Crystal stoichiometry of Czochralski grown rare-earth gallium garnets

Single crystal and transparent ceramic Nd-doped oxide laser materials: a comparative spectroscopic investigation

“…The density of dodecahedral sites is medium, ∼1.39 × 10 22 cm −3 . The previous structural and chemical investigation of Nd:YAG [1][2][3] revealed that the composition of the crystals could show departures from the ideal composition Y 3 Al 5 O 12 , that depend on the temperature of crystal growth: for the melt-grown crystals (∼2000 • C), the crystals show an excess of Y 3+ ions of 1.5-2%, which are supposed to enter in the octahedral a-sites of the garnet lattice normally occupied by Al 3+ (centres (Y 3+ (a)), while in case of flux-grown crystals (∼1350 • C) these departures from stoichiometry are very small, almost negligible. Another possible chemical defect of Czochralski crystals is the presence of hydroxyl impurities, whose localisation in the vicinity of Nd ions ('dead Nd sites') was invoked [20] in order to explain the low emission quantum efficiency of some crystals, although the infrared spectroscopy data show concentrations of hydroxyl much smaller than those required to explain the observed reduction of efficiency.…”

“…In the most usual method of melt-growth, pulling from melt of the crystal using a oriented seed (Czochralski technique), owing to the low segregation coefficient, the volume of the crystal for which the Nd concentration varies within acceptable limits is usually much smaller than that of the melt contained in the crucible. In many instances the melt-grown garnet crystals show a deterioration of the chemical composition [1][2][3] as well as structural defects such as coring, faceting, dislocations, inclusions and so on and an increased concentration of the active ion could favour formation of these defects; this limits severely the concentration of Nd (typically ∼1-1.2 at.% Nd for Nd:YAG). Owing to particularities of crystal growth with pulling along the direction 1 1 1 , the Nd:YAG crystals grown by the Czochralski method contain a central core and part of the off-core crystal contains regions of accentuated growth striations.…”

Preparation and characterization of Nd doped gadolinium gallium garnet nanopowders and crystals

“…Starting material were Nd-doped nanopowders prepared following the procedure described above as well as mixtures of the (high purity) metal oxides. The latter were mixed in a molar ratio [Gd 2 O 3 ]/[Ga 2 O 3 ] = 38.0/62.0 roughly corresponding to the congruently melting composition [23,24] and pre-reacted at 1500 °C for 48 hours. Completeness of the garnet formation reaction was verified by X-ray powder diffraction analysis.…”

Passively Q-switched 1.33 μm Nd:GAGG laser with Co2+:LMA saturable absorber

“…The garnet family is an excellent example that classified as the so called "disordered multi-center crystal". [8,9]. The laser properties of Nd:GGG crystal have been widely studied [10][11][12][13].…”