An experimental investigation and theoretical modeling of nonlinear refraction in a CW-pumped Cr<sup>4+</sup>:YAG crystal at wavelength 1.06┬Ám is reported. An analysis of the processes resulting in nonlinear change of refractive index of Cr<sup>4+</sup>:YAG allows to conclude that the main contributions in the change are the effect of Cr<sup>4+</sup> centers' population perturbation due to the ground-state absorption saturation and the thermo-lensing effect. The role of the refractive index change anisotropy stemming from both the effects is addressed for the first time to our knowledge.

© 2003 Optical Society of America

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