Inhomogeneity of Nd doped yttrium aluminum garnet

Abstract

Neodymium doped yttrium aluminum garnet is the most practical and widely used rare earth doped crystalline laser crystal. Although extensive studies on this material have been carried out, there are still some interesting physical properties of this system which are not disclosed and well characterized. We studied the lifetime decay characteristic of Nd:YAG and correlated it with the inhomogeneities in the Nd-ion distribution in the sample. A 4% variation of the decay constants from point to point inside a single crystal is found and ascribed to the variation of Nd-ion concentration inside the crystal. The same setup as in Ref. 1 was used to measure the lifetimes where a small diameter (lOO-μm) pump beam excited regions that were at least 2 mm apart. The absorption of the sample in these regions was obtained at the same time by measuring the laser power before and after the sample. Since the sample ends were not antireflection coated, the Fresnel reflection of the rod ends was taken into account. The variation of the absorption coefficients from point to point in a single crystal is 25%. Since the absorption coefficient is proportional to the concentration of Nd- ions N, this observation suggests a 25% variation of N from point to point in a single Nd:YAG crystal.