Effect of Si-induced defects on 1 μm absorption losses in laser-grade YAG ceramics

High sensitivity optical absorption at 1 mu m was measured in 40 undoped and Nd-doped Y3Al5O12 (YAG) transparent ceramics and single crystals using photothermal common-path interferometry. Concurrently, chemical trace analysis was performed on those samples by glow discharge mass-spectroscopy. Silicon and calcium were found to be the major impurities with concentrations up to 250wt. ppm. A univocal linear correlation between the Si content and the absorption loss at 1 mu m is revealed and a possible mechanism for the formation of Si-induced color centers based on a bound polaron model is discussed. Solutions to reduce this optical absorption in ceramics are also proposed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709756]