Step II - Preprocessing

The next window offers many preprocessing options like DC offset removal, time-domain windowin, phase correction and appending zeros. Furthermore, the frequency range for which parameters should be extracted can be determined here.
 
loading time domain data in the teralyzer
 

In our case, we select the full available data range from 0 to 100 ps and apply a chebychev window with a slope of 3 ps. The DC offset is removed by averaging over the first 2 ps of the time domain data and subtracting this average from the data set. As phase errors may occur at very low frequencies due to non-planar phase fronts and strong diffraction, we select a trusted phase regime from 0.3 to 0.8 THz. From the spectral data, we see that the noise starts at roughly 4 THz, so we chose this value and enter it into the program. By hitting the "Apply" button, the changes take place.

Next, we chose the sample thickness to be within 2000 µm +-100 µm and the iteration step size to 10µm. The material parameter extraction frequency range is set to 0.3 THz to 1.8 THz. By hitting the "Analyze Sample" button, an initial evaluation is performed and the position of the Fabry Perot echoes is displayed in the time domain data plot. We see that 3 Fabry Perot echoes lie within our sample range.

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