Application of the Z-scan technique for determining non-linear anisotropic change of refractive index in Cr4+ : YAG at powerful continuous-wave 1.06-μm probing

An experimental study and a theoretical modeling of non-linear refraction in a continuous-wave-pumped Cr4+:YAG crystal at wavelength 1.06 mum are reported. Analysis of the processes that result in the non-linear change of Cr4+:YAG refractive index allows us to conclude that the physical mechanisms contributing to the change are the ground-state absorption saturation (minor part) and the sample inhomogeneous heating (dominant part). The role of the refractive index change anisotropy, appearing when the crystal is bleached, is addressed for the first time to our knowledge.