Upconversion Processes in Transition Metal and Rare Earth Metal Systems

The design and characterization of new luminescent materials is an active area of research. Here we present several current topics in the area of upconversion by transition-metal and rare-earth-metal doped halide lattices. Following introduction to the necessary background material related to upconversion mechanisms and kinetics, a series of topics are discussed which illustrate some key areas of developing interest in the field. These include the use of unconventional experimental and theoretical techniques for gaining insight into upconversion processes in rare-earth-doped lattices (e.g., power-dependence measurements, two-color laser excitation schemes, and correlated crystal field calculations), as well as several specific examples of exciting and unusual upconversion behavior in both transition-metal and rareearth-metal systems. Finally, we discuss the variety of interesting effects host-lattice variation can have on the upconversion processes of a dopant ion, ranging from multiphonon relaxation properties to exchange interactions.