TITLE:
Nonlinear Change in Refractive Index and Transmission Coefficient of ZnSe:Fe2+ at Long-Pulse 2.94-μm Excitation
AUTHORS:
Alexander V. Kir’yanov, Nikolai N. Il’ichev, Elmira S. Gulyamova, Alexander S. Nasibov, Peter V. Shapkin
KEYWORDS:
Nonlinear Refractive index, Nonlinear Transmission, Z-Scan Technique, Thermal lens, ZnSe:Fe2+
JOURNAL NAME:
Optics and Photonics Journal,
Vol.5 No.1,
January
20,
2015
ABSTRACT: An
experimental study of the nonlinear changes in refractive index and
transmission coefficient of single-crystal ZnSe:Fe2+, fabricated
through the Fe-diffusion method, at long-pulse (~300 ns), sub-mJ, 2.94-mm
Z-scan probing is reported. As well, a theoretical model based on the
generalized Avizonis-Grotbeck equations is developed and applied for
straightforward fitting of the open- and closed-aperture Z-scans, obtained for
ZnSe:Fe2+ with different Fe2+ centers concentrations. The
modeling results reveal that the contributions in the absorption and refractive
index nonlinearities of ZnSe:Fe2+ are “common” resonant-absorption
saturation (the minor part) and pulse-induced heating of the samples (the major
part), which are strongly dependent on Fe2+ concentrations. Large
values of the index change (>~10-3) and partial
resonant-absorption bleaching (limited by ~50%), both produced via the thermal
effect mainly, are the features of the ZnSe:Fe2+ samples inherent to
this type of excitation.