In order to state which part of the sample I was watching exactly, I used the sample boundaries as reference.

First I made a map with the DC signal in order to define the boundaries. I put it together in the same plot of the last absorption measurement (See Figure1.png). I could do that because I didn't remove the sample from the holder since the last measurement.

Then I took many pictures at the microscope and I put them together to make all mirror map. (See Figure2.jpg)

I overlap the two images making a matching of the boundaries. (See Figure3.jpg)

Finally I found the corresponding area. (See Figure4.jpg). The problem is that the pattern of dots at the microscope doesn't completely correspond to the absorption peaks pattern.