FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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The alignment is on hold until next week 17th - 18th Jan
an Alignment attempt will be done when the ring part close to the FP cavity is opened.
Manar |
FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics 
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***** Continuation of the alignment ---- FP Cavity Open --- ****
The cavity was put under outer pressure and was opened for the alignment
The alignment was done using CW koheras infrared laser and the inside mirrors irises |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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Yesterday, we did the alignment again using Iris and beam profilers to obtain a more precise result.
at the end of the alignment procedure, we successfully obtained the beating modes.
the geometrical alignment seems good (weak odd modes) but we could need to put a telescope on the Koheras line as the beam size seems quite different |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Installed and inputs:
CW laser ; power = 101 mW
PDH ;
at output
Low pass filter 50 ohm DC-1.9 MHz
at
input
freq = 8.4 MHz , Ampl = 1.2 V , phase = 160 /
voltage = ~ 6 V
EOM |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This afternoon, I did some alignment of the injection mirrors with a fast scan on the LaseLock to get a regular transmission photodiode signal.
the coupling increased to 10-15%
I got a first lock of the cavity only with the PZT. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning with Manar, we installed the AOM+RF amplifier and the associated fast feedback loop.
Now the locking with the Koheras is good with a coupling of 20%.
Tomorrow is dedicated to the measurement of the Finesse.... we will have to add the 2nd EOM. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Adding Oscilloscope images
delocked + locked intervals showing the 20% coupling
lock when the housing panels are closed + airflow on .
lock
when the housing panels are closed + air flow at lowest setting
an additional factor to the PZT voltage sensitivity |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Ending alignment series !!
Manar
Amer wrote:
Adding Oscilloscope images |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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As it can be seen on the first plot, even with a good locking (good reduction of "high" frequencies noise: we had better locking than on the
picture) we still have very low frequency (~ 1Hz) fluctuations
these fluctuations prevent having a good measurement of the Finesse and they need to be understood. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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The fluctuation problem has been solved.
It was simply the new scheme to inject 2 RF frequencies in a single EOM.
It maybe produces some standing waves in the EOM RF input and creates some phase noise. |
FP cavity alignment, posted by Ronic Chiche at ThomX igloo about lasers and optics
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as the iris used to locate the FP-cavity axis have been removed before moving the table inside the Igloo, we have to find again this FP-cavity axis.
this morning with Viktor, we started to make the alignment of the FP-cavity with a red laser using only the "input window" iris mount
built by Yann. |
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FP cavity alignment, posted by Ronic Chiche at ThomX igloo about lasers and optics
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This afternoon, we continued the alignment of the red laser.
we did it using the 2 final injection mirrors.
we still see a clear transmission after M2, a weak transmission after M3, and almost nothing after M4 due to the power loss going through the dielectric |
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FP cavity alignment, posted by Ronic Chiche at ThomX igloo about lasers and optics
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A continuation of the alignment process was done, there was change in it due to variation in temperature,
it was done using the semiconducting laser, and we were able to obtain an output at M2.
2 references were placed before the alignment mirrors Ma and Mb , to fix the line when changing from semiconducting laser to CW "koheras" |
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FP Finesse measurement using CW, posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning, with Ronic and Daniele, we locked the cavity again (The lock was relatively easy and stable during the reading of the finesse)
We took 2 reading of finesse
1st : @ 33.2808 MHz (what the cavity length was at) : Finesse = |
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Etuvage cavité THOMX, posted by Ronic Chiche at Optical room about vacuum
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Mail de Bruno Mercier du 19/11/2018 :
Une première cavité a été étuvée, la pression est actuellement de
3.10-10 mbar, l' étuvage
de la deuxième cavité vient de commencer et se
finira en début de la semaine prochaine.
Bonne journée,
Bruno
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Equipments shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics
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on the August 30rd and 31th, a global power shutdown was forseen for ThomX.
to prevent damage on equipments, I switched off all of them (and disconnected power cables from the wall plugs).
yesterday, after the week-end, all the equipments have been restarted and the cavity as been locked properly. |
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End of vacuum test and cavity ready for cleaning, posted by Loïc Amoudry at Optical room about vacuum
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Vacuum tests finished on 19 december 2018.
Spent last two days to discuss the importance of removing aluminium and baking wires before to insert mirrors for cleanliness issues. Finally
we took pictures to support our demand. |
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End of cleaning, plastic fixed on cavity, posted by Loïc Amoudry at Optical room about utilities
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| 08/02/19 - End of the cleaning process. |
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Electrons-Photons phase stability measurement, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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we installed a measurement at the IP with the BPM for ion cleaning for electrons and we used a fast photodiode at the output of the FP-cavity and measured
with a fast oscilloscope the phase jitter between the 2 signals.
in red, the BPM signal |
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Electrons-Photons phase stability measurement, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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the phase between the 500Mhz ring RF oscillator and the electrons is measured on a BPM and is very stable after 2-3ms (<< 6ps, typically) !
in the same time, we can use the residual phase beating after our 500MHz mixer to estimate the phase noise coming from the laser part.
the rms noise of this signal is around 60mV for 1.25V peak (2.5 pk-pk) signal => ~ 50mrad rms |