Recent Progress in the Development of Neodymium-Doped Ceramic Yttria

Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium-doped yttria (Nd:Y₂O₃) is considered to be an attractive material due to its possible lasing wavelengths of ~914 and ~946 nm for ozone profiling. These wavelengths, when frequency tripled, can generate ultraviolet (UV) light at ~305 and ~315 nm, which is particularly useful for ozone sensing using differential absorption light detection and ranging (LIDAR) technique. For practical realization of space-based UV transmitter technology, ceramic Nd:Y₂O₃ material is considered to possess a great potential. A plasma melting and quenching method has been developed to produce Nd3^+-doped powders for consolidation into Nd: Y₂O₃ ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises two main steps: 1) plasma melting and quenching to generate dense, and homogeneous doped metastable powders and 2) pressure-assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several in 1times1 ceramic cylinders have been produced. The infrared transmission of a 2-mm-thick undoped Y₂O₃ ceramic was as high as ~75% without antireflection coating. In the case of Nd:Y₂O₃, ceramics infrared transmission values of ~50% were achieved for a similar sample thickness. Furthermore, Nd:Y₂O₃ samples with dopant concentrations of up to ~2 at.% were prepared without significant emission quenching.