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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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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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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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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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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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 !!! |
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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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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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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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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Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics
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After mirrors were going back from LMA for cleaning and thermal anealing, they have been installed in FP cavity for Finesse measurement.
after getting strange results when the cavity is closed (very low Finesse...maybe too much ethanol inside cavity procucing some lineic losses),
we get 12k-12k5 Finesse with primary vacuum (~4 mbar) and a clean lock (very flat transmission signal and quite noiseless reflection signal) |
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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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Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics
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To complete these observations:
Finesse has been measured on thursday, right after cleaning the cavity with ethanol @6000.
Finesse has been measured on friday, after opening the cavity for few tens of minutes @12000-12500. The cavity was openned while |
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ThomX amplifier M2, posted by Loïc Amoudry at Optical room about lasers and optics
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| The ThomX M2 has been measured between 1.5-1.6 for x and y |
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Improvement holder amplifier fiber, posted by Loïc Amoudry at Optical room about lasers and optics
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| We've added a clamp in the 3rd stage to prevent the pump fiber from moving and tilting (it was tilting to the left). |
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Free Spectral Range (FSR), posted by Loïc Amoudry at Optical room about lasers and optics
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FSR is 33.347 MHz @1e-8 mbar
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Fiber injection and onefive output power, posted by Loïc Amoudry at Optical room about lasers and optics
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Fiber injection is finished with the new ThomX stretching CVBG in double pass (+50% injection power compared to K-BOX CVBG in simple pass).
- Output Onefive: 27 mW
- After Onefive + lambda/2 + isolator: 25.8 mW |
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Onefive spectrum and CVBG spectrum, posted by Loïc Amoudry at Optical room about lasers and optics
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| The Onefive spectrum has shifted a little bit to lower lambda. It's still enough for the experiment (3mW injection of ampli intead of 1mW needed). |
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First mode degeneracy on ThomX, posted by Loïc Amoudry at Optical room about lasers and optics
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Yesterday, we've observed the first degeneracy on ThomX cavity at ~115 kW stored. The shape of the stored power on the oscilloscope is really close
to what has been published in the D-shape mirror's paper ("tek0000" transmission in yellow, piezoelectric activator in green, error
signal in blue). |