Analysis and Comparison of Single Crystal and Polycrystalline Nd:YAG, Absorption

The optical properties of polycrystalline and single crystal Nd:YAG materials are reported. Materials include undoped, 1%, 1.5%, 2%, 4%, 6%, and 10% at. Nd doped polycrystalline YAG and undoped and 1% at. Nd doped single crystal YAG. The motivation of this paper is to determine the ideal material type and doping percentage gain media for use in a high energy 0.946 μm Nd:YAG laser. Room temperature transmittance measurements for all samples are performed between the midinfrared and ultraviolet edges of absorption. From this calibrated transmittance data, an extinction coefficient and extinction cross section are calculated across the entire spectra. We determine that, for the doping percentages measured, the extinction cross section is independent of doping level. Our measured extinction cross sections are consistent with previously reported values. Temperature dependent transmittance measurements are conducted on 1% and 6% polycrystalline Nd:YAG material. A classical oscillator model for the diode pump band absorption coefficient is presented. A comparison of strengths and weaknesses of single crystal and polycrystalline is presented. This comparison reveals areas of parasitic absorption in polycrystalline YAG.