Anisotropy of nonlinear absorption in a V3+:YAG crystal

Impurity-activated V3+:YAG crystals are used as passive laser switches in near-infrared lasers [1-3]. The phototropic properties of these crystals are due to the presence of wide additional-absorption (AA) bands with maxima near 0.8 and 1.3 μm. This additional absorption becomes saturated even at a low energy density of the incident radiation. For example, the absorption cross section for the λ≈1.3 pin band is ∝10-18 cm2 [2]. The AA bands are due to the V3+ ions in the YAG crystal matrix, which have the tetrahedral coordination of the garnet lattice ligands.