Diffusion ULE spherical mirror (S3) vs Fused Silicate injection planar mirror (P1), posted by Loïc Amoudry at Optical room about lasers and optics 
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Observation made with IR Beam Viewer:
The observation of P1 and S3 simultaneously while locking shows much higher diffusion on the ULE mirror. The diffusion on the two other ULE mirrors
(S2 and P4) shows similar diffusion as S3. |
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New Suprasil mirror from LMA, posted by Loïc Amoudry at Optical room about lasers and optics
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14/05/19:
New Suprasil mirror received. It will replace the S-BOX suprasil mirror on ThomX which was already replacing the sapphire mirror.
First finesse measurement: 14000 |
New Suprasil mirror from LMA, posted by Loïc Amoudry at Optical room about lasers and optics
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19/09/2019 : email from Chrisophe Michel about AR coating of LMA mirrors after reading that Ta2O5 layers can be damaged in vacuum if not protected by
a SiO2 layer :
"oui tous nos coating standards HR se terminent par une couche de protection SiO2 Lambda/2. |
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Motor issue, posted by Ronic Chiche at Optical room about mechanics | detectors and electronics
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Today, Axis 9 (Z-axis of P1) has blocked the software which drives all the motors.
impossible to bypass the problem.
I had to : |
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Motor issue, posted by Ronic Chiche at Optical room about mechanics | detectors and electronics
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Today again, same problem with axis 9 blocking the controlling software during the mirror alignment procedure.
after opening the motor 9-16 controlling crate, we saw 2 screws (RX- and TX+ of the controller) which were badly screwed.
we firmly screwed them... could it be the cause ? |
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Cavity dust source check, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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Several experiments have been done in order to check the potential source of dust in the ThomX cavity. For each step, we look at a clean surface, put
the cavity under vacuum, go back at ambient pressure and check back the "clean surface".
1st: Primary pump on |
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LMA cleaning technique, posted by Loïc Amoudry at Optical room about lasers and optics
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Christophe MICHEL told us more precise informations about spin coater cleaning.
They always clean with pur water and cotton tipped sticks.
First a spray of water, then they put the wet cotton tipped sitck onto the mirror from the center to the edge ~x3 while continuing to spread |
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Primary vacuum to check dust, posted by Loïc Amoudry at Optical room about mechanics | vacuum
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The cavity has been cleaned then put under primary vacuum (primary pump without vacuum flow control). Dusts presence was checked at air and no significant
changes have been observed.
1ST image before cleaning |
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Mirrors sent to LMA, posted by Loïc Amoudry at Optical room about lasers and optics
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| Mirrors have been sent today to LMA for cleaning and maybe annealing (recuit). 3 ULE of ThomX and the fused silicate for injection (trans @140ppm ). |
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Finesse measurement after mirror cleaning using the spin coater, posted by Ronic Chiche at Optical room about lasers and optics
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Last Finesse measurement in air : ~ 17 000 the 20th of may (see logbook)
28th and 29th of august, we cleanned, with Loïc, mirrors S3 then P1 successively using only ultra pure water with the spin coater.
we measured the finesse after each cleaning by modulation technique and in both cases, F ~ 12 500 !!! |
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Finesse measurement after mirror cleaning using the spin coater, posted by Ronic Chiche at Optical room about lasers and optics
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today I cleaned S3 with isopropanol and then with pure water on spin coater.
Finesse is only 10 700.(coupling 50% ? => to be confirmed...)
maybe we have to redo the procedure with a different way of cleanig (pushing less on the mirror ... ?) |
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Finesse measurement after mirror cleaning using the spin coater, posted by Ronic Chiche at Optical room about lasers and optics
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Following finesse measurements (start @10700):
Clean P1 with SC (water) + isoprop (wipe) finesse @15000
Clean S2 with SC (water) + isoprop (wipe) finesse @13000 |
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Vessel cleanliness, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | vacuum
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looking in the vessel of the FP cavity using a UV lamp shows a lot of dust... more dust than outside the cavity !!!
here is picture where one can see a cleaned zone using a finger (with gloves).
question : where does come from this dust ? |
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Spin coater air supply removed and front panel changed, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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Spin coater firstly needed vacuum and air supply. The air supply being useless for our experiments, it has been disabled.
The process is the following and is reversible:
1) Remove the hub from the top of the spin coater, (see picture 1), 4 screws |
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2nd stage output power validated , posted by Loïc Amoudry at Optical room about lasers and optics
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Onefive output power : 28mW
Power before fiber injection : 7.8mW
After EOM and 99% coupling fiber : 1.8mW |
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Onefive 33MHz unmodelocked, posted by Loïc Amoudry at Optical room about lasers and optics
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Oscillator randomly unmodelocked on 3rd july afternoon (during oscillator power measurement, maybe a reflection from the powermeter power filter
?)
Modelocked this afternoon by putting Onefive motor and phase at reference on the PTC software. |
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New design for PDH boxes, posted by Ronic Chiche at Optical room about detectors and electronics
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A new design has been studied for the 5 PDH boxes to better match the low (33MHz) repetition rate of the ThomX laser.
the 5 PDH boxes have been modified and tested (see the attached report).
A mixer has been integrated to the PDH box for a more simple use. |
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telescope for Koheras, posted by Huan Wang at Optical room about lasers and optics
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telescope of Koheras is removed, information record here:
- distance between collimator edge and -50 lens mount edge is 14.7cm,
- distance between another edge of -50 lens mount and +250 lens mount edge is 14.3cm, |
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Polarization, posted by Loïc Amoudry at Optical room about lasers and optics
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Polariztion measured with Input vertically/horizontally polarized (~100% DOLP)
- Transmission (P4) locked on cavity horizontal polarization is ~50% linearly polarized and ~50% unpolarized ?
- Transmission (P4) locked on cavity vertical polarization is ~50% linearly polarized and ~50% unpolarized ? |
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Amplifier mission Bordeaux, posted by Loïc Amoudry at Other about mechanics | lasers and optics
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Voyage Bordeaux au CELIA avec Jérôme LHERMITE (Loïc et Titoutan)
1er jour (34°) :
Mesure du spectre et de la puissance des 4 diodes de pompe 3ème étage jusqu’à ~60W (12A). |
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Amplifier mission Bordeaux, posted by Loïc Amoudry at Other about mechanics | lasers and optics
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M² mesuré à 10W.
M²x = 1.17
M²y = 1.14 |
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Transmission of Sapphire mirror, posted by Loïc Amoudry at Optical room about lasers and optics
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| See image. |
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Finesse measurement by decay time technique, posted by Ronic Chiche at Optical room about lasers and optics
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5 Files attached:
- Note on the technique and results for the present cavity on 2019, May 21th : F ~ 18 000
- 2Tektronix scope raw data |
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Finesse after cleaning (new suprasil mirror), posted by Loïc Amoudry at Optical room about lasers and optics
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15/05/19-20/05/19:
Cleaning of the mirrors:
Initial finesse 14000 @air |
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33MHz Onefive power overtime decrease, posted by Loïc Amoudry at Optical room about lasers and optics
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Power of the 33MHz Onfive decreases over time. Have to pay attention to that.
Note that air dryers have never been stopped.
10th april 2018: ~40mW (first picture, 10dB filter) |