40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Typeup Category Subject
  2560   Wed Apr 21 16:45:01 2021 AidanLab InfrastructureCamerasTelephoto and macro lenses for smartphones

I purchased a set of telephoto and macro lenses for the lab. They're stored in the tool cabinet.

 

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  2612   Wed Jul 21 13:14:11 2021 PacoLab Infrastructure2micronLasersBrimrose AOM and amplifier

Yesterday I came in the QIL and performed an express kidnapping of the 2um in fiber AOM (Brimrose) and the 5 W RF amplifier that was hooked to the RF in port (though it seems it saturates at ~ 600 mW from past elogs). I will test it with the 1419 nm ECDL fiber pickoff port to see that it works and if it doesn't I will reinstall it in the 2um testing facility.

  2640   Fri Aug 6 16:15:03 2021 PacoLab Infrastructure2micronLasersBrimrose AOM and amplifier

Also borrowed Mini-Circuits amplifier ZFL-500LN+ from same setup.

Quote:

Yesterday I came in the QIL and performed an express kidnapping of the 2um in fiber AOM (Brimrose) and the 5 W RF amplifier that was hooked to the RF in port (though it seems it saturates at ~ 600 mW from past elogs). I will test it with the 1419 nm ECDL fiber pickoff port to see that it works and if it doesn't I will reinstall it in the 2um testing facility.

 

  2646   Wed Aug 18 13:06:03 2021 Aidan, StephenLab InfrastructureCleanlinessNorth table clean-up

Stephen and I spent about an hour today tidying up the North Table in preparation for 2um photodiode testing in the Megastat.

Decepticon - Transformers Wiki

I ordered two more wire racks (24" deep, 36" wide, 27" high with two shelves each) to go under the table and serve as instrumentation racks.

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  2652   Thu Aug 26 16:10:16 2021 AidanLab InfrastructureCleanlinessTwo under table equipment racks purchased for North Table - one installed so far

I bought two racks to house all our electronics which is currently taking up space on the North Table. The legs were exactly the same length as the clearance between the floor and the bottom fo the table - but not after I got the hacksaw involved. Thankfully the legs have plugs on the top whic cover up the sharp bits that I cut.

Next step is to start transferring the equipment below the table.

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  2758   Wed Apr 20 00:00:39 2022 YehonathanLab InfrastructureGeneralPreparing for planned power outage

{Yehonathan, Shruti}

We shut down the workstations and the FBs by doing sudo shutdown and unplugged them from the wall.

Electronic equipment on the FB rack was shut down and unplugged from the wall.

Diablo's current was ramped down and the control unit was shutdown. Optical table electronic equipment was shutdown and the table's powerstrip was switched off.

Equipment under the optical table was switched off and unplugged.

  2766   Tue May 10 14:27:26 2022 AidanLab InfrastructureCleanlinessCeiling tile replacement - Day 1

Henry from the Carpentry Shop has started replacing ceiling tiles. They need to be cut to fit each location. There was a lot of set up getting equipment across to Bridge before lunch so not that much progress was made replacing tiles in QIL and TCS Labs. Expect work will speed up as we find our groove. 

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  2767   Wed May 11 15:53:06 2022 AidanLab InfrastructureCleanlinessCeiling tile replacement - Day 2

Tiles are replaced.

Quote:

Henry from the Carpentry Shop has started replacing ceiling tiles. They need to be cut to fit each location. There was a lot of set up getting equipment across to Bridge before lunch so not that much progress was made replacing tiles in QIL and TCS Labs. Expect work will speed up as we find our groove. 

 

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  2   Sun Oct 21 23:11:20 2007 ranaLaserMOPALaser Turn on report
When the laser was first turned on (slowly, as per the manual), the output power was only ~14 W instead of 35.

Some tweaking of the mirrors M4 & M5 (~1 full turn each in both pitch and yaw) restored the power. The peak
power was 37.0 W as measured on the Big Head. Cool

The beam is also not centered on the monitor PD and so its more likely a small shift of some earlier
mount than such large shifts of those last two mirrors.

With the cold temperature, the power has drooped to 35.5 W. Frown
  4   Wed Oct 24 23:50:27 2007 dmassLaserGeneralTip Tilt Frequency Response
Here are screens of the Tip Tilt mirrors transfer function and associated xml files. Prettier unified plots will follow. The first one has the wrong header, the 071024 file is displayed with the 071014 header.
Attachment 1: TTL_low_freq.png
TTL_low_freq.png
Attachment 2: TTL_mid_freq.png
TTL_mid_freq.png
Attachment 3: TTL_high_freq.png
TTL_high_freq.png
Attachment 4: AngleTF_UL-071019.xml.zip
Attachment 5: AngleTF_UL-071020.xml.zip
Attachment 6: AngleTF_UL-071024.xml.zip
  5   Fri Oct 26 15:38:43 2007 Tobin FrickeLaserPSLPolarizer
On Tuesday we installed a λ/2 plate and a polarized beamsplitter after the laser aperture; attached to this entry is a measurement of transmitted power versus polarizer angle.
Attachment 1: polarizer.pdf
polarizer.pdf
Attachment 2: polarizer.m
% Polarizer calibration / Rana's lab
% Tobin Fricke 2007-10-26

% Experimental setup:
%                                [Dump]   
%                                  |
%  +-------+                       |
%  | Laser |-------|lambda/2|----|PBS|----[Power Meter]
%  +-------+ 
%  
... 53 more lines ...
  6   Sun Nov 4 23:44:36 2007 ranaLaserPSLMore Laser setup info
Brought over a PMC mount from the 40m which Nergis is letting us borrow. Steve has made up a plate to
adapt that up to a 4" height from 3".

Still to do to get the optics of it set up:

  • RF Amp to boost the 35.5 MHz Wenzel
  • Attenuators to get the splitter output to not destroy the LO
  • Bandpass filters for 35.5 MHz
  • RFPD to take the PMC reflection and do locking
  • 2 steering mirrors
  • Mode matching lenses
  7   Thu Nov 8 01:58:37 2007 dmassLaserGeneralTip Tilt Frequency Response

Quote:
Here are screens of the Tip Tilt mirrors transfer function and associated xml files. Prettier unified plots will follow. The first one has the wrong header, the 071024 file is displayed with the 071014 header.


Here are the plots with more useful units, and a doodle of the 'experimental' set-up at the end

Scroll down for a close up in the HF range.

The embedded .jpg is also available at the bottom of this entry as PitYaw.pdf
Attachment 1: allfour.jpg
allfour.jpg
Attachment 2: TTstruc.JPG
TTstruc.JPG
Attachment 3: Pit_Yaw.pdf
Pit_Yaw.pdf
  8   Thu Nov 8 18:54:41 2007 StefanLaserPSL35W laser ISS loop closed with LIGO ISS electronics
I closed the ISS loop using a iLIGO type ISS board, with an additional 2kHz pole at the last stage.

I haven't carefully measured noise or OLG yet, but it is not famous yet:
Looking at the in-loop diode I get a RIN of ~3e-7/rtHz at 100Hz, and ~1e-8 at 10kHz.

The gain is limited by two sharp resonances that rise at ~40kHz when the gain is increased.

TBD:
- Fix the ISS test point wiring - these cables have 800Ohm resistance!
(No not impedance... shield to core measures 800Ohms at DC...)
This brought back painful mamories from ~3years ago when we installed
the H1 ISS... apparently the known problem wasn't fixed on all versions.
- Measure OLG, in particular check whether weird AOM transfer function still
exists - it could be killing our gain.
- Measure sensing noise in-situ
- Install sensitive OL PD
  9   Mon Nov 12 21:33:41 2007 StefanLaserPSLISS servo work
I fixed a few things on the ISS board:
- Fixed the input THS4131 on the ISS board
- Fixed all monitoring point cables for the inner loop part.

With that I was able to lock the ISS with up to 400kHz UGF (limited by variable gain at max).

The sensing noise is about 60nV/rtHz at 100Hz without light, but there is some additional noise pick-up when the VCO driver is connected.

The In-loop noise, with 6V DC (~8mWatt on the diode) and a UGF of 400kHz is
100Hz: 170nV/rtHz (2.8e-8/rtHz)
200Hz: 60nV/rtHz (1.0e-8/rtHz)
500Hz: 50nV/rtHz (8.3e-9/rtHz)

The out-of loop noise is still a lot worse ( a few e-7/rtHz at 100Hz), but that's not surprising:
The table is quite noisy and not much care went into choosing good mounts.
  10   Tue Nov 13 19:06:18 2007 ranaLaserPSLISS servo work
400 kHz !? Wow.

We should lower the resistors in the PD head so that we can put ~20-30 mA per diode
and use the ISS style diodes for both the in-the-loop as well as out-of-loop diodes.


Then we have to dump the beams reflecting off the diodes onto razor dumps and also
put in a lens so that the beam has a 0.3 mm dia. on the diodes.


Then we make an acrylic box with an entrance hole for the beam and put it over both
diodes.
  17   Wed Dec 26 21:30:05 2007 ranaLaserPSLlaser power
I have rewired the laser power so now the Diode Box goes directly to one of the
overhead umbilicals (circuit #29) which is energized by the wall switch which
is marked as "Master Laser". Cutting off that switch is NOT the desired way to
power down the laser; use the Beckoff touchpad instead. The wall switch is the
emergency cutoff.

The HEPA fans on the laser table are both routed to power strips on the table now.

With the laser on, the beam looks well clipped. As far as I can tell this comes
from inside the box so the next thing is to do a little more re-alignment inside
the box.

Also need some more lenses for cameras and more IR cards.

And we should slice the tires of anyone who borrows equipment without leaving a note!
  20   Mon Jan 28 16:51:06 2008 Stefan BallmerLaserPSLPDH locked pre-mode cleaner
Since we suspect that the ISS might be jitter-noise limited I started looking at the Pre-Mode Cleaner (PMC).

- Did a rough mode-matching with one lense into the PMC
- Aligned the PMC. Note that the camera is now in transmission of the PMC.
- Used 3MHz drive to the laser's EOM and a photo diode in reflection of the PMC for
PDH locking. Successfully closed the loop using a mixer and SR560, driving
the laser's piezo - however only on a 2-0 mode.
- The 30V power supply I currenctly use to pre-set the PMC PZT does not have
enough range to scan a full FSR, and I can't get the 00 mode into range.

David - feel free to dismantle the path into the PMC and properly measure the beam parameters.
  21   Mon Jan 28 18:02:04 2008 Stefan BallmerLaserGeneral1.2MHz Laser intensity oscillation
While working on the PDH loop for the PMC I noticed
a 1.2MHz oscillation on the laser intensity:

- It seems to be a bistable state: it was generally
started by some transient in the piezo input of the laser.
- The oscillation persists even when all control inputs to the laser
(EOM, PZT, AOM) are disconnected.
- It's extremely strong: about 20% fractional modulation
- Power-cycling the laser usually fixes the problem.
  22   Tue Jan 29 12:47:44 2008 DmassLaserGeneralStrange Noise
Something on the table or under it is periodically making a squeeking noise. Stefan claims this is not new though neither of us can localize it (it's < 1sec duration). Unsure as to what is the offending noisemaker.

[Update - the noise happens when the laser is off, comes from side of table (possibly beneath) opposite laser]
  24   Wed Jan 30 12:57:53 2008 DmassLaserPSLCharacterizing Beam
1/28/08 - Took a series of beam waist measurements on the YAG.


-The polarizations (as measured by the photon beamscanner) had very different profiles. One polarization has a dual peak (probably a reflection from some optic). This shows up after the beam has passed through the polarizer, the PBS, and one mirror.

-Initial beam characterization yielded a waist inside the Laser Box by ~3", at a width of 200 microns. Will be rechecking this. (Impossible if there is a lens at the opening, which I'm not sure is the case).
  25   Tue Feb 5 18:59:07 2008 Stefan BallmerLaserGeneralBork-space running
- Used the new Bork-space system to lock the PMC with a UGF of 100Hz.
- Hooked up a temporary power monitor (using the DC of one of the ISS PD's)
to ADC Channel 6. For the moment this can be used to trend the power.

- Accidentally blew the output opamp in the ISS monitoring chain - i.e. the ISS out-of-loop
monitor is currently unusable. Needs to be fixed.
  26   Sun Feb 10 13:18:07 2008 Stefan BallmerLaserGeneralTrend of Laser Power over 20h
Attached is a snapshot of the laser power over the last 24h.
The input gain is such that 1 count corresponds to about 1 mWatt
of power after the polarizing beam splitter, i.e. the the lambda/2 plate
was set to about 4 Watts.

I don't know where the short surges of power come from.
Attachment 1: LaserPower20h.png
LaserPower20h.png
  28   Tue Feb 12 16:54:13 2008 DmassLaserPSL35W profile/waist
The beam output by the 35W in 058 was significantly elliptical (up to a 10% difference in the waist measurements). I used the profile given by the "more gaussian" axis, and found a waist 9.7 cm inside the front of the enclosure, 250 microns in radius. We ended up using this axis to mode match to, but this ellipticity will probably need to be addressed as we try to maximize the power output through the PMC.

[plots to be added]
  29   Tue Feb 12 17:00:35 2008 DmassLaserPSLMode Matching/Lock
I got a solution for mode matching the 35W to the PMC with 2 100mm (focal length) lenses. I abandoned this since they were deemed too fast by Stefan, and were seperated by ~1 focal length. We ended up using a 1m and .5m lens (all lenses from the newport kit in 058). My code choked on this solution and needs some bugs ironed out (will attach afterwards), so we used Stefan's.

We then managed to get a 00 lock, at a somewhat meager power throughput. Pictures of the layout below:
Attachment 1: PMC_MM.JPG
PMC_MM.JPG
Attachment 2: lenses_mmJPG.JPG
lenses_mmJPG.JPG
  30   Sat Feb 16 13:46:19 2008 DmassLaserPSLLaser Aperture closed.
Laser was powered up with the aperture closed. It was fairly warm to the touch. I opened the aperture. I don't know if it is a "bad thing" to be dumping all 35W on the stop for large times. Sat @ 1:40.
  31   Sat Feb 16 15:33:25 2008 DmassLaserPSLRadial Beam Profile
The following were taken with the beam scanner (having gone through a number of optical elements).

After leaving the main laser housing, the beam hits:
polarizer -> PBS -> low reflectivity pickoff mirror -> 1m lens -> 0.5m lens -> 45-P HR mirror -> 45 P HR mirror -> beamscan.

In taking my initial waist measurements, I had the beamscan after the LR pickoff, and the beam looked similar.
Attachment 1: 2_16_0835w.bmp
  33   Tue Feb 26 21:05:47 2008 Stefan BallmerLaserGeneral 
Additionally to what Rana mentioned, there are two more signals hooked up:

SUS_LEFT (Ch4): PMC PZ control signal (from the SR560 loop)
SUS_RIGHT (Ch5): PMC transmitted power

We also hooked up the SUS_L_ACT (Ch4) DAC to the Laser temperature control.
Using this we closed the slow loop for the PMC
  36   Mon Mar 3 01:21:19 2008 ranaLaserMOPApower drift
This plot shows the power drift over the last few days.
The SIDE_OUT16 channel is the one. The y scale is zoomed in here but
zero corresponds to zero power. The faster spikes have a ~45 minute time scale.

No idea what this is yet.
Attachment 1: test.png
test.png
Attachment 2: test2.png
test2.png
  37   Tue Mar 4 16:00:28 2008 DmassLaserPSLISS
I moved the (non logging) ISS PD after the PMC, and changed the mirror/camera setup some.

Setup post PMC should now have ~5% of the power going to the camera, with the rest going to a BS for the ISS photodiodes.
  38   Fri Mar 7 15:33:14 2008 DmassLaserEOMEOM shipped
I packaged up and shipped the EOM back to UF. The translation stage, also theirs, was sent with it. Everything is marked c/o Guido Mueller.
  39   Thu Mar 27 13:25:38 2008 Stefan BallmerLaserISSModifications to ISS (D080149-00-C)
Attachment 1: D080149-00-C.pdf
D080149-00-C.pdf D080149-00-C.pdf D080149-00-C.pdf D080149-00-C.pdf D080149-00-C.pdf
  40   Tue Apr 1 20:50:37 2008 DmassLaserEOMTransfer Function
(With Stefan's help) I took the transfer function between the EOM of the PSL, and the Photodiode on the PMC's reflected light. We looked at the lower frequency as well with another analyzer (up to 50 MHz).

The very low frequency features seem to be junk, and we can see what looks like ~f in the low frequency transfer function.

In the higher frequency range, there seem to be resonances corresponding to a FSR of about 22 MHz (long.) starting around 11 MHz. The low end seems to behave as expected, and go as frequency. (Note that the units on the non-log bottom plot are in x10^7 Hz)
Attachment 1: EOM_PD_xsfer.jpg
EOM_PD_xsfer.jpg
Attachment 2: HFlogxsfer.jpg
HFlogxsfer.jpg
Attachment 3: HFxsfer.jpg
HFxsfer.jpg
  41   Thu Apr 3 17:56:35 2008 DmassLaserEOMTransfer Function
Transfer function part 2:

I repeated the measurement with impedence matching where I could (not inside the laser box), and did some CRUDE fitting with matlab.

I also herby acknowledge that png > jpg.

The tau is the time delay which makes the green curve on the phase plot coincide with the data at high frequency.

No locking was used. The 00 mode was reached for short periods of time through input to the laser crystal temperature during which time the measurement was taken.

-Calibration-
The input to the EOM was removed and connected to the PD output and calibrated out with the network analyzer.

The analyzer used to do this measurement has now been traded for a HP 4395A (which goes down to 10Hz).
Attachment 1: EOMPMCTF.png
EOMPMCTF.png
  42   Mon Apr 7 16:43:15 2008 DmassLaserPSLProfile of 35W PSL
I scanned the beam on the 35W laser again (for the first time since it was fixed by our German friends during the LSC meeting).

A picture of the setup is below.

Images of the profile, 2d and 3d are below as .bmp, and the generating data for these is in Apr7_08scan.asc (zipped text)

This profile is significantly cleaner than the one measured in entry 31 of the elog.
Attachment 1: scancap.png
scancap.png
Attachment 2: 3dbeamprof.bmp
Attachment 3: flatprof.bmp
Attachment 4: Apr7_08scan.asc.zip
  44   Fri Apr 11 17:15:49 2008 DmassLaserEOMTransfer Function
We traded network analyzers and now can go below 100kHz in our measurement. The following transfer function was taken with an HP 4395A.

The previous measurements were done with the PMC not locked to the laser, so the measurement was repeated using RF Reflection locking (sidebands @ 35MHz).

Another important thing we discovered was that the frame of the table is ungrounded, which led to significant noise leaking into the error signal when we let a BNC cable touch it. Schematic of experimental set up to follow.

Not all of the cables/electronics were calibrated out in the measurement below.
Attachment 1: EOM_PMC_tf.png
EOM_PMC_tf.png
  45   Tue Apr 22 16:25:24 2008 robLaserPSLProfile of 35W PSL

Quote:
I scanned the beam on the 35W laser again (for the first time since it was fixed by our German friends during the LSC meeting).



What did they fix? And how?
  46   Tue Apr 22 20:07:50 2008 DmassLaserPSLProfile of 35W PSL
The total power seemed to be down about 10%, and that lower number was divided between two beams at the output. They opened up the amplifier and realigned things within it, which seems to have fixed the multibeam/lower power we were encountering before.


Quote:

Quote:
I scanned the beam on the 35W laser again (for the first time since it was fixed by our German friends during the LSC meeting).



What did they fix? And how?
  47   Fri Apr 25 13:33:35 2008 DmassLaserPSLpower drift
Here is a trend of the power drift taken over 10 days. The units are in counts produced by a photodiode stationed at a lower power pickoff of the beam.

The first plot is a full 10 days - you can see the times during which the laser was off where the counts go to zero.

The second plot is the full data over 10 hours, which seems to imply that the sharp increases in power are real.

Negative values correspond to an increase in power.
Attachment 1: trend2.png
trend2.png
Attachment 2: trend3.png
trend3.png
  48   Fri May 2 21:09:26 2008 DmassLaserGeneralStrange Noise
We may want to set up a microphone and see if the noise is correlated to the sharp power fluctuations in the laser.


Quote:
Something on the table or under it is periodically making a squeeking noise. Stefan claims this is not new though neither of us can localize it (it's < 1sec duration). Unsure as to what is the offending noisemaker.

[Update - the noise happens when the laser is off, comes from side of table (possibly beneath) opposite laser]
  49   Fri May 2 21:39:13 2008 DmassLaserPSLLaser power on table lowered
I have changed the polarizer before the polarizing beam splitter to minimize output power.

I did this to measure the PMC pole at as low a power as possible.

This will make power trends (which are picked off after the PBS) look VERY low for a bit.
  53   Tue May 6 18:18:59 2008 DmassLaserEOMEOM Phase lag
I used the experimental setup below to measure the transfer function between the EOM (which is before the amplifier) and the reflections off the PMC. The light blue line is what I shorted to each other when I used the 4395's calibrate feature to correct for the cabling/rf components.

The "modulation summation box" is shown below the schematic. I will update this later when I figure out what the components are.
Attachment 1: TF_setup1.png
TF_setup1.png
Attachment 2: MODSUM.png
MODSUM.png
  55   Tue May 13 12:37:31 2008 DmassLaserFiberNew fiber
We got a box of fiber from Boston (Marie Woods). It is now on the optics table in the bridge basement.

The fiber has some writing on it. It says printed on the fiber in ink:
"OZ OPTICS LTD BC# 2887" and gives their tel # as 613-831-0981.
There is also a label on the fiber that says:
"PMJ-3AF,3AF-1064-6/125-3-60-1
SN: T872391-01"

Picture below:
Attachment 1: 00011.png
00011.png
  56   Mon May 19 17:28:44 2008 DmassLaserPMCCavity Pole Measurement on the PMC
Measurement of the PMC cavity pole:

The following was done at powers of .234 W and .42 W.
I turned the laser power on the table down low (using a polarizer and a PBS to dump the majority of the beam).

I then used a function generator to input a triangle wave into the Piezo driver and sweep the cavity. This was done at a frequency of .04 Hz (for reasons dictated by dataviewer).

I found the HWHM (half width half max) of the transmitted intensity (when the DC bias was subtracted out) to be 0.00054 and 0.00053 free spectral ranges for .234 and .42 W, respectively.
I also noticed some nonlinearity in the PMC/Piezo as I scanned through more FSR's, and thus used the data from the bias voltages closest to zero.

I calculated the FSR frequency to be 713.8 MHz (in agreement to what we have on file for the PMC at the 40m).

Using the equality \delta L / L = \delta f / f, I get pole frequencies of 385 kHz and 378 kHz for .234 and .42 W, which is about a 2% agreement between measurements.

Again - the cavity pole was measured to be about 380 kHz to within a couple percent. - this differs significantly from the pole quoted for the 40m PMC at
http://www.ligo.caltech.edu/~ajw/PSLPMC.png (which is 488 kHz)
  57   Tue May 20 15:55:31 2008 DmassLaserEOMEOM Phase lag
The attached transfer function was measured with the experimental setup outlined in entry 53. The first transfer function (Raw Data) is the output of the 4395 when I calibrated away the cabling as described in the drawing in entry 53. The high frequency junk is pickup from something; it shows up with the photodiode blocked.

The second transfer function is the first one with the following model divided out:
model=@(f) (i*f).*(1./(1+i*f/380e3)).*exp(-i*2*pi*f*60e-9)
The zero at zero is due to the EOM modulating in phase, not frequency.
The time delay was generated by roughly fitting to the data (to get a white phase response)
The pole at 380 kHz is the cavity pole of the PMC (experimentally determined in entry 56)

The measured time delay based on propagation of cables/free space is 41 ns, so there is an additional time delay of 19 ns +/- 10 ns in our model.
This corresponds to a phase shift of 0.7 degrees at 100 kHz

As we can see from the transfer function - there is clearly more going on than our model takes into account (probably a number of poles). Adding poles would put a tighter constraint on the time delay, which is fine/good.




Quote:
I used the experimental setup below to measure the transfer function between the EOM (which is before the amplifier) and the reflections off the PMC. The light blue line is what I shorted to each other when I used the 4395's calibrate feature to correct for the cabling/rf components.

The "modulation summation box" is shown below the schematic. I will update this later when I figure out what the components are.
Attachment 1: RawTF.png
RawTF.png
Attachment 2: corrtf.png
corrtf.png
  63   Thu Jul 17 16:44:27 2008 DmassLaserPSLLaser is off
Leaving laser off while I hack at screens downstairs. Feel free to turn on for anything.

I also turned the ISS drive box off.
  68   Fri Jul 25 15:23:14 2008 DmassLaserPSLNew Vertical PSL
With the installation of the new "clear top" on the PSL (see picture), an interesting design feature has come to light.

There are a few noteworthy things about this feature:

-We have a vertically oriented window after the NPRO.
-The vertically oriented window shoots some beam up.
-The new clear top appears to be transparent to IR.
-The HEPA filter is right above the window.

Possible worries:

-Light leaking back into the NPRO.
-Dumping beam onto the HEPA filter might not be the best thing.

It might be a good idea to do a proper dumping of that beam. I am unsure as to whether it would be better to do so inside or outside the enclosure.
Attachment 1: NPRO.png
NPRO.png
Attachment 2: HEPA.png
HEPA.png
  69   Fri Jul 25 17:07:34 2008 DmassLaserPMCCavity Pole Measurement on the PMC

Quote:
Measurement of the PMC cavity pole:

The following was done at powers of .234 W and .42 W.
I turned the laser power on the table down low (using a polarizer and a PBS to dump the majority of the beam).

I then used a function generator to input a triangle wave into the Piezo driver and sweep the cavity. This was done at a frequency of .04 Hz (for reasons dictated by dataviewer).

I found the HWHM (half width half max) of the transmitted intensity (when the DC bias was subtracted out) to be 0.00054 and 0.00053 free spectral ranges for .234 and .42 W, respectively.
I also noticed some nonlinearity in the PMC/Piezo as I scanned through more FSR's, and thus used the data from the bias voltages closest to zero.

I calculated the FSR frequency to be 713.8 MHz (in agreement to what we have on file for the PMC at the 40m).

Using the equality \delta L / L = \delta f / f, I get pole frequencies of 385 kHz and 378 kHz for .234 and .42 W, which is about a 2% agreement between measurements.

Again - the cavity pole was measured to be about 380 kHz to within a couple percent. - this differs significantly from the pole quoted for the 40m PMC at
http://www.ligo.caltech.edu/~ajw/PSLPMC.png (which is 488 kHz)


I looked back at the old data, and measured the V/cts ratio of the ADC (which at low frequency was 0.000622 V/ct). Using this, and the data from the above measurement of the cavity pole, the response of the PMC PZT is about 3.235 V/FSR.

Nota Bene:

The old data from the sweep of the PMC was taken by driving with a function generator, and tee-ing off the output of the generator to the ADC. However, I got the data from the output of one of the ADC channels, so it was post filtration. I am ALMOST POSITIVE that all gains were unity, but there is some small but finite possibility that one of them was not, and this would bebunk my number for Volts per free spectral range.
  71   Tue Jul 29 00:47:37 2008 MashaLaserFibermach zehnder setup
As per dmass's prodding, I am putting up some pictures of what I'm doing.

Currently there is a working Mach Zehnder, but it needs to be improved.
Right now the fluctuations due to phase are about 15% of the total DC voltage,
where they were over 50% back at the 40m.On the list are more stable mounts
and better mode matching for fiber input and output with the laser. Also, we
will be putting in an AOM in the fiber arm.
Attachment 1: setup1.JPG
setup1.JPG
Attachment 2: setup3.JPG
setup3.JPG
Attachment 3: setup4.JPG
setup4.JPG
  72   Tue Jul 29 00:58:36 2008 MashaLaserFiberfirst fiber noise measurement
I'm attaching the fiber noise measurement from one mach zehnder channel
along with some noise sources. The total rms phase noise comes out to about
0.075 radians, which translates to a frequency noise of 20Hz rms.

I will take spectra at lower frequencies once the DAQ is back up so I don't
have to wait an hour for the spectrum analyzer.
Attachment 1: MZnoise_sources0727.png
MZnoise_sources0727.png
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