Power during ~20h, power after turn on, spectrum image and excel datas, polarisation and pulse length.

Powermeter measurments were done with a /10 filter.. 3 mW means 30 mW

Important: Onefive does not automatically locks after being turned on.

one rotate a lambda/2 before a PBS and meausure the refected power:

Pmax=35.6 mW

Pmin=107 µW

Ellipticity ~ 3 per mille

29/01/19 - ThomX mirrors have also been checked with binocular microscope. They shown the same spots as S-BOX mirrors. 

1st image shows reflective face of a spherical mirror.

2nd image shows reflective face of M1 (sapphire).

30/01/19 - As LMA people came, we discussed about the spots on ThomX mirrors which should be clean. As mentionned in "SBOX commissioning", these spots are normal.

An other question appeared during the conversation about the storage time and location of these mirrors. They have been stored for more than two years in plastic boxes. LMA people explained that some company do not let anything more than 6 months in these boxes for pollution issues.

We merged into the same conclusion, clean the mirrors in case of pollution. Finally, they took the mirrors and we will go to LMA to recover them between 11/02 and 14/02. 

FSR initiale : 33.34 MHz (S3 = -825000 et S4 = -825000)

Beam size initiale : wx=2.05mm et wy=2.15mm

Finesse initiale : 3400

FSR après éloignement des miroirs sphériques : 33.29 MHz (S3 ~= -1496000 et S4 ~= -1496000)

Beam size : wx=1.7mm et wy=1.85mm

Finesse : 3600

FSR après rapprochement des miroirs sphériques : 33.39 MHz (S3 ~= -250000 et S4 ~= -500000)

Beam size : wx = 2.1mm et wy=2.4mm

Fit de la caméra jamais au dessus de 90%. ~~80%.

Direction of HR face of P1 and P4 have been checked, there was no problem. The mirrors are in the good direction and the coating is on the good face.

Once P1 and P4 outside of the cavity, we checked the coating position by sending the HeNe laser with an angle. There was two reflections and the most intense was the one closer to the normal to the mirror.

On P4 we noticed a spot which seems to be in the coating (does not move while sending nitrogen).

19/04/01: We removed the wires from the beam path in the cavity. Finesse stayed at 3400. FSR: 33.342 MHz.

When locked:

Input Power: ~4mW
Through S2: ~0.950uW
Through S3: ~0.930uW
Through P4: ~0.850uW

We openned the cavity, removed S2 and measured trans of P1 and same for S2.

Pin ~= 3.91 mW
PS2 ~= 20 nW --> ~~ 5 ppm !!!
PP1 ~= 5.23 uW --> ~~ 1337 ppm !?!?!

P1 is the Sapphire mirror. 3mm thick. Tomorrow we'll measure its trans again, being out of the mount for constraint issues.

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