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Quest for photo-stable amorphous thin films in ternary Ge(x)As(y)Se(100-x-y) chalcogenide system is reported. Studied layers were fabricated using pulsed laser deposition technique. Scanning electron microscope with energy dispersive X-ray analyzer, Raman scattering spectroscopy, transmittance measurements, variable angle spectroscopic ellipsometry, and non-linear imaging technique with phase object inside the 4f imaging system were employed to characterize prepared thin films. Their photo-stability/photo-induced phenomena in as-deposited and relaxed states were also investigated, respectively. In linear regime, we found intrinsically photo-stable relaxed layers within Ge(20)As(20)Se(60) composition. This composition presents also the highest optical damage threshold under non-linear optical conditions.

We report experimental characterization of a very small rectangular phase shift (<0.3 rad) obtained from the far-field diffraction patterns using a closed aperture Z-scan technique. The numerical simulations as well as the experimental results reveal a peak-valley configuration in the far-field normalized transmittance, allowing us to determine the sign of the dephasing. The conditions necessary to obtain useful Z-scan traces are discussed. We provide simple linear expressions relating the measured signal to the phase shift. A very good agreement between calculated and experimental Z-scan profiles validates our approach. We show that a very well known nonlinear characterization technique can be extended for linear optical parameter estimation (as refractive index or thickness).