2 research outputs found
Na Modification of Lanthanide Doped Ca<sub>3</sub>Nb<sub>1.5</sub>Ga<sub>3.5</sub>O<sub>12</sub>-Type Laser Garnets: Czochralski Crystal Growth and Characterization
The Na<sup>+</sup>-Yb<sup>3+</sup> (or Er<sup>3+</sup>) co-substitution
of Ca<sup>2+</sup> in Ca<sub>3</sub>Nb<sub>1.5</sub>Ga<sub>3.5</sub>O<sub>12</sub> (CNGG) laser crystal is studied. In contrast to other
garnets whose structural disorder is exclusively based on the presence
of differently sized cations on the same crystal sites, Na<sup>+</sup> incorporated in the dodecahedral site (a site also shared by Ca<sup>2+</sup> and trivalent lanthanides) creates diverse electric charge
distributions over the dodecahedral sublattice, which adds to the
disorder associated with Nb<sup>5+</sup> and Ga<sup>3+</sup> simultaneous
occupation of the octahedral and tetrahedral sites. The currently
determined cationic compositions of Czochralski grown congruent CNGG
and Na-modified CNGG crystals show that Na<sup>+</sup> incorporation
reduces the cationic vacancy concentration on dodecahedral and octahedral
sites but does not affect that in tetrahedral sites. Physical properties
of interest for laser design (optical transmission, elastic constants,
hardness, specific heat, thermal conductivity, thermal expansion,
refractive index dispersion, group velocity dispersion, and thermo
optic coefficients) have been systematically determined at cryogenic
temperatures and above room temperature. Na<sup>+</sup> incorporation
into CNGG decreases the crystal growth temperature, promotes Yb<sup>3+</sup> doping, and importantly, increases the Yb<sup>3+</sup> optical
bandwidth, offering good prospects for the implementation of ultrashort
pulses in mode-locked laser oscillators