Measurements of lot of points with D-shape mirrors well positionned.

Power not optimized to the best but almost. (@4A could have 350 mW).

Matlab code for size vs position and power : 

clear all
close all

x = [1820 1820 1925 1936 2117 2260];
y = [2013 2013 2029 2090 2249 2392];
Position = [0 0.2 0.4 0.6 0.8 1];
Trans = [337 330 306 245 128 17]

hold on
[ax,h1,h2] = plotyy(Position,x,Position,Trans)
set(get(ax(1), 'Ylabel'), 'String', 'Beam diameter (um)');
set(get(ax(2), 'Ylabel'), 'String', 'Transmitted power (mW)');
xlabel('Position of the D-shape (mm)')
plot(Position,y,'g')
hold off

Measurement done on 18/10/18.

At high power, the shape of the 0.0 mode does not change. The D-shape only generate losses in the cavity. Then the power stored in the cavity decrease. As with this configuration, the cavity beam size decrease when power increase, the beam size decreased.

Measurements done @4A on 3rd stage.

Then we get the D-shape away from the beam to not cut it and decreased the amplifier power to validate the beam size at a known value. So the power as been decreased to 2A (= 125 mW in trans) and the beam size was x=2079 y=2255, similar to the 125 mW with D-shape mirrors values.

Measurements have been done on 18/10/18.

Datas are on excel file, also matlab file.

Motors have been installed on 16/10/18. No problem with them.

Effect of the motors tested on 17/10/18. No improvement. But they give the possibility to perfectly cut HOM or let them go through as show the following picture of a 2.2 mode at ~340 mW in trans and 70% coupling @4A.

Measurement made on 03/10/18 (nothing has been done since there).

Stable power in the cavity of 225 kW.

Optimization of the polarization has been made the 03/10/18. Checked in reflection of the cavity in reflection&transmission of a PBS, locked and unlocked. Only with 2nd stage.

Ratio values are reflection of PBS divided by transmission or the opposite.

with just intensity, the coupling is 98%, and with phase, x direction coupling is 95%, y direction 97%, so the telescope is good.

* Loic has to fix the number of files (3) regarding the number of measurements (2)

* splitted Intensity and phase HASO files

* image for each file

2 measurement.

First one locked, in transmission of M2 with 2nd stage 0A.Total 89 cm from the big waist (planar mirrors). 2 wedges used.

Second one at input beam with the same power. Datas taken at the same equivalent position than the first one. 3 wedges used.

Measurments of Finesse with the 2 polarization states, let's call them H (higher) and L (lower): 24500 for the H and 23500 for the L.

We checked the polarization states in transmission of the FP cavity after a PBS. The H was stronger in PBS trans and the L stronger in PBS ref.

We measured the power in reflection of the PBS and added a half WP that we aligned with the PBS polarization. Then, to get the maximum power we had to tilt the half WP of 22° for the H and 18° for the L.

Finally we checked the extinction through half WP and PBS for H and L. 

- For H : max 75 mW min 5 mW. Ratio 6.66%

- For L : max 70 mW min 4 mW. Ratio 5.7%

Right after Koheras : max 3.5 mW min 47 uW. Ratio 1.3%