M² mesuré à 10W.
M²x = 1.17
M²y = 1.14

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 ?

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. 

Onefive output power : 28mW
Power before fiber injection : 7.8mW
After EOM and 99% coupling fiber : 1.8mW
After EOM and 1% coupling fiber : 14 uW (~1%), ~7.5V @ 1MOhm on DET36
Frep : 33.326 MHz
Output 1^st stage + collimator & dichroic mirror: 36uW
Output 2^nd stage @6A (~260mV @50Ohm on DET36): 300mW --> after 20-30min

Output 2nd stage is the same value as Onefive 133.33MHz

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 hold the hub in place, once these screws are removed the hub will lift off the motor shaft.
2)            Remove the 2 screws holding the stainless steel top decks in place (see picture 2), please be careful when removing the top deck as the lid switch wire will be attached.
Once these have been removed, you can access the inside of the spin coater.
You must add a bypass wire to the timing block (see picture Purge Bypass 1), the wire must be connected to the A1 and 28 ports on the timing block and remove the red wires from connexion. This will now cause the spin coater to bypass the purge check switch and allow the machine to boot up without air/nitrogen being supplied. To revert this change, simply remove the bypass wire you have installed and plug the 2 red wires back to A1 and 28.

The "enter" button of the front panel had some trouble and has been changed.

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 ).

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
2ND image after cleaning
No changes after coming back from primary vacuum

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 water. They finish by putting more water without the cotton tipped stick.

WARNING: WATER HAS TO BE CHANGED EVERY DAY 

They said they only use clean water but in case of grease/oil onto the mirror they would use first acetone then clean water.

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
2nd: Primary pump + Turbo pump on
3rd: Primary pump + Turbo pump + Ion pump on
4th: Primary pump + Turbo pump + Ion pump on + 10 "open/close" displacement of the pneumatic valve
5th: Primary pump + Turbo pump + Ion pump on + 1 full range displacement of P1 z motor
6th : Primary pump + Turbo pump + Ion pump on + RGA

None of these experiences have shown good correlation with dust generation. 
The RGA has shown reasonable values.
Conclusion is that dust was already in the cavity and was only displaced by all combined motors, pneumatic valves, cavity opening and closing movements.

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.
Dans certains cas (spécifications du projet) l'épaisseur de la couche de silice de sortie peut être ajustée. 
Par exemple pour matcher une transmission très précise.
Pour les coating AR la couche de sortie est en silice mais pas lambda/2.

20/09/2019 : new email from Chrisophe Michel after he sent back the mirrors (LMA made a cleaning and thermal annealing) :

"le colis avec les 4 optiques, nettoyées 2 faces après traitement thermique et caractérisation, a été envoyé cet après midi par DHL (tracking number 4995967550).

Dans le colis j'ai ajouté le miroir en saphir C16115-11.

Les mesures donnent des absorptions entre 0.12 et 0.5 ppm (nous avons réussit à faire fonctionner de nouveau le banc mais il est mode dégradé avec une incertitude plus grande sur les mesures mais l'ordre de grandeur est bon et correspond aux valeurs mesurées en 2016 qui était de 0.24 ppm).

Pour les pertes par diffusion voila ce que Laurent à mesurer (les valeurs sont identiques à celles mesurées en 2016 sauf pour le C16116/11):

- C16116/11: 9 ppm sur diamètre 10mm (6 ppm mesurées en 2016); 4.5 ppm sur diamètre 6 mm; T=1.5 ppm @ 1064 & 1031 nm (simulée)

- C16116/12: 8.5 ppm sur diamètre 10mm; 4.5 ppm sur diamètre 6 mm; T=1.5 ppm @ 1064 & 1031 nm (simulée)

- C16116/13: 14 ppm sur diamètre 10mm; 10 ppm sur diamètre 6 mm; T=1.5 ppm @ 1064 & 1031 nm (simulée)

- C16115/11 (saphir): 9 ppm sur diamètre 10mm; 4 ppm sur diamètre 6 mm; T=148 ppm @ 1064 nm soit 120 ppm simulée @ 1031 nm"

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.

Frederic and Manu from vacuum group came this morning to fix again the pneumatic valves which had a leak again.

The cavity is right now at 6.5e-8 mbar (turbo pumps on for 1 night and ionic pumps for 3h), primary pumps and turbo pumps are cut, ionic pump are on and the pressure level is still going down. 
Therefore there aren't any big leak in the cavity and we can expect a final vacuum level close to e-9 mbar.

The circuit breaker on ThomX cavity drops @1.5-1.8kW when we turn on 1/2nd stage of the amplifier or 3rd stage of the amplifier.
Amplifiers are now connected to K-BOX UPS.

We are buying a clamp ammeter for further investigations.

The ThomX M2 has been measured between 1.5-1.6 for x and y

We've added a clamp in the 3rd stage to prevent the pump fiber from moving and tilting (it was tilting to the left).

FSR is 33.347 MHz @1e-8 mbar

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
- After Onefive + lambda/2 + isolator + lambda/2 + PBS + CVBG*2 + PBS: 9.6 mW
- After injection into fiber and EOM (+all preceding): 3.2 mW
- Input 99% of the amplifier: 2.86 mW

> 660 mW on 1% photodiode DET100 @1Mohm

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).

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).
This mode could be a 8.0 or 9.0. 
We have also observed a change of the angle of the mode (the pictures "degenere", "degenere2" and "degenere3" were taken by order). The only changing parameters are the alignement and the length of the cavity. 
The last thing we noticed is the shape of the mode which could not be an hermite-gauss mode (Bessel mode ?).