RESUMO
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.
RESUMO
We demonstrate the generation of 99 fs pulses by a mode-locked laser oscillator built around a Yb:CaF(2) crystal. An average power of 380 mW for a 13 nm bandwidth spectrum centered at 1053 nm is obtained. The short-pulse operation is achieved thanks to a saturable absorber mirror and is stabilized by the Kerr lens effect. We investigated the limits of the stabilization process and observed a regime slowly oscillating between mode locking and Q switching.
RESUMO
We report n2 measurements of selected chalcogenide glasses using a modified Z-scan technique. Measurements were made with picosecond pulses emitted by a 10 Hz Q-switched, mode-locked Nd:YAG laser at 1064 nm under conditions suitable to characterize ultrafast nonlinearities. The nonlinear index increases significantly up to 246 times the n2 for fused silica with an increase of SbS3 units and also very slightly with the replacement of Ge by Ga or S by Se. We have attributed the variation of n2 to the total number of electronic lone pairs and to the position of the absorption band gap, which are induced by the presence of GaS4 units or Se-Se bonds in the glass structure.