The growth of large, laser quality Nd xRE 1- xP 5O 14 crystals

Abstract

The growth of Nd x RE 1- x P 5O 14 crystals with x varying between 0.1 and 1, and RE = La, Y was investigated. The Nd 2O 3-P 2O 5-H 2O phase diagram, solubilities, evaporation rates, seeding procedures and growth rates were determined. With this knowledge the reproducible flux solution growth of laser-quality crystals was achieved by two methods: crystals up to 2 cm in size were grown in a simple semisealed system with a polished lid and others up to 3 cm in size were grown in a semisealed system with a double vessel. The solubility of the rare earth pentaphosphates varied with their composition. Seeded growth was performed at constant temperature in both systems, which permitted control over the dehydration. Influence of size and orientation of the seed as well as the growth rate on the quality of the crystals is discussed. Although these crystals show ferroelastic domains in the c-plane, lasing in pulsed operation along the c-axis normal to the domain walls was achieved in fabricated mini-laser rods with no degradation of the laser emission caused by the domains. On the other hand during the cw operation of some NdP 5O 14 crystals degradation in the laser emission was observed, especially with waveguide lasers. The measured fluorescence lifetime of these crystals is compared with the lifetimes of similar materials reported in the literature.