Three-Dimensional Grain Boundary Spectroscopy in Transparent High Power   Ceramic Laser Materials
  Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, we show direct evidence for Nd3+-Nd3+ interactions across grain boundaries (GBs) in Nd3+:YAG laser ceramics. It is clearly shown that Nd3+ segregation takes place at GBs leading to self-fluorescence quenching which affects a volume fraction as high as 20%. In addition, we show a clear trend of increasing spatial inhomogeneities in Nd3+ concentration when the doping levels exceeds 3 at%, which is not detected by standard spectrometry techniques. These results could point the way to further improvements in what is already an impressive class of ceramic laser materials. 
Mariola O. Ramirez, Jeffrey Wisdom, Haifeng Li, Yan Lin Aung, Joseph   Stitt, Gary L. Messing, V. Dierolf, Zhiwen Liu, Akio ...