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  463   Tue Nov 29 15:54:47 2022 KojiGeneralConfigurationWindows laptop for WincamD Beam'R2 recovery

Aaron took the set to Cryo lab

 

  6   Fri Jun 29 11:26:04 2012 ZachOpticsCharacterizationRoC 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.

RoC_measurement_setup.png

Attachment 2: RoC_measurement_setup.graffle.zip
  8   Wed Jul 18 23:20:13 2012 KojiOpticsCharacterizationMode 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 ZachOpticsCharacterizationRoC measurement setup

Here is a more detailed version of the setup, so that we can gather the parts we will need.

detailed_RoC_setup.png

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.

 

Attachment 2: detailed_RoC_setup.graffle.zip
  31   Thu Oct 18 20:23:33 2012 KojiOpticsCharacterizationImproved 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.

 

Attachment 1: Cav_scan_response_zoom_20121017.pdf
Cav_scan_response_zoom_20121017.pdf
Attachment 2: detailed_RoC_setup.pdf
detailed_RoC_setup.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]

  35   Thu Nov 8 13:24:53 2012 KojiOpticsCharacterizationMore 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

Attachment 1: wedge_measurement_overall.pdf
wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf
  39   Fri Nov 9 00:43:32 2012 KojiOpticsCharacterizationFurther 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



 

Attachment 1: wedge_measurement_overall.pdf
wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf wedge_measurement_overall.pdf
Attachment 2: 121108a_A1.pdf
121108a_A1.pdf 121108a_A1.pdf 121108a_A1.pdf 121108a_A1.pdf
  40   Sat Nov 17 02:31:34 2012 KojiOpticsCharacterizationMirror 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   Mon Nov 19 13:33:14 2012 KojiOpticsCharacterizationResuming 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

Attachment 1: Cav_scan_response_zoom_20121016.pdf
Cav_scan_response_zoom_20121016.pdf
  42   Mon Nov 26 01:40:00 2012 KojiOpticsCharacterizationMore 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)

Attachment 1: RoC_measurement.pdf
RoC_measurement.pdf RoC_measurement.pdf RoC_measurement.pdf RoC_measurement.pdf RoC_measurement.pdf
  44   Tue Dec 18 20:04:40 2012 KojiOpticsCharacterizationPrism 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

prism.png

  49   Mon Dec 31 03:11:45 2012 KojiOpticsCharacterizationFurther 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

Attachment 1: Cav_scan_response_zoom_20121125_C6_9.pdf
Cav_scan_response_zoom_20121125_C6_9.pdf Cav_scan_response_zoom_20121125_C6_9.pdf Cav_scan_response_zoom_20121125_C6_9.pdf Cav_scan_response_zoom_20121125_C6_9.pdf
  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

  51   Wed Jan 2 07:45:39 2013 KojiOpticsCharacterizationFirst 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?

Attachment 1: Cav_scan_response_zoom_20121125_C2_before.pdf
Cav_scan_response_zoom_20121125_C2_before.pdf
Attachment 2: Cav_scan_response_zoom_20121125_C2_after.pdf
Cav_scan_response_zoom_20121125_C2_after.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
  54   Wed Jan 16 14:10:50 2013 KojiOpticsCharacterizationAutocollimator 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   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
  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

 

  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.

  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
  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.

  72   Fri Mar 15 02:15:45 2013 KojiElectronicsCharacterizationDiode 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.

 

Attachment 1: QPD_GR_TEST_130316.pdf
QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf QPD_GR_TEST_130316.pdf
  73   Sun Mar 17 21:59:47 2013 KojiElectronicsCharacterizationDiode 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

Attachment 1: OMCPD_TEST_130317.pdf
OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf OMCPD_TEST_130317.pdf
  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.

  78   Sat Mar 23 16:36:15 2013 KojiElectronicsCharacterizationDiode 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}
};

Attachment 1: P3213308.JPG
P3213308.JPG
Attachment 2: P3213310.JPG
P3213310.JPG
  92   Wed Apr 3 17:39:38 2013 KojiMechanicsCharacterizationCalibration 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.

P4033491.JPG

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

Attachment 2: shadow_sensor_calib.pdf
shadow_sensor_calib.pdf
  95   Thu Apr 4 01:35:04 2013 KojiOpticsCharacterizationMode 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 KojiOpticsCharacterizationMirror 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   Fri Apr 5 14:39:26 2013 KojiMechanicsCharacterizationCalibration 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

Attachment 1: shadow_sensor_calib_after_bake.pdf
shadow_sensor_calib_after_bake.pdf
Attachment 2: PZTresponse.pdf
PZTresponse.pdf
  100   Mon Apr 8 11:11:37 2013 KojiOpticsCharacterizationMore 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 KojiOpticsCharacterizationMirror/PZT Characterization links
  102   Mon Apr 8 11:49:18 2013 KojiMechanicsCharacterizationPZT 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 KojiOpticsCharacterizationAlignment 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 KojiOpticsCharacterizationFurther 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 KojiOpticsCharacterizationFurther 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 KojiOpticsCharacterizationSpot 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

Attachment 1: DCPD1.png
DCPD1.png
Attachment 2: DCPD2.png
DCPD2.png
Attachment 3: QPD1.png
QPD1.png
Attachment 4: QPD2.png
QPD2.png
  121   Wed May 8 15:08:57 2013 KojiOpticsCharacterizationSpot 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
 

Attachment 1: DCPD1.png
DCPD1.png
Attachment 2: DCPD2.png
DCPD2.png
Attachment 3: QPD1.png
QPD1.png
Attachment 4: QPD2.png
QPD2.png
  124   Mon May 13 14:49:35 2013 KojiMechanicsCharacterizationMounting 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 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
  137   Wed Jun 5 01:06:35 2013 ZachGeneralCharacterizationL1 OMC as-built diagram

 D1300507

 L1OMC_asbuilt.pdf

  145   Tue Jun 18 10:01:11 2013 KojiOpticsCharacterizationCavity 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.

Attachment 1: finesse_measurements.pdf
finesse_measurements.pdf
  148   Sat Jul 6 17:10:07 2013 KojiMechanicsCharacterizationPZT 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).

Attachment 1: PZT_Scan.pdf
PZT_Scan.pdf
Attachment 2: L1OMC_PZT_Response.pdf
L1OMC_PZT_Response.pdf
  154   Wed Aug 21 08:31:21 2013 KojiOpticsCharacterizationH1 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

  158   Tue Aug 27 17:02:31 2013 KojiMechanicsCharacterizationSpot position measurement on the diode mounts

After the PZT test, the curved mirrors were aligned to the cavity again.

In order to check the height of the cavity beam, the test DCPD mount was assembled with 2mm shim (D1201467-3)
The spot position was checked with a CCD camera.

According to the analysis of the picture, the spot height is about 0.71mm lower than the center of the mount.

Attachment 1: DCPD1.png
DCPD1.png
  159   Thu Aug 29 02:52:50 2013 KojiOpticsCharacterizationH1OMC Curved Mirror Alignment

Cavity parameter was measured with 50V bias on PZT1 (CM1)

- PZT combination was changed: PZT1 #21 (PZT ASSY#6) / PZT2 #25 (PZT ASSY #4)

- 19th HOMs of the USB makes accidental resonance with the nominal cavity length.
  Because of the mirror astigmatism, HOMs spreads more than the design.
  In order to avoid these modes, the cavity length had to be moved from the nominal value (1.134m).

- The clearance between the fixture and the prism was limited. This prevents to shorten the cav length.
  The cavity length was made longer about 10mm.

-----

Cavity parameter obtained from the pitch misalignment

Free Spectral Range (FSR): 261.777947 +/− 0.000299 MHz
Cavity roundtrip length: 1.145217 +/− 0.000001 m
Lock offset: 1.636183 +/− 0.238442 kHz
Transverse mode spacing (TMS): 57.581950 +/− 0.000163 MHz
TMS/FSR: 0.219965 +/− 0.000001
Cavity pole (1st order modes, avg and stddev): 353.465396 +/− 0.657630 kHz
Finesse (1st order modes, avg and stddev): 370.302940 +/− 0.688585

Carrier 9th-order HOM: -8.1 line width away
Upper Sideband 13th-order HOM: 13.3 LW away
Lower Sideband 19th-order HOM: 2.2 LW away

-----

Cavity parameter obtained from the pitch misalignment

Free Spectral Range (FSR): 261.777106 +/− 0.000226 MHz
Cavity roundtrip length: 1.145220 +/− 0.000001 m
Lock offset: 0.215937 +/− 0.183434 kHz
Transverse mode spacing (TMS): 57.875622 +/− 0.000116 MHz
TMS/FSR: 0.221087 +/− 0.000000
Cavity pole (1st order modes, avg and stddev): 356.862001 +/− 0.448102 kHz
Finesse (1st order modes, avg and stddev): 366.776766 +/− 0.460598

Carrier 9th-order HOM: -4.1 line width away
Upper Sideband 13th-order HOM: 19.1 LW away
Lower Sideband 19th-order HOM: 10.8 LW away

-----

We could avoid hitting the 19th modes of the 45MHz sidebands.

First accidental hit is the 28th order modes of the lower sideband.

Red: Carrier
Blue: Upper sideband (45MHz)
Green: Lower sideband (45MHz)

Attachment 1: Cav_scan_response_130828_Pitch.pdf
Cav_scan_response_130828_Pitch.pdf
Attachment 2: Cav_scan_response_130828_Yaw.pdf
Cav_scan_response_130828_Yaw.pdf
  163   Fri Aug 30 12:24:28 2013 KojiOpticsCharacterizationH1OMC Spot positions

Beam heights on the diodes

DCPD1: 14.459mm -> With 1.5mm shim, the beam will be 0.038mm too low.

DCPD2: 14.221mm -> With 1.25mm shim, the beam will be 0.026mm too low.

QPD1: 14.691mm -> With 1.75mm shim, the beam will be 0.056mm too low.

QPD2: 14.379mm -> With 1.5mm shim, the beam will be 0.118mm too low.

Attachment 1: DCPD1.png
DCPD1.png
Attachment 2: DCPD2.png
DCPD2.png
Attachment 3: QPD1.png
QPD1.png
Attachment 4: QPD2.png
QPD2.png
  169   Mon Oct 14 13:40:16 2013 KojiOpticsCharacterizationH1 OMC Optical testing

Since the middle of September, the optical tests of H1 OMC were took place.
Here is summary of the progress.

TEST1: FSR/FINESSE measurement before applying First Contact
TEST2: Power budget

MIrror cleaning with First Contact

TEST3: FSR/FINESSE measurement after First Contact application
TEST4: Power budget

TEST5: N/A

TEST6: HOM measurement @PZT V=0
TEST7: HOM measurement @PZT V=0-200

TEST8: DC response of the PZT
TEST9: AC response of the PZT

TEST10: PD/QPD alignment / output check

 

 

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