Three-dimensional grain boundary spectroscopy in transparent high power ceramic laser materials

Abstract

Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, we show direct evidence of inhomogeneous Nd(3+) distribution across grain boundaries (GBs) in Nd(3+):YAG laser ceramics. It is clearly shown that Nd(3+) 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 Nd(3+) 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.

Microstructuration induced differences in the thermo-optical and luminescence properties of Nd:YAG fine grain ceramics and crystals

“…This is at variance with the case of large grain ceramics in which confocal fluorescence imaging experiments have revealed a relevant Nd 3+ fluorescence quenching at the grain boundaries. 47 Since the time-resolved fluorescence comparative studies have not revealed a higher density of lattice defects in Nd:YAG ceramics with respect to Nd:YAG crystals, the reduced phonon mean free path obtained for Nd:YAG ceramics by TLS should be attributed to the phonon scattering at grain boundaries.…”

Narrow inhomogeneous and homogeneous optical linewidths in a rare earth doped transparent ceramic

“…To confirm this last conclusion, we examined the ceramic microstructure by confocal luminescence 33 , using the 5 D 0 → 7 F 2 transition intensity to map the spatial distribution of Eu 3+ ions (Fig. 2a).…”

Effect of Nd 3+ ions on phase transformations and microstructure of 0–4 at.% Nd 3+ :Y 3 Al 5 O 12 transparent ceramics

“…It is known that the increase of Nd 3+ ions concentration in the garnet matrix reduces grain boundaries mobility that results in inhibition of the grain growth for Nd 3+ :YAG [37]. At the same time, the Nd 3+ cations segregation at the grain boundaries may occurs that decreases their surface energy and mobility (due to the higher solubility limit of the impurity at the boundaries of crystallites as compared with the grain volume) [38].…”