40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  OMC elog, Page 1 of 9  Not logged in ELOG logo
New entries since:Wed Dec 31 16:00:00 1969
ID Date Author Type Category Subjectdown
  362   Thu May 16 12:41:28 2019 ChubGeneralGeneralfire pillow found on optics table

That is an expanding fire pillow, also known as firebrick.  It is used to create a fire block where holes in fire-rated walls are made and prevents lab fires from spreading rapidly to adjacent labs.  I had to pull cable from B254 to our labs on either side during a rather narrow window of time.  Some of the cable holes are partially blocked, making it difficult to reach the cable to them. The cable is then just guided to the hole from a distance.  With no help, it's not possible to see this material getting shoved out of the hole.  I can assure you that I took great pains not to allow the CYMAC coax to fall into any equipment, or drag against any other cables.   

  107   Wed Apr 10 00:40:30 2013 ZachOpticsConfigurationfauxMC locked

[Koji, Zach]

Tonight, we locked the "fauxMC". We obtained a visibility of >99%.

Koji had aligned it roughly last night, but we wanted to have a couple steering mirrors in the path for this practice cavity (the periscope mirrors will serve this function in the real setup), so we marked the alignment with irises and installed two extra mirrors.

After obtaining flashes with the WinCam placed at the output coupler, we removed the WinCam and put a CCD camera at one of the curved mirror transmissions and used this to get a strong TEM00 flash. Then, we installed the REFL PD/CCD, swept the laser PZT and optimized the alignment by minimizing the REFL dips. Finally, we connected the RF electronics and locked the cavity with the LB box. We used whatever cables we had around to trim the RF phase, and then Koji made some nice SMA cables at the 40m.

One thing we noticed was that we don't have enough actuation range to keep the cavity locked for very long---even with the HV amp (100V). We are going to offload to the NPRO temperature using an SR560 or pomona box circuit. We may also make an enclosure for the cavity to protect it from the HEPA blasting.

Tomorrow, after we do the above things, we will practice measuring the transmission, length (FSR) and mode spectrum of the cavity before moving on to the real McCoy.

fauxMC_labeled.jpg

  67   Tue Mar 5 19:37:00 2013 ZachOpticsCharacterizationeLIGO OMC visibility vs. power measurement details

EDIT (ZK): Koji points out that (1 - Ti) should really be the non-resonant reflectivity of the aligned cavity, which is much closer to 1. However, it should *actually* be the non-resonant reflectivity of the entire OMC assembly, including the steering mirror (see bottom of post). The steering mirror has T ~ 0.3%, so the true results are somewhere between my numbers and those with (1 - Ti) -> 1. In practice, though, these effects are swamped by the other errors.

More information about the power-dependent visibility measurement:

As a blanket statement, this measurement was done by exact analogy to those made by Sam and Sheon during S6 (c.f. LHO iLog 11/7/2011 and technical note T1100562), since it was supposed to be a verification that this effect still remains. There are absolutely better ways to do (i.e., ways that should give lower measurement error), and these should be investigated for our characterization. Obviously, I volunteer.

All measurements were made by reading the output voltages produced by photodetectors at the REFL and TRANS ports. The REFL PD is a BBPD (DC output), and the TRANS is a PDA255. Both these PDs were calibrated using a Thorlabs power meter (Controller: PM100D; Head: S12XC series photodiode-based---not sure if X = 0,2... Si or Ge) at the lowest and highest power settings, and these results agreed to the few-percent level. This can be a major source of error.

The power was adjusted using the HWP/PBS combination towards the beginning of the experiment. For reference, an early layout of the test setup can be seen in LLO:5978 (though, as mentioned above, the REFL and TRANS PDs have been replaced since then---see LLO:5994). This may or may not be a "clean" way to change the power, but the analysis should take the effect of junk light into account.

eOMC_visibility_3_4_13.png

Below is an explanation of the three traces in the plot. First:

  • TRANS: TRANS signal calibrated to W
  • REFL_UL: REFL signal while cavity is unlocked, calibrated to W
  • REFL_L: REFL signal while cavity is locked, calibrated to W
  • Psb: Sideband power (relative to carrier)
  • Ti: Input mirror transmission (in power)

Now, the traces

  1. Raw transmission: This measurement is simple. It is just the raw throughput of the cavity, corrected for the power in the sidebands which should not get through. I had the "AM_REF" PD, which could serve as an input power monitor, but I thought it was better to just use REFL_UL as the input power monitor and not introduce the error of another PD. This means I must also correct for the reduction in the apparent input power as measured at the REFL PD due to the finite transmission of the input coupler. This was not reported by Sam and Sheon, but can be directly inferred from their data.
    • trans_raw = TRANS ./ ( REFL_UL * (1 - Psb) * (1 - Ti) )
    • Equivalently, trans_raw = (transmitted power) ./ (input power in carrier mode)
  2. Coupling: This is how much of the power incident on the cavity gets coupled into the cavity (whether it ends up in transmission or at a loss port). Sheon plots something like (1 - coupling) in his reply to the above-linked iLog post on 11/8/2011.
    • coupling = ( REFL_UL * (1 - Ti) - REFL_L ) ./ ( REFL_UL * (1 - Psb) * (1 - Ti) )
    • Equivalently, coupling = [ (total input power) - (total reflected power on resonance) ] ./ (input power in carrier mode)
  3. Visibility: How much of the light that is coupled into the cavity is emerging from the transmitted port? This is what Sam and Sheon call "throughput" or "transmission" and is what is reported in the majority of their plots.
    • visibility = TRANS ./ ( REFL_UL * (1 - Ti) - REFL_L )
    • Equivalently, visibility = (transmitted power) ./ [ (total input power) - (total reflected power on resonance) ]
    • Also equivalently, visibility = trans_raw ./ coupling

The error bars in the measurement were dominated, roughly equally, by 1) systematic error from calibration of the PDs with the power meter, and 2) error from noise in the REFL_L measurement (since the absolute AC noise level in TRANS and REFL_L is the same, and TRANS >> REFL_L, the SNR of the latter is worse).

(1) can be helped by making ALL measurements with a single device. I recommend using something precise and portable like the power meter to make measurements at all the necessary ports. For REFL_L/UL, we can place a beam splitter before the REFL PD, and---after calibrating for the T of this splitter very well using the same power meter---both states can be measured at this port.

(2) can probably be helped by taking longer averaging, though at some point we run into the stability of the power setting itself. Something like 30-60s should be enough to remove the effects of the REFL_L noise, which is concentrated in the few-Hz region in the LLO setup.

One more thing I forgot was the finite transmission of the steering mirror at the OMC input (the transmission of this mirror goes to the QPDs). This will add a fixed error of 0.3%, and I will take it into account in the future.

  68   Wed Mar 6 23:24:58 2013 ZachOpticsCharacterizationeLIGO OMC visibility vs. power measurement details

I found that, in fact, I had lowered the modulation depth since when I measured it to be 0.45 rads --> Psb = 0.1.

Here is the sweep measurement:

TEK00005.PNG TEK00007.PNG

This is Psb = 0.06 --> gamma = 0.35 rads.

This changes the "raw transmission" and "coupling", but not the inferred visibility:

eOMC_visibility_3_4_13.png

I also measured the cavity AMTF at three powers today: 0.5 mW, 10 mW, and 45 mW input.

eOMC_AMTF_vs_power_3_6_13.png

They look about the same. If anything, the cavity pole seems slightly lower with the higher power, which is counterintuitive. The expected shift is very small (~10%), since the decay rate is still totally dominated by the mirror transmissions even for the supposed high-loss state (Sam and Sheon estimated the roundtrip loss at high power to be ~1400 ppm, while the combined coupling mirrors' T is 1.6%). I have not been able to fit the cavity poles consistently to within this kind of error.

  291   Thu Feb 22 20:21:02 2018 KojiOpticsCharacterizationaLIGO EOM test

POSTED to 40m ELOG

  292   Mon Apr 2 17:27:04 2018 KojiOpticsCharacterizationaLIGO EOM test

2nd optical test http://nodus.ligo.caltech.edu:8080/40m/13725

  153   Fri Aug 16 17:21:38 2013 KojiGeneralGeneral[OMC002] Build started

[Jeff Koji]

The breadboard (SN2) was loaded on the transportation fixture.

The laser side template was installed and the cavity mirrors were placed.

The laser beam will be resonated in the cavity next week.

  74   Wed Mar 20 09:38:02 2013 ZachOpticsCharacterization[LLO] OMC test bench modified

 For various reasons, I had to switch NPROs (from the LightWave 126 to the Innolight Prometheus).

I installed the laser, realigned the polarization and modulation optics, and then began launching the beam into the fiber, though I have not coupled any light yet.

A diagram is below. Since I do not yet have the AOM, I have shown that future path with a dotted line. Since we will not need to make AMTFs and have a subcarrier at the same time, I have chosen to overload the function of the PBS using the HWP after the AEOM. We will operate in one of two modes:

  1. AMTF mode: The AOM path is used as a beam dump for the amplitude modulation setup. A razor dump should physically be placed somewhere in the AOM path.
  2. Subcarrier mode: The AEOM is turned off and the HWP after it is used to adjust the carrier/subcarrier power ratio. I chose a 70T / 30R beamsplitter for the recombining, since we want to be able to provide ~100 mW with the carrier for transmission testing, and we don't need a particularly strong subcarrier beam for probing.

new_setup_traced.jpg

One thing that concerns me slightly: the Prometheus is a dual-output (1064nm/532nm) laser, with separate ports for each. I have blocked and locked out the green path physically, but there is some residual green light visible in the IR output. Since we are planning to do the OMC transmission testing with a Si-based Thorlabs power meter---which is more sensitive to green than IR---I am somewhat worried about the ensuing systematics. I *think* we can minimize the effect by detuning the doubling crystal temperature, but this remains to be verified.

 EDIT (ZK): Valera says there should be a dichroic beam splitter in the lab that I can borrow. This should be enough to selectively suppress the green.

  146   Tue Jun 18 15:45:38 2013 KojiGeneralGeneral[LLO] OMC installation in HAM6

OMC installed in HAM6!
https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=7486

 

  140   Fri Jun 7 16:04:44 2013 KojiGeneralGeneral[LLO] OMC arrived

[Koji Zach Suresh]

The OMC arrived at LLO without any destruction!

  • We found that one shock sensor on the box turned red, the other stayed white.
  • We brought the Perican case to the changing room and the wrapping was opened in the optics lab.
  • The OMC was discovered without any obvious damage. Successful shipment!
  • The inspection with a halogen light indicated some amount of particules on the breadboard.
    The both sides of the breadboard were wiped with the cleanroom cloth.
  • The First Contact layers on the optics were removed while the ionized nitrogen gas was brew.

 

  143   Thu Jun 13 12:12:20 2013 ZachGeneralGeneral[LLO] OMC and OMCS in LVEA

https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=7395

  141   Mon Jun 10 10:04:37 2013 KojiGeneralGeneral[LLO] OMC Test

[Koji Zach]

We worked on the OMC test over the weekend.

- At the beginning, the measured OMC transmission was ~85% even after subtracting the junk light and sidebands from the calculation.

- A pretty visible (by eye) dust were on CM1. Also a small residue of First Contact was found on the same mirror.

- We applied FC only on CM1 to remove these.

- The measued transmission went up to the level of 96%.

- We swept the incident power from 0.3mW to 30mW in order to see the dependence of the transmission against the incident power.

- The variation of the transmission ~10% was observed (attached figure 1, Red). This was compared with the similar dependence measured at Caltech (Magenta)

- So, the reduction of the transmission was observed as in eLIGO, although the measurements at Caltech and LLO are not consistent.

- Can this be attributed to the dependence of the PD efficiency? We measured the incident power on the PDs together with the preamp DC output. (Figure.2)
  This gives us how the responsivity changes with the incident power.

- Nevertheless, the dependence remains. We'll make more accurate measurement today.

Attachment 1: OMC_pow_cal.pdf
OMC_pow_cal.pdf
Attachment 2: responsivity.pdf
responsivity.pdf
Attachment 3: OMC_pow_cal_compensated.pdf
OMC_pow_cal_compensated.pdf
  142   Thu Jun 13 12:04:57 2013 KojiGeneralGeneral[LLO] OMC Optical Test - completed

https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=7373

  144   Fri Jun 14 06:35:21 2013 JeffGeneralGeneral[LLO] L1 OMC status

https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=7410

Weights:

Suspension cage and transportation box: 250.8lb
Suspension cage and transportation box: 150.2lb ==> 100.6lb ==> 45,630 g

Metal Breadboard: 7261 g

Glass Breadboard and transportation fixture: 16382 g
Transportation fixture only: 9432 g ==> 6950 g
Added mass (up to now): 300 g ==> 7250 g

Preamp arrangement

preamp_arrangement.png 

  19   Wed Aug 22 20:16:43 2012 KojiFacilityGeneralWorkbenches have been installed / Clean room stools

Last Friday, new workbenches were installed. Vladimir got a new table and a cleanroom stool.

P8171968.jpg

The other two workbenches were also nicely set.

P8171969.jpg

  300   Mon Jul 2 15:27:31 2018 Rich AbbottElectronicsGeneralWork on EOM (3rd IFO unit)

Koji, Rich

We took apart the unit removed from the 3rd IFO (Unit serial number aLIGO #3, XTAL 10252004) to see what makes it tick.  Koji has done a fine job of adding the plots of the impedance data to this log book.  Attached are some details of the physical construction showing the capacitor values used in shunt before the coils.

Attachment 1: EOM3_aLIGO_3rdIfo.JPG
EOM3_aLIGO_3rdIfo.JPG
  33   Wed Nov 7 20:21:42 2012 KojiGeneralGeneralWork completed in October [!]

Completed work of the previous months: [Jul] [Aug] [Sep] [Oct] [Nov] [Dec]


 

  47   Mon Dec 31 01:45:04 2012 KojiGeneralGeneralWork completed in Nov and Dec [!]

Completed work of the previous months: [Jul] [Aug] [Sep] [Oct] [Nov] [Dec]


  • Work done
  • Things delivered
    • The ionized gun used in the clean room at Downs: made by Terra Universal.com (Jeff's room)
      http://www.terrauniversal.com/static-control/ionizing-blow-off-guns.php
    • Flow path: N2 cylinder - Filter - Gun (Jeff's room)
    • Power strips Tripp Lite PS3612 (Ordered Nov. 8, Delivered Nov. 12)
    • Kapton tapes (1in x 6, 1/2in x 12 Delivered Nov. 15)
    • Sticky Mats (VWR 18888-216 Delivered Nov. 12 and 21992-042)
    • Duck tape (PK3) (Delivered Nov. 12)
    • Wipers 12"x12" 2ply x 119 pairs x case15 (Delivered Nov. 12)
    • Syringes (1mL&2mL) & Needles (20G x dozen)
    • Stainless trays with cover (Steve Delivered Nov. 12)
    • Gold Plated allen keys (Steve Delivered Nov. 12)
    • Forceps (Delivered Nov. 12) / Tweezers / Scissors (Delivered Nov. 12)
    • OMC testing optics / opto-mechanics
    • SolidWorks raytracing model
    • Mode design for HAM6 layout [Zach]
       
    • Black Glass / Black Glass holder / AR ==> Some at the 40m, some from LLO
    • Ionized air blow
      • N2 or Air cylinder: 4N - UHP or 5N - Research Grade.  (... steal from Downs)
  12   Tue Jul 31 21:29:43 2012 KojiGeneralGeneralWork completed in July [!]

 

  28   Tue Oct 16 15:50:09 2012 KojiGeneralGeneralWork completed in August/September [!]
  • Work done
  • Things ordered
    • Office Depot
      • [delivered] Office Depot(R) Brand Stretch Wrap Film, 20 x 1000 Roll, Clear / 445013
      • [delivered] Eveready(R) Gold AA Alkaline Batteries, Pack Of 24 / 158448
      • [delivered] Rubbermaid(R) Roller Sponge Mop / 921841
      • [delivered] Rubbermaid(R) Roller Sponge Mop Replacement / 921858
      • [delivered] Rubbermaid(R) Sanitizing Caddy, 10 Quarts, Yellow / 674125
      • [delivered] Glad(R) Tall Kitchen Trash Bags, 13 Gallon, White, Box Of 28 / 269268
    • Global Industrial Equipment
      • [delivered] Extended Surface Pleated Cartridge Filter Serva-Cell Mp4 Slmp295 12X24X2 Gl    WBB431699
    • Global Industrial Equipment
      • [delivered] Nexel Poly-Z-Brite Wire Shelving 30"W x 21"D x 63"H Nexel Poly-Z-Brite™ Wire Shelving Starter Unit WB189209
      • [delivered] Stem Casters Set of (4) 5" Polyurethane Wheel, 2 With Brakes 1200 lb. Capacity WB500592    
    • Rack Solutions
      • [delivered] Open Frame Server Racks
        1 x 20" Depth Kit (Ideal for Audio/Video or Networking Racks) P/N: 111-1779
        1 x 36U, Rack-111 Post Kit P/N: 111-1728
        1 x Caster Kit for Open Frame RACK-111 P/N: 111-1731
      • [delivered] 36U Side Panel Kit $199.99 P/N: 102-1775
    • Rack shelf
      • [delivered] 1 RMS 19 X 15 SINGLE SIDED NON-VENTED SHELF 70121637
    • Work bench, Stools
      • [not yet] 72"L X 30"W Production Bench - Phenolic Resin Square Edge-Blue Form attached WB237381LBL    
      • [not yet] 72"W Lower Shelf For Bench - 15"D- Blue Form attached WB606951    
      • [not yet] ESD-Safe Vinyl Clean Room Stool with Nylon Base with Drag Chain Blue Form attached WBB560852    
    • P Touch
      • [delivered] Brother PT-2030 Desktop Office Labeler Punch-out product 672828    
      • [delivered] Brother(R) TZe-241 Black-On-White Tape, 0.75 x 26.2 Punch-out product 239384    
      • [delivered] Brother(R) TZe-231 Black-On-White Tape, 0.5 x 26.2 Punch-out product 239400    
    • UV light guide
      • [delivered] Fiber Optic Single Light Guide 5mm OD X 3mm ID X 1M L Note: This light guide can be used with MKIII UV Cure unit. OLB1081
    • Gloves (7.5, 8.0)
      • [delivered] GLOVE ACCTCH NR-LTX SZ7.5 PK25 Punch-out product 79999-306
      • [delivered] GLOVE ACCTCH NR-LTX SZ8 PK25 Punch-out product 79999-308
    • Lab coat (L,XL), Sticky Mat, Shoe Covers (L, XL), Cap, Mask
      • [delivered] LAB XP WH EL WR.COLL. NP L30EA Punch-out product 82007-618
      • [delivered] LAB XPWH EL WR.COLL. NP XL30EA Punch-out product 82007-620    
      • [delivered] VWR MAT ADHESIVE 30L 18X36 BLU Punch-out product 21924-110 (This was too small)
      • [delivered] VWR SHOECVR NSKID AP 2XL 150PR Punch-out product 414004-651    
      • [delivered] VWR SHOECVR NSKID AP XL 150PR Punch-out product 414004-650    
      • [delivered] CAP BOUFFANT 24IN RAYON CS500 Punch-out product 10843-053    
      • [delivered] MASK VLTC TIES N/STRL PK50 Punch-out product 10869-020
    • VWR
      • [delivered] FACE SHIELD UVC-803 Supplier: UVP 33007-151
         
    • [Delivered] Laser safety glasses

 

  361   Wed May 15 19:07:53 2019 KojiCleanGeneralWhat is this???

Suddenly something dirty emerged in the lab. What is this? It looks like an insulation foam or similar, but is quite degraded and emits a lot of particulates.

This does not belong to the lab. I don't see piping above this area which shows broken insulation or anything. All the pipes in the room are painted white.

The only possibility is that it comes from the hole between the next lab (CRIME Lab). I found that the A.C. today is much stronger and colder than last week. And there is a positive pressure from CRIME Lab. Maybe the foam was pushed out from the hole due to the differential pressure (or any RF cable action).

 

Attachment 1: P_20190515_185602.jpg
P_20190515_185602.jpg
Attachment 2: P_20190515_185844.jpg
P_20190515_185844.jpg
  371   Thu Aug 22 12:35:53 2019 StephenOpticsCharacterizationWedging of the debonded PZTs 2019 August

Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it format).

These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material while mechanically removing glue. It is also possible that there is systematic error between the two sets of measurements. I did not run any calculations of wedge ange or orientation on these data.

Note that cleaning of debonded PZTs involved mechanically separating glue from the planar faces of PZTs. The second image shows the razer blade used to scrape the glue away.

There were thick rings of glue where there had been excess squeezed out of the bond region, and there was also a difficult-to-remove bond layer that was thinner. I observed the presence of the thin layer by its reflectivity. The thick glue came off in patches, while the thin glue came off with a bit of a powdery appearance. It was hard to be certain that all of the thin bond layer came off, but I made many passes on each of the faces of the 2 PZTs that had been in the bonded CM assemblies. I found it was easiest to remove the glue in the bonded

I was anticipating that the expected 75-90 micron bond layer would affect the micrometer thickness measurements if it was still present, but I did not notice any irregularities (and certainly not at the 10 micron level), indicating that the glue was removed successfully (at least to the ~1 micron level).

 

Quote:

Yesterday I measured the thickness of the PZTs in order to get an idea how much the PZTs are wedged.

For each PZT, the thickness at six points along the ring was measured with a micrometer gauge.
The orientation of the PZT was recognized by the wire direction and a black marking to indicate the polarity.

A least square fitting of these six points determines the most likely PZT plane.
Note that the measured numbers are assumed to be the thickness at the inner rim of the ring
as the micrometer can only measure the maximum thickness of a region and the inner rim has the largest effect on the wedge angle.
The inner diameter of the ring is 9mm.



The measurements show all PZTs have thickness variation of 3um maximum.

The estimated wedge angles are distributed from 8 to 26 arcsec. The directions of the wedges seem to be random
(i.e. not associated with the wires)



As wedging of 30 arcsec causes at most ~0.3mm spot shift of the cavity (easy to remember),
the wedging of the PZTs is not critical by itself. Also, this number can be reduced by choosing the PZT orientations
based on the estimated wedge directions --- as long as we can believe the measurements.



Next step is to locate the minima of each curved mirror. Do you have any idea how to measure them?

 

Attachment 1: IMG_4775.JPG
IMG_4775.JPG
Attachment 2: IMG_4770.JPG
IMG_4770.JPG
  373   Thu Aug 29 11:51:49 2019 shrutiOpticsCharacterizationWedging of the debonded PZTs - Calculation

Using the measurements of PZTs 12,13 taken by Stephen, I estimated the wedging angle and orientation following Section 2.3.1 of T1500060. The results can be found in Attachment1 and is summarised as follows.

For PZT 12, PZT 13 respectively:

Avg. height = 2.0063 mm, 2.0035 mm

Wedge direction (from the same direction as in the doc: positive right) = 120 deg, 120 deg

Wedge angles = 45.8 arcsec, 30.6 arcsec

 

This was done assuming that the measurements were taken uniformly at intervals of 60deg along the inner rim of the PZT. The diameter (2r) of the inner rim, according to T1500060, is 9mm. The measured heights were fitted with the function

h = h_0 + \tan(\Omega)\text{ }r(1-\cos(\theta - \alpha))

as depicted in Attachment2 to find wedging angle (\Omega) and orientation (\alpha).

Quote:

Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it format).

These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material while mechanically removing glue. It is also possible that there is systematic error between the two sets of measurements. I did not run any calculations of wedge ange or orientation on these data.

Note that cleaning of debonded PZTs involved mechanically separating glue from the planar faces of PZTs. The second image shows the razer blade used to scrape the glue away.

There were thick rings of glue where there had been excess squeezed out of the bond region, and there was also a difficult-to-remove bond layer that was thinner. I observed the presence of the thin layer by its reflectivity. The thick glue came off in patches, while the thin glue came off with a bit of a powdery appearance. It was hard to be certain that all of the thin bond layer came off, but I made many passes on each of the faces of the 2 PZTs that had been in the bonded CM assemblies. I found it was easiest to remove the glue in the bonded

I was anticipating that the expected 75-90 micron bond layer would affect the micrometer thickness measurements if it was still present, but I did not notice any irregularities (and certainly not at the 10 micron level), indicating that the glue was removed successfully (at least to the ~1 micron level).

 

Quote:

Yesterday I measured the thickness of the PZTs in order to get an idea how much the PZTs are wedged.

For each PZT, the thickness at six points along the ring was measured with a micrometer gauge.
The orientation of the PZT was recognized by the wire direction and a black marking to indicate the polarity.

A least square fitting of these six points determines the most likely PZT plane.
Note that the measured numbers are assumed to be the thickness at the inner rim of the ring
as the micrometer can only measure the maximum thickness of a region and the inner rim has the largest effect on the wedge angle.
The inner diameter of the ring is 9mm.



The measurements show all PZTs have thickness variation of 3um maximum.

The estimated wedge angles are distributed from 8 to 26 arcsec. The directions of the wedges seem to be random
(i.e. not associated with the wires)



As wedging of 30 arcsec causes at most ~0.3mm spot shift of the cavity (easy to remember),
the wedging of the PZTs is not critical by itself. Also, this number can be reduced by choosing the PZT orientations
based on the estimated wedge directions --- as long as we can believe the measurements.



Next step is to locate the minima of each curved mirror. Do you have any idea how to measure them?

 

 

Attachment 1: PZT_Wedging_Results.pdf
PZT_Wedging_Results.pdf
Attachment 2: PZT_Wedging_Calc.pdf
PZT_Wedging_Calc.pdf
  53   Thu Jan 10 18:37:50 2013 KojiOpticsCharacterizationWedging of the PZTs

Yesterday I measured the thickness of the PZTs in order to get an idea how much the PZTs are wedged.

For each PZT, the thickness at six points along the ring was measured with a micrometer gauge.
The orientation of the PZT was recognized by the wire direction and a black marking to indicate the polarity.

A least square fitting of these six points determines the most likely PZT plane.
Note that the measured numbers are assumed to be the thickness at the inner rim of the ring
as the micrometer can only measure the maximum thickness of a region and the inner rim has the largest effect on the wedge angle.
The inner diameter of the ring is 9mm.



The measurements show all PZTs have thickness variation of 3um maximum.

The estimated wedge angles are distributed from 8 to 26 arcsec. The directions of the wedges seem to be random
(i.e. not associated with the wires)



As wedging of 30 arcsec causes at most ~0.3mm spot shift of the cavity (easy to remember),
the wedging of the PZTs is not critical by itself. Also, this number can be reduced by choosing the PZT orientations
based on the estimated wedge directions --- as long as we can believe the measurements.



Next step is to locate the minima of each curved mirror. Do you have any idea how to measure them?

Attachment 1: PZT_wedging.pdf
PZT_wedging.pdf
  59   Mon Feb 4 00:39:08 2013 KojiOpticsCharacterizationWedge measurement with the autocollimator and the rotation stage

Method:

  • Mount the tombstone prism on the prism mount. The mount is fixed on the rotation stage.
  • Locate the prism in front of the autocollimator.
  • Find the retroreflected reticle in the view. Adjust the focus if necessary.
  • Confirm that the rotation of the stage does not change the height of the reticle in the view. 

    If it does, rotate the AC around its axis to realize it.
    This is to match the horizontal reticle to the rotation plane.
  • Use the rotation stage and the alignment knobs to find the reticle at the center of the AC.
Make sure the reticle corresponds to the front surface.
  • Record the micrometer reading.
  • Rotate the micrometer of the rotation stage until the retroreflected reticle for the back surface.
  • There maybe the vertical shift of the reticle due to the vertical wedging. Record the vertical shi
  • Record the micrometer reading. Take a difference from the previous value.
     

Measurement:

  • A1: α = 0.68 deg, β = 0 arcmin (0 div)
  • A2: α = 0.80 deg, β = -6 arcmin (3 div down)
  • A3: α = 0.635 deg, β = -1.6 arcmin (0.8 div down)
  • A4: α = 0.650 deg, β = 0 arcmin (0div)
  • A5: α = 0.655 deg, β = +2.4 arcmin (1.2 div up)

Analysis:

  • \theta_H = ArcSin[Sin(α) / n]
  • \theta_V = ArcSin[Sin(β) / n]/2
     
  • A1: \theta_H = 0.465 deg, \theta_V = 0.000 deg
  • A2: \theta_H = 0.547 deg, \theta_V = -0.034 deg
  • A3: \theta_H = 0.434 deg, \theta_V = -0.009 deg
  • A4: \theta_H = 0.445 deg, \theta_V = 0.000 deg
  • A5: \theta_H = 0.448 deg, \theta_V = 0.014 deg

 

Attachment 1: autocollimator_wedge_measurement.pdf
autocollimator_wedge_measurement.pdf
  60   Wed Feb 6 02:34:10 2013 KojiOpticsCharacterizationWedge measurement with the autocollimator and the rotation stage

Measurement:

  • A6:   α = 0.665 deg, β = +3.0 arcmin (1.5 div up)
  • A7:   α = 0.635 deg, β =   0.0 arcmin (0.0 div up)
  • A8:   α = 0.623 deg, β = - 0.4 arcmin (-0.2 div up)
  • A9:   α = 0.670 deg, β = +2.4 arcmin (1.2 div up)
  • A10: α = 0.605 deg, β = +0.4 arcmin (0.2 div up)
  • A11: α = 0.640 deg, β = +0.8 arcmin (0.4 div up)
  • A12: α = 0.625 deg, β = - 0.6 arcmin (-0.3 div up)
  • A13: α = 0.630 deg, β = +2.2 arcmin (1.1 div up)
  • A14: α = 0.678 deg, β =   0.0 arcmin (0.0 div up)
  • B1:   α = 0.665 deg, β = +0.6 arcmin (0.3 div up)
  • B2:   α = 0.615 deg, β = +0.2 arcmin (0.1 div up)
  • B3:   α = 0.620 deg, β = +0.9 arcmin (0.45 div up)
  • B4:   α = 0.595 deg, β = +2.4 arcmin (1.2 div up)
  • B5:   α = 0.635 deg, β = - 1.8 arcmin (-0.9 div up)
  • B6:   α = 0.640 deg, β = +1.6 arcmin (0.8 div up)
  • B7:   α = 0.655 deg, β = +2.5 arcmin (1.25 div up)
  • B8:   α = 0.630 deg, β = +2.8 arcmin (1.4 div up)
  • B9:   α = 0.620 deg, β = - 4.0 arcmin (-2.0 div up)
  • B10: α = 0.620 deg, β = +1.2 arcmin (0.6 div up)
  • B11: α = 0.675 deg, β = +3.5 arcmin (1.75 div up)
  • B12: α = 0.640 deg, β = +0.2 arcmin (0.1 div up)

Analysis:

  • \theta_H = ArcSin[Sin(α) * n]
  • \theta_V = ArcSin[Sin(β) / n]/2
     
  • A6:   \theta_H = 0.490 deg, \theta_V =  0.017 deg
  • A7:   \theta_H = 0.534 deg, \theta_V =  0.000 deg
  • A8:   \theta_H = 0.551 deg, \theta_V = -0.0023 deg
  • A9:   \theta_H = 0.482 deg, \theta_V =  0.014 deg
  • A10: \theta_H = 0.577 deg, \theta_V =  0.0023 deg
  • A11: \theta_H = 0.526 deg, \theta_V =  0.0046 deg
  • A12: \theta_H = 0.548 deg, \theta_V = -0.0034 deg
  • A13: \theta_H = 0.541 deg, \theta_V =  0.013 deg
  • A14: \theta_H = 0.471 deg, \theta_V =  0.000 deg
  • B1:   \theta_H = 0.490 deg, \theta_V =  0.0034 deg
  • B2:   \theta_H = 0.563 deg, \theta_V =  0.0011 deg
  • B3:   \theta_H = 0.556 deg, \theta_V =  0.0051 deg
  • B4:   \theta_H = 0.592 deg, \theta_V =  0.014 deg
  • B5:   \theta_H = 0.534 deg, \theta_V = -0.010 deg
  • B6:   \theta_H = 0.526 deg, \theta_V =  0.0091 deg
  • B7:   \theta_H = 0.504 deg, \theta_V =  0.014 deg
  • B8:   \theta_H = 0.541 deg, \theta_V =  0.016 deg
  • B9:   \theta_H = 0.556 deg, \theta_V = -0.023 deg
  • B10: \theta_H = 0.556 deg, \theta_V =  0.0068 deg
  • B11: \theta_H = 0.475 deg, \theta_V =  0.020 deg
  • B12: \theta_H = 0.526 deg, \theta_V =  0.0011 deg

Quote:

Measurement:

  • A1: α = 0.68 deg, β = 0 arcmin (0 div)
  • A2: α = 0.80 deg, β = -6 arcmin (3 div down)
  • A3: α = 0.635 deg, β = -1.6 arcmin (0.8 div down)
  • A4: α = 0.650 deg, β = 0 arcmin (0div)
  • A5: α = 0.655 deg, β = +2.4 arcmin (1.2 div up)

Analysis:

  • \theta_H = ArcSin[Sin(α)*n]
  • \theta_V = ArcSin[Sin(β) / n]/2
     
  • A1: \theta_H = 0.465 deg, \theta_V = 0.000 deg
  • A2: \theta_H = 0.547 deg, \theta_V = -0.034 deg
  • A3: \theta_H = 0.434 deg, \theta_V = -0.009 deg
  • A4: \theta_H = 0.445 deg, \theta_V = 0.000 deg
  • A5: \theta_H = 0.448 deg, \theta_V = 0.014 deg

 

  66   Fri Mar 1 23:52:18 2013 KojiOpticsCharacterizationWedge measurement with the autocollimator and the rotation stage

Measurement:

  • E1:   α = 0.672 deg, β = +0.0 arcmin (0 div up)
  • E2:   α = 0.631 deg, β = - 0.3 arcmin (-0.15 div down)
  • E3:   α = 0.642 deg, β = +0.0 arcmin (0 div up)
  • E4:   α = 0.659 deg, β = +1.4 arcmin (0.7 div up)
  • E5:   α = 0.695 deg, β = +0.5 arcmin (0.5 div up)
  • E6:   α = 0.665 deg, β = - 0.4 arcmin (-0.2 div down)
  • E7:   α = 0.652 deg, β = +1.0 arcmin (0.5 div up)
  • E8:   α = 0.675 deg, β = +2.0 arcmin (1.0 div up)
  • E9:   α = 0.645 deg, β = - 2.4 arcmin (-1.2 div down)
  • E10: α = 0.640 deg, β = +2.2 arcmin (1.1 div up)
  • E11: α = 0.638 deg, β = +1.6 arcmin (0.8 div up)
  • E12: α = 0.660 deg, β = +1.6 arcmin (0.8 div up)
  • E13: α = 0.638 deg, β = +0.8 arcmin (0.4 div up)
  • E14: α = 0.655 deg, β = +0.4 arcmin (0.2 div up)
  • E15: α = 0.640 deg, β = +1.4 arcmin (0.7 div up)
  • E16: α = 0.655 deg, β = +0.6 arcmin (0.3 div up)
  • E17: α = 0.650 deg, β = +0.8 arcmin (0.4 div up)
  • E18: α = 0.640 deg, β = +2.4 arcmin (1.2 div up)

Analysis:

  • \theta_H = ArcSin[Sin(α) / n]
  • \theta_V = ArcSin[Sin(β) / n]/2
     
  • E1:   \theta_H = 0.460 deg, \theta_V =   0.000 deg
  • E2:   \theta_H = 0.432 deg, \theta_V =  -0.0034 deg
  • E3:   \theta_H = 0.439 deg, \theta_V =   0.000 deg
  • E4:   \theta_H = 0.451 deg, \theta_V =  0.016 deg
  • E5:   \theta_H = 0.475 deg, \theta_V =  0.011 deg
  • E6:   \theta_H = 0.455 deg, \theta_V =  -0.0046 deg
  • E7:   \theta_H = 0.446 deg, \theta_V =  0.011 deg
  • E8:   \theta_H = 0.462 deg, \theta_V =  0.023 deg
  • E9:   \theta_H = 0.441 deg, \theta_V =  -0.027 deg
  • E10:   \theta_H = 0.438 deg, \theta_V = 0.025 deg
  • E11:   \theta_H = 0.436 deg, \theta_V = 0.018 deg
  • E12:   \theta_H = 0.451 deg, \theta_V = 0.018 deg
  • E13:   \theta_H = 0.436 deg, \theta_V = 0.0091 deg
  • E14:   \theta_H = 0.448 deg, \theta_V = 0.0046 deg
  • E15:   \theta_H = 0.438 deg, \theta_V = 0.016 deg
  • E16:   \theta_H = 0.448 deg, \theta_V = 0.0068 deg
  • E17:   \theta_H = 0.444 deg, \theta_V = 0.0091 deg
  • E18:   \theta_H = 0.438 deg, \theta_V = 0.027 deg
  56   Sat Jan 19 20:47:41 2013 KojiOpticsCharacterizationWedge measurement with the autocollimator

The wedge angle of the prism "A1" was measured with the autocollimator (AC).

The range of the AC is 40 arcmin. This means that the mirror tilt of 40arcmin can be measured with this AC.
This is just barely enough to detect the front side reflection and the back side reflection.

The measured wedge angle of the A1 prism was 0.478 deg.

Ideally a null measurement should be done with a rotation stage.

Attachment 1: autocollimator_wedge_measurement.pdf
autocollimator_wedge_measurement.pdf
  32   Wed Nov 7 01:28:20 2012 KojiOpticsCharacterizationWedge angle test (A1)

Wedge angle test

Result: Wedge angle of Prism A1: 0.497 deg +/- 0.004 deg


 

Principle:

o Attach a rail on the optical table. This is the reference of the beam.

o A CCD camera (Wincam D) is used for reading out spot positions along the rail.

o Align a beam path along the rail using the CCD.

o Measure the residual slope of the beam path. (Measurement A)

o Insert an optic under the test. Direct the first surface retroreflectively. (This means the first surface should be the HR side.)

o Measure the slope of the transmitted beam. (Measurement B)

o Deflection angle is derived from the difference between these two measurements.

Setup:

wedge_measurement_setup.png

o An Al plate of 10" width was clamped on the table. Four other clamps are located along the rail to make the CCD positions reproducible.

o A prism (Coating A, SN: A1) is mounted on a prism mount. The first surface is aligned so that the reflected beam matches with the incident beam
with precision of +/-1mm at 1660mm away from the prism surface. ==> precision of +/- 0.6mrad

o In fact, the deflection angle of the transmission is not very sensitive to the alignment of the prism.
The effect of the misalignment on the measurement is negligible.

o Refractive index of Corning 7980 at 1064nm is 1.4496

Result:

Without Prism
Z (inch / mm), X (horiz [um] +/-4.7um), Y (vert [um] +/-4.7um)
0” / 0, -481.3, -165.1
1.375" / 34.925, -474.3, -162.8
3" / 76.2, -451.0, -186.0
4.375" / 111.125, -432.5, -181.4
6" / 152.4, -432.5, -181.4
7.375" / 187.325, -330.2, -204.6
9" / 228.6, -376.7, -209.3

With Prism / SN of the optic: A1
Z (inch / mm), X (horiz [um] +/-4.7um), Y (vert [um] +/-4.7um)
0” / 0, -658.3, -156.8
1.375" / 34.925, -744.0, -158.1
3" / 76.2, -930.0, -187.4
4.375" / 111.125, -962.6, -181.4
6" / 152.4, -1190.4, -218.6
7.375" / 187.325, -1250.9, -232.5
9" / 228.6, -1418.3, -232.5

Analysis:

Wedge angle of Prism A1: 0.497 deg +/- 0.004 deg

wedge_measurement.png[Click for a sharper image]

  11   Tue Jul 24 11:41:29 2012 KojiGeneralGeneralUseful references

Nicolas Smith,
LIGO Document T0900383-v1
3mm Photodiode Characterization for Enhanced LIGO
https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=4498

Tobin Fricke,
LIGO Document P1000010-v1
Homodyne detection for laser-interferometric gravitational wave detectors
https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=8443

Nicolas Smith,
LIGO Document P1200052-v1
Techniques for Improving the Readout Sensitivity of Gravitational Wave Antennae
https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=90498

  239   Sun Sep 6 16:50:51 2015 KojiElectronicsGeneralUnit test of the EOM/AOM Driver S1500118

TEST Result: S1500118

Additional notes

- Checked the power supply. All voltages look quiet and stationary.

- Checked the internal RF cables too see if there is any missing shield soldering => Looked fine

- Noticed that the RFAM detector board has +/-21V for the +/-24V lines => It seems that this is nominal according to the schematic

- Noticed that the RFAM detector sensitivity were doubled fomr the other unit.
  => This is reated to the modification (E1500353) of  "Controller Board D0900761-B Change 1" (doubling the monitor output gain)

- Noticed that the transfer function of the CTRL signal on the BNC and the DAQ output.
  => This is reated to the modification (E1500353) of  "Servo Board D0900847-B Change 1"  (servo transfer function chage)
  => The measured transfer function did not agree with the prediction from the circuit constants in this document
  => From the observation of the servo board it was found that R69 was not 200Ohm but 66.5 Ohm (See attachment 1).
       This explained the measured transfer function. The actuator TF has: P 2.36, Z 120., K -1@DC (0.020@HF)

- Similarly, the TF between the CTRL port on the unit and the CTRL port on the test rig was also modified.

Noise level

Attachment 2

- The amplitude noise in dBc (SSB) was measured at the output of 27dBm. From the test sheet, the noise level with 13dBm output was also referred. From the coherence of the MON1 and MON2, the noise level was inferred. It suggests that the floor level is better than 180dBc/Hz. However, there is a 1/f like noise below 1k and is dominating the actual noise level of the RF output. Daniel suggested that we should check nonlinear downconversion from the high frequency noise due to the noise attenuator. This will be check with the coming units.

Attachment 1: P9037810.JPG
P9037810.JPG
Attachment 2: RF_AM_spectra.pdf
RF_AM_spectra.pdf
  89   Mon Apr 1 03:23:48 2013 KojiOpticsGeneralUV power calibration

[Koji Lisa Jeff Zach]

Eric G bought a UV power meter from American Ultraviolet.

Our UV illuminator was calibrated by this power meter.

The first blast (i.e. cold start): 3.9W/cm^2

After many blasting: 8.3W/cm^2

The spec is 20W/cm^2

  62   Thu Feb 7 23:01:45 2013 KojiOpticsCharacterizationUV epoxy gluing test

 [Jeff, Yuta, Koji]

Gluing test with UV-cure epoxy Optocast 3553-LV-UTF-HM

- This glue was bought in the end of October (~3.5 months ago).

- The glue was taken out from the freezer at 1:20pm.
- Al sheet was laid on the optical table. We made a boat with Al foil and pour the glue in it (@1:57pm)
- We brought two kinds of Cu wires from the 40m. The thicker one has the diameter of 1.62mm.
The thinner one has the diameter of 0.62mm. We decided to use thinner one being cut into 50mm in length.

- The OMC glass prisms have the footprint of 10mmx20mm = 200mm^2. We tested several combinations
of the substrates. Pairs of mirrors with 1/2" mm in dia. (127mm) and a pair of mirrors with 20mm in dia. (314mm).

- Firstly, a pair of 1/2" mirrors made of SF2 glass was used. A small dub on a thinner Cu wire was deposited on a mirror.
  We illuminated the glue for ~10sec. When the surfaces of the pair was matched, the glue did not spread on the entire
  surface. The glue was entirely spread once the pressure is applied by a finger. Glue was cured at 2:15pm. 12.873mm
  thickness after the gluing.

Some remark:
1. We should be careful not to shine the glue pot by the UV illuminator.
2. The gluing surface should be drag wiped to remove dusts on the surface.

- Secondly, we moved onto 20mm mirror pair taken from the remnant of the previous gluing test by the eLIGO people.
This time about 1.5 times more glue was applied.

- The third trial is to insert small piece of alminum foil to form a wedge. The thickness of the foil is 0.041mm.
The glue was applied to the pair of SF2 mirror (1/2" in dia.). A small dub (~1mm in dia) of the glue was applied.
The glue filled the wedge without any bubble although the glue tried to slide out the foil piece from the wedge.
So the handling was a bit difficult. After the gluing we measured the thickness of the wedge by a micrometer gauge.
The skinny side was 12.837mm, and the thicker side was 12.885mm. This is to be compared with the total thickness
12.823mm before the gluing. The wedge angle is 3.8mrad (0.22deg). The glue dub was applied at 2:43, and the UV
illumination was applied at 2:46.

- At the end we glued a pair of fused silica mirrors. The total thickness before the gluing was 12.658 mm.
The glue was applied at 2:59pm. The thickness after the gluing is 12.663 mm.
This indicates the glue thickess is 5um.

  265   Mon Aug 22 12:58:16 2016 KojiGeneralGeneralUV bond samples -> Garilynn

- FS base + Mounting Prism

- FS or SF2 1/2" piece + FS or SF2 1/2" piece

- FS? plate + FS or SF2 1/2" piece + FS or SF2 1/2" piece + FS? plate

  134   Fri May 31 14:07:54 2013 KojiOpticsCharacterizationTransverse Mode Spacing measurement afte the baking

Measurement for pitch

Free Spectral Range (FSR): 264.9703 +/− 0.0007 MHz
Cavity roundtrip length: 1.131419 +/− 0.000003 m
Transverse mode spacing (TMS): 57.9396 +/− 0.0002 MHz
TMS/FSR: 0.218664 +/− 0.000001
 
Assuming the line width of the cavity 1/400 of the FSR...
- the 9th modes of the carrier is 12.8 line width (LW) away from the carrier resonance
- the 13th modes of the lower f2 sideband are 5.7 LW away
- the 19th modes of the upper f2 sideband are -6.8 LW away

Measurement for yaw

Free Spectral Range (FSR): 264.9696 +/− 0.0004 MHz
Cavity roundtrip length: 1.131422 +/− 0.000002 m
Transverse mode spacing (TMS): 58.0479 +/− 0.0002 MHz
TMS/FSR: 0.219074 +/− 0.000001
 
- the 9th modes of the carrier is 11.3 line width (LW) away from the carrier resonance
- the 13th modes of the lower f2 sideband are 7.8 LW away
- the 19th modes of the upper f2 sideband are -3.7 LW away

The followings are the previous values before the bake
[from this entry]

- After everything was finished, more detailed measurement has been done.

- FSR&TMS (final)
 
FSR: 264.963MHz => 1.13145m
  TMS(V): 58.0177MHz => gamma_V = 0.218966
  TMS(H): 58.0857MHz => gamma_H = 0.219221
  the 9th modes of the carrier is 10.8~11.7 LW away
  the 13th modes of the lower f2 sideband are 7.3~8.6 LW away
  the 19th modes of the upper f2 sideband are 2.6~4.5 LW away

Attachment 1: Cav_scan_response_130530_Pitch.pdf
Cav_scan_response_130530_Pitch.pdf
Attachment 2: Cav_scan_response_130530_Yaw.pdf
Cav_scan_response_130530_Yaw.pdf
  278   Fri May 26 21:53:20 2017 KojiGeneralConfigurationTrans RF PD setup

Recent work

- DC output of the trans RF PD was connected to the BNC patch panel. => Now CH4 of the scope is monitoring this signal

- The RF sweep signal from the network analyzer is connected to the power combiner for the EOM drive via the SMA patch panel.

- The trans RF PD was aligned first to the leakage beam. It turned out that this signal is too weak. Then the PD was aligned to one of the main OMC transmission. For this purpose, the OMC DCPD (T) was removed from the OMC breadboard.

- It seems that there is a significant amount of RF AM from the EOM. I suspect it is associated with the residual S-pol and birefringence of the steering mirrors (45deg HR). But the HWP at the output of the Faraday is fixed on the Faraday body with a screw and cumbersome for fine adjustment. A PBS and an HWP are added right before the EOM. This made the fiber coupler slightly misaligned. I suppose this new setup still has S&P on the fiber too. Thus, readjustment of the fiber rotations at the input is necessary.

Next step

- Input power to the fiber should be determined before the EOM. Otherwise, touching the HWP before the EOM causes too much power change at the optics of the OMC side.

- Precise adjustment of the RFAM is still necessary.

- The OMC curved mirror should be held by the new fixture.

- Check the beam spots

- Measure cavity parameters. (transmission/FSR/HOM/etc)

==> Then the curved mirror and the PZT will be glued on the prism

  279   Tue Jun 6 00:49:48 2017 KojiGeneralConfigurationTrans RF PD setup

Last week, I further worked on the RF system to install 20dB coupler on the agilent unit and setup the R channel. This allowed me to make the FSR/TMS measurement of the OMC.

And today several optical improvement has been done.

- The input/output fiber couplers were adjusted to have the maximum transmission through the PBS right before the OMC.
- The HWP on the output side of the faraday was adjusted to have ~40mW input to the OMC.

Then, the OMC curved mirror is now held by the new in-situ gluing fixture instead of the conventional fixture attached upside down.
The OMC was ocked again and the input alignment was adjutsed. The fixture is blocking the QPD path, so it's not possible to confirm the proper alignment of the cavity (w.r.t. the QPD paths).

The precise positions of the spots could not be confirmed as the battery of the IR viewer was empty. Quick check of the spots by the card tells that the spot on the CM2 (PD side) is slightly too close to FM2 (output coupler). I wonder if this could be solved by rotating the curved mirror.

Otherwise everything look good. Let's try to glue the curved mirror tomorrow.

Note: Spot on CM2 is too close to the edge of the hole on the mounting prism. The meausrementof CM1 is telling that the curverture center is located 2.7mm upper side of the center of the mirror if the HR side arrow is up (and it is the case). If we move the arrow to the QPD path side (90deg CW viewed from the face side), this corresponds to ~1.1mrad CCW tilt in Yaw (viewed from the top of the prism). According to the matrix calculation (T1500060) this will induce ~1.5mm shift of the beam. This should be tried before gluing.

  280   Tue Jun 6 22:00:36 2017 KojiGeneralConfigurationTrans RF PD setup

- Replaced the PZT with the one used from the beginning. This must be PZT #21. After the replacement, the spot positions look very good. I even went up. So I decided this is the configuration to proceed to the gluing. The CM1 mirror has the HR arrow at the top.

- The input beam was realigned w.r.t. the OMC.

- Tried to use the IR viewer with the new rechargable battery brought from the 40m. But the view still didn't work. The possibility is a) the viewer is broken b) the battery is empty.

- Tried to use the stainless clean regulartor for the UHP N2. The outlet has a short tube with a different diameter. The O.D. of the old tube is 6.3mm, while the new one is 9.5mm. If I insert the thinner tube in the new tube, it approximately fits. But I don't believe this is the way...

  4   Wed Jun 20 20:37:45 2012 ZachOpticsConfigurationTopology / parameter selection

EDIT (ZK): All the plots here were generated using my MATLAB cavity modeling tool, ArbCav. The utility description is below. The higher-order mode resonance plots are direct outputs of the function. The overlap plots were made by modifying the function to output a list of all HOM resonant frequencies, and then plotting the closest one as a function of cavity length. This was done for various values of highest mode order to consider, as described in the original entry.

Description:

This function calculates information about an arbitrary optical cavity. It can plot the cavity geometry, calculate the transmission/reflection spectrum, and generate the higher-order mode spectrum for the carrier and up to 2 sets of sidebands.

The code accepts any number of mirrors with any radius of curvature and transmission, and includes any astigmatic effects in its output.

As opposed to the previous version, which converted a limited number of cavity shapes into linear cavities before performing the calculation, this version explicitly propagates the gouy phase of the beam around each leg of the cavity, and is therefore truly able to handle an arbitrary geometry.

----------------Original Post----------------

I expressed concern that arbitrarily choosing some maximum HOM order above which not to consider makes us vulnerable to sitting directly on a slightly-higher-order mode. At first, I figured the best way around this is to apply an appropriate weighting function to the computed HOM frequency spacing. Since this will also have some arbitrariness to it, I have decided to do it in a more straightforward way. Namely, look at the spacing for different values of the maximum mode number, nmax, and then use this extra information to better select the length.

Assumptions:

  • The curved mirror RoC is the design value of 2.50±0.025 m
  • The ±9 MHz sidebands will have ~1% the power of the other fields at the dark port. Accordingly, as in Sam's note, their calculated spacing is artificially increased by 10 linewidths.
  • The opening angle of 4º is FIXED, and the total length is scaled accordingly

Below are the spacing plots for the bowtie (flat-flat-curved-curved) and non-bowtie (flat-curved-flat-curved) configurations. Points on each line should be read out as "there are are no modes of order N or lower within [Y value] linewidths of the carrier TEM00 transmission", where N is the nmax appropriate for that trace. Intuitively, as more orders are included, the maxima go down, because more orders are added to the calculation.

*All calculations are done using my cavity simulation function, ArbCav. The mode spacing is calculated for each particular geometry by explicitly propagating the gouy phase through each leg of the cavity, rather than by finding an equivalent linear cavity*

 ovlp_bowtie.pngovlp_non-bowtie.png

Since achievable HOM rejection is only one of the criteria that should be used to choose between the two topologies, the idea is to pick one length solution for EACH topology. Basically, one maximum should be chosen for each plot, based on how how high an order we care about.

Bowtie

For the bowtie, the nmax = 20 maximum at L = 1.145 m is attractive, because there are no n < 20 modes within 5 linewidths, and no n < 25 modes within ~4.5 linewidths. However, this means that there are also n < 10 modes within 5 linewidths, while they could be pushed (BLUE line) to ~8.5 linewidths at the expense of proximity to n > 15 modes.

Therefore, it's probably best to pick something between the red and green maxima: 1.145 m < L < 1.152 m.

By manually inspecting the HOM spectrum for nmax = 20, it seems that L = 1.150 m is the best choice. In the HOM zoom plot below and the one to follow, the legend is as follows

  • BLUE: Carrier
  • GREEN: +9 MHz
  • RED: -9 MHz
  • CYAN: +45 MHz
  • BLACK: -45 MHz

spect_zoom_bowtie.png

Non-bowtie

Following the same logic as above, the most obvious choice for the non-bowtie is somewhere between the red maximum at 1.241 m and the magenta maximum at 1.248 m. This still allows for reasonable suppression of the n < 10 modes without sacrificing the n < 15 mode suppression completely.

Upon inspection, I suggest L = 1.246 m

spect_zoom_non-bowtie.png

I reiterate that these calculations are taking into account modes of up to n ~ 20. If there is a reason we really only care about a lower order than this, then we can do better. Otherwise, this is a nice compromise between full low-order mode isolation and not sitting directly on slightly higher modes.

 

RoC dependence

One complication that arises is that all of these are highly dependent on the actual RoC of the mirrors. Unfortunately, even the quoted tolerance of ±1% makes a difference. Below is a rendering of the RED traces (nmax = 20) in the first two plots, but for R varying by ±2% (i.e., for R = 2.45 m, 2.50 m, 2.55 m).

ovlp_vs_R_bowtie.pngovlp_vs_R_non-bowtie.png

The case for the non-bowtie only superficially seems better; the important spacing is the large one between the three highest peaks centered around 1.24 m.

Also unfortunately, this strong dependence is also true for the lowest-order modes. Below is the same two plots, but for the BLUE (nmax = 10) lines in the first plots.

 ovlp_vs_R_N10_bowtie.pngovlp_vs_R_N10_non-bowtie.png

Therefore, it is prudent not to pick a specific length until the precise RoC of the mirrors is measured.

 

Conclusion

Assuming the validity of looking at modes between 10 < n < 20, and that the curved mirror RoC is the design value of 2.50 m, the recommended lengths for each case are:

  • Bowtie: LRT = 1.150 m
  • Non-bowtie: LRT = 1.246 m

 HOWEVER, variation within the design tolerance of the mirror RoC will change these numbers appreciably, and so the RoC should be measured before a length is firmly chosen.

  2   Sat Jun 16 08:53:09 2012 KojiGeneralGeneralTo Do List

Facility

Mechanics

  • Work 
    •  
  • Design
    • How do we hold the PDs, QPDs, and black glass - we put 2 PDs and 2 QPDs on the PD mounting blacket.
    •  
  •  
  • Test
     
  • Things to be tested
    • New suspension scheme (cup & cone design)
    • Balancing the plates
    • Dummy metal payload?
  • => Suspending test with a suspension cage for a Faraday isolator@CIT
    • Supporting block for the suspension cage (to mimic the OMC suspension)
  • Things to be designed
    • Wire end (cone)
    • Diode holding structures
      PD/QPD/PZT holding structure
  • PZT alignment
  • Prototyping with metal parts?
  • UV glue? (heat) / gluing test
  • Balance / ballast
     
  • Solid works

Optics

  • Mirrors to be delivered ~Aug
  • Design down select
    • Between "Single output & BS" vs "Two outputs & no BS"
  • Mode design
  • Finalization of scattering paths / PD angles etc
     
  • Things to be decided / confirmed:
    • How to handle optics / assemblies (Talk to the prev people)
    • First contact? (Margot: applicable to a short Rc of ~2.5m)
    • Gluing templates to be designed (how to handle it?)
  • Things to be tested:
    • R&T of each mirror
    • Cavity ref/trans/finesse
    • PD QE / incident angle
       
  • What PD do we use?
     
  • CCD beam analyzer (Zach: It is fixed.)
     
  • PD angle measurement
  • Obtain EG&G 3mm PDs

Electronics

  • Electronics / CDS electronics / software
     
  • Things to be tested
    • QPD/PD pre-selections (QE/noise)
    • Functionality test of QPD/PD/PZT

Shipping, storage etc


Jun/July
    - Lab renovtion
    - Mechanics design
    - Glue training
Aug
    - Mirror delivery
    - Basic optics test
Sept
    - Cavity test
    - Suspending test
NOV~DEC
    - Shipping to LLO

Open questions
    Two optical designs
    Procedure
    Modeling
    Clamp design / stencil design
    gluing-installation procedure

  200   Mon Jul 7 01:36:03 2014 KojiGeneralGeneralTo Do

Optical tests

  • Cleaning
  • Power Budget
  • FSR measurement
  • TMS measurement
  • TMS measurement (with DC voltage on PZTs)
  • PZT DC response
  • PZT AC response
  • QPD alignment
  • DCPD alignment

Backscattering test

Cabling / Wiring

  • Attaching cable/mass platforms
  • PZT cabling
  • DCPD cabling
  • QPD cabling

Vibration test

Baking

First Contact

Packing / Shipping

  204   Thu Jul 10 08:34:57 2014 KojiGeneralGeneralTo Do

Optical tests

  • Cleaning
  • Power Budget
  • FSR measurement
  • TMS measurement
  • TMS measurement (with DC voltage on PZTs)
  • PZT DC response
  • PZT AC response
  • QPD alignment
  • DCPD alignment

Backscattering test

Cabling / Wiring

  • Attaching cable/mass platforms
  • PZT cabling
  • DCPD cabling (to be done at LHO)
  • QPD cabling (to be done at LHO)

Vibration test

Baking

First Contact

Packing / Shipping

  177   Tue Dec 10 16:41:51 2013 KojiGeneralGeneralTo Buy

Masks / Wipes => done

  50   Wed Jan 2 07:35:55 2013 KojiOpticsCharacterizationThickness of a curved mirror

Measured the thickness of a curved mirror:

Took three points separated by 120 degree.

S/N: C2, (0.2478, 0.2477, 0.2477) in inch => (6.294, 6.292, 6.292) in mm

  404   Mon Nov 23 23:17:19 2020 KojiElectronicsCharacterizationThe dark noise of the Q3000 QPDs

The dark noise levels of the four Q3000 QPDs were measured with FEMTO DLPCA200 low noise transimpedance amp.

The measurement has been done in the audio frequency band. The amp gain was 10^7 V/A. The reverse bias was set to be 5V and the DC output of the amplifier was ~40mV which corresponds to the dark current of 4nA. It is consistent with the dark current measurement.

The measured floor level of the dark current was below the shot noise level for the DC current of 0.1mA (i.e. 6pA/rtHz).
No anomalous behavior was found with the QPDs.

Note that there is a difference in the level of the power line noise between the QPDs. The large part of the line noises was due to the noise coupling from a soldering iron right next to the measurement setup, although the switch of the iron was off. I've noticed this noise during the measurement sets for QPD #83. Then the iron was disconnected from the AC tap.
 

Attachment 1: Q3000_dark_noise_81.pdf
Q3000_dark_noise_81.pdf
Attachment 2: Q3000_dark_noise_82.pdf
Q3000_dark_noise_82.pdf
Attachment 3: Q3000_dark_noise_83.pdf
Q3000_dark_noise_83.pdf
Attachment 4: Q3000_dark_noise_84.pdf
Q3000_dark_noise_84.pdf
  405   Tue Nov 24 10:45:07 2020 gautamElectronicsCharacterizationThe dark noise of the Q3000 QPDs

I see that these measurements are done out to 100 kHz - I guess there is no reason to suspect anything at 55 MHz which is where this QPD will be reading out photocurrent given the low frequency behavior looks fine? The broad feature at ~80 kHz is the usual SR785 feature I guess, IIRC it's got to do with the display scanning rate.

Quote:

The measured floor level of the dark current was below the shot noise level for the DC current of 0.1mA (i.e. 6pA/rtHz).

  406   Tue Nov 24 12:27:18 2020 KojiElectronicsCharacterizationThe dark noise of the Q3000 QPDs

The amplifier BW was 400kHz at the gain of 1e7 V/A. And the max BW is 500kHz even at a lower gain. I have to setup something special to see the RF band dark noise.
With this situation, I stated "the RF dark noise should be characterized by the actual WFS head circuit." in the 40m ELOG.

  285   Wed Jul 5 16:59:44 2017 KojiGeneralGeneralThe OMC #002 was packed

[Stephen Koji]

The OMC #002 was packed for the transportation to Downs.

===> And transported to Downs 227 on Jul 6th.

Attachment 1: DSC_0360.JPG
DSC_0360.JPG
  212   Sun Jul 20 17:20:39 2014 KojiGeneralGeneralThe 3rd (LIO) OMC was shipped out to LHO

The 3rd (LIO) OMC was shipped out to LHO on Friday (Jul 18) Morning.

At LHO

- All of the on-breadboard cables should be attached and tied down.

- Peel First Contact paint and pack the OMC for storage.

 

  86   Thu Mar 28 03:37:07 2013 ZachOpticsConfigurationTest setup input optics progress

[Lisa, Zach]

Last night (Tuesday), I finished setting up and aligning most of the input optics for the OMC characterization setup. See the diagram below, but the setup consists of:

  • Faraday isolator/polarization definition
  • HWP+PBS for power splitting into two paths:
    • EOM path
      • Resonant EOM for PDH sideband generation
      • Broadband EOM for frequency scanning
    • AOM path
      • Double-passed ~200-MHz Isomet AOM for subcarrier generation. NOTE: in this case, I have chosen the m = -1 diffraction order due to the space constraints on the table.
  • Recombination of paths on a 50/50 beam splitter---half of the power is lost through the unused port into a black glass dump
  • Coupler for launching dual-field beam into a fiber (to OMC)

OMC_test_setup_IO.jpg 2013-03-27_05.48.20.jpg

Today, we placed some lenses into the setup, in two places:

  1. In the roundabout section of the AOM path that leads to the recombination, to re-match the AOM-path beam to that of the EOM path
  2. After the recombination beam splitter, to match the combined beam mode into the fiber

We (Koji, Lisa, and myself) had significant trouble getting more than ~0.1% coupling through the fiber, and after a while we decided to go to the 40m to get the red-light fiber illuminator to help with the alignment.

Using the illuminator, we realigned the input to the coupler and eventually got much better---but still bad---coupling of ~1.2% (0.12 mW out / 10 mW in). Due to the multi-mode nature of the illuminator beam, the output cannot be used to judge the collimation of the IR beam; it can only be used to verify the alignment of the beam.

With 0.12 mW emerging from the other end of the fiber, we could see the output quite clearly on a card (see photo below). This can tell us about the required input mode. From the looks of it, our beam is actually focused too strongly. We should probably replace the 75mm lens again with a slightly longer one.

Lisa and I concurred that it felt like we had converged to the optimum alignment and polarization, which would mean that the lack of coupling is all from mode mismatch. Since the input mode is well collimated, it seems unlikely that we could be off enough to only get ~1% coupling. One possibility is that the collimator is not well attached to the fiber itself. Since the Rayleigh range within it is very small, any looseness here can be critical.

2013-03-28_02.29.36.jpg

I think there are several people around here who have worked pretty extensively with fibers. So, I propose that we ask them to take a look at what we have done and see if we're doing something totally wrong. There is no reason to reinvent the wheel.

ELOG V3.1.3-