The measurement performed during the golden week were using too low power (I_laser =3A ie P_laser~3.5W) that made it hard to really acquire signals.
The measurements have been restarted with higher power (I_laser=6A ie P_laser~8W?).
We'll have to check carefully the incident and transmitted power after the measurements.
Abe, Marc
Following the 3 maps measurements we performed again the bulk calibration where this time we moved the imagining unit by 0.32 mm in order to compensate the thickness difference between surface and bulk reference samples. We got the following result (also see last figure of this entry) :
AC_bulkref = 0.0731;
DC_bulkref = 4.164;
ACDC = 0.01755;
P_in = 29.5e-3;
P_t = 13.3e-3;
T_bulkref = P_t/P_in;
abs_bulkref = 1.04;
R_bulk = AC_bulkref/(DC_bulkref*sqrt(T_bulkref)*P_in*abs_bulkref) = 0.852 cm/W
Using this new calibration factor and using :
P_t = 6.25 W;
P_in = 7.322 W;
the absorption of this sample seems to be around 60 ppm/ cm for all 3 maps (see attached figures)
Today we will double check the bulk calibration as the change was quite larger than expected.
It seems that the bulk calibration was overestimated. This is especially apparent when computing its transmission that was 45% instead of the expected 55%.
I performed again the bulk calibration and got :
AC_bulkref = 0.062;
DC_bulkref = 4.14;
P_in = 26.4e-3;
P_t = 13.1e-3;
T_bulkref = P_t/P_in
abs_bulkref = 1.04;
R_bulk = AC_bulkref/(DC_bulkref*sqrt(T_bulkref)*P_in*abs_bulkref) = 0.7743 W/cm
I used this new calibration to compute again the absorption map of the sample (see the 3 attached figures.
In the figure, the absorption is extracted from a fit using 2 normal distributions.
Here I also add the overall mean and standard deviation of each map (ie without any fittting) :