Analysis and Comparison of Single-Crystal and Polycrystalline Nd:YAG, Scatter

The extrinsic scatterance properties of polycrystalline and single crystal Nd:YAG materials are reported. Materials include undoped, 1%, 1.5%, 2%, 4%, and 6% Nd doped polycrystalline YAG, and undoped and 1% Nd doped single crystal YAG. The motivation of this study is to determine the ideal material type, and doping percentage gain media for use in 0.946 μm Nd:YAG lasers. In-plane bidirectional scatterance distribution function measurements are collected at multiple wavelengths from 0.405 μm to 1.55 μm for all samples. Scatterance data is fit to standard models and a total integrated scatter (TIS) for each sample at various wavelengths is determined. Using the TIS at multiple wavelengths, some conclusions on material quality and suitability are presented. A coated sphere anomalous diffraction (ADA) model is developed and applied to known sources of scatter in polycrystalline and single-crystal Nd:YAG. A Kubelka-Munk wavelength-dependant scatter coefficient model is developed using our ADA model. The model provides an accurate estimate of scatter at 0.946 μm. A comparison of strengths and weaknesses of single-crystal and polycrystalline materials is presented. This comparison reveals a possible continuing problem with background scatter present in single-crystal YAG.