Enhancement of Rare-Earth Ion Fluorescence by Lattice Processes in Oxides

In the absence of a suitable absorption band for a rare-earth ion, its fluorescence can be excited by ultraviolet radiation through interaction with the host lattice when the latter is excited near its absorption edge. Rare-earth ion fluorescence can be enhanced by localized lattice processes at frequencies lower than the absorption edge. Longer range effects occur as the absorption region of the crystal is approached. The enhancement due to these processes can be quenched by effects resulting from an increase in rare-earth ion content.