Optical properties of Nd-doped ceramic yttrium aluminum garnet

Abstract

The ceramic form of yttrium aluminum garnet (YAG) was studied to determine its suitability for high power lasers. The high Nd³⁺ doping, the large material size, and the variable doping level with position in the sample, all achievable in ceramics as opposed to single crystal, may lead to higher power solid state lasers than those currently available. We have compared the optical properties of ceramic YAG doped with 0-9 at% Nd³⁺ to single-crystal, 1 at% Nd:YAG material. Measurements included scattering, thermo-optic behavior, absorption, fluorescence, and laser damage. Measurements of absorption and emission features showed a small but approximately linear increase in line width with increasing Nd3+ concentration. Nd³⁺ fluorescence lifetime was rapidly concentration quenched with the 240-μs lifetime for the 1 at% material decreasing to 30 μs for the 9 at% ceramic material. Bulk and surface laser damage thresholds were measured for undoped and 1% Nd-doped ceramic YAG samples using ns-duration laser pulses at 1.064 μm. Both bulk and surface damage threshold values were found to be at least as high as that of single crystals. Measurements of the refractive index and thermo-optic coefficients showed no difference between the single crystal and ceramic materials at 1% Nd³⁺ doping levels. The scattering in the ceramic material was less than half that of the single crystal. These results suggest that for most optical characteristics, the ceramic material is equal to and in some cases superior to the single crystal material.