Optical and defect studies of wide band gap materials

Non-destructive, optical techniques can be used to find and identify defects in solid-state laser materials that can inhibit the material's laser performance. With accurate detection and identification, these defects can be eliminated or their effects minimized through an array of methods. Two materials, YVO4 and YAG (Y3Al5O12) are studied, and their most common and problematic defects are optically identified. The presence of grain boundaries in a-axis grown YVO4 and their absence in c-axis grown YVO4 as well as the ability of c-axis grown YVO4 to accommodate a higher concentration level of Nd3+ ion suggest that the change of growth-axis direction from a-axis to c-axis may improve optical quality and laser performance of Nd:YVO4 laser elements. In Nd:YAG, the improvement in laser performance through aluminum diffusion and oxidizing heat treatment may point to the improvement in stoichiometry by the elimination of both oxygen and aluminum vacancies. Also, the multiple valence state impurity ion, iridium, is identified in YAG through optical measurement techniques and neutron activation analysis, and the minimization of its affect on laser performance through a process of aluminum diffusion and oxidation heat treatment is discussed