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  10894   Tue Jan 13 13:22:54 2015 JenneUpdateGeneralAUX Y + PSL beat note at 1064nm: needs work

I'm super excited about this new frequency readbacklaugh, but I'm not sure that it's reliable yetfrown.  Without touching any settings, the readback is currently saying 78.6MHz, and is changing slightly (as is the FSS Slow Temp), so something is working.  However, the beatnote as measured on the spectrum analyzer is 158.2MHz.  So, either the calibration or the tracking or something isn't quite finished being tuned yet.cheeky

It's going to be super awesome when we have this though!!cool

  10895   Tue Jan 13 14:01:20 2015 manasaUpdateGeneralAUX Y + PSL beat note at 1064nm: needs work
Quote:

I'm super excited about this new frequency readback, but I'm not sure that it's reliable yet.  Without touching any settings, the readback is currently saying 78.6MHz, and is changing slightly (as is the FSS Slow Temp), so something is working.  However, the beatnote as measured on the spectrum analyzer is 158.2MHz.  So, either the calibration or the tracking or something isn't quite finished being tuned yet.

It's going to be super awesome when we have this though!!

As Jenne pointed out, this is still not fully tuned. 

For example, I found today that the frequency counter requires more power at the input >= -20dBm to measure frequency inputs < 40 MHz. Since the RFPD gives ~ -40dBm at its output, the ~20dB gain amplifier will not be enough to measure low frequencies in case the beat power at the PD drops (which is very much possible when the alignment drifts or things move around on the PSL table).  So I am shopping for an RF amplifier with higher gain to replace the current one. In the meantime, I will test the PID loop for set point frequency > 40MHz.

I have also observed the frequency difference between the measured frequencies on FC and the spectrum analyzer. I am not sure where this comes from as yet. 

At this point, the FC readout is only reliable enough to find a beatnote that is lost on the spectrum analyzer.

  11921   Fri Jan 8 14:47:33 2016 ericqUpdateLSCAUX Y Freq Noise measured

Here are some results from measuring the PSL / AUX Y beat. 

With the Y end laser, I was able to lock the PLL with a lower actuation range (1.6MHz/V), and with the PSL in both the free-running and MCL locked configurations. (In the latter, I had to do a bit of human-turning-knob servo to keep the control signal from running away). I also took a spectrum with the marconi detuned from the beat frequency, to estimate the noise from the PD+mixer+SR560. 

It looks like the AUX X laser is about 3 times noisier than the Y, though the Y laser looks more like a 10^5 noise-frequency product, whereas I thought we needed 10^4. 

Gautam is investigating the PSL / AUX PSL beat with Koji's setup now. 

Attachment 1: AUX_freqnoises.pdf
AUX_freqnoises.pdf
Attachment 2: AUXY_Jan8.zip
  11922   Fri Jan 8 20:02:49 2016 ranaUpdateLSCAUX Y Freq Noise measured

Unless this is the limit from the way you guys set up the PLL, it seems like there's no difference between the two lasers that's of any import. So then the locking problem has been something else all along - perhaps its noise in the X-PDF lock somehow? PDH box oscillations?

  11924   Sat Jan 9 00:39:15 2016 gautamUpdateLSCAUX Y Freq Noise re-measured
Quote:

With the Y end laser, I was able to lock the PLL with a lower actuation range (1.6MHz/V), and with the PSL in both the free-running and MCL locked configurations.

I took spectra (attached) with the same actuation range (3.2 MHz/V) for the AUX X+PSL and AUX Y+PSL combinations (PSL shutter closed) just to keep things consistent. It looks like there is hardly any difference between the two combinations - could the apparent factor of 3 worse performance of the X end laser have been due to different actuation ranges on the Marconi? 

I've not managed to take a spectrum for the proposed replacement Lightwave laser on the PSL table, though with Eric's help, I've managed to find the beatnote (at a temperature of 53.0195 degrees). I had to do some minor alignment tweaking for this purpose on the PSL table - the only optics I touched were the ones in the pink beam path in attachments 1 and 2 in this elog (the setup used to make the measurement is also qualitatively similar to attachment 3 in the same elog, except for the fact that we are feeding back to the Marconi and not the laser - a detailed sketch with specific components used will be put up later). I'll try and measure the frequency noise of this laser as well over the weekend and put up some spectra. 

With regards to possibly switching out the Lightwave on the PSL table for the (faulty?) Innolight at the X end, I've verified the following:

  • The beam-height from the Lightwave on the mount it is currently sitting on is the same as that from the Innolight on the X end table.
  • There is sufficient space on the X end table to house the Lightwave laser+mount

It remains to characterize the beam coming out from the Lightwave laser and do a mode matching calculation to see if we can use the same optics currently in place (with slight rearrangement) to realize a satisfactory mode-matching solution - I've obtained a beam profiler to do this from Liyuan and have the software setup, but have yet to do the beam scan - the plan is to do this on the SP table, but we've put off moving the Lightwave laser off the PSL table until we (i) establish conclusively that the X end laser is malfunctioning and (ii) check the frequency nosie of the Lightwave relative to the Aux lasers currently at the ends. 

The area around the Marconi is in a little disarray at the moment with a bunch of cables, SR560s, analyzers etc - I didn't want to disconnect the measurement setup till we're done with it. I have however turned both IR beat PDs on the PSL table off, and have reconnected the Marconi output to the Frequency Generation Unit and have set the carrier back to 11.066209MHz, +13dBm. 

Attachment 1: AuxPLL.pdf
AuxPLL.pdf
  10299   Wed Jul 30 18:09:08 2014 HarryUpdateGeneralAUX and PSL Coupling Telescopes

 Purpose

These telescopes will be used to mode match//couple the dumped SHG light from both PSL and AUX (Y-Arm) lasers into PM fibers for use in FOL.

Methods

Using the waist measurements I made yesterday (29/7/14) as seed waists, I used a la mode to design coupling telescopes.

These are designed to match the output mode of the fibers with collimators.

AUXTelescope.m    PSLTelescope.png

 

 

ALM files are attached in .zip file.

AUXTelescopePlot.png PSLTelescopePlot.png

Moving Forward

Once the fibers are coupled, I will continue in assembling the Y-Arm FOL setup, using fiber coupled beam combiner and photodiodes.

I will also do the same procedure for the X-Arm, access permitting.

Attachment 2: AUXTelescope.png
AUXTelescope.png
Attachment 3: telescopes.zip
  13968   Thu Jun 14 22:45:05 2018 johannesUpdateGeneralAUX beam SRC alignment

[Jon, Gautam, Johannes]

Jon spent some time trying to align the AUX beam to the SRC today, I got to the game kind of late so maybe others can add more detail.

The AUX beam that is reflected by the SRM looks terribly misshapen - it is quite elongated in vertical direction. Unfortunately I didn't snap a picture of it - anybody? It seemed at first as if this could be clipping - but after confirming the alignment of the AUX beam with the PSL output beam with aligned SRM, a slow dither of the SRM just moved the ugly pattern on the AS camera with no change to its shape - so clipping is unlikely. I'm now thinking that this is just the output beam of the fiber coupler after propagating ~15 meters to the SRM and back - even though this aspheric lens triplet coupler is supposed to be super-duper. I found that if I loosen the fiber slightly and pull it back just a bit at least the spot on the AS camera becomes nice and round - so maybe the fiber just doesn't sit well in this collimator? Not sure why that would be. I checked the fiber tip with the microscope, and while there was some gunk present, the central region and the core were clear (still cleaned using the fiber cleaning kit, which got rid of the debris). Either way, before switching to a different collimator I think we should give the Guoy phase measurement a shot - after all there was plenty of RF signal present on both AS110 and the PDA10CF placed at the YEND.

Looking for rogue beams on the AS table, I started placing some beam dumps. There was one particularly strong source of stray beams - a lens that was labeled with KPX094AR.33_F100. It became apparent after alignment efforts to the IFO had moved the AUX beam signifcantly off-center on this lens. According to the label it should have an AR coating for 1064nm, however judging by the amount of reflected light, it was certainly NOT AR-coated for 1064nm. I replaced it with a bi-convex f=100mm lens with confirmed AR-behavior.

The AUX laser is currently shuttered.


Per our Wednesday meeting, some items to work on are

  • Align the zero-order AUX beam into a second collimator on the PSL table, so we can switch the fiber output and look for RF signals at the offset-phaselock frequency without the additional frequency shift from the AOM. This will simpligy the mode spectroscopy scheme significantly
  • Abandon the R10/T90 beamsplitters in favor of R90/T10 beamsplitters. We'll swap the large mirror in front of the AS camera with an R90/T10 BS, and follow it up with a second R90/T10 BS that sends the AUX beam to the IFO. This way we'll have identical power levels on AS110 and AS55, and still 90% of the current AUX light going into the IFO, but without strong secondary beams from R10/T90 optics.
  13987   Tue Jun 19 18:56:55 2018 JonUpdateGeneralAUX beam alignment issues

Not much progress today with the AUX cavity scans. I've determined there still are some alignment issues.

At the start of today a large AUX/PSL beat note was visible on the AS110 sensor, at a similar power as where we left off last night (-60 dBm). Proceeding from there, I attempted to reproduce Johannes' measurement of the cavity transmission resonances. I misaligned the X-arm, locked the Y-arm cavity, and scanned the AUX RF offset approximately 8 MHz in 2 kHz steps. This should have swept through two FSRs, but nothing was visible.

Further inspection revealed that none of the PSL light was making it back to through the AUX fiber to the PSL table. I take this to mean that the beam seen earlier on AS110 was the ITMY reflection, and that the AUX injection axis was no longer reaching ETMY. I also found that the AUX beam size just after the 90/10 beasmsplitter looks anomolously large. Maybe a lens was recently changed? In any case, the mode-matching looks like it is going to need to be readjusted.

  13989   Wed Jun 20 00:57:04 2018 johannesUpdateGeneralAUX beam alignment issues

We did swap a lens as discussed in elog 13968, but they both had f=100mm specified, the difference being one was AR-coated for 1064 and bi-convex, while the other one was plano-convex and had a different coating. The reason for the large beam spot was something else: The fiber wasn't sitting in the coupler properly. When reconnecting the fiber after taking it out make sure to align the key on the fiber end with the notch in the coupler before tightening. After discovering this the following was done:

  • Fixed fiber mounting situation
  • Tested AUX alignment into fiber on PSL table, was still good
  • The AUX polarization was aligned to the wrong fiber axis. I fixed this. The coupler on the PSL table has it's noth oriented vertically since we're using s-polarized light. The AS-table coupler is rotated by 90 degrees, such that the notch points to the side. This way we technically don't need any halfwaveplates for rotation. However, there are still current HWPs installed.
  • Locked both arms and ran dither alignment until satisfactory
  • Misaligned ITMX and ETMX, and further set the ITMX pitch offset to 0.0
  • Started overlapping the expectedly misaligned beams by eye. For this I turned the power of the deflected beam down to 50mV bias voltage, which gives the PSL and AUX lasers similar card-brightness on the shared path
  • Misaligned SRM more because there was still the strong prompt reflection coming out the AS port.
  • Restored phaselock between AUX and PSL, with beat at 30MHz between 1st-order diffracted in fiber and PSL
  • Immediately saw STRONG 30MHz RF signal on AG4395. Disappeared when blocking AUX, and optimized alignment brought the signal up to -10dBm, as shown in attachment #1
  • Checked YEND PDA10CF and saw a -80dBm RF signal at 30 MHz (#2), compatible with earlier observations.

Before leaving I restored the XARM alignment. SRM remains misaligned, LSC off. Alignment shouldn't change drastically over night, so I suggest when picking this work up tomorrow to directly look for the beats after phaselocking AUX and PSL

Attachment 1: as110_rf_30MHz.pdf
as110_rf_30MHz.pdf
Attachment 2: yend_rf_30MHz.pdf
yend_rf_30MHz.pdf
  14013   Sun Jun 24 23:13:46 2018 johannesUpdateGeneralAUX beam alignment issues

At some point we want to change the AUX injection on the AS table to interfere less with the normal interferometer path, and avoid 10/90 beamsplitters which produce a fair amount of ghosting. The plan is to replace the 99/1 BS whose reflection goes to AS110 and AS55, while the transmission goes to the AS camera, with a 90/10 BS as shown in the attachment. This results in ~10% less light on the PDs compared to the pre-AUX era. Between this BS and the AS camera there will be a second 90/10 BS that sends the AUX light into the IFO, so we end up with marginally less AUX power into the IFO and the same PSL power on the AS cam. We're short optics, so this has to wait until two new beamsplitters arrive from CVI.

Attachment 1: AS_AUX_SETUP.pdf
AS_AUX_SETUP.pdf
  14045   Sun Jul 8 22:27:25 2018 keerthanaUpdate AUX diagram

(Analisa, Keerthana, Sandrine)

So far we tried four different techniques to scan the AUX laser. They are,

1. Scanning the marconi frequency to sweep the central frequency of the AUX laser.

2. Sweeping the side band frequency of the AUX laser by providing RF frequency from the spectrum analyser.

3. Double demodulation technique.

4. Single demodulation technique.

Now we are taking all the scan data with the help of Single demodulation technique.

Attachment 1: PLL-single_demodulation.pdf
PLL-single_demodulation.pdf
Attachment 2: PLL-double_demodulation.pdf
PLL-double_demodulation.pdf
  13834   Fri May 11 18:17:07 2018 gautamUpdateDetCharAUX laser PLL setup

[koji, gautam]

As discussed at the meeting earlier this week, we will use some old *MOPA* channels for interfacing with the PLL system Jon is setting up. He is going to put a sketch+photos up here shortly, but in the meantime, Koji helped me identify a channel that can be used to tune the temperature of the Lightwave NPRO crystal via front panel BNC input. It is C1:PSL-126MOPA_126CURADJ, and is configured to output between +/-10V, which is exactly what the controller can accept. The conversion factor from EPICS value to volts is currently set to 1 (i.e. EPICS value of +1 corresponds to +1V output from the DAC). With the help of the wiring diagram, we identified pins 3 and 4 on cross-connect #J7 as the differential outputs corresponding to this channel. Not sure if we need to also setup a TTL channel for servo ENABLE/DISABLE, but if so, the wiring diagram should help us identify this as well. 

The cable from the DAC to the cross-connect was wrongly labelled. I fixed this now.

  14501   Fri Mar 29 15:47:58 2019 gautamUpdateAUXAUX laser fiber moved from AS table to PSL table

[anjali, gautam]

To facilitate the 1um MZ frequency stabilization project, I decided that the AUX laser was a better candidate than any of the other 3 active NPROs in the lab as (i) it is already coupled into a ~60m long fiber, (ii) the PSL table has the most room available to set up the readout optics for the delayed/non-delayed beams and (iii) this way I can keep working on the IR ALS system in parallel. So we moved the end of the fiber from the AS table to the SE corner of the PSL table. None of the optics mode-matching the AUX beam to the interferometer were touched, and we do not anticipate disturbing the input coupling into the fiber either, so it should be possible to recover the AUX beam injection into the IFO relatively easily.

Anjali is going to post detailed photos, beam layout, and her proposed layout/MM solutions later today. The plan is to use free space components for everything except the fiber delay line, as we have these available readily. It is not necessarily the most low-noise option, but for a first pass, maybe this is sufficient and we can start building up a noise budget and identify possible improvements.

The AUX laser remians in STANDBY mode for now. HEPA was turned up while working at the PSL table, and remains on high while Anjali works on the layout.

  14504   Sun Mar 31 18:39:45 2019 AnjaliUpdateAUXAUX laser fiber moved from AS table to PSL table
  • Attachment #1 shows the schematic of the experimental setup for the frequency noise measurement of 1 um laser source.

  • AUX laser will be used as the seed source and it is already coupled to a 60 m fiber (PM980). The other end of the fiber was at the AS table and we have now removed it and placed in the PSL table.

  • Attachment # 2 shows the photograph of the experimental setup. The orange line shows the beam that is coupled to the delayed arm of MZI and the red dotted line shows the undelayed path.

  • As mentioned, AUX is already coupled to the 60 m fiber and the other end of the fiber is now moved to the PSL table. This end needs to be collimated. We are planning to take the same collimator from AS table where it was coupled into before. The position where the collimator to be installed is shown in attachment #2. Also, we need to rotate the mirror (as indicated in attachment #2) to get the delayed beam along with the undelayed beam and then to combine them. As indicated in attachment #2, we can install one more photo diode to perform  balanced detection.

  • We need to decide on which photodetector to be used. It could be NF1801 or PDA255.

  • We also performed the power measurement at different locations in the beam path. The different locations at which power measurement is done is shown attachment #3

  • There is an AOM in the beam path that coupled to the delayed arm of MZI. The output beam after AOM was coupled to the zero-order port during this measurement. That is the input voltage to the AOM was at 0 V, which essentially says that the beam after the AOM is not deflected and it is coupled to the zero-order port. The power levels measured at different locations in this condition are as follows. A)282 mW B)276 mW C)274 mW D)274 mW E)273 mW F)278 mW G)278 mW H)261 mW I)263 mW J)260 mW K)131 mW L)128 mW M)127 mW N)130 mW

  • It can be seen that the power is halved from J to K. This because of a neutral density filter in the path of the beam

  • In this case, we measured a power of 55 mW at the output of the delayed fiber. We then adjusted the input voltage to the AOM driver to 1 V such that the output of AOM is coupled to the first order port. This reduced the power level in the zero-order port of AOM that is coupled to the delayed arm of the MZI. In this case we measured a power of 0.8 mW at the output of delayed fiber.

  •  We must be careful about the power level that is reaching the photodetector such that it should not exceed the damage threshold of the detector.

  • The power measured at the output of undelayed path is 0.8 mW.

  • We also must place the QWP and HWP in the beam path to align the polarisation.

Quote:

[anjali, gautam]

To facilitate the 1um MZ frequency stabilization project, I decided that the AUX laser was a better candidate than any of the other 3 active NPROs in the lab as (i) it is already coupled into a ~60m long fiber, (ii) the PSL table has the most room available to set up the readout optics for the delayed/non-delayed beams and (iii) this way I can keep working on the IR ALS system in parallel. So we moved the end of the fiber from the AS table to the SE corner of the PSL table. None of the optics mode-matching the AUX beam to the interferometer were touched, and we do not anticipate disturbing the input coupling into the fiber either, so it should be possible to recover the AUX beam injection into the IFO relatively easily.

Anjali is going to post detailed photos, beam layout, and her proposed layout/MM solutions later today. The plan is to use free space components for everything except the fiber delay line, as we have these available readily. It is not necessarily the most low-noise option, but for a first pass, maybe this is sufficient and we can start building up a noise budget and identify possible improvements.

The AUX laser remians in STANDBY mode for now. HEPA was turned up while working at the PSL table, and remains on high while Anjali works on the layout.

 

Attachment 1: Schematic_of_experimental_setup_for_frequency_stabilisation_of_1_micron_source.png
Schematic_of_experimental_setup_for_frequency_stabilisation_of_1_micron_source.png
Attachment 2: 1_micron_setup_for_frequency_noise_measurement.JPG
1_micron_setup_for_frequency_noise_measurement.JPG
Attachment 3: 1_micron_setup_for_frequency_noise_measurement_power_levels.png
1_micron_setup_for_frequency_noise_measurement_power_levels.png
  13948   Tue Jun 12 03:22:25 2018 gautamUpdateLSCAUX laser shuttered

I worked a bit on recovering the DRMI locking again tonight. I decided to shutter the AUX laser on the PSL table at least until I figured out the correct locking settings. As has become customary now, there was a cable in the AS beampath (leading from the AS55 DC monitor to nothing, through the enclosure side panel, it is visible in Attachment #3 in this elog) which I only found after 30mins of futility - please try and remove all un-necessary cables and leave the AS beampath in a usable state after working on the AS table! angry In the end, I got several short (~3mins) stretches in tonight, but never long enough to do the loop characterization I wanted to get in tonight, probably wrong gains in one or more of the loops. In the last 30 minutes, the IMC has been frequently losing lock, so I am quitting for now. The AUX laser remains shuttered.

  13900   Thu May 31 02:04:55 2018 johannesUpdatePSLAUX laser state of mind

The AUX laser is down to 5.4 mW output power sad

What's worse, because we wanted those fast switching times by the AOM for ringdowns, I made the beam really small, which

  1. came with a severe tradeoff against conversion efficiency. I tried to squeeze the last out of it today, but there's only about 1.3 mW of diffracted light in the first order that reaches the fiber, with higher diffraction orders already visible.
  2. produced a very elliptical mode which was difficult to match into the fiber. Gautam and I measured 600 uW coming out of the fiber on the AS table. This per se is enough for the SRC spectroscopy demonstration, but with the current setup of the drive electronics there's no amplitude modulation of the deflected beam.

When going though the labs with Koji last week I discovered a stash of modulators in the Crackle lab. Among them there's an 80 MHz AOM with compact driver that had a modulation bandwidth of 30MHz. The fall time with this one should be around 100ns, and since the arm cavities have linewidths of ~10kHz their ringdown times are a few microseconds, so that would be sufficient. I suggest we swap this or a similar one in for the current one, make the beam larger, and redo the fiber modematching. That way we may get ~3mW onto the AS table.

I think I want to use AS110 for the ringdowns, so in the next couple days I'll look into its noise to get a better idea about what power we need for the arm ringdowns.

Attachment 1: IMG_20180530_220058190.jpg
IMG_20180530_220058190.jpg
  14085   Thu Jul 19 01:56:25 2018 gautamSummaryVACAUX pump shutdown

[koji, gautam]

Per Steve's instructions, we did the following:

  • TP3fl pressure reading was 65 torr.
  • TP3 controller reported pumping current of ~0.18A, temperature of 24C.
  • We throttled the manual valve which was connecting the "AUX" pump to the TP3fl.
  • The TP3fl pressure went up to 330 torr.
  • TP3fl controller reported current of 0.22A, temperature of 24C.
  • After ~5mins, we shut the AUX pump off.
  • We have monitored it over the last 1hour, no red flags.
    • (Before stopping AUX RP)
      0:56AM TP3 I=0.18A, P=6W, 23degC, TP3FL: 66
    • 0:59AM TP3 I=0.22A, P=7W, 23degC, TP3FL: 336
    • 1:15AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 320
    • 1:31AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 310
    • 2:06AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 301
    • 5:06AM TP3 I=0.21A, P=7W, 23degC, TP3FL: 275
  13867   Fri May 18 19:59:55 2018 Jon RichardsonConfigurationElectronicsAUX-PSL PLL Characterization Measurements

Below is analysis of measurements I had taken of the AUX-PSL PLL using an SR560 as the servo controller (1 Hz single-pole low-pass, gain varied 100-500). The resulting transfer function is in good agreement with that found by Gautam and Koji (#13848). The optimal gain is found to be 200, which places the UGF at 15 kHz with a 45 deg phase margin.

For now I have reverted the PLL to use the SR560 instead of the LB1005. The issue with the LB1005 is that the TTL input for remote control only "freezes" the integrator, but does not actually reset it. This is fine if the lock is disabled in a controlled way (i.e., via the medm interface). However, if the lock is lost uncontrollably, the integrator is stuck in a garbage state that prevents re-locking. The only way to reset this integrator is to manually flip a switch on the controller box (no remote reset). Rana suggests we might be able to find a workaround using a remote-controlled relay before the controller.

Attachment 1: SR560_OL.pdf
SR560_OL.pdf
Attachment 2: SR560_CL.pdf
SR560_CL.pdf
  13814   Fri May 4 13:24:56 2018 Jon RichardsonConfigurationElectronicsAUX-PSL PLL Implementation & Characterization

Attached are final details of the phase-locked loop (PLL) implementation we'll use for slaving the AUX 700 mW NPRO laser to the PSL.

The first image is a schematic of the electronics used to create the analog loop. They are curently housed on an analyzer cart beside the PSL table. If this setup is made permanent, we will move them to a location inside the PSL table enclosure.

The second image is the measured transfer function of the closed loop. It achieves approximately 20 dB of noise suppression at low frequencies, with a UGF of 50 kHz. In this configuration, locks were observed to hold for 10s of minutes.

Attachment 1: PLL_Schematic.pdf
PLL_Schematic.pdf
Attachment 2: PLL_AUX-PSL_40m.pdf
PLL_AUX-PSL_40m.pdf
  13816   Fri May 4 19:06:28 2018 ranaConfigurationElectronicsAUX-PSL PLL Implementation & Characterization

this doesn't make much sense to me; the phase to frequency conversion (mixer-demod to PZT ) should give us a 1/f loop as Johannes mentioned in the meeting. That doesn't agree with your loop shape.

How about give us some more details of the setup including photos and signal/power levels? And maybe measure the LB1005 TF by itself to find out what's wrong with the loop.

  13567   Mon Jan 22 20:54:58 2018 KojiSummaryGeneralAUX-PSL beat setup

The beat setup has been made on the PSL table. The BS and the PD were setup. The beat was found at 29.42degC and 50.58degC for the PSL and AUX crystal temperatures, respectively.
We are ready for the EOM test. I have instruments stacked around the PSL table. Please leave them as they are for a while. If you need to move them, please contact with me. Thanks.


A picked-off PSL after the main modulator was used as the PSL beam. This was already introduced close to the setup thanks to the previous 3f cancellation test ELOG 11029. The AUX beam was obtained from the transmission of 90% mirror. Both paths have S polarization. The beams are combined with a S-pol 50% BS. The combined beam is detected by a new focus 1GHz PD.

The PSL crystal temp (actual) was 50.58degC. The AUX crystal temp was swept upward and the string beat was found at 50.58degC. After a bit of alignment, the beat strength was -18dBm (at 700V/A RF transimpedance of NF1611) .

Attachment 1: IMG_3051.JPG
IMG_3051.JPG
  11944   Fri Jan 22 11:33:20 2016 gautamUpdateGreen LockingAUX-X AM/PM investigations

I was trying to characterize the AM/PM response of the X end laser. I tried to measure the AM response first, as follows:

  • I used the Thorlabs PDA 55, whose datasheet says it has 10MHz bandwidth - I chose it because it has a larger active area than the PDA 255, but has sufficient bandwidth for this measurement. 
  • My earlier measurement suggested the IR power coming out of the laser is ~300mW. As per the datasheet of the PDA 55, I expect its output to be (1.5 x 10^4 V/A) * (~0.25 A/W) ~ 4000 V/W => I expect the PD output (driving the 50ohm input of the Agilent NA) to saturate at ~1.3mW. So I decided to use a (non-absorptive) ND 3.0 filter in front of the PD (i.e. incident power on the PD ~0.3 mW).
  • I measured the AM response (inputA/inputR) by using the RF output from the Agilent analyzer (divided using a mini-circuits splitter half to input R and half to the laser PZT), and the PD output to input A. I set the power of the RF output on the analyzer to 0 dBm. 
  • Attachment #1 shows the measured AM response. It differs qualitatively in shape from the earlier measurements reported in this elog and on the wiki below the 100kHz region. 
  • I also took a measurement of the RIN with no drive to the laser PZT (terminated with a 50ohm terminator) - see Attachment #2. Qualitatively, this looks like the "free-running" RIN curve on the Innolight datasheet (see Attachment #3, the peak seems slightly shifted to the left though), even though the Noise Eater switch on the laser controller front panel is set to "ON". I neglected taking a spectrum with it OFF, I will update this elog once I do (actually I guess I have to take both spectra again as the laser diode and crystal temperatures have since been changed - this data was taken at T_diode = 28.5deg, I_diode = 1.90A, and T_crystal = 47.5 deg). But does this point to something being broken?
  • I was unable to lock the PLL yesterday to measure the PM response, I will try again today.
Attachment 1: AUX_X_AM.pdf
AUX_X_AM.pdf
Attachment 2: AUX_X_RIN.pdf
AUX_X_RIN.pdf
Attachment 3: NE_Mephisto.png
NE_Mephisto.png
  11945   Fri Jan 22 13:33:37 2016 ericqUpdateGreen LockingAUX-X AM/PM investigations
Quote:

Attachment #1 shows the measured AM response. It differs qualitatively in shape from the earlier measurements reported in this elog and on the wiki below the 100kHz region. 

It looks like some of the features may have shifted in frequency. The previous measurement results can be found in /users/OLD/mott/PZT/2NPRO, can you plot the two AM measurements together?

  11946   Fri Jan 22 17:22:06 2016 gautamUpdateGreen LockingAUX-X AM/PM investigations

There were a number of directories in /users/OLD/mott/PZT/2NPRO, I've used the data in Innolight_AM_New. Also, I am unsure as to what their "calibration" factor is to convert the measured data into RIN, so I've just used a value of 0.8, with which I got the plot to match up as close as possible to the plot in this elog. I also redid the measurement today, given that the laser parameters have changed. The main difference was that I used an excitation amplitude of +15dBm, and an "IF Bandwidth" of 30Hz in the parameter files for making these measurements, which I chose to match the parameters Mott used. There does seem to be a shift in some of the features, but the <100kHz area seems similar to the old measurement now. 

Having put the PD back in, I also took measurements of the RIN with the input to the laser PZT terminated. There is no difference with the Noise Eater On or OFF! 

Quote:
Quote:

Attachment #1 shows the measured AM response. It differs qualitatively in shape from the earlier measurements reported in this elog and on the wiki below the 100kHz region. 

It looks like some of the features may have shifted in frequency. The previous measurement results can be found in /users/OLD/mott/PZT/2NPRO, can you plot the two AM measurements together?

 

Attachment 1: AM_response.pdf
AM_response.pdf
Attachment 2: NE_investigations.pdf
NE_investigations.pdf
  11947   Fri Jan 22 18:46:03 2016 ranaUpdateGreen LockingAUX-X AM/PM investigations

The PDA photodetectors are DC coupled, so you cannot use them to go directly into the analyzer. Must use the DC block so that you can reduce the input attenuation on the B channel and then lower the drive amplitude.

Good policy for TF measurements: drive as softly as you can and still measure in a reasonable amount of time, but no softer than that.

  5600   Mon Oct 3 13:04:12 2011 JenneUpdateSUSAUXEX, AUXEY rebooted

Quote:

  + I found that burtrestore for the ETMX DC coil forces were not functional.

  => currently ETMX's "restore" and "mislalign" buttons on the C1IFO_ALIGN screen are not working.

  => According to the error messages, something seemed wrong on c1auxex, which is a slow machine controlling the DC force.

 [Suresh, Jenne]

Suresh pointed out the oddity that all of the EX, EY slow channels were showing white boxes on the medm screens on all of the workstations except Rosalba.  I don't know why Rosalba seemed to be working, but whatever.  I'm not 100% sure that Rosalba was even working properly....I shutdown ETMX and ETMY's watchdogs before we went to boot computers, but when I came back to the control room the 2 optics were rung up anyway.  Turning back on the watchdogs, the optics immediately began to damp happily.

Since Kiwamu had trouble with the slow channels for EX, we decided to key some crates. 

We keyed the c1auxey, and c1auxex crates, waited a few seconds, and then things looked okay in medm-land.  I looked at the "View Backup" for ETMX, and there were no values for the DC sliders, so since the arms are both flashing right now, I did a "save", and then confirmed that I can misalign and restore the optic.  However, since I didn't fully align/lock the cavity, the saved value for right now shouldn't be fully trusted.  We might have to manually align the cavity using the BS.

  9396   Fri Nov 15 13:26:00 2013 JenneUpdateCDSAUXEY is back

Quote:

Quote:

Please just try rebooting the vxworks machine.  I think there is a key on the card or create that will reset the device.  These machines are "embeded" so they're designed to be hard reset, so don't worry, just restart the damn thing and see if that fixes the problem.

 This is what I remember doing all the time when Rob was around, but with all the new computers, I forgot whether or not this was allowed for the slow computers.

Anyhow, I went down there and keyed the crate, but auxey isn't coming back.  I'll give it a few more minutes and check again, but then I might go and power cycle it again.  If that doesn't work, we may have a much bigger problem.

 I went and keyed the crate again, and this time the computer came back.  I burt restored to Nov 10th.  ETMY is damping again.

  10006   Fri Jun 6 14:56:09 2014 ericqUpdateelogAaaaaand we're back!

ELOG is back up and running after last Friday's disk-crash-a-thon. SVN is still a work in progress. Jenne and I are now restarting computers and such.

  2249   Thu Nov 12 10:45:02 2009 AlbertoUpdatePSLAbandoned Frequency Generator

This morning I found a frequency generator connected to something on the PSL table sitting on the blue step next to the sliding doors.

Is anyone using it? Has it been forgotten there? If that's the case, can the interested person please take care of removing it?

  2251   Thu Nov 12 11:19:10 2009 KojiUpdatePSLAbandoned Frequency Generator

Last night there was an activity for a calibratuon work, which I helped. I can take care of the FG.

Quote:

This morning I found a frequency generator connected to something on the PSL table sitting on the blue step next to the sliding doors.

Is anyone using it? Has it been forgotten there? If that's the case, can the interested person please take care of removing it?

 

  6129   Sat Dec 17 03:59:32 2011 kiwamuUpdateSUSAborted Hysteresis test

Quote from #6128

To test it, we are shaking all of the suspension biases +/-1.0 with a script.

The hysteresis test has been aborted.

All of the suspensions have accumulated unexpectedly big DC biases of about 5 from their nominal points.

In fact the ITMX and ITMY mirrors started being stacked to their OSEMs.
The script process has been force-quit and I have restored all the DC biases to their nominal points.
They still look okay: MC can be locked at the 00 mode, DRMI fringe is visible at AS, the green beams are resonating the arm cavities
Need another trial.
  6130   Sat Dec 17 11:53:46 2011 ZachUpdateSUSAborted Hysteresis test

Do you guys have timestamps for when you started/ended the test? I have been trying to take some long-term RAM data but keep getting foiled by stuff (this test, RTS upgrade, switching of RAMmon channels, etc.)

Quote:

Quote from #6128

To test it, we are shaking all of the suspension biases +/-1.0 with a script.

The hysteresis test has been aborted.

All of the suspensions have accumulated unexpectedly big DC biases of about 5 from their nominal points.

In fact the ITMX and ITMY mirrors started being stacked to their OSEMs.
The script process has been force-quit and I have restored all the DC biases to their nominal points.
They still look okay: MC can be locked at the 00 mode, DRMI fringe is visible at AS, the green beams are resonating the arm cavities
Need another trial.

 

  6131   Sat Dec 17 12:41:46 2011 KojiUpdateSUSAborted Hysteresis test

The test was from: 2011-12-17 09:48 to 11:49 (UTC).
This corresponds to the period from 2011-12-17 01:48 to 3:49 (PST).

ZK: Thanks

  12163   Thu Jun 9 18:54:40 2016 AakashUpdateGeneralAbout Acromag | SURF 2016

Today I tried to setup Acromag Busworks card. I was able to calibrate and test it over USB but I couldn't test it over ethernet. I'll utilize a few hours tomorrow to test it over ethernet and see if I can make it work. I have also found a few RTDs which I want to use for temperature sensing via four probe method. So, tomorrow I'll get these RTD details revived by Gautam and Steve.

I was wondering if we have a basic DAQ card with maybe 4 channels which is simple to setup like NI DAQ cards.

  12352   Fri Jul 29 03:44:04 2016 AakashSummary About Acromag | SURF 2016

I tried to recompile the modbusApp binary for linux-arm acrhitecture since I suspected someting wrong with it. But still the problem persists; I can connect to acromag but cannot access the channels. I have also reconfigured new acromag bus works terminal XT 1221-000 and I want to test if I could access its channels. My target is to complete this acromag setup work before sunday morning so that I can focus towards having some useful results for my presentation.
 

  1072   Thu Oct 23 15:27:19 2008 AlbertoUpdateGeneralAbs length
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.
Attachment 1: TRX_aplot_03_04_05_together.png
TRX_aplot_03_04_05_together.png
  1073   Thu Oct 23 18:23:47 2008 AlbertoUpdateGeneralAbs length

Quote:
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.


Today I repeated the measurement and I'm attaching the resulting plot. Still, not clear and (and most of all) not nice.
It seems like tilting ITMX is introducing a lot of unwanted higher modes that don't let us to clearly identify TEM01 and TEM10.
I think I'm going to stop it to get back to technique in which the arm cavity is locked to the TEM01/10 of the main beam.
Attachment 1: TRX_plot_06_07_08_together.png
TRX_plot_06_07_08_together.png
  1074   Thu Oct 23 18:27:04 2008 AlbertoUpdateGeneralAbs length

Quote:
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.


Here is the Matlab code I use to calculate the HOM frequencies.
Attachment 1: HOM_Frequencies.m
% FP Cavity HOM Frequencies Estimate
% Alberto Stochino, October 2008

R1 = 7280;      % Mirror1 radius of curvature
R2 = 57.57;     % Mirror2 radius of curvature
L = 38.458;     % Length of the FP Cavity
n = 1;          % X Order of the Mode
m = 0;          % Y Order of the Mode

c = 299792458;  % Speed of Light
... 11 more lines ...
  1084   Fri Oct 24 11:42:48 2008 AlbertoUpdateGeneralAbs length: locking the X arm cavity in TEM01/10
I went back to lock the arm cavity in either TEM01 or TEM10 mode. Attached are the results. We still have several resonances which we can't clearly identify. I expect TEM01/10 to be at 6.276MHz but we don't have a peak exactly there. What we have is:
- a peak at 6.320MHz in the measurement of the TEM01 mode (the one with the lobes of the spot almost on the vertical axis)
- a peak at 6.590MHz in both the TEM01 and TEM10 measurements.

I'm either missing the real TEM01/10 mode or the peaks at 6.590MHz are those. If that were true, that would mean that the radius of curvature of ETMX is 49.29 m instead of 57.57 m as listed in the IFO data sheets. I think it's much more likely that the measurements are missing the right peaks.
Attachment 1: TRX_armTEM00-plot_09-10_together.png
TRX_armTEM00-plot_09-10_together.png
  1086   Fri Oct 24 17:21:13 2008 AlbertoUpdateGeneralAbs length: the right amount of beam clipping
I found the reason why the peak at about 6.3MHz appeared only on the TEM10 mode: the blade was clipping the beam too much and it was probably totally killing the mode. I'm attaching a plot that shows that difference when I did that.
Attachment 1: 24OCT08_levels_of_clipping_comparison.png
24OCT08_levels_of_clipping_comparison.png
  1087   Fri Oct 24 18:05:01 2008 AlbertoUpdateGeneralAbs length: transverse mode spacing measured for the X arm
The ETMX suffers of astigmatism. I measured the following frequencies for the higher order modes:
- f_01 = 6317500 +/- 500 Hz
- f_10 = 6305500 +/- 500 Hz

From

g2=1/g1*(cos(A*L*pi/c))^2

where A= (fsr-f_i), fsr=(3897654+/-15)Hz (see elog entry 956), L=(38.4580+/-0.0003)m, g1=0.9947 (from R1=7280m), I get the following values for the g-factor coefficients:

g2_x = 0.3164 +/- 0.0002
g2_y = 0.3209 +/- 0.0002

from which we have the radius of curvature of ETMX:

R_x = 56.26 +/- 0.01 m
R_y = 56.63 +/- 0.01 m


The specs for the mirror have R2= 57.57 m (unc).

So, they seem conditions similar of those of ETMY that Koji measured:

Rx = 56.1620 +/- 0.0013 [m]
Ry = 57.3395 +/- 0.0011 [m]

for which L_yarm: 38.6462 m +/- 0.0003 m
Attachment 1: 24OCT08_TEM10-01_comparison(file12-14).png
24OCT08_TEM10-01_comparison(file12-14).png
  788   Mon Aug 4 00:56:07 2008 KojiHowToGeneralAbs. Len. Meas. ~ Auto freq scanner with GPIB
Work log on August 3rd - Part1

o Yesterday I was too much tired of changing the RF frequency, reading peaks on the RF spectrum, and writing the values. Rana saw me and thought I was such poor that he gave me an USB-GPIB adapter.

o I dig into the internet for the manuals of the adapter, IFR2023A(Marconi), and HP8591E(RF spectrum analyzer) in order to learn how to use them.

o I had LabVIEW installed on my laptop. Finally I understand how to use that adapter (by Agilent) with LabVIEW. I made a small program to scan the frequency of IFR2023A, and read the peak values from HP8591E. It is unfortunate that there is no LabVIEW in the 40m lab. I think I can make an independent executable which does not need the LabVIEW itself. Give me some time to understand how to do it.
Attachment 1: freq_scan.png
freq_scan.png
  556   Tue Jun 24 10:24:43 2008 KojiUpdateGeneralAbs. Len. Meas. ~ Cavity Swing Measurement (2)
At the entry 555, Alberto reported the results of the cavity length measurement using cavity sweeping.
As expected, each result inevitably has an ambiguity depending on which resonance do we take as an upper sideband.

In order to exclude this ambiguity Steve and Koji performed a primitive non-optical measurement using a tape and photos:
This morning Steve and Koji did tape measurements to know the lengths between the ITM/ETM chambers.
Yesterday, Koji took photos of the optical tables in vacuum to know the actual positions of the suspensions.

The results are shown in the figures attached. From those non-optical measurements the lengths of the X/Y arm are known to be 38.48+-0.03 / 38.67+-/0.03 [m].

Then, we could exclude the shorter lengths of the values in the entry 555. i.e. The Y arm is longer than the X arm about 0.2 m.

These approximate lengths will be used in the further precise measurements which use precise scans of the FSR frequencies.
Attachment 1: armlength.png
armlength.png
Attachment 2: armlength2.png
armlength2.png
  795   Tue Aug 5 00:05:57 2008 KojiUpdateGeneralAbs. Len. Meas. ~ IFR2023A calibration
Work log on August 4th

o IFR2023A (Marconi) was calibrated by the SR620 frequency counter which is locked to the GPS signal.
o The frequency of the IFR2023A was scanned from 1MHz to 20MHz with 1MHz interval. The readout of the frequency counter was recorded.
o The linear fit was taken.
f_freq_count = K0 + K1 * f_IFR [Hz]
K0 = 0.00        +/- 0.02
K1 = 0.999999470 +/- 0.000000001

o So, the IFR seems to have -0.5ppm systematic error.
  789   Mon Aug 4 05:23:57 2008 KojiUpdateGeneralAbs. Len. Meas. ~ Measurement for Y-arm completed
Finally, I have completed the abs length and g-factor measurements for Y-arm.
>>>GO FOR THE VENT<<<

I will report the results later.

Some notes on the status:
o Y-arm was aligned at the end of the experiment by the script. The values were saved.

o At the AP table, the injection beam and the flipper were left aligned so that the inj. beam can be used as a reference of the SRM and the ITMs. But the shutter of the NPRO was closed.

o The experiment setup was mostly left at the side of the AP table. I tried not to disturb the walk as much as possible.

o The long cable from the Y-end was wound and placed at the Y-end. The knife-edge was left on the Y-end bench. It is not disturbing any beam.
  748   Mon Jul 28 15:54:04 2008 KojiUpdateGeneralAbs. Len. Meas. ~ More on the beat / the PLL setup
Alberto and Koji,

Last Friday evening, Koji found that the power adj setting (indicated by ADJ) of the NPRO was somehow set to be 
ADJ=-45 and yielded the output power of about 200mW instead of 700mW. This is not good because too small pump power 
varies thermal conditions of the crystal such as thermal lensing, thermal gradient, and os on. The ADJ setting and the 
crystal temperature had been restored to ADJ=0 and LT=~48deg (nominal of the controller), respectively.

Today we tried the quest of the beating again and the above power setting helped a lot! The beating was immediately 
found at LT=48.55deg that is very close to the laser's nominal temp. Also the beating got significantly bigger. 
After the alignment adjustment 50%-intenisity modulated signal was obtained. From the power calculation it was 
estimated that the power coupling of the injected beam is to be 12%~13%. This not so good yet, but something which we 
can work.

This time the modulation structure of the PSL beam was clearly observed. I could obtain the beating of the injection 
beam with the carrier, the upper/lower sidebands of the 33MHz and 166MHz modulations, and the 2nd order of the 
33MHz. They were beautiful as if working with an OSA. Very nice.

In reality, those additional intenisty modulations as well as the residual 33MHz signal from the main IFO are 
disturbing for the PLL to be locked at the proper frequency. So, now Alberto is working on a passive LPF with 
notch at 33MHz. The design was already done. This allows us to work up to 20MHz and at the same time, provides 
60dB attenuation at 33MHz (in principle). Very cool.

Koji, on the other hand, continued to work with the PLL servo with some ready-made passive filters. Owing to the 
fillters, the error signal was cleaner and the PLL was locked at the proper frequency. The PLL setup is as attatched. 
Sideband rejection filter will be replaced to Alberto's one. The photo is the display of the RF spectrum analyzer with 
beat locked at 8MHz.

So the next step, we try to find the resonances of the arm cavity with the injection beam once the IFO comes back.

At the last of the experiment "Last autoalignment" was restored, the flipper for the 
inj beam was down, and the shutter for the NPRO was closed.
Attachment 1: PLL_setup.png
PLL_setup.png
Attachment 2: beat_at_8MHz.jpg
beat_at_8MHz.jpg
  782   Sat Aug 2 12:53:43 2008 KojiUpdateGeneralAbs. Len. Meas. ~ New PLL at the PSL table
Report of the work last night:
The new heterodyne interferometer on the PSL table was built.
The length of the Yarm cavity was measured with better precision.

-------------
Yarm is locked. The injection beam was aligned. The beat was there at around LT=48.9 [C_deg] of the NPRO.

The new PLL setup on the PSL table has been built. The two beams from the MC incident beam and the injection beam are
mode-matched with lenses. I measured the Rayleigh ranges of the beams by a sensor card and my eyes, and then placed
appropriate lenses so that they can have 5~6 [m] Rayleigh range. They looks a bit too thick but just ok for an inch
optics. The new PLL setup shows ~70% intensity modulation which is enormous. The servo is still SR560-based so far.

Now the PLL has no singular frequency within its range. I could sweep the 4th FSR of the cavity with 500Hz interval. I
was still observing at the transmitted DC.

At each freqency from 15.51MHz to 15.52MHz, a timeseries data of the Yarm transmitted was recorded at sampling of 32Hz for 10
seconds. The figure shows the averaged values of the transmitted DC with errors. An increase of the transmitted power by
3-4% was found. If we consider the resonance is at f_PLL = 15.515 +/- 0.0005 [MHz], this indicates the
arm cavity length of 38.6455 +/- 0.0012 [m].
Y-arm length
e-log    length [m]
-----------------------------
556      38.70   +/- 0.08   Cavity swinging measurement
556      38.67   +/- 0.03   tape & photo
776      38.640  +/- 0.007  Beam injection, poor PLL, Transmitted DC
this     38.6455 +/- 0.0012 Beam injection, independent PLL, Transmitted DC
-----------------------------

NEXT STEPS:
o RF detection at the transmitted
o Better PLL: PLL stability (in-loop / out-of-loop)
o Measurement for the 1st~3rd FSR
o Reproducibility of the measurement
o Higher order mode search
o Check the acuuracy and presicion of the Marconi
Attachment 1: yarm_dc.png
yarm_dc.png
  796   Tue Aug 5 02:39:55 2008 KojiConfigurationGeneralAbs. Len. Meas. ~ Optical Layout on the AP / PSL table 2008-Aug-05
Here are the PDF and the PNG of the AP and PSL table layouts.
After this photo, the squeezing setup at the AP table was removed.
Attachment 1: optical_layout_ap_table3.png
optical_layout_ap_table3.png
Attachment 2: optical_layout_ap_table3.pdf
optical_layout_ap_table3.pdf
Attachment 3: optical_layout_PSL_table1.png
optical_layout_PSL_table1.png
Attachment 4: optical_layout_PSL_table1.pdf
optical_layout_PSL_table1.pdf
  590   Sun Jun 29 02:33:28 2008 KojiUpdateGeneralAbs. Len. Meas. ~ Optical setup (I)
I have constructed the beam injection optics for the abs length measurement.

The injection beam was coarsely aligned to the interferometer. The reflected beam from SRM was already seen at AS CCD.
I have attached the optical configration for this measurement and the optics layout at the AP table.

I am going to go to LHO for three weeks. During the absence Alberto tunes the mode matching and the alignment of the interferometer.

In the process of making this report, I noticed that one of the iris apertures is about disturbing the beam for OMCR CCD. I will check this before I go to Hanford. Also an RF spectrum analyzer is at the AP table. I try to return this near the PSL on Monday morning.

Attachment 1: Optical configuration for the abs length measurement.
1) One of the arms is locked to the PSL beam by the main control system (red).
2) A laser beam is injected from the AS port (blue). This laser essentially has different frequency from that of PSL.
3) The injected beam and the outgoing PSL beam appear at the output of the faraday in the injection system.
4) They beat each other at the frequency difference of those two lasers.
5) A PLL is used to lock the frequency difference to a local oscillator (LO).
6) The LO frequency is swept at around 3.87MHz, that is the approximate FSR frequency of the arm cavity.
7) If the LO frequency hits the FSR within the resonant width, the beating also appears at the transmitted light as the injected beam also becomes resonant to the arm cavity.
8) Amplitude of the beating at the transmitted light is measured by a RF spectrum analyzer as a function of the LO frequency. We get the FSR frequency (= the arm cavity length) from the top of the resonance.

Attachment 2: Optics at the AP table for the laser injection
700mW NPRO, laser source. vertically polarized.
Periscope, to raise the beam 1 inch to make the beam at the 4 inch elevation.
INJ_SM1/INJ_SM2, steering mirrors to align the injection beam to the IFO beam.
HWP1, half wave plate to make the beam to the farady horiz-polarized. nominal 42deg on the readout.
FI, Faraday isolator for protection of the NPRO from the returning light, for obtaining the returning light.
HWP2, to make the beam from the Faraday horiz-polarized. nominal 357deg on the readout.
MM_Lens, f=125mm to match the laser mode to the IFO beam.
SM1/SM2, steering mirrors to align the IFO beam to the Farady Isolator.
IRIS1/IRIS2, for the coarse alignment of the injection beam.
FLIP, flipper mount to turn on/off the injection optics.

Alignment procedure of the injection system
0) Ignite NPRO several hours before the experiment so that the laser frequency can be stable.
1) Turn up FLIP. Close the shutter of NPRO.
2) Adjust SM1/SM2 so that the ifo beam can appear at the output of FI.
3) Adjust height and position of IRIS1/IRIS2 with regard to the ifo beam so that the ifo beam goes through IRIS1/IRIS2 even when they are closed.
4) Turn down FLIP. Open the shutter of NPRO.
5) Adjust INJ_SM1/INJ_SM2 so that the injection beam can go through IRIS1/IRIS2 even when they are closed.
6) At this time, it is expected that the reflection of the injection beam from SRM appears at AS CCD, if SRM is aligned.
7) Adjust INJ_SM1/INJ_SM2 so that the injection beam at AS CCD can overlap to the IFO beam.
8) Confirm the beam at the output of the FI also overlaps.
---- We are here ----
9) Change the ifo configuration to the X or Y arm only.
10) Scan the crystal temperature of the 700mW NPRO in order to try to have the beating of the two beams at the PD. AS OSA may be useful to obtain the beating.
11) Once the beating is obtained, adjust INJ_SM1/INJ_SM2 such that the beating amplitude is maximized.
Attachment 1: optical_configuration.png
optical_configuration.png
Attachment 2: optical_layout_ap_table2.png
optical_layout_ap_table2.png
Attachment 3: optical_layout_ap_table2.pdf
optical_layout_ap_table2.pdf
  599   Mon Jun 30 05:33:38 2008 KojiUpdateGeneralAbs. Len. Meas. ~ Optical setup (II)
o The position of the iris was adjusted so as not to disturub the beam for OMCR CCD.

o The RF spectrum analyzer was returned to the place of the network analyzer.


Quote:

In the process of making this report, I noticed that one of the iris apertures is about disturbing the beam for OMCR CCD. I will check this before I go to Hanford. Also an RF spectrum analyzer is at the AP table. I try to return this near the PSL on Monday morning.
ELOG V3.1.3-