ID |
Date |
Author |
Type |
Category |
Subject |
374
|
Thu Sep 5 15:40:42 2019 |
shruti | Optics | Configuration | PZT Sub-Assembly | Aim: To find the combinations of mounting prism+PZT+curved mirror to build two PZT sub-assemblies that best minimises the total vertical beam deviation.
(In short, attachment 1 shows the two chosen sets of components and the configuration according which they must be bonded to minimize the total vertical angular deviation.)
The specfic components and configuration were chosen as follows, closely following Section 2.3.3 of T1500060:
Available components:
Mounting prisms: 1,2,12,14,15 (Even though there is mention of M17 in the attachments, it can not be used because it was chipped earlier.)
PZTs: 12,13
Curved mirrors: 10,13
Method:
For a given choice of prism, PZT and mirror, the PZT can be placed either at 0deg or 180deg, and the mirror can rotated. This allows us to choose an optimal mirror rotation and PZT orientation which minimises the vertical deviation.
Total vertical angle 
was measured by Koji as described in elog 369.
, are the wedge angle and orientation respectively and were measured earlier and shown in elog 373 .
, The measurement of the location of the curvature bottom (d, ) of the mirrors is shown in elog 372 . The optimal is to be found.
These steps were followed:
- For every combination of prism, PZT, and mirror, the total vertical deviation was minimized with respect to the angle of rotation of the curved mirror computationally (SciPy.optimize.minimize). The results of this computation can be found in Attachment 2: where Tables 1.1 and 2.1 show the minimum achievable deviations for mirrors C10 and C13 respectively, and Tables 1.2 and 2.2 show the corresponding angle of rotation of the mirrors
.
- From the combinations that show low total deviations (highlighted in red in Attachment 2), the tolerances for 5 arcsec and 10 arcsec deviations with mirror rotation were calculated, and is shown in Tables 1.3, 1.4, 2.3, 2.4 of Attachment 2.
- While calculating the tolerances, the dependence of the vertical deviations with rotation were also plotted (refer Attachment 3).
- Two sets from available components with low total deviation and high tolerance were chosen.
Result:
These are the ones that were chosen:
- M14 + PZT13 at 0deg + C13 rotated by 169deg anticlockwise (tot vertical dev ~ -3 arcsec)
- M12 + PZT12 at 0deg + C10 rotated by 88deg clockwise (tot vertical dev ~0 arcsec)
The method of attaching them is depicted in Attachment 1.
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418
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Thu Jul 21 13:21:27 2022 |
Koji | General | Configuration | Windows laptop for WincamD Beam'R2 recovery | The Windows laptop for WincamD/Beam'R2 (DELL Vostro3300) was not functional.
- Windows 7 got stuck in the starting up process (Google "startup repair loop")
- The battery can't charge and the adapter connection is flaky
I decided to newly install Win10.
I made a new bootable Win10 DVD from the ISO downloaded from IMSS. The ISO file was converted to CDR using Disk Utility on Mac.
This deleted the past disk partitions. The installation process has no trouble and Win10 ran successfully. The machine is slow but still acceptable for our purpose.
Dataray Version 7.1H25Bk was downloaded from the vendor website https://dataray.com/blogs/software/downloads and installed successfully.
The devices ran as expected by connecting the heads and selecting the proper device in the software.
Then, the Win10 fell into "Hibernation Loop" and "Shutdown loop" (after disabling hibernation in the safe mode).
This is probably the combination of extremely slow windows update (feature update i.e. beta OS update) and the occasional shutdown due to the flakiness of the AC connection
Win10 was reinstalled and automatic Win update was disabled via windows policy manager or something like that. Still, it tries to download and update some of the updates (what's happening there!?
Here are my strong recommendations on how to use this laptop
- Do not use any network connection. It will enable Windows Update kicks in and destroy the machine.
- Use a USB stick for data transportation if necessary
- The laptop should always be connected to the power supply at a stable location. (The adapter connection is flaky and the battery is dead)
- Buy a replacement battery (maybe a 3rd-party cheap one
- The Win10 DVD should always be inserted into the laptop's drive so that we can reinstall the windows anytime.
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451
|
Mon Nov 7 21:16:16 2022 |
Camille | Optics | Configuration | Setting up the fiber couplers | [Camille, Koji]
Began setting up fiber assembly for OMC testing:
-Aligned fiber mount to maximize transmission through fiber
-Adjusted polarization at output of fiber to minimize s-polarized output.
Power measurements:
fiber input: 56.7 mW
fiber output:43.2 mW
s-polarized output: 700 uW |
452
|
Mon Nov 7 22:00:33 2022 |
Koji | Optics | Configuration | Setting up the fiber couplers | Fiber matching: 43.2/56.7 = 76%
S/P-pol ratio 0.7/43.2 = 1.6%
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463
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Tue Nov 29 15:54:47 2022 |
Koji | General | Configuration | Windows laptop for WincamD Beam'R2 recovery | Aaron took the set to Cryo lab
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6
|
Fri Jun 29 11:26:04 2012 |
Zach | Optics | Characterization | RoC measurement setup | Here is the proposed RoC measurement setup. Koji tells me that this is referred to as "Anderson's method".
We would like to use a linear cavity to measure the RoC of the curved mirrors independently (before forming the ring cavity), since the degeneracy of HOMs will make the fitting easier.
- An NPRO is PDH locked to a linear cavity formed of a high-quality flat mirror on one end, and the OMC curved optic on the other.
- A second, broadband EOM is placed after the first one, and its frequency is swept with a VCO to generate symmetric sidebands about the carrier
- A TRANS RFPD's signal is demodulated at the secondary EOM frequency, to give a DC signal proportional to HOM transmission
- This HOM scan is fit to a model, with RoC the free parameter. Since there are two sidebands, the HOM spectrum of the model must be folded about the carrier frequency.
- To get a good signal, we should slightly misalign the input beam, allowing for higher overlap with HOMs.
If we decided that the symmetric sidebands are too unwieldy, or that we have issues from sidebands on sidebands, we can accomplish the same style measurement using an AOM-shifted pickoff of the pre-PDH EOM beam. The advantage of the former method is that we don't have to use any polarization tricks.

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8
|
Wed Jul 18 23:20:13 2012 |
Koji | Optics | Characterization | Mode scan results of ELIGO | Nic Smith sent me a bunch of elog lists where the results of the mode scan can be found.
From Nic:
There have been many mode scan analyses done at LLO:
http://ilog.ligo-la.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=06/07/2008&anchor_to_scroll_to=2008:06:07:20:55:41-jrsmith
http://ilog.ligo-la.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=06/16/2008&anchor_to_scroll_to=2008:06:16:17:47:11-waldman
http://ilog.ligo-la.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=08/06/2009&anchor_to_scroll_to=2009:08:06:12:23:16-kissel
http://ilog.ligo-la.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=09/25/2009&anchor_to_scroll_to=2009:09:25:20:57:47-kate
We didn't do as much of this at LHO. At some point we were trying to figure out how the arm cavity mode was different from the carrier mode:
http://ilog.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=04/17/2009&anchor_to_scroll_to=2009:04:17:23:15:05-kawabe
http://ilog.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=03/27/2009&anchor_to_scroll_to=2009:03:27:21:38:14-kawabe
http://ilog.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=02/18/2009&anchor_to_scroll_to=2009:02:18:20:15:00-kawabe
Here's a long mode scan that was done, and the data is attached to the elog, but none of the amplitudes are analyzed.
http://ilog.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=07/08/2009&anchor_to_scroll_to=2009:07:08:17:02:19-nicolas |
9
|
Sun Jul 22 15:56:53 2012 |
Zach | Optics | Characterization | RoC measurement setup | Here is a more detailed version of the setup, so that we can gather the parts we will need.

Parts list:
- Optics, etc.:
- 1 NPRO
- 2 QWP
- 3 HWP
- 2 PBS
- 2 EOM (at least one broadband)
- 2 RFPD (at least one very-high-bandwidth for TRANS, e.g., 1611)
- 1 CCD camera
- OMC curved mirrors to be tested
- 1 low-loss flat reference mirror with appropriate transmission (e.g., G&H, ATF, etc.)
- ~3 long-ish lenses for MMT, EOM focusing
- ~2 short lenses for PD focusing
- 1 R ~ 80% power splitter for TRANS (can be more or less)
- ~7 steering mirrors
- ~3 beam dumps
- Mounts, bases, clamps, hardware
- Electronics:
- 1 fixed RF oscillator (e.g., DS345, etc.)
- 1 VCO (e.g., Marconi, Tektronix, etc.)
- 2 Minicircuits RF mixers
- 2 Minicircuits RF splitters
- 2 SMA inline LPFs
- Locking servo (SR560? uPDH? PDH2?)
- Some digital acquisition/FG system
- Power supplies, wiring and cabling.
Quote: |
Here is the proposed RoC measurement setup. Koji tells me that this is referred to as "Anderson's method".
We would like to use a linear cavity to measure the RoC of the curved mirrors independently (before forming the ring cavity), since the degeneracy of HOMs will make the fitting easier.
- An NPRO is PDH locked to a linear cavity formed of a high-quality flat mirror on one end, and the OMC curved optic on the other.
- A second, broadband EOM is placed after the first one, and its frequency is swept with a VCO to generate symmetric sidebands about the carrier
- A TRANS RFPD's signal is demodulated at the secondary EOM frequency, to give a DC signal proportional to HOM transmission
- This HOM scan is fit to a model, with RoC the free parameter. Since there are two sidebands, the HOM spectrum of the model must be folded about the carrier frequency.
- To get a good signal, we should slightly misalign the input beam, allowing for higher overlap with HOMs.
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|
31
|
Thu Oct 18 20:23:33 2012 |
Koji | Optics | Characterization | Improved measurement | Significant improvement has been achieved in the RoC measurement.
- The trans PD has much more power as the BS at the cavity trans was replaced by a 50% BS. This covers the disadvantage of using the a Si PD.
- The BB EOM has a 50Ohm terminator to ensure the 50Ohm termination at Low freq.
- The length of the cavity was changed from 1.2m to 1.8m in order to see the effect on the RoC measurement.
By these changes, dramatic increase of the signal to noise ratio was seen.
Now both of the peaks corresponds to the 1st-order higher-order modes are clearly seen.
The peak at around 26MHz are produced by the beat between the carrier TEM00 and the upper-sideband TEM01 (or 10).
The other peak at around 57MHz are produced by the lower-sideband TEM01 (or 10).
Peak fitting
From the peak fitting we can extract the following numbers:
- Cavity FSR (hence the cavity length)
- Cavity g-factor
- Approximate measure of the cavity bandwidth
Note that the cavity itself has not been touched during the measurement.
Only the laser frequency and the incident beam alignment were adjusted.
The results are calculated by the combination of MATLAB and Mathemaica. The fit results are listed in the PDF files.
In deed the fitting quality was not satisfactory if the single Lorentzian peak was assumed.
There for two peaks closely lining up with different height. This explained slight asymmetry of the side tails
This suggests that there is slight astigmatism on the mirrors (why not.)
The key points of the results:
- FSR and the cavity length: 83.28~83.31MHz / L=1.799~1.800 [m] (surprisingly good orecision of my optics placement!)
- Cavity g-factor: Considering the flatness of the flat mirror from the phase map, the measured g-factors were converted to the curvature of the curved mirror.
RoC = 2.583~4 [m] and 2.564~7 [m]. (Note: This fluctuation can not be explained by the statistical error.)
The mode split is an order of 10kHz. This number also agrees with the measurement taken yesterday.
If the curved mirror had the nominal curvature of 2.5m, the flat mirror should have the curvature of ~20m. This is very unlikely.
- Approximate cavity line width: FWHM = 70~80kHz. This corresponds to the finesse of ~500. The design value is ~780.
This means that the locking offset is not enough to explain the RoC discrepancy between the design and the measurement.
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32
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Wed Nov 7 01:28:20 2012 |
Koji | Optics | Characterization | Wedge 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:

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
[Click for a sharper image]
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35
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Thu Nov 8 13:24:53 2012 |
Koji | Optics | Characterization | More wedge measurement | A1
Horiz Wedge 0.497 +/- 0.004 deg
Vert Wedge 0.024 +/- 0.004 deg
A2
Horiz Wedge 0.549 +/- 0.004 deg
Vert Wedge 0.051 +/- 0.004 deg
A3
Horiz Wedge 0.463 +/- 0.004 deg
Vert Wedge 0.009 +/- 0.004 deg
A4
Horiz Wedge 0.471 +/- 0.004 deg
Vert Wedge 0.019 +/- 0.004 deg
A5
Horiz Wedge 0.458 +/- 0.004 deg
Vert Wedge 0.006 +/- 0.004 deg |
39
|
Fri Nov 9 00:43:32 2012 |
Koji | Optics | Characterization | Further more wedge measurement | Now it's enough for the first OMC (or even second one too).
Today's measurements all distributed in theta>0.5deg. Is this some systematic effect???
I should check some of the compeled mirrors again to see the reproducibility...
A1 Horiz Wedge 0.497039 +/- 0.00420005 deg / Vert Wedge 0.02405210 +/- 0.00420061 deg
A2 Horiz Wedge 0.548849 +/- 0.00419993 deg / Vert Wedge 0.05087730 +/- 0.00420061 deg
A3 Horiz Wedge 0.463261 +/- 0.00420013 deg / Vert Wedge 0.00874441 +/- 0.00420061 deg
A4 Horiz Wedge 0.471536 +/- 0.00420011 deg / Vert Wedge 0.01900840 +/- 0.00420061 deg
A5 Horiz Wedge 0.458305 +/- 0.00420014 deg / Vert Wedge 0.00628961 +/- 0.00420062 deg
B1 Horiz Wedge 0.568260 +/- 0.00419988 deg / Vert Wedge -0.00442885 +/- 0.00420062 deg
B2 Horiz Wedge 0.556195 +/- 0.00419991 deg / Vert Wedge -0.00136749 +/- 0.00420062 deg
B3 Horiz Wedge 0.571045 +/- 0.00419987 deg / Vert Wedge 0.00897185 +/- 0.00420061 deg
B4 Horiz Wedge 0.563724 +/- 0.00419989 deg / Vert Wedge -0.01139000 +/- 0.00420061 deg
B5 Horiz Wedge 0.574745 +/- 0.00419986 deg / Vert Wedge 0.01718030 +/- 0.00420061 deg
E1 Horiz Wedge 0.600147 +/- 0.00419980 deg / Vert Wedge 0.00317778 +/- 0.00420062 deg
E2 Horiz Wedge 0.582597 +/- 0.00419984 deg / Vert Wedge -0.00537131 +/- 0.00420062 deg
E3 Horiz Wedge 0.592933 +/- 0.00419982 deg / Vert Wedge -0.01082830 +/- 0.00420061 deg
-------
To check the systematic effect, A1 and B1 were tested with different alignment setup.
A1 Horiz Wedge 0.547056 +/- 0.00419994 deg / Vert Wedge 0.0517442 +/- 0.00420061 deg
A1 Horiz Wedge 0.546993 +/- 0.00419994 deg / Vert Wedge 0.0469938 +/- 0.00420061 deg
A1 Horiz Wedge 0.509079 +/- 0.00420003 deg / Vert Wedge 0.0240255 +/- 0.00420061 deg
B1 Horiz Wedge 0.547139 +/- 0.00419994 deg / Vert Wedge 0.0191204 +/- 0.00420061 deg
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40
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Sat Nov 17 02:31:34 2012 |
Koji | Optics | Characterization | Mirror T test | Mirror T test
The mirror was misaligned to have ~2deg incident (mistakenly...) angle.
C1: Ptrans = 7.58uW, Pinc = 135.0mW => 56.1ppm
C1 (take2): Ptrans = 7.30uW, Pinc = 134.4mW => 54.3ppm
C2: Ptrans = 6.91uW, Pinc = 137.3mW => 50.3ppm
C3: Ptrans = 6.27uW, Pinc = 139.7mW => 44.9ppm
C4: Ptrans = 7.62uW, Pinc = 139.3mW => 54.7ppm
C5: Ptrans = 6.20uW, Pinc = 137.5mW => 45.1ppm
A1: Ptrans = 1.094mW, Pinc = 133.6mW => 8189ppm |
41
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Mon Nov 19 13:33:14 2012 |
Koji | Optics | Characterization | Resuming testing mirror RoCs | In order to resume testing the curvatures of the mirrors, the same mirror as the previous one was tested.
The result looks consistent with the previous measurement.
It seems that there has been some locking offset. Actually, the split peaks in the TF@83MHz indicates
the existence of the offset. Next time, it should be adjusted at the beginning.
Curved mirror SN: C1
RoC: 2.5785 +/- 0.000042 [m]
Previous measurements
=> 2.5830, 2.5638 => sqrt(RoC1*RoC2) = 2.5734 m
=> 2.5844, 2.5666 => sqrt(RoC1*RoC2) = 2.5755 m |
42
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Mon Nov 26 01:40:00 2012 |
Koji | Optics | Characterization | More RoC measurement | C1: RoC: 2.57845 +/− 4.2e−05m
C2: RoC: 2.54363 +/− 4.9e−05m
C3: RoC: 2.57130 +/− 6.3e−05m
C4: RoC: 2.58176 +/− 6.8e−05m
C5: RoC 2.57369 +/− 9.1e−05m
==> 2.576 +/- 0.005 [m] (C2 excluded) |
44
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Tue Dec 18 20:04:40 2012 |
Koji | Optics | Characterization | Prism Thickness Measurement | The thicknesses of the prism mirrors (A1-A5) were measured with micrometer thickness gauge.
Since the thickness of the thinner side (side1) depends on the depth used for the measurement,
it is not accurate. Unit in mm.
A1: Side1: 9.916, Side2: 10.066 => derived wedge angle: 0.43deg
A2: Side1: 9.883, Side2: 10.065 => 0.52
A3: Side1: 9.932, Side2: 10.062 => 0.38
A4: Side1: 9.919, Side2: 10.060 => 0.40
A5: Side1: 9.917, Side2: 10.058 => 0.40

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49
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Mon Dec 31 03:11:45 2012 |
Koji | Optics | Characterization | Further more RoC measurement | Total (excluding C2, C7, C8): 2.575 +/- 0.005 [m]
New results
C6: RoC: 2.57321 +/− 4.2e-05m
C7: RoC: 2.56244 +/− 4.0e−05m ==> Polaris mount
C8: RoC: 2.56291 +/− 4.7e-05m ==> Ultima mount
C9: RoC: 2.57051 +/− 6.7e-05m
Previous results
C1: RoC: 2.57845 +/− 4.2e−05m
C2: RoC: 2.54363 +/− 4.9e−05m ==> Josh Smith @Fullerton for scattering measurement
C3: RoC: 2.57130 +/− 6.3e−05m
C4: RoC: 2.58176 +/− 6.8e−05m
C5: RoC 2.57369 +/− 9.1e−05m |
50
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Wed Jan 2 07:35:55 2013 |
Koji | Optics | Characterization | Thickness 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 |
51
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Wed Jan 2 07:45:39 2013 |
Koji | Optics | Characterization | First Contact test | Conclusion: Good. First contact did not damage the coating surface, and reduced the loss
- Construct a cavity with A1 and C2
- Measure the transmission and FWHM (of TEM10 mode)
- Apply First Contact on both mirrors
- Measure the values again
Transmission:
2.66 +/- 0.01 V -> 2.83 +/- 0.01 V
==> 6.3% +/- 0.5 % increase
FWHM of TEM10:
Before: (66.1067, 65.4257, 66.1746) +/- (0.40178, 0.38366, 0.47213) [kHz]
After: (60.846, 63.4461, 63.7906) +/- (0.43905, 0.56538, 0.51756) [kHz]
==> 5.1% +/- 2.7% decrease
Question: What is the best way to measure the finesse of the cavity? |
53
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Thu Jan 10 18:37:50 2013 |
Koji | Optics | Characterization | Wedging 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? |
54
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Wed Jan 16 14:10:50 2013 |
Koji | Optics | Characterization | Autocollimator tests of optics perpendicularity/parallelism | The items:
- Autocollimator (AC) borrowed from Mike Smith (Nippon Kogaku model 305, phi=2.76", 67.8mm)
- Retroreflector (corner cube)
- Two V grooves borrowed from the 40m
Procedure:
- Autocollimator calibration
o Install the AC on a optical table
o Locate the corner cube in front of the AC.
o Adjust the focus of the AC so that the reflected reticle pattern can be seen.
o If the retroreflection and the AC are perfect, the reference reticle pattern will match with the reflected reticle pattern.
o Measure the deviation of the reflected reticle from the center.
o Rotate the retroreflector by 90 deg. Measure the deviation again.
o Repeat the process until total four coordinates are obtained.
o Analysis of the data separates two types of the error:
The average of these four coordinates gives the systematic error of the AC itself.
The vector from the center of the circle corresponds to the error of the retroreflector.
- Wedge angle measurement
To be continued |
56
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Sat Jan 19 20:47:41 2013 |
Koji | Optics | Characterization | Wedge 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. |
59
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Mon Feb 4 00:39:08 2013 |
Koji | Optics | Characterization | Wedge 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
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60
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Wed Feb 6 02:34:10 2013 |
Koji | Optics | Characterization | Wedge 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
|
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62
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Thu Feb 7 23:01:45 2013 |
Koji | Optics | Characterization | UV 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.
|
66
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Fri Mar 1 23:52:18 2013 |
Koji | Optics | Characterization | Wedge 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
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67
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Tue Mar 5 19:37:00 2013 |
Zach | Optics | Characterization | eLIGO 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.

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
- 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)
- 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)
- 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. |
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Wed Mar 6 23:24:58 2013 |
Zach | Optics | Characterization | eLIGO 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:

This is Psb = 0.06 --> gamma = 0.35 rads.
This changes the "raw transmission" and "coupling", but not the inferred visibility:

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

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. |
72
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Fri Mar 15 02:15:45 2013 |
Koji | Electronics | Characterization | Diode testing | Diode testing
o Purpose of the measurement
- Test Si QPDs (C30845EH) for ISC QPDs Qty 30 (i.e. 120 elements)
- Test InGaAs PDs (C30665GH) for OMC Qty 10 (i.e. 10 elements)
o Measurement Kit
- Inherited from Frank.
- Has relays in it.
- D0 and D1 switches the measurement instrument connected to an element
- D2 and D3 switches the element of the QPDs
- Digital switch summary
d0 d1 0 0 - ln preamp
d0 d1 1 0 - dark c
d0 d1 0 1 - omc preamp
d0 d1 1 1 - impedance
d2 d3 0 0 - A x x x
d2 d3 1 0 - C x o x
d2 d3 0 1 - B o x o
d2 d3 1 1 - D o o o
- The universal board in the box is currently configured for C30845.
Pin1 - Elem A. Pin3 - B, Pin7 - C, Pin9 - D, Pin 12 - Case&Bias
o Labview interface
- Controls NI-USB-6009 USB DAQ interface and Agilent 82357B USB-GPIB interface
o Dark current measurement
- Borrowed Peter's source meter KEITHLEY 2635A
- For C30845GH the maxmum reverse bias is set to -20V. This drops the voltage of the each element to the bias voltage.
o Spectrum measurement
- The elements are connected to FEMTO LN current amp DLPCA-200.
- Bias voltage is set to +10V. This lifts up the outside of the amplifier input to +10V.
o Impedance measurement
- Agilent 4395A at PSL lab with impedance measurement kit
- For C30845GH the maxmum reverse bias is set to -15V. This drops the voltage of the each element to the bias voltage.
- Calibration: open - unplug the diode from the socket, short - use a piece of resister lead, 50Ohm - a thin metal resister 51Ohm
- Freq range: 30-50MHz where the response of the cables in the setup is mostly flat.
- Labview VI is configured to read the equivalent circuit parameters in the configuration "D" (series LCR).
- Labview fails to read the series resistance. This was solved by first read the equiv circuit param and then read it with Sim F-CHRST.
F-CHRST does nothing on the parameters so the second request successfully acquires the first ones.
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73
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Sun Mar 17 21:59:47 2013 |
Koji | Electronics | Characterization | Diode testing ~ DCPD | - For the dark noise measurement, the lid of the die-cast case should also contact to the box for better shielding. This made the 60Hz lines almost completely removed, although unknown 1kHz harmonics remains.
- The precise impedance of the setup can not be obtained from the measurement box; the cable in between is too long. The diode impedance should be measured with the impedance measurement kit.
- With the impedance measurement kit, the bias voltage of +5V should be used, in stead of -5V.
- diode characteristics measured at 10-100MHz
- Typical impedance characteristics of the diodes
Excelitas (Perkin-Elmer) C30665GH Rs=9Ohm, Cd=220pF, L=0~1nH (Vr=5V)
Excelitas (Perkin-Elmer) C30642G Rs=12Ohm, Cd=100pF, L=~5nH (Vr=5V) longer thin wire in a can?
Excelitas (Perkin-Elmer) C30641GH Rs=8Ohm, Cd=26pF, L=12nH (Vr=5V) leg inductance? (leg ~30mm)
- PD serial
C30665GH, Ls ~ 1nH
1 - 0782 from PK, Rs=8.3Ohm, Cd=219.9pF
2 - 1139 from PK, Rs=9.9Ohm, Cd=214.3pF
3 - 0793 from PK, Rs=8.5Ohm, Cd=212.8pF
4 - 0732 from PK, Rs=7.4Ohm, Cd=214.1pF
5 - 0791 from PK, Rs=8.4Ohm, Cd=209.9pF
6 - 0792 from PK, Rs=8.0Ohm, Cd=219.0pF
7 - 0787 from PK, Rs=9.0Ohm, Cd=197.1pF
8 - 0790 from PK, Rs=8.4Ohm, Cd=213.1pF
9 - 0781 from PK, Rs=8.2Ohm, Cd=216.9pF
10 - 0784 from PK, Rs=8.2Ohm, Cd=220.0pF
11 - 1213 from the 40m, Rs=10.0Ohm, Cd=212.9pF
12 - 1208 from the 40m, Rs=9.9Ohm, Cd=216.8pF
13 - 1209 from the 40m, Rs=10.0Ohm, Cd=217.5pF
C30642G, Ls ~ 12nH
20 - 2484 from the 40m EG&G, Rs=12.0Ohm, Cd=99.1pF
21 - 2487 from the 40m EG&G, Rs=14.2Ohm, Cd=109.1pF
22 - 2475 from the 40m EG&G glass crack, Rs=13.5Ohm, Cd=91.6pF
23 - 6367 from the 40m ?, Rs=9.99Ohm, Cd=134.7pF
24 - 1559 from the 40m Perkin-Elmer GH, Rs=8.37Ohm, Cd=94.5pF
25 - 1564 from the 40m Perkin-Elmer GH, Rs=7.73Ohm, Cd=94.5pF
26 - 1565 from the 40m Perkin-Elmer GH, Rs=8.22Ohm, Cd=95.6pF
27 - 1566 from the 40m Perkin-Elmer GH, Rs=8.25Ohm, Cd=94.9pF
28 - 1568 from the 40m Perkin-Elmer GH, Rs=7.83Ohm, Cd=94.9pF
29 - 1575 from the 40m Perkin-Elmer GH, Rs=8.32Ohm, Cd=100.5pF
C30641GH, Perkin Elmer, Ls ~ 12nH
30 - 8983 from the 40m Perkin-Elmer, Rs=8.19Ohm, Cd=25.8pF
31 - 8984 from the 40m Perkin-Elmer, Rs=8.39Ohm, Cd=25.7pF
32 - 8985 from the 40m Perkin-Elmer, Rs=8.60Ohm, Cd=25.2pF
33 - 8996 from the 40m Perkin-Elmer, Rs=8.02Ohm, Cd=25.7pF
34 - 8997 from the 40m Perkin-Elmer, Rs=8.35Ohm, Cd=25.8pF
35 - 8998 from the 40m Perkin-Elmer, Rs=7.89Ohm, Cd=25.5pF
36 - 9000 from the 40m Perkin-Elmer, Rs=8.17Ohm, Cd=25.7pF
Note:
1mm Au wire with dia. 10um -> 1nH, 0.3 Ohm
20mm BeCu wire with dia. 460um -> 18nH, 0.01 Ohm |
74
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Wed Mar 20 09:38:02 2013 |
Zach | Optics | Characterization | [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:
- 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.
- 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.

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. |
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Sat Mar 23 16:36:15 2013 |
Koji | Electronics | Characterization | Diode QE measurement | Quantum efficiencies of the C30665GH diodes were measured.
- The diode was biased by the FEMTO preamplifier.
- Diode Pin 1 Signal, Pin 2 +5V, Pin 3 open
- Preamp gain 10^3 V/A
- Beam power was measured by the thorlabs power meter.
PD #1
Incident: 12.82 +/- 0.02 mW
Vout: 9.161 +/- 0.0005 V
PD Reflection (Prompt): 0.404 mW
PD Reflection (Total): 1.168 mW
PD #2
Incident: 12.73 +/- 0.02 mW
Vout: 9.457 +/- 0.0005 V
PD Reflection (Prompt): 0.364 mW
PD Reflection (Total): 0.937 mW
PD #3
Incident: 12.67 +/- 0.02 mW
Vout: 9.1139 +/- 0.01 V
PD Reflection (Prompt): 0.383 mW
PD Reflection (Total): 1.272 mW
PD #4
Incident: 12.71 +/- 0.02 mW
Vout: 9.3065 +/- 0.0005 V
PD Reflection (Prompt): 0.393 mW
PD Reflection (Total): 1.033 mW
PD #5
Incident: 12.69 +/- 0.02 mW
Vout: 9.1071 +/- 0.005 V
PD Reflection (Prompt): 0.401 mW
PD Reflection (Total): 1.183 mW
PD #6
Incident: 12.65 +/- 0.02 mW
Vout: 9.0310 +/- 0.01 V
PD Reflection (Prompt): 0.395 mW
PD Reflection (Total): 1.306 mW
PD #7
Incident: 12.67 +/- 0.02 mW
Vout: 9.0590 +/- 0.0005 V
PD Reflection (Prompt): 0.411 mW
PD Reflection (Total): 1.376 mW
PD #8
Incident: 12.63 +/- 0.01 mW
Vout: 9.0790 +/- 0.0005 V
PD Reflection (Prompt): 0.420 mW
PD Reflection (Total): 1.295 mW
PD #9
Incident: 12.67 +/- 0.02 mW
Vout: 9.2075 +/- 0.0005 V
PD Reflection (Prompt): 0.384 mW
PD Reflection (Total): 1.091 mW
PD #10
Incident: 12.70 +/- 0.01 mW
Vout: 9.0880 +/- 0.001 V
PD Reflection (Prompt): 0.414 mW
PD Reflection (Total): 1.304 mW
PD #11
Incident: 12.64 +/- 0.01 mW
Vout: 9.2861 +/- 0.0005 V
PD Reflection (Prompt): 0.416 mW
PD Reflection (Total): 1.152 mW
PD #12
Incident: 12.68 +/- 0.02 mW
Vout: 9.3650 +/- 0.001 V
PD Reflection (Prompt): 0.419 mW
PD Reflection (Total): 1.057 mW
PD #13
Incident: 12.89 +/- 0.01 mW
Vout: 9.3861 +/- 0.001 V
PD Reflection (Prompt): 0.410 mW
PD Reflection (Total): 1.047 mW
PD serial number
1 - 0782
2 - 1139
3 - 0793
4 - 0732
5 - 0791
6 - 0792
7 - 0787
8 - 0790
9 - 0781
10 - 0784
11 - 1213
12 - 1208
13 - 1209
{
{1, 12.82, 9.161, 0.404, 1.168},
{2, 12.73 , 9.457, 0.364 , 0.937} ,
{3, 12.67 , 9.1139, 0.383 , 1.272 },
{4, 12.71 , 9.3065, 0.393 , 1.033 },
{5, 12.69, 9.1071, 0.401 , 1.183 },
{6, 12.65, 9.0310, 0.395 , 1.306} ,
{7, 12.67, 9.0590, 0.411 , 1.376} ,
{8, 12.63 , 9.0790, 0.420 , 1.295} ,
{9, 12.67 , 9.2075, 0.384 , 1.091} ,
{10, 12.70, 9.0880, 0.414 , 1.304 },
{11, 12.64 , 9.2861, 0.416 , 1.152} ,
{12, 12.68 , 9.3650, 0.419 , 1.057} ,
{13, 12.89 , 9.3861, 0.410 , 1.047}
};
|
92
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Wed Apr 3 17:39:38 2013 |
Koji | Mechanics | Characterization | Calibration of the test PZTs before the glue test | We want to make sure the responses of the PZT actuator does not change after the EP30-2 gluing.
A shadow sensor set up was quickly set-up at the fiber output. It turned out the ring PZTs are something really not-so-straightforward.
If the PZT was free or just was loosely attached on a plane by double-sided tape, the actuation response was quite low (30% of the spec).
After some struggle, I reached the conclusion that the PZT deformation is not pure longitudinal but some 3-dimensional, and you need to
use a "sandwitch" with two flat surfaces with some pressue.
I turned the setup for horizontal scans to the vertical one, and put the PZT between quarter-inch spacers.
Then two more spacers are placed on the stack so that the weight applies the vertical pressure on the PZT.
This is also use ful to adjust the height of the shadow.

The calibration plot is attached. It gives us ~21k V/m.
Voltage swing of 150V results the output voltage change of ~50mV. This is pretty close to what is expected from the spec (16nm/V).
The PZT#3 (which had the mirror glued on) showed significantly large response.
Test PZT #1: 17.4nm/V
Test PZT #2: 17.2nm/V
Test PZT #3: 30.6nm/V
UHV PZT #24: 17.6nm/V
These numbers will be checked after the heat cure of EP30-2 |
95
|
Thu Apr 4 01:35:04 2013 |
Koji | Optics | Characterization | Mode matching to the OMC cavity | The fiber output was matched with the lenses on a small bread board.
The detailed configuration is found in the following elog link.
http://nodus.ligo.caltech.edu:8080/OMC_Lab/105 |
96
|
Thu Apr 4 01:43:06 2013 |
Koji | Optics | Characterization | Mirror T measurement | [Zach, Koji]
The measurement setup for the transmission measurement has been made at the output of the fiber.
- First, we looked at the fiber output with a PBS. It wasn't P-pol so we rotated the ourput coupler.
What we found was that it wasn't actually linearly polarized.
So the input coupler was rotated to correct it. This terribly misaligned the input coupling.
After some iteration of rotating and aligning the input/output couplers, we obtained reasonable
extiction ratio like 10mW vs 100uW (100:1) with 11mW incidence. (Where is the rest 0.9mW!?)
- The P-pol (transmission) out of PBS goes into the mirror. Here we tested mirror A1.
The mirror is mounted on the prism mount supported by a rotational stage for precise angle adjustment
We limited the input power down to 5mW so that we can remove the attenuator on the power meter.
The reading of the power meter was fluctuating, indeed depending on MY position.
So we decided to turn off the lighting of the room. This made the reading very stable.
The offset of the power meter was -0.58uW
The transmitted power for the normal incidence was 39.7uW with the incident 4.84mW.
[39.7-(-0.58)] / [4.84*1000-(-0.58)] *10^6 = 8320 ppm
The transmitted power for the 4deg incidence was 38.0uW with the incident 4.87mW.
[38.0-(-0.58)] / [4.87*1000-(-0.58)] *10^6 = 7980 ppm
cf. The specification is 7931ppm
|
98
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Fri Apr 5 14:39:26 2013 |
Koji | Mechanics | Characterization | Calibration of the test PZTs after the heat cure | We attached fused silica windows on the test PZTs. http://nodus.ligo.caltech.edu:8080/OMC_Lab/93
The glued assemblies were brought to Bob's bake lab for the heat cure. There they are exposed to 94degC heat for two hours (excluding ramp up/down time).
After the heat cure, we made the visual inspection.
The photos are available here.
Pre-bake
Test PZT #1: 17.4nm/V
Test PZT #2: 17.2nm/V
Test PZT #3: 30.6nm/V
Post-bake
Test PZT #1: 27.2 nm/V
Test PZT #2: 26.9 nm/V
Test PZT #3: 21.4 nm/V
Measurement precision is ~+/-20%
Spec is 14nm/V |
100
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Mon Apr 8 11:11:37 2013 |
Koji | Optics | Characterization | More Mirror T measurement | More Ts of the mirrors were measured.
A mirror specification:
Request: 8300+/-800 ppm
Data sheet: 7931ppm
C mirror specification:
Request: 50+/-10 ppm
Data sheet: 51.48ppm or 46.40ppm
Mirror | P_Incident P_Trans P_Offset | T_trans
| [mW] [uW] [uW] | [ppm]
-------+------------------------------+---------
A1 | 10.28 82.9 -0.205 | 8.08e3
A2 | ----- ----- ------ | ------
A3 | 10.00 83.2 -0.205 | 8.34e3
A4 | 10.05 80.7 -0.205 | 8.05e3
A5 | 9.94 81.3 -0.205 | 8.20e3
A6 | 10.35 78.1 -0.205 | 7.57e3
A7 | 10.35 77.8 -0.205 | 7.54e3
A8 | 10.30 78.0 -0.205 | 7.60e3
A9 | 10.41 84.1 -0.205 | 8.10e3
A10 | 10.35 77.3 -0.205 | 7.49e3
A11 | 10.33 77.9 -0.205 | 7.56e3
A12 | 10.34 78.7 -0.205 | 7.63e3
A13 | 10.41 85.4 -0.205 | 8.22e3
A14 | 10.34 84.4 -0.205 | 8.18e3
-------+------------------------------+---------
C1 | 10.30 0.279 -0.225 | 48.9
C2 | ----- ----- ------ | ------
C3 | 10.37 0.240 -0.191 | 41.6
C4 | 10.35 0.278 -0.235 | 49.6
C5 | 10.40 0.138 -0.235 | 35.9 => PZT assembly #2
C6 | 10.34 0.137 -0.235 | 36.0 => PZT assembly #1
C7 | 10.37 0.143 -0.229 | 35.9
C8 | 10.41 0.224 -0.237 | 44.3
C9 | 10.36 0.338 -0.230 | 54.8
C10 | 10.39 0.368 -0.228 | 57.4
C11 | 10.38 0.379 -0.209 | 56.6
C12 | 10.28 0.228 -0.238 | 45.3
C13 | 10.36 0.178 -0.234 | 39.8
-------+------------------------------+---------
|
101
|
Mon Apr 8 11:29:08 2013 |
Koji | Optics | Characterization | Mirror/PZT Characterization links | |
102
|
Mon Apr 8 11:49:18 2013 |
Koji | Mechanics | Characterization | PZT actuator tested at LLO | Test result of the PZTs by Valera and Ryan
PZT Length Angle
# [nm/V] [urad/um]
11 14.5 17.6
12 13.8 17.8
13 11.2 25.0
14 14.5 6.6
15 12.5 10.6
21 14.5 9.7
22 13.8 28.8
23 14.5 6.8 ==> Assembly #2
24 18.5 51.7 ==> Used for prototyping
25 17.1 13.8
26 14.5 6.6 ==> Assembly #1
|
109
|
Fri Apr 12 09:25:31 2013 |
Koji | Optics | Characterization | Alignment of the OMC (without glue) | [Zach Koji]
The first attempt not to touch the curved mirrors did not work. (Not surprising)
The eigenmode is not found on the mirror surface.
We decided to touch the micrometers and immediately found the resonance.
Then the cavity alignment was optimized by the input steering mirrors.
We got the cavity length L and f_TMS/f_FSR (say gamma, = gouy phase / (2 pi) ) as
L=1.1347 m (1.132m nominal)
gamma_V = 0.219176 (0.21879 nominal)
gamma_H = 0.219418 (0.21939 nominal)
This was already sufficiently good:
- the 9th modes of the carrier is away from the resonance 10-11 times
of the line width (LW)
- the 13th modes of the lower f2 sideband are 9-10 LW away
But
- the 19th modes of the upper f2 sideband are 1-3 LW away
This seems to be the most dangerous ones.
and
- The beam spots on the curved mirrors are too marginal
So we decided to shorten the cavity round-trip 2.7mm (= 0.675mm for each micrometer)
and also use the curved mirrors to move the eigenmode toward the center of the curved mirrors.
After the movement the new cavity length was 1.13209 m.
The spot positions on the curved mirrors are ~1mm too close to the outside of the cavity.
So we shortened the outer micrometers by 8um (0.8 div).
This made the spot positions perfect. We took the photos of the spots with a IR sensor card.
The measured cavity geometry is (no data electrically recorded)
L=1.13207 m (1.132m nominal, FSR 264.8175MHz)
gamma_V = 0.218547 (0.21879 nominal, 57.8750MHz)
gamma_H = 0.219066 (0.21939 nominal, 58.0125MHz)
- the 9th modes of the carrier is 11-13 LW away
- the 13th modes of the lower f2 sideband are 5-8 LW away
- the 19th modes of the upper f2 sideband are 4-8 LW away
The raw transmission is 94.4%. If we subtract the sidebands and
the junk light contribution, the estimated transmission is 97.6%.
Note:
Even if a mirror is touched (i.e. misaligned), we can recover the good alignment by pushing the mirror
onto the fixture. The fixture works pretty well!
|
112
|
Tue Apr 16 08:12:14 2013 |
Koji | Optics | Characterization | Further More Mirror T measurement | T&Rs of the B mirrors and some of the E mirrors are measured.
I found that these BSs have high loss (1%~3%) . As this loss will impact the performance of the squeezer
we should pick the best ones for the DCPD path. B5, B6, and B12 seems the best ones.
Mirror | P_Incident P_Trans P_Refl | T R loss |
| [mW] [mW] [mW] | |
-------+--------------------------------------+-------------------------------------------+
B1 | 13.80+/-0.05 7.10+/-0.05 6.30+/-0.05 | 0.514+/-0.004 0.457+/-0.004 0.029+/-0.005 |
B2 | 14.10+/-0.05 6.50+/-0.05 7.15+/-0.05 | 0.461+/-0.004 0.507+/-0.004 0.032+/-0.005 |
B3 | 13.87+/-0.05 7.05+/-0.05 6.55+/-0.05 | 0.508+/-0.004 0.472+/-0.004 0.019+/-0.005 |
B4 | 13.85+/-0.05 6.78+/-0.05 6.70+/-0.05 | 0.490+/-0.004 0.484+/-0.004 0.027+/-0.005 |
B5 | 13.65+/-0.05 6.93+/-0.05 6.67+/-0.05 | 0.508+/-0.004 0.489+/-0.004 0.004+/-0.005 |
B6 | 13.75+/-0.05 6.70+/-0.05 6.92+/-0.05 | 0.487+/-0.004 0.503+/-0.004 0.009+/-0.005 |
B7 | 13.83+/-0.05 7.00+/-0.05 6.60+/-0.05 | 0.506+/-0.004 0.477+/-0.004 0.017+/-0.005 |
B8 | 13.90+/-0.05 6.95+/-0.05 6.68+/-0.05 | 0.500+/-0.004 0.481+/-0.004 0.019+/-0.005 |
B9 | 13.84+/-0.05 6.95+/-0.05 6.70+/-0.05 | 0.502+/-0.004 0.484+/-0.004 0.014+/-0.005 |
B10 | 13.97+/-0.05 6.98+/-0.05 6.72+/-0.05 | 0.500+/-0.004 0.481+/-0.004 0.019+/-0.005 |
B11 | 13.90+/-0.05 7.05+/-0.05 6.70+/-0.05 | 0.507+/-0.004 0.482+/-0.004 0.011+/-0.005 |
B12 | 13.90+/-0.05 6.98+/-0.05 6.78+/-0.05 | 0.502+/-0.004 0.488+/-0.004 0.010+/-0.005 |
-------+--------------------------------------+-------------------------------------------+
Mirror | P_Incident P_Trans P_Refl | T R loss |
| [mW] [uW] [mW] | [ppm] |
-------+-------------------------------------------+------------------------------------------+
E4 | 13.65+/-0.05 0.0915+/-0.0005 13.50+/-0.05 | 6703+/-44ppm 0.989+/-0.005 0.004+/-0.005 |
E12 | 13.75+/-0.05 0.0978+/-0.0005 13.65+/-0.05 | 7113+/-45 0.993+/-0.005 0.000+/-0.005 |
E16 | 13.90+/-0.05 0.0975+/-0.0005 13.30+/-0.05 | 7014+/-44 0.957+/-0.005 0.036+/-0.005 |
-------+-------------------------------------------+------------------------------------------+
|
114
|
Tue Apr 16 23:26:51 2013 |
Koji | Optics | Characterization | Further More Mirror T measurement | Since the previous measurement showed too high loss, the optical setup was checked.
It seemed that a PBS right before the T&R measurement setup was creating a lot of scattering (halo) visible with a sensor card.
This PBS was placed to confirm the output polarization from the fiber, so it was ok to remove it.
After the removal, the R&T measurement was redone.
This time the loss distributed from 0.2% to 0.8% except for the one with 1.3%. Basically 0.25% is the quantization unit due to the lack of resolution.
At least B7, B10, B12 seems the good candidate for the DCPD BS.
The AR reflection was also measured. There was a strong halo from the main reflection with an iris and sense the power at ~.5mm distance to separate the AR reflection from anything else. Now they are all somewhat realistic. I'll elog the measurement tonight.
33.6 +/- 0.2 uW out of 39.10+/-0.05 mW was observed. The offset was -0.236uW.
This gives us the AR reflectivity of 865+/-5ppm . This meets the spec R<0.1%
Mirror | P_Incident P_Trans P_Refl | T R loss |
| [mW] [mW] [mW] | |
---------------------------------------------------------------------------------------------
B1 | 39.10+/-0.05 19.65+/-0.05 19.25+/-0.05 | 0.503+/-0.001 0.492+/-0.001 0.005+/-0.002 |
B2 | 39.80+/-0.05 19.90+/-0.05 19.70+/-0.05 | 0.500+/-0.001 0.495+/-0.001 0.005+/-0.002 |
B4 | 39.50+/-0.05 19.70+/-0.05 19.30+/-0.05 | 0.499+/-0.001 0.489+/-0.001 0.013+/-0.002 |
B5 | 39.50+/-0.05 19.70+/-0.05 19.50+/-0.05 | 0.499+/-0.001 0.494+/-0.001 0.008+/-0.002 |
B6 | 39.55+/-0.05 19.50+/-0.05 19.95+/-0.05 | 0.493+/-0.001 0.504+/-0.001 0.003+/-0.002 |
B7 | 40.10+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.494+/-0.001 0.504+/-0.001 0.002+/-0.002 |
B8 | 40.15+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.493+/-0.001 0.503+/-0.001 0.004+/-0.002 |
B9 | 40.10+/-0.05 19.90+/-0.05 19.90+/-0.05 | 0.496+/-0.001 0.496+/-0.001 0.008+/-0.002 |
B10 | 40.10+/-0.05 19.70+/-0.05 20.30+/-0.05 | 0.491+/-0.001 0.506+/-0.001 0.002+/-0.002 |
B11 | 40.20+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.493+/-0.001 0.502+/-0.001 0.005+/-0.002 |
B12 | 40.20+/-0.05 19.90+/-0.05 20.20+/-0.05 | 0.495+/-0.001 0.502+/-0.001 0.002+/-0.002 |
---------------------------------------------------------------------------------------------
|
120
|
Mon May 6 19:31:51 2013 |
Koji | Optics | Characterization | Spot position measurement on the diode mounts | Measurement Order: DCPD2->DCPD1->QPD1->QPD2
DCPD1: 1.50mm+0.085mm => Beam 0.027mm too low
DCPD2: 1.75mm+0.085mm => Beam 0.051mm too high (...less confident)
QPD1: 1.25mm+0.085mm => Beam 0.077mm too low
QPD2: 1.25mm+0.085mm => Beam 0.134mm too low
or 1.00mm+0.085mm => Beam 0.116mm too high
|
121
|
Wed May 8 15:08:57 2013 |
Koji | Optics | Characterization | Spot position measurement on the diode mounts | Remeasured the spot positions:
DCPD1: 1.50mm+0.085mm => Beam 0.084mm too high
DCPD2: 1.50mm+0.085mm => Beam 0.023mm too high
QPD1: 1.25mm+0.085mm => Beam 0.001mm too low
QPD2: 1.25mm+0.085mm => Beam 0.155mm too low
|
124
|
Mon May 13 14:49:35 2013 |
Koji | Mechanics | Characterization | Mounting Glass Bracket still broke with tightenin stress | [Koji / Jeff]
This is the elog about the work on May 9th.
We made two glass brackets glue on the junk 2" mirrors with the UV glue a while ago when we used the UV bonding last time.
On May 7th:
We applied EP30-2 to the glass brackets and glued invar shims on them. These test pieces were left untouched for the night
and brought to Bob for heat curing at 94degC for two hours.
On May 9th:
We received the test pieces from Bob.
First, a DCPD mount was attached on one of the test pieces. The fasteners were screwed at the torque of 4 inch lb.
It looked very sturdy and Jeff applied lateral force to break it. It got broken at once side of the bracket.
We also attached the DCPD mount to the other piece. This time we heard cracking sound at 2 inch lb.
We found that the bracket got cracked at around the holes. As the glass is not directly stressed by the screws
we don't understand the mechanism of the failure.
After talking to PeterF and Dennis, we decided to continue to follow the original plan: glue the invar shims to the brackets.
We need to limit the fastening torque to 2 inch lb.
|
134
|
Fri May 31 14:07:54 2013 |
Koji | Optics | Characterization | Transverse 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 |
137
|
Wed Jun 5 01:06:35 2013 |
Zach | General | Characterization | L1 OMC as-built diagram | D1300507
 |
145
|
Tue Jun 18 10:01:11 2013 |
Koji | Optics | Characterization | Cavity Finesse analysis | This is the analysis of the cavity finesse data taken on Apr/13/2013 (before baking), May/30/2013 (after baking), and Jun/02/2013 (after cleaning).
If we believe this result, baking contaminated the cavity, and the first contact removed it. That agrees with the power measurement of the transmitted light. |
148
|
Sat Jul 6 17:10:07 2013 |
Koji | Mechanics | Characterization | PZT Response analysis | Analysis of the PZT scan / TF data taken on May 31st and Jun 1st.
[DC scan]
Each PZT was shaken with 10Vpp 1Hz triangular voltage to the thorlabs amp.
The amp gain was x15. Abut 4 TEM00 peaks were seen on a sweep between 0 and 10V.
The input voltage where the peaks were seen was marked. Each peak was mapped on the
corresponding fringe among four. Then the each slope (up and down) was fitted by a iiner slope.
Of course, the PZTs show hystersis. Therefore the result is only an approximation.
PZT1: PZT #26, Mirror C6 (CM1)
PZT2: PZT #23, Mirror C5 (CM2)
PZT arrangement [ELOG Entry]
PZT1:
Ramp Up 13.21nm/V
Ramp Down 13.25nm/V
Ramp Up 13.23nm/V
Ramp Down 13.29nm/V
=> 13.24+/-0.02 nm/V
PZT2:
Ramp Up 13.27nm/V
Ramp Down 12.94nm/V
Ramp Up 12.67nm/V
Ramp Down 12.82nm/V
=> 12.9+/-0.1 nm/V
[AC scan]
The OMC cavity was locked with the fast laser actuation. Each PZT was shaken with a FFT analyzer for transfer function measurments.
(No bias voltage was given)
The displacement data was readout from the laser fast feedback. Since the UGF of the control was above 30kHz, the data was
valid at least up to 30kHz. The over all calibration of the each curve was adjusted so that it agrees with the DC response of the PZTs (as shown above).
The response is pretty similar for these two PZTs. The first series resonance is seen at 10kHz. It is fairly high Q (~30). |
154
|
Wed Aug 21 08:31:21 2013 |
Koji | Optics | Characterization | H1 OMC cavity alignment | Alignment of the H1 OMC cavity mirrors
- The cavity mirrors as well as the first steering mirror were aligned on the cavity side template.
- The locking of the cavity was not so stable as before. Some high freq (several hundreds Hz) disturbance makes the cavity
deviate from the linear range. This can be mitigated by turning off the HEPA units but this is not an ideal condition.
- FSR and TMS were measured.
FSR: 264.305MHz
TMS(V): 58.057MHz
TMS(H): 58.275MHz
These suggest the cavity length L and f_TMS/f_FSR (say gamma, = gouy phase / (2 pi) ) as
L=1.1343 m (1.132m nominal)
gamma_V = 0.219659 (0.21879 nominal)
gamma_H = 0.220484 (0.21939 nominal)
- the 9th modes of the carrier is away from the resonance 6-9 times of the line width (LW)
- the 13th modes of the lower f2 sideband are 11-15 LW away
- the 19th modes of the upper f2 sideband are 0.6-7 LW away
We still need precise adjustment of the gouy phase / cavity length, this was enough for the gluing of the flat mirrors |
|