Integrated analysis of non-linear loss mechanisms in Yb:YAG ceramics for laser applications

Transparent 9.8at% Yb:YAG ceramic samples were prepared by reactive sintering of commercial oxides and using 0 or 1wt% polyethylene glycol (PEG) as dispersant. The optical quality of the samples turns out to be improved by using a dispersant and optical transmittance close to the commercial samples has been obtained. On the other hand the laser characterization evidenced the activation of a non-linear loss mechanism occurring only in the sample containing PEG and despite its better optical quality, at high excitation level. A SEM analysis of material microstructure could not explain this behavior. A state of the art TEM analysis at nanometric scale was performed providing high resolution chemical spectroscopic results that indicate the presence of amorphous and crystalline silicate phases playing different roles in the two samples.