer.

Attachment 1: Picture1.jpg
ELOG V3.1.3-