Nd 3+ -activated strontium lanthanum aluminate Sr1−xNdyLax−yMgxAl12−xO19 (ASL:Nd) crystals give efficient F43/2→I49/2 laser emission at 900 nm, whose properties depend on the x and y composition parameters. Based on high-resolution spectroscopy and emission decay, this paper demonstrates that the composition dependence of the laser emission is caused by the presence of two structural centers, C1 and C2, whose relative proportion in crystals is determined by composition parameter x. From the spectral data and crystal structure it is inferred that C2 center that prevails at low x, corresponds to a Nd3+ in a Sr2+ (2d) site of D3h local symmetry with no nearby Ln3+ (La3+ or Nd3+) ions. The C1 center lines, prevailing at large x parameter, which are broader and shift with composition, are composite lines of various structural centers of Nd3+ in a Sr2+ site with different occupancy of nearest-neighbor sites by Ln3+. The influence of the spectral and emission dynamics features of these centers on the laser properties is discussed and criteria for the selection of optimal composition is inferred.

The spectroscopic characteristics of Dy3+ in YAG (Y3Al5O12) transparent ceramics prepared by solid state synthesis were investigated, with special attention to the visible (yellow, blue) emissions that could be pumped directly by the new developed blue–violet or near UV laser diodes. The absorption and emission spectra, recorded at different temperatures from 10 to 300 K, were analyzed and relevant new parameters, improved energy level scheme, temperature effects, intensity parameters based on Judd-Ofelt theory and radiative transition rates, branching ratios, etc., were estimated and the data are compared with previous reports on garnet single crystals. The potential of the Dy3+: YAG transparent ceramics for yellow or blue laser emission is discussed.

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