S3 and S2 @ +1 640 000 and P1 and P4 @ -825 000

Diameter in x: 4.7mm
Diameter in y: 4.7mm

After verification, transmission of P1 correspond to ~150ppm.

The 1337ppm come from a beam leakage. Reflection from P1 goes to the input window which reflects again a part of the beam directly into the cavity between P1 and S3 then between P4 and S2.

P1 transmission out of the mount (means angle of the mirror is not the real angle):

Pin = 3.2 mW
Pout = 545 nW
Offset = 68 nW

Transmission = (545-68)/3.2e6 = 149 ppm

P1 SUPRASIL has been installed instead of P1 Sapphire. It has been cleaned 3 times on each face with wipe+isopropanol before to be installed.

Finesse ~= 10 000 - 11 000 (EOM Sweep of 100 kHz in 10sec, see last image.)
Coupling ~= 45%

Motors position:
P1 = -825 000
S2 = +825 000
S3 = +825 000
P4 = -825 000

Finesse measured this morning after P1 SUPRASIL being into the cavity for two days. In order to check if it's getting dirty.

Finesse still ~= 11 000

P4 cleaned with isopropanol.

Finesse measured afterward: ~=13 000 (clear increase)

Summary of what have been cleaned the last week:

P1 with isopropanol, finesse 11000
P4 with isopropanol, finesse 13000
S2 with isopropanol, finesse 13000
S3 with isopropanol, finesse 14000
S2 with isopropanol, finesse 14000
P4 with isopropanol, finesse 12500
P4 with isopropanol, finesse 12500

Finesse decreased with last steps which probably means our cleaning technique is at its maximum. We will probably try a cavity axis change with the mirror's motors to increase the finesse  to the maximum like that.
Next step is to clean P1 with acetone + pur ethanol, then install the Onefive.

Output power of the Onefive, and power after injection and different components have been measured.

Coupling ~= 90%
Each of our two EOM roughly have the same loses ~3dB

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)
25th september 2018: ~36mW (second picture, 10dB filter)
16th april 2019: ~29mW (third picture, no filter)
 

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

Features sent by Christophe Michel:

"- Transmission mesurée (1064 nm)= 172 ppm ; Transmission estimée (1031 nm)= 140 ppm
- Réflexion (1064 nm)= 1025 ppm; doit être inférieure à 1031 nm
L'AR n'est pas bon alors que l'on obtenu 170 ppm pour le run de calage!
J'espère que vous pourrez néanmoins l'utiliser.
- Diffusion moyenne sur diamètre 12 mm: 2.6 ppm"

15/05/19-20/05/19:

Cleaning of the mirrors:

Initial finesse 14000 @air
S2 with isopropanol, finesse 17000 @air
P4 with isopropanol, finesse 17000 @air
S3 with isopropanol, finesse 17000 @air
S3 with first contact, finesse 17000 @air
S2 with first contact, finesse 17000 @air

5 Files attached:

- Note on the technique and results for the present cavity on 2019, May 21th : F ~ 18 000

- 2Tektronix scope raw data

- 2 matlab files to fit the scope raw data and extract the Finesse

See image.

Voyage Bordeaux au CELIA avec Jérôme LHERMITE (Loïc et Titoutan)

1^er jour (34°) :

Mesure du spectre et de la puissance des 4 diodes de pompe 3^ème étage jusqu’à ~60W (12A).
Mécanique et câblage ampli.

2^ème jour (30°) :

Soudure des fibres des diodes de pompe 3^ème étage avec les fibres du recirculateur.
Câblage entre les 2 boitiers et fixation des fibres dans le boitier du 3^ème étage.

3^ème jour (26°) :

Connexion refroidissement à eau du recirculateur (chiller).
Soudure fibre CFBG avant 1^er étage (temporaire pour faire des mesure).
Mise en place des éléments 1^er et 2^ème étage sur le support de l’ampli.
Montée en puissance 35W.

4^ème jour :

Adaptation du mode de sortie en contrôlant la position de la fibre avant le collimateur.
Mesure de M².
 

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 ?

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,

- distance between another edge of +250 lens mount and edge of bread board is 25cm.

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.

the PDH N°1 has been lend to Huan for her experiment in China.

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